Proliferation Rate Of Chondrocytes Research Articles

Study on the mechanism of cross-linked hyaluronic acid-dexamethasone hydrogelin post-traumatic osteoarthritis

Objective: To explore the mechanism of cross-linked hyaluronic acid-dexamethasone hydrogel (cHA-Dex) in inhibiting chondrocyte apoptosis and alleviating early post-traumatic osteoarthritis (PTOA). Methods: To generate PTOA model, anterior cruciate ligament transection (ACLT)was performed on SD rats (n=70), and the sham surgery group (n=70) was set as control. The changes in inflammatory indicators such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), matrix metalloproteinase-3 (MMP-3), and matrix metalloproteinase-13 (MMP-13) in the joint lavage fluid were measured at different time points (1-14 days, 5 rats at each time point) after surgery. The cHA-Dex (0.5 mg/ml) hydrogel (experimental group, n=70) and ordinary low-molecular-weight hyaluronic acid (HA) hydrogel premixed with Dex, that was, HA-Dex (0.5 mg/ml) hydrogel (control group, n=70) were injected into the joint cavity of PTOA rats, and the release amount and cumulative release amount of Dex in the joint fluid of rats at each time point(1-14 days, 5 rats at each time point) were detected to reveal the release mechanism of cHA-Dex hydrogel. The cartilage of knee joint of patients with osteoarthritis (OA) who underwent knee arthroplasty in the Second Hospital of Shanxi Medical University from January 2020 to December 2022 was taken for in vitro tissue block culture (Outbridge score=1 or 2,n=18). After the cartilage tissue block was treated with cHA-Dex hydrogel premixed with 0.1, 0.2, and 0.5 mg/ml Dex, the mRNA expression levels of IL-1β, IL-6, TNF-α, MMP-3, and MMP-13 in the articular cartilage tissue block were detected. OA chondrocytes were isolated from cartilage samples using enzymatic hydrolysis and cultured in vitro (n=18). Chondrocytes were divided into 4 groups: saline, cHA hydrogel, Dex (0.5 mg/ml), and cHA-Dex (0.5 mg/ml) hydrogel group. The effects of different interventions on chondrocyte proliferation and apoptosis were tested. Results: The Osteoarthritis Research Society International (OARSI) score of safranine O-solid green staining in PTOA group was 3.34±0.35, and it was 1.17±0.21 in Sham group(P=0.010). The Meachim score of knee joint osteophytes in PTOA rats was significantly higher than that in the Sham group (2.66±0.41 vs 0.22±0.17, P=0.010), indicating PTOA model in rat was established successfully. The cHA-Dex hydrogel, which corresponded to the peak changes of inflammatory factors in the joints of PTOA rats in the early stage, was also released in the early stage and sustained-released in the late stage. After the OA articular cartilage tissue block was treated with cHA-Dex hydrogel premixed with 0.1, 0.2, and 0.5 mg/ml Dex, the mRNA expression levels of IL-1 β, IL-6, TNF-α, MMP-3, and MMP-13 in the tissue block were reduced significantly (all P<0.05) and in a dose-dependent manner. Compared with Dex (0.5 mg/ml) alone group, the apoptosis rate of cHA-Dex (0.5 mg/ml) hydrogel group was significantly reduced (0.60±0.07 vs 6.63±0.98, P=0.010).Compared with the normal saline or the cHA hydrogel alone group, the cHA-Dex (0.5 mg/ml) hydrogel group had significant cell proliferation, and the difference at each time point were all significant statistically (all P<0.05). Conclusion: For the early inflammation of PTOA, cHA-Dex hydrogel can not only inhibit cartilage inflammation, but also reverse the increased apoptosis and decreased proliferation rate of chondrocytes caused by Dex, and finally alleviate the progress of PTOA by releasing Dex.

BMP-7 modified exosomes derived from synovial mesenchymal stem cells attenuate osteoarthritis by M2 polarization of macrophages

BackgroundAlthough the exosomes derived from mesenchymal stem cells (MSCs) display a therapeutic effect on inflammatory diseases, its application on OA has great limitations due to lack of specificity and targeting. The current study aimed to elucidate the potential therapeutic role of bone morphogenetic proteins-7(BMP-7) modified synovial mesenchymal stem cells-derived exosomes (SMSCs-exo) on OA and mechanism. MethodsFor in vitro experiments, LPS-treated macrophages RAW264.7 were treated with SMSCs-exo (exo) or BMP-7 modified SMSCs-exos (BMP-7-exo). The levels of inflammatory factors were assessed by ELISA. Also, the proportion of iNOS and CD206 positive cells were quantified by flow cytometry. Chondrocytes and RAW264.7 were co-culture to evaluate the effects of macrophage polarization on chondrocytes cellular behaviors. This effect on KOA was verified by an experiment in vivo. HE staining and Safranin fast green staining were used to observe the damage of articular cartilage. Immunohistochemistry was used to determine the expression of collagen II and aggrecan in articular cartilage, as well as the expression of iNOS and CD206 in synovial tissues. ResultsOur in vitro results showed that BMP-7-exo treatment promoted LPS-induced proliferation of macrophages and chondrocytes, and showed a better ability to reduce inflammation by promoting macrophages M2 polarization. After co-culture with LPS treated macrophages, the proliferation rate and migration of chondrocytes were significantly decreased, while the apoptosis was significantly increased. The macrophages treated with BMP-7-exo and exo partially reversed these changes. The chondrocytes in BMP-7-exo group had higher proliferation rate and migration, as well as lower apoptosis compared with the exo group. Also, the in vivo results showed BMP-7-exo treatment improved the pathological changes of KOA and promoted synovial macrophages M2 polarization. ConclusionsOur results demonstrated that BMP-7-exo attenuated KOA inflammation and cartilage injury by synovial macrophages M2 polarization, suggesting that BMP-7-exo carry much therapeutic potential for OA.

Exosomes from Kartogenin-Pretreated Infrapatellar Fat Pad Mesenchymal Stem Cells Enhance Chondrocyte Anabolism and Articular Cartilage Regeneration.

Objective To evaluate the effect of Kartogenin-pretreated exosomes derived from infrapatellar fat pad mesenchymal stem cells on chondrocyte in vitro and articular cartilage regeneration in vivo. Methods Infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) were isolated from rabbits to harvest exosomes. After identification of mesenchymal stem cells and exosomes, rabbit chondrocytes were divided into three groups for further treatment: the EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells), KGN-EXO group (chondrocytes treated with exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN), and control group. After processing and proliferation, phenotypic changes of chondrocytes were measured. In the in vivo study, 4 groups of rabbits with articular cartilage injury were treated with KGN-EXO, EXO, IPFP-MSCs, and control. Macroscopic evaluation and histological evaluation were made to figure out the different effects of the 4 groups on cartilage regeneration in vivo. Results The proliferation rate of chondrocytes in the EXO or KGN-EXO group was significantly higher than that in the control group (P < 0.05). The qRT-PCR results showed that the expression of Sox-9, Aggrecan, and Col II was the highest in the KGN-EXO group compared with the EXO group and the control group (P < 0.05). The results of Western blot were consistent with the results of qRT-PCR. In vivo, the cartilage defects in the KGN-EXO group showed better gross appearance and improved histological score than those in IPFP-MSC groups, EXO groups, and control groups (P < 0.05). At 12 weeks, the defect site in the KGN-EXO group was almost completely repaired with a flat and smooth surface, while a large amount of hyaline cartilage-like structures and no obvious cracks were observed. Conclusion Our study demonstrates that the exosomes isolated from infrapatellar fat pad mesenchymal stem cells pretreated with KGN have potent ability to induce chondrogenic differentiation of stem cells, effectively promoting the proliferation and the expression of chondrogenic proteins and genes of chondrocytes. The KGN-EXO can also promote the repair of articular cartilage defects more effectively, which can be used as a potential therapeutic method in the future.

MicroRNA-146a-Mediated IL-6/Signal Transducer and Activator of Transcription 3 Signaling Pathway in Chondrocyte Proliferation and Apoptosis in Mice with Osteoarthritis

Background: To investigate the MicroRNA-146a targeting regulation of IL-6/STAT3 signaling pathway activity and influence the proliferation and apoptosis behavior-related mechanisms of OA chondrocytes. Material and Methods: 10 C57 mice were isolated and cultured with membrane protease and type II collagenase. The experiment was divided into blank group, MicroRNA-146a overexpression group and low expression group. The chondrocytes were transfected with plasmid vector. After 48 hours of culture, the proliferation rate of chondrocytes was detected by MTT method. The levels of type ii collagen, MMP-9, IL-1, IL-6, and TNF-α in culture medium were detected by ELISA. Luciferase reported experimental analysis of MircoRNA-146a targeting regulation of IL-6 genes. Results: Compared with the blank group, the proliferation rate of chondrocytes in the overexpression group was significantly decreased, the apoptosis rate was increased, the levels of IL-6 and p-STAT3 protein, type II collagen, MMP-9, IL-1, IL-6 and TNF-α were increased, while the low expression group was correlated (P &lt; 0.05). Luciferase reporter experiments confirmed that MicroRNA-146a had a better binding effect with the IL-6 gene. Conclusion: MicroRNA-146a overexpression may mediate activation of IL-6/STAT3 signaling pathway and participate in decreased proliferation activity and increased apoptosis activity in OA chondrocytes. IL-6 gene may have targeted regulatory sites for MicroRNA-146a.

A mutation in SLC20A2 (c.C1849T) promotes proliferation while inhibiting hypertrophic differentiation in ATDC5 chondrocytes.

AimsThis study aimed to investigate the effect of solute carrier family 20 member 2 (SLC20A2) gene mutation (identified from a hereditary multiple exostoses family) on chondrocyte proliferation and differentiation.MethodsATDC5 chondrocytes were cultured in insulin-transferrin-selenium medium to induce differentiation. Cells were transfected with pcDNA3.0 plasmids with either a wild-type (WT) or mutated (MUT) SLC20A2 gene. The inorganic phosphate (Pi) concentration in the medium of cells was determined. The expression of markers of chondrocyte proliferation and differentiation, the Indian hedgehog (Ihh), and parathyroid hormone-related protein (PTHrP) pathway were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting.ResultsThe expression of SLC20A2 in MUT group was similar to WT group. The Pi concentration in the medium of cells in MUT group was significantly higher than WT group, which meant the SLC20A2 mutation inhibited Pi uptake in ATDC5 chondrocytes. The proliferation rate of ATDC5 chondrocytes in MUT group was greater than WT group. The expression of aggrecan (Acan), α-1 chain of type II collagen (COL2A1), and SRY-box transcription factor 9 (SOX9) were higher in MUT group than WT group. However, the expression of Runt-related transcription factor 2 (Runx2), α-1 chain of type X collagen (COL10A1), and matrix metallopeptidase 13 (MMP13) was significantly decreased in the MUT group. Similar results were obtained by Alcian blue and Alizarin red staining. The expression of Ihh and PTHrP in MUT group was higher than WT group. An inhibitor (cyclopamine) of Ihh/PTHrP signalling pathway inhibited the proliferation and restored the differentiation of chondrocytes in MUT group.ConclusionA mutation in SLC20A2 (c.C1948T) decreases Pi uptake in ATDC5 chondrocytes. SLC20A2 mutation promotes chondrocyte proliferation while inhibiting chondrocyte differentiation. The Ihh/PTHrP signalling pathway may play an important role in this process.Cite this article: Bone Joint Res 2020;9(11):751–760.

Chondrocyte proliferation is promoted by 7-H-pyrrolo[2,3- d]pyrimidine via up-regulation of type II collagen matrix

Purpose: To investigate the effect of 7-H-pyrrolo[2,3-d]pyrimidine derivative (7-HPPD) on the viability of chondrocytes in vitro, and to elucidate the associated mechanisms.Methods: Chondrocyte proliferation was determined by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay while cell cycle was assessed by flow cytometry. Western blot and immunohistochemical staining assays were used to determine protein levels.Results: The results show that 7-HPPD significantly increased the proliferation rate of chondrocytes in a concentration-dependent manner (p &lt; 0.05). The proportion of chondrocytes in S phase increased significantly with subsequent reduction in G0/G1 phase of cell cycle on treatment with 7-HPPD (p &lt;0.05). Thus, 7-HPPD increased the rate of chondrocyte proliferation by promoting transition through G1/S phase of cell cycle. Reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis revealed that treatment of chondrocytes with 7-HPPD caused a marked increase in the level of cyclin D1, cyclin dependent kinase (CDK)-4 and CDK6 proteins (p &lt; 0.05). Western blot and immunohistochemical staining assays showed that 7-HPPD treatment caused a significant increase in the levels of type II collagen matrix in the chondrocytes.Conclusion: Proliferation of chondrocytes is increased by 7-HPPD and this occurs by facilitating G1/S phase transition and increasing expression of cyclin D1, CDK4 and CDK6 proteins. Therefore, 7-HPPD may be developed as a chemotherapeutic agent for the treatment of osteoarthritis.&#x0D; Keywords: Immunohistochemistry, Type II collagen, G1/S phase, Cyclin D1, Osteoarthritis

LncRNA CTBP1-AS2 is upregulated in osteoarthritis and increases the methylation of miR-130a gene to inhibit chondrocyte proliferation.

LncRNA CTBP1-AS2 has been reported to be involved in type 2 diabetes and cardiomyocyte hypertrophy, while its roles in other human diseases are unknown. Our preliminary deep sequencing analysis showed altered expression of CTBP1-AS2 in osteoarthritis (OA). In addition, CTBP1-AS2 was inversely correlated with miR-130a. This study was therefore carried out to investigate the interactions between CTBP1-AS2 and miR-130a in OA. Synovial fluid was collected from 62 OA patients and 62 healthy controls. RT-qPCR was performed to determine the expression levels of CTBP1-AS2 and miR-130a in synovial fluid. Cell transfections were performed to investigate the interactions between CTBP1-AS2 and miR-130a. Methylation-specific PCR (MSP) was performed to assess the effects of CTBP1-AS2 on the methylation of miR-130a. Cell counting Kit-8 (CCK-8) assay was performed to evaluate the roles of CTBP1-AS2 and miR-130a in regulating proliferation of chondrocytes. The results showed that CTBP1-AS2 was upregulated in OA and inversely correlated with miR-130a. In chondrocytes of OA patients, overexpression of CTBP1-AS2 led to increased methylation of miR-130a gene and downregulated expression of miR-130a, while overexpression of miR-130a did not affect the expression of CTBP1-AS2. In contrast, no interaction between CTBP1-AS2 and miR-130a was observed in chondrocytes from healthy adults. Analysis of chondrocyte proliferation showed that overexpression of miR-130a led to increased proliferation rate of chondrocytes extracted from OA patients. Overexpression of CTBP1-AS2 led to decreased proliferation rate of chondrocytes and reversed the effects of overexpressing miR-130a. Therefore, CTBP1-AS2 is upregulated in OA and may increase the methylation of miR-130a gene to inhibit chondrocyte proliferation. Key Points • CTBP1-AS2 is overexpressed in OA and may downregulate miR-130a through methylation to suppress the proliferation of chondrocytes. • The interaction between CTBP1-AS2 and miR-130a is indirect and mediated by certain pathological mediators.

IFT80 Is Required for Fracture Healing Through Controlling the Regulation of TGF-β Signaling in Chondrocyte Differentiation and Function.

Primary cilia are essential cellular organelles that are anchored at the cell surface membrane to sense and transduce signaling. Intraflagellar transport (IFT) proteins are indispensable for cilia formation and function. Although major advances in understanding the roles of these proteins in bone development have been made, the mechanisms by which IFT proteins regulate bone repair have not been identified. We investigated the role of the IFT80 protein in chondrocytes during fracture healing by creating femoral fractures in mice with conditional deletion of IFT80 in chondrocytes utilizing tamoxifen inducible Col2α1-CreER mice. Col2α1cre IFT80f/f mice had smaller fracture calluses than IFT80f/f (control) mice. The max-width and max-callus area were 31% and 48% smaller than those of the control mice, respectively. Col2α1cre IFT80f/f mice formed low-density/porous woven bony tissue with significantly lower ratio of bone volume, Trabecular (Tb) number and Tb thickness, and greater Tb spacing compared to control mice. IFT80 deletion significantly downregulated the expression of angiogenesis markers-VEGF, PDGF and angiopoietin and inhibited fracture callus vascularization. Mechanistically, loss of IFT80 in chondrocytes resulted in a decrease in cilia formation and chondrocyte proliferation rate in fracture callus compared to the control mice. Meanwhile, IFT80 deletion downregulated the TGF-β signaling pathway by inhibiting the expression of TGF-βI, TGF-βR, and phosphorylation of Smad2/3 in the fracture callus. In primary chondrocyte cultures in vitro, IFT80 deletion dramatically reduced chondrocyte proliferation, cilia assembly, and chondrogenic gene expression and differentiation. Collectively, our findings demonstrate that IFT80 and primary cilia play an essential role in fracture healing, likely through controlling chondrocyte proliferation and differentiation, and the TGF-β signaling pathway. © 2019 American Society for Bone and Mineral Research.

Effect of low expression of PTHrp receptor on proliferation of tibial growth plate chondrocytes in chronic renal insufficiency young rats

Objective: To observe the effect of parathyroid hormone-related protein (PTHrp) receptor on the proliferation of tibial growth plate chondrocytes in chronic renal insufficiency (CRI) young rats. Methods: Two-week-old male SD rats were randomly divided into two groups: (1) Sham group (n=6), only left ureter was exposed; (2) CRI group(n=6), left ureter was ligated to induce chronic renal insufficiency. Rats were sacrificed 2 weeks after operation and the blood concentration of PTHrp was detected by intracardiac blood sampling. Chondrocytes isolated from growth plate in two groups were cultured in vitro to P3 generation. The level of PTHrp receptor in chondrocytes was observed by immunohistochemistry and quantitative analysis was completed by Western blot. The proliferation rate of chondrocytes from two groups at 24 h was detected by using 5-ethynyl-2'-deoxyuridine (EDU) technique. Three types of PTHrp receptor mRNA plasmids (overexpressed, empty vector and knockdown) were used to treat the chondrocytes from CRI group. The mRNA and protein levels of PTHrp receptor were detected after 24 h and 48 h intervention, respectively. The chondrocyte proliferation rate at 24 h was detected by EDU. Results: Blood concentration of PTHrp in CRI group was higher than that in Sham group [(1.36±0.42) ng/L vs (0.77±0.21) ng/L, t=3.913, P=0.001]. The results of Western blot showed that the level of PTHrp receptor in growth plate chondrocytes from CRI group decreased (0.15±0.07 vs 0.41±0.13, t=5.569, P<0.001). Chondrocyte proliferation rate of CRI group was lower than that in Sham group at 24 h [(11.3±3.1)% vs (24.6±5.7)%, t=6.482, P<0.001]. The mRNA and protein levels of PTHrp receptor increased in chondrocytes of CRI group after intervention with overexpressed plasmid. The chondrocyte proliferation rate increased at 24 h. On the contrary, the mRNA and protein levels of PTHrp receptor decreased afer intervention with knockdown plasmid, and the chondrocyte proliferation rate also decreased [overexpression: (22.8±6.5)%, empty carrier: (10.2±4.3)%, knockdown: (5.6±2.1)%, F=29.840, P<0.001]. Conclusion: Increased PTHrp concentration in the blood of CRI young rats leads to decreased PTHrp receptors in growth plate chondrocytes, which results in decreasing PTHrp activity and proliferation rate of chondrocyte.

MiR-101-3p alleviates IL-1β-induced chondrocyte injury by targeting stanniocalcin 1

To explore the effects of miR-101-3p on IL-1β-induced chondrocyte injury and its underlying mechanisms. Methods: Chondrocytes were divided into 4 groups: a control group (NC group), a IL-1β group, a negative control group (IL-1β+miR-NC group), and a miR-101-3p group (IL-1β+miR-101-3p group), which were treated with IL-1β after transfecting with miR-101-3p mimic or negative mimic. The expressions of miR-101-3p-5p and stanniocalcin 1 (STC1) at different concentrations of IL-1β (1, 5, 10 ng/mL)-induced chondrocytes were detected by Western blotting and real-time PCR. MTT assay was used to detect cell proliferation rate, while caspases assay kits and flow cytometry were used to measure the cell caspase and apoptosis level. Western blotting assay was used to detect the expression levels of pro-inflammatory and ECM-related protein, such as matrix metalloproteinase 9 (MMP9) and collagen Type II. In addition, 3'-untranslated regions (UTR) of wild-type STC1 (STC1-3'-UTR-WT) or 3'-UTR of mutant STC1 (STC1-3'-UTR-MUT) were co-transfected with miR-101-3p mimic or miR-NC, respectively, while luciferase reporter assay was used to examine the regulative role of miR-101-3p in STC1. In order to detect whether STC1 was involved in the effect of miR-101-3p on chondrocytes, miR-NC (miR-NC group), miR-101-3p (miR-101-3p group), anti-NC (anti-NC group) and anti-miR-101-3p (anti-miR-101-3p group) were respectively transfected into the cells, and the expression of STC1 protein was detected by Western blotting. Subsequently, the cells were randomly divided into a miR-101-3P group (IL-1β+miR-101-3p group), an over-expression control group (IL-1β+miR-101-3p+ad-GFP group), and an over-expression STC1 group (IL-1β+miR-101-3p+ad-STC1 group) to investigate whether STC1 was involved in the role of miR-101-3p in chondrocyte. Similarly, MTT assay was used to detect cell proliferation rate, caspases assay kits and flow cytometry were used to measure the cell caspase and apoptosis level. Western blotting assay was used to detect the expression levels of pro-inflammatory and ECM-related protein MMP9 and collagen Type II. Results: Compared with the 0 ng/mL IL-1β, the expression of miR-101-3p was decreased in chondrocyte at different concentration of IL-1β (1, 5, 10 ng/mL) (all P<0.05), while the level of STC1 was increased (P<0.05). Compared with the NC group, the chondrocyte proliferation rate was down-regulated (P<0.05), while the apoptosis rate, the levels of caspases, IL-6 and TNF-α were increased in the IL-1β group (P<0.05). Moreover, the MMP9 levels were increased obviously, and the protein levels of collagen Type II were decreased in the IL-1β group compared with the NC group (both P<0.05). Compared with the IL-1β+miR-NC group, the proliferation rate was increased (P<0.05), whereas the apoptosis rates, the caspase-3/9 levels, the IL-6 and TNF-α levels were increased in the IL-1β+miR-101-3p group (all P<0.05). Then MMP9 levels were decreased obviously (P<0.05), and the protein levels of collagen Type II were increased in IL-1β+miR-101-3p group compared with the IL-1β+miR-NC group (both P<0.05). In addition, the double luciferase assay showed that the STC1 levels could be inhibited in the miR-101-3p group compared with the miR-NC group (P<0.05). STC1 levels were decreased in the miR-101-3p group compared with the miR-NC group (P<0.05), and the STC1 levels were increased in the anti-miR-101-3p group compared with those in the anti-NC group (P<0.05). The results of miR-101-3p+ad-STC1 group showed that compared with the miR-101-3p+ad-GFP group, the STC1 could reverse the effects of miR-101-3p on IL-1β-induced proliferation, apoptosis, inflammatory responses and ECM protein of chondrocytes. Conclusion: The regulation of miR-101-3p/STC1 signal pathway may have a role in reducing the IL-1β-induced chondrocyte injury.

Three-Dimensional Porous Scaffolds with Biomimetic Microarchitecture and Bioactivity for Cartilage Tissue Engineering.

Ideal tissue-engineering cartilage scaffolds should possess the same nanofibrous structure as the microstructure of native cartilage as well as the same biological function provided by the microenvironment for neocartilage regeneration. In the present study, three-dimensional composite biomimetic scaffolds with different concentration ratios of electrospun gelatin-polycaprolactone (gelatin-PCL) nanofibers and decellularized cartilage extracellular matrix (DCECM) were fabricated. The nanofibers with the biomimetic microarchitecture of native cartilage served as a skeleton with excellent mechanical properties, and the DCECM served as a biological functionalization platform for the induction of cell response and the promotion of cartilage regeneration. Experimental results showed that the composite nanofiber/DCECM (NF/DCECM) scaffolds had stronger mechanical properties and structural stability in wet state compared with those of DCECM scaffolds. In vitro experiments demonstrated that all scaffolds had good biocompatibility, but the chondrocyte proliferation rate of the composite NF/DCECM scaffolds was higher than that of the NF scaffolds. In vitro and in vivo cartilage regeneration results indicated that the DCECM component of the composite scaffolds facilitated early maturation of the cartilage lacuna and the secretion of collagen and glycosaminoglycan. The macroscopic and histological results at 12 weeks postsurgery exhibited that the composite NF/DCECM scaffolds yielded better cartilage repair outcomes than those of the nontreated group and NF scaffolds group. Overall, the present study demonstrated that the structurally and functionally biomimetic NF/DCECM scaffold is a promising tissue engineering scaffold for cartilage regeneration and cartilage defect repair.

Exosome-mediated Bidirectional Signaling between Mesenchymal Stem Cells and Chondrocytes for Enhanced Chondrogenesis

Exosomes of human mesenchymal stem cells (hMSC) are known to effectively increase the proliferation rate of chondrocytes and stimulate cartilage extracellular matrix. However, the therapeutic efficacy of the other signaling direction (i.e., the effect of chondrocyte-derived exosomes on hMSC) has not been extensively investigated. Therefore, the present study was designed to investigate exosome-mediated in vitro bidirectional signalings between progenitor hMSC and mature chondrocytes in cartilage tissues with various culture medial formulations. The exosomes isolated from bovine chondrocytes (BC) and hMSC (50 µg/ mL of exosomes per 3000 cells) were treated to hMSC and BC, respectively. Both cells were cultured in media formulations with 10% FBS, 10% exosome free-FBS, and 0.5% FBS. A variety of cellular responses by exosome treatments including proliferation, chondrogenic differentiation, cartilage extracellular matrix (ECM) deposition were evaluated using WST-1 assay, RT-PCR, and alcian blue staining for glycosaminoglycan (GAG) content. The results demonstrated that bidirectional exosome treatments increased proliferation of both BC and hMSC, and similar bidirectional influences including chondrogenic differentiation, glycosaminoglycan (GAG) ECM deposition were also up-regulated in both cell populations. Moreover, exosome-mediated in vitro activation between two cell populations could be regulated by media formulations. Therefore, exosomes could play important signaling roles in communication between two major cell populations in cartilage tissues.

Effect of primary cilia on growth plate chondrocyte proliferation of young rats with chronic renal insufficiency

Objective: To observe the effect of primary cilia on growth plate chondrocyte proliferation of young rats with chronic renal insufficiency (CRI). Methods: Male 2-week-old Sprague-Dawley rats were randomly divided into two groups (with 10 in each group): Sham group (only left ureter was exposed) and CRI group (left ureter was ligated). Rats were sacrificed 2 weeks after operation and the total length of tibia was measured. Histological sections of tibia were taken to observe the chondrocytes of growth plate proliferative region and the expression rate of primary cilia. Chondrocytes from growth plate in two groups were isolated and cultured in vitro to P3 generation and the chondrocyte proliferation rate at 24 h were detected. The primary cilia expression rate and cilia length of chondrocytes were measured. Western blot was used to detect the expression of intraflagellar transport 88 (IFT88) protein and the gray scale was analyzed. Results: The total length of tibia was shorter in CRI group [(35.84±4.56) mm vs (42.33±3.44) mm, P=0.002]. The results of tibial histological section showed that chondrocytes of growth plate proliferative region were unorganized and the number of chondrocyte with columnar structure was less in CRI group (2.71±1.10 vs 7.68±1.32, P<0.001). The primary cilia expression rate of chondrocytes was higher in CRI group [(35.53±7.41)% vs (18.31±5.12)%, P<0.001]. The chondrocyte proliferation rate at 24 h was lower in CRI group [(11.38±6.10)% vs (24.35±8.46)%, P=0.001]. The primary cilia expression rate of chondrocytes was higher in CRI group [(60.12±7.86)% vs (32.17±8.97)%, P<0.001], and the primary cilia length of chondrocytes was longer in CRI group [(3.54±1.61) μm vs (1.96±0.82) μm, P=0.012]. The protein IFT88 was more highly expressed in CRI group (0.47±0.23 vs 0.17±0.10, P=0.001). Conclusion: The primary cilia expression rate of growth plate chondrocytes was higher in the rats with CRI, resulting in decreased chondrocyte proliferation rate and growth retardation of tibial growth plate.

Marked alterations in the structure, dynamics and maturation of growth plate likely explain growth retardation and bone deformities of young Hyp mice.

Mechanisms underlying growth impairment and bone deformities in X-linked hypophosphatemia are not fully understood. We here describe marked alterations in the structure, dynamics and maturation of growth plate in growth-retarded young Hyp mice, in comparison with wild type mice. Hyp mice exhibited reduced proliferation and apoptosis rates of chondrocytes as well as severe disturbance in the process of chondrocyte hypertrophy disclosed by abnormal expression of proteins likely involved in cell enlargement, irregular chondro-osseous junction and disordered bone trabecular pattern and vascular invasion in the primary spongiosa. (Hyp mice had elevated circulating FGF23 levels and over activation of ERK in the growth plate.) All these findings provide a basis to explain growth impairment and metaphyseal deformities in XLH. Hyp mice were compared with wild type mice serum parameters, nutritional status and growth impairment by evaluation of growth cartilage and bone structures. Hyp mice presented hyphosphatemia with high FGF23 levels. Weight gain and longitudinal growth resulted reduced in them with numerous skeletal abnormalities at cortical bone. It was also observed aberrant trabecular organization at primary spongiosa and atypical growth plate organization with abnormal proliferation and hypertrophy of chondrocytes and diminished apoptosis and vascular invasion processes. The present results show for the first time the abnormalities present in the growth plate of young Hyp mice and suggest that both cartilage and bone alterations may be involved in the growth impairment and the long bone deformities of XLH.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

[Purpose] To investigate the influence of knee immobilization period on recovery of histological damages in the anterior cruciate ligament (ACL) insertion and articular cartilage in rabbits. This knowledge is important for determining the appropriate rehabilitation approach for patients with ligament injuries, fracture, disuse atrophy, and degenerative joint disease. [Materials and Methods] Forty-eight male Japanese white rabbits were divided equally into the remobilization and control groups. The remobilization group had the right knee surgically immobilized, and was divided equally into four subgroups according to the duration of immobilization (1, 2, 4 and 8 weeks). After the immobilization was removed, the rabbits moved freely for 8 weeks. The control group underwent sham operation and followed the same time course as the remobilization group. The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage were analyzed after remobilization. [Results] In the ACL insertion, the remobilization group had a higher chondrocyte apoptosis rate than the control group after 8 weeks of immobilization, and a lower chondrocyte proliferation rate than the control group after 4 and 8 weeks of immobilization. In the articular cartilage, the remobilization group had a lower chondrocyte proliferation rate than the control group after 8 weeks of immobilization. After 8 weeks of remobilization, the ACL insertion and articular cartilage are not completely recovered after 4 and 8 weeks of immobilization, respectively. [Conclusion] Our results suggest that 8 weeks of remobilization will result in recovery of the ACL insertion after 2 weeks of knee immobilization, and recovery of the articular cartilage after 4 weeks of knee immobilization. If 8 weeks of immobilization occurs, a remobilization duration of more than 8 weeks may be necessary.

Functional testing on engineered cartilage to identify the role played by shearing

Compressive loading is crucial for tissue regeneration in cartilage; however, the role played by shearing induced from translational or rotational motion of the knee joint has yet to be identified. This study aims at investigating the effects of in vivo like dynamic load–compression integrated with shearing on tissue regeneration, particularly to identify the role played by shearing induced from rotational motion. Tissue samples fabricated from a calcium alginate hydrogel embedded with chondrocytes were subjected to a dynamic tissue culture. Three culturing regimes were included: a static culture control (CON), compression combined with shearing induced from translational motion (CS), and compression combined with shearing induced from both translational and rotational motion (CSR). The results indicate that the CS group has a significantly larger chondrocyte proliferation rate (p < .01), and that the CSR group has no advantages over the CS group. However, the CSR group was found to have a marked influence on the matrix synthesis compared to that of the CS group (p < .01). It can be concluded that shearing from individual joint motions offers a different contribution to the chondrocyte proliferation, matrix synthesis, and phenotype maintenance, and better insight into these individual roles will be necessary for determining the efficacy of in vivo/vitro cartilageous tissue functionalization.

Influence of Knee Immobilization on Chondrocyte Apoptosis and Histological Features of the Anterior Cruciate Ligament Insertion and Articular Cartilage in Rabbits.

This study examined the influence of immobilization on chondrocyte apoptosis and histological features of the anterior cruciate ligament (ACL) insertion and knee articular cartilage in rabbits. Forty-eight male Japanese white rabbits were assigned to an immobilization (n = 24) or sham (n = 24) group. Rabbits in the immobilization group underwent complete unilateral surgical knee immobilization and rabbits in the sham group underwent a sham surgery. The average thickness of the glycosaminoglycan (GAG) stained red area by safranin O staining, the chondrocyte apoptosis rate and the chondrocyte proliferation rate in the cartilage layer in the ACL insertion and the articular cartilage of the medial tibial condyle were measured at one, two, four and eight weeks in six animals from each group. In the ACL insertion, the chondrocyte apoptosis rate was higher in the immobilization group than in the sham group at two and eight weeks after surgery (p < 0.05). The chondrocyte proliferation rate gradually decreased from two weeks to eight weeks in the immobilization group. The GAG layer was thinner in the immobilization group than in the sham group at two, four and eight weeks after surgery (p < 0.05). In the articular cartilage, the chondrocyte apoptosis rate in the immobilization group was higher than in the sham group at four and eight weeks after surgery (p < 0.05). The GAG layer was significantly thinner in the immobilization group than that in the sham group at four and eight weeks after surgery (p < 0.05). Knee immobilization significantly increased chondrocyte apoptosis at two and eight weeks after surgery in the ACL insertion and at four and eight weeks after surgery in the articular cartilage of the medial tibial condyle, and decreased GAG layer thickness from two to eight weeks after surgery in the ACL insertion and from four to eight weeks after surgery in the articular cartilage.

Impact of expansion and redifferentiation under hypothermia on chondrogenic capacity of cultured human septal chondrocytes

A critical limitation in the cultivation of cartilage for tissue engineering is the dedifferentiation in chondrocytes, mainly during in vitro amplification. Despite many previous studies investigating the influence of various conditions, no data exist concerning the effects of hypothermia. Our aim has been to influence chondrocyte dedifferentiation in vitro by hypothermic conditions. Chondrocytes were isolated from cartilage biopsies and seeded in monolayer and in three-dimensional pellet-cultures. Each cell culture was either performed at 32.2°C or 37°C during amplification. Additionally, the influence of the redifferentiation of chondrocytes in three-dimensional cell culture was examined at 32.2°C and 37°C after amplification at 32.2°C or 37°C. An 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay was used to measure cell proliferation in monolayer, whereas the polymerase chain reaction and immunohistochemical and histological staining were used in three-dimensional pellet-cultures. Real-time polymerase chain reaction was employed to measure the relative expression of the target genes collagen II, collagen I, aggrecan and versican. Ratios were estimated between collagen II/collagen I and aggrecan/versican to evaluate differentiation. A higher value of these ratios indicated an advantageous status of differentiation. In monolayer, hypothermia at 32.2°C slowed down the proliferation rate of chondrocytes significantly, being up to two times lower at 32.2°C compared with culture at 37°C. Simultaneously, hypothermia in monolayer decelerated dedifferentiation. The ratio of aggrecan/versican was significantly higher at 32.2°C compared with that at 37°C. In three-dimensional pellet-culture, the chondrocytes redifferentiated at 32.2°C and at 37°C, and this process is more distinct at 37°C than at 32.2°C. Similar results were obtained for the ratios of collagen II/collagen I and aggrecan/versican and were supported by immunochemical and histological staining. Thus, hypothermic conditions for chondrocytes are mainly advantageous in monolayer culture. In three-dimensional pellet-culture, redifferentiation predominates at 37°C compared with at 32.2°C. In particular, the results from the monolayer cultures show potential in the avoidance of dedifferentiation.

Differences in joint morphology between the knee and ankle affect the repair of osteochondral defects in a rabbit model.

BackgroundAlthough differences in the results of the bone marrow stimulation technique between the knee and ankle have been reported, a detailed mechanism for those differences has not been clarified. The purpose of this study was to examine whether morphological differences between the knee and ankle joint affect the results of drilling as treatment for osteochondral defects in a rabbit model.MethodsOsteochondral defects were created at the knee and ankle joint in the rabbit. In the knee, osteochondral defects were created at the medial femoral condyle (MFC) and patellar groove (PG). At the ankle, defects were created in the talus at either a covered or uncovered area by the tibial plafond. After creating the osteochondral defect, drilling was performed. At 4, 8, and 12 weeks after surgery, repair of the osteochondral defects were evaluated histologically. The proliferation of rabbit chondrocytes and proteoglycan release of cartilage tissue in response to IL-1β were analyzed in vitro in both joints.ResultsAt 8 weeks after surgery, hyaline cartilage repair was observed in defects at the covered area of the talus and the MFC. At 12 weeks, hyaline cartilage with a normal thickness was observed for the defect at the covered area of the talus, but not for the defect at the MFC. At 12 weeks, subchondral bone formation progressed and a normal contour of subchondral bone was observed on CT in the defect at the covered area of the talus. No significant differences in chondrocyte proliferation rate and proteoglycan release were detected between the knee and ankle in vitro.ConclusionsOur results demonstrate that the covered areas of the talus show early and sufficient osteochondral repair compared to that of the knee and the uncovered areas of the talus. These results suggest that the congruent joint shows better subchondral repair prior to cartilage repair compared to that of the incongruent joint.

Longitudinal bone growth is impaired by direct involvement of caffeine with chondrocyte differentiation in the growth plate.

We showed previously that caffeine adversely affects longitudinal bone growth and disrupts the histomorphometry of the growth plate during the pubertal growth spurt. However, little attention has been paid to the direct effects of caffeine on chondrocytes. Here, we investigated the direct effects of caffeine on chondrocytes of the growth plate invivo and invitro using a rapidly growing young rat model, and determined whether they were related to the adenosine receptor signaling pathway. A total of 15 male rats (21days old) were divided randomly into three groups: a control group and two groups fed caffeine via gavage with 120 and 180mgkg-1 day-1 for 4weeks. After sacrifice, the tibia processed for the analysis of the long bone growth and proliferation of chondrocytes using tetracycline and BrdU incorporation, respectively. Caffeine-fed animals showed decreases in matrix mineralization and proliferation rate of growth plate chondrocytes compared with the control. To evaluate whether caffeine directly affects chondrocyte proliferation and chondrogenic differentiation, primary rat chondrocytes were isolated from the growth plates and cultured in either the presence or absence of caffeine at concentrations of 0.1-1mm, followed by determination of the cellular proliferation or expression profiles of cellular differentiation markers. Caffeine caused significant decreases in extracellular matrix production, mineralization, and alkaline phosphatase activity, accompanied with decreases in gene expression of the cartilage-specific matrix proteins such as aggrecan, type II collagen and type X. Our results clearly demonstrate that caffeine is capable of interfering with cartilage induction by directly inhibiting the synthetic activity and orderly expression of marker genes relevant to chondrocyte maturation. In addition, we found that the adenosine type 1 receptor signaling pathway may be partly involved in the detrimental effects of caffeine on chondrogenic differentiation, specifically matrix production and mineralization, as evidenced by attenuation of the inhibitory effects of caffeine by blockade of this receptor. Thus, our study provides novel information on the integration of caffeine and adenosine receptor signaling during chondrocyte maturation, extending our understanding of the effect of caffeine at a cellular level on chondrocytes of the growth plate.