Regulates Chondrocyte Proliferation Research Articles

Key Roles of Gli1 and Ihh Signaling in Craniofacial Development.

The Hedgehog (Hh) signaling pathway orchestrates its influence through a dynamic interplay of Hh proteins, the cell surface receptor Ptch1, Smo, and Gli transcription factors, contributing to a myriad of developmental events. Indian Hedgehog (Ihh) and Gli zinc finger transcription factor 1 (Gli1) play crucial roles in developmental regulation within the Hh signaling pathway. Ihh regulates chondrocyte proliferation, differentiation, and bone formation, impacting the development of cranial bones, cartilage, and the temporomandibular joint (TMJ). Losing Ihh results in cranial bone malformation and decreased ossification and affects the formation of cranial base cartilage unions, TMJ condyles, and joint discs. Gli1 is predominantly expressed during early craniofacial development, and Gli1+ cells are identified as the primary mesenchymal stem cells (MSCs) for craniofacial bones, crucial for cell differentiation and morphogenesis. In addition, a complex mutual regulatory mechanism exists between Gli1 and Ihh, ensuring the normal function of the Hh signaling pathway by directly or indirectly regulating each other's expression levels. And the interaction between Ihh and Gli1 significantly impacts the normal development of craniofacial tissues. This review summarizes the pivotal roles of Gli1 and Ihh in the intricate landscape of mammalian craniofacial development and outlines the molecular regulatory mechanisms and intricate interactions governing the growth of bone and cartilage exhibited by Gli1 and Ihh, which provides new insights into potential therapeutic strategies for related diseases or researches of tissue regeneration.

Biological functions and applications of LncRNAs in the regulation of the extracellular matrix in osteoarthritis.

Osteoarthritis (OA) is a major cause of disability, characterized by chronic pain, irreversible destruction, and loss of function of the articular cartilage. The integrity and arrangement of the composition and structure of the extracellular matrix (ECM) are essential for maintaining the elasticity, integrity, and mechanical support function of the cartilage tissue. Osteoarthritis causes substantial changes in the ECM, driving the progression of the disease. Recent studies have shown that the ECM plays a critical role in the development of cartilage tissue as well as the occurrence and development of osteoarthritis by directly or indirectly regulating chondrocyte proliferation, apoptosis, differentiation, and gene expression. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs derived from large transcripts. Mutations and disorders of lncRNAs are closely related to the development of osteoarthritis. Abnormal expression of lncRNAs in osteoarthritic cartilage regulates the synthesis and decomposition of the cartilaginous ECM. Therefore, the use of lncRNAs as nucleic acid drugs that regulate their targets may reduce ECM degradation, thereby delaying the pathological progression of osteoarthritis. In this review, the regulatory effects of lncRNAs on ECM in different cell behaviors related to OA are summarized. The roles of lncRNAs in the proliferation, apoptosis, differentiation, and ECM-related gene activity of chondrocytes, as well as the application of lncRNAs as potential gene therapy drugs for the repair and regeneration of osteoarthritic tissue, are also reviewed. A better understanding of the roles of lncRNAs in guiding chondrocyte behavior and ECM metabolism is critical for their future applications in osteoarthritis therapy and regenerative medicine.

Amarogentin Alleviates Osteoarthritis by Regulating Chondrocyte Proliferation and Autophagy

Although amarogentin has been shown to play an amelioration role in several disease states, its role in osteoarthritis progression remains unexplored. To this end, we have examined the role of amarogentin in interleukin-1β-treated chondrocytes, a cell model of osteoarthritis. We observed that chondrocyte proliferation was attenuated after interleukin-1β treatment, which was reversed by amarogentin treatment. In addition, the protein expressions for matrix metalloproteinase-3 and matrix metalloproteinase-9 were enhanced, and collagen II was reduced after interleukin-1β treatment, but these changes were reversed by amarogentin treatment, indicating that amarogentin inhibited interleukin-1β-stimulated extracellular matrix degradation. Moreover, amarogentin strengthened interleukin-1β-triggered chondrocyte autophagy by enhancing LC3II/LC3I, Beclin1, and Atg7 levels and reducing the level of P62, a cargo adaptor protein that interacts with autophagic substrates and delivers them to autophagosomes for degradation. Besides, the expressions of p-AMPK/AMPK and SIRT1 proteins were diminished after interleukin-1β treatment, but these effects were restored by amarogentin treatment, illustrating that amarogentin activated the AMPK/SIRT1 pathway. In conclusion, amarogentin alleviates osteoarthritis by regulating chondrocyte proliferation and autophagy through the AMPK/SIRT1 pathway.

Metabolic rewiring controlled by c-Fos governs cartilage integrity in osteoarthritis

ObjectivesThe activator protein-1 (AP-1) transcription factor component c-Fos regulates chondrocyte proliferation and differentiation, but its involvement in osteoarthritis (OA) has not been functionally assessed.Methodsc-Fos expression was evaluated by immunohistochemistry on...

Whole-Transcriptome Sequencing of Antler Tissue Reveals That circRNA2829 Regulates Chondrocyte Proliferation and Differentiation via the miR-4286-R+1/FOXO4 Axis.

The antler is the unique mammalian organ found to be able to regenerate completely and periodically after loss, and the continuous proliferation and differentiation of mesenchymal cells and chondrocytes together complete the regeneration of the antler. Circular non-coding RNAs (circRNAs) are considered to be important non-coding RNAs that regulate body development and growth. However, there are no reports on circRNAs regulating the antler regeneration process. In this study, full-transcriptome high-throughput sequencing was performed on sika deer antler interstitial and cartilage tissues, and the sequencing results were verified and analyzed. The competing endogenous RNA (ceRNA) network related to antler growth and regeneration was further constructed, and the differentially expressed circRNA2829 was screened out from the network to study its effect on chondrocyte proliferation and differentiation. The results indicated that circRNA2829 promoted cell proliferation and increased the level of intracellular ALP. The analysis of RT-qPCR and Western blot demonstrated that the mRNA and protein expression levels of genes involved in differentiation rose. These data revealed that circRNAs play a crucial regulatory role in deer antler regeneration and development. CircRNA2829 might regulate the antler regeneration process through miR-4286-R+1/FOXO4.

Comparative transcriptome analysis provides insight into the molecular targets and signaling pathways of deer TGF-1 regulating chondrocytes proliferation and differentiation.

Chondrocytes are the only cell components in the cartilage, which has the poor regeneration ability. Thus, repairing damaged cartilage remains a huge challenge. Sika deer antlers are mainly composed of cartilaginous tissues that have an astonishing capacity for repair and renewal. Our previous study has demonstrated the transforming growth factor β (TGF-β1) is considered to be a key molecule involved in rapid growth, with the strongest expression in the cartilage layer. However, it remains to be clarified whether deer TGF-β1 has significantly different function from other species such as mouse, and what is the molecular mechanism of regulating cartilage growth. Primary chondrocytes was collected from new born mouse rib cartilage. The effect of TGF-β1 on primary chondrocytes viability was elucidated by RNA sequencing (RNA-seq) technology combined with validation methods such as quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence assay (IFA). Differential expression genes were identified using the DEGseq package. Our results demonstrated that the overexpression of deer TGF-β1 possibly promoted chondrocyte proliferation and extracellular matrix (ECM) synthesis, while simultaneously suppressing chondrocyte differentiation through regulating transcription factors, growth factors, ECM related genes, proliferation and differentiation marker genes, such as Comp, Fgfr3, Atf4, Stat1 etc., and signaling pathways such as the MAPK signaling pathway, inflammatory mediator regulation of TRP channels etc. In addition, by comparing the amino acid sequence and structures between the deer TGF-β1 and mouse TGF-β1, we found that deer TGF-β1 and mouse TGF-β1 proteins are mainly structurally different in arm domains, which is the main functional domain. Phenotypic identification results showed that deer TGF-β1 may has stronger function than mouse TGF-β1. ​These results suggested that deer TGF-β1 has the ability to promote chondrogenesis by regulating chondrocyte proliferation, differentiation and ECM synthesis. This study provides insights into the molecular mechanisms underlying the effects of deer TGF-β1 on chondrocyte viability.

SDF-1α Promotes Chondrocyte Autophagy through CXCR4/mTOR Signaling Axis

SDF-1α, the most common isoform of stromal cell-derived factor 1, has shown vital effects in regulating chondrocyte proliferation, maturation, and chondrogenesis. Autophagy is a highly conserved biological process to help chondrocytes survive in harsh environments. However, the effect of SDF-1α on chondrocyte autophagy is still unknown. This study aims to investigate the effect of SDF-1α on chondrocyte autophagy and the underlying biomechanism. Transmission electron microscope assays and mRFP-GFP-LC3 adenovirus double label transfection assays were performed to detect the autophagic flux of chondrocytes. Western blots and immunofluorescence staining assays were used to detect the expression of autophagy-related proteins in chondrocytes. RNA sequencing and qPCR were conducted to assess changes in autophagy-related mRNA expression. SDF-1α upregulated the number of autophagosomes and autolysosomes in chondrocytes. It also increased the expression of autophagy-related proteins including ULK-1, Beclin-1 and LC3B, and decreased the expression of p62, an autophagy substrate protein. SDF-1α-mediated autophagy of chondrocytes required the participation of receptor CXCR4. Moreover, SDF-1α-enhanced autophagy of chondrocytes was through the inhibition of phosphorylation of mTOR signaling on the upstream of autophagy. Knockdown by siRNA and inhibition by signaling inhibitor further confirmed the importance of the CXCR4/mTOR signaling axis in SDF-1α-induced autophagy of chondrocytes. For the first time, this study elucidated that SDF-1α promotes chondrocyte autophagy through the CXCR4/mTOR signaling axis.

Neuropeptide Y Promotes mTORC1 to Regulate Chondrocyte Proliferation and Hypertrophy.

Peripheral neuropeptide Y (NPY) has been reported to regulate bone metabolism and homeostasis; however, its potential roles in growth plate chondrogenesis remain unclear. Here, we found that NPY expression decreased during chondrocyte differentiation in vitro and in vivo. NPY was required for chondrocyte proliferation; in contrast, knockdown of NPY facilitated chondrocyte hypertrophic differentiation. Administration of recombinant NPY in rat chondrocytes and metatarsal bones uncoupled normal proliferation and hypertrophic differentiation during chondrogenesis and thereby inhibited growth plate chondrogenesis and longitudinal bone growth. Remarkably, NPY activated the mTORC1 pathway in chondrocytes, whereas attenuation of mTORC1 activity by administration of rapamycin in vitro partially abrogated NPY-mediated effects on chondrocyte proliferation and hypertrophic differentiation. In addition, a combination of Y2R antagonist but not Y1R antagonist with NPY abolished NPY-mediated inhibition of metatarsal growth and growth plate chondrogenesis. Mechanistically, NPY activated Erk1/2 by NPY2R, then phosphorylated ERK1/2 activated mTORC1 to initiate PTHrP expression, which in turn promoted chondrocyte proliferation and inhibited chondrocyte hypertrophic differentiation. In conclusion, our data identified NPY as a crucial regulator of chondrogenesis and may provide a promising therapeutic strategy for skeletal diseases.

Suppressor of fused-restrained Hedgehog signaling in chondrocytes is critical for epiphyseal growth plate maintenance and limb elongation in juvenile mice.

Hedgehog (Hh) signaling plays multiple critical roles in regulating chondrocyte proliferation and differentiation during epiphyseal cartilage development. However, it is still unclear whether Hh signaling in chondrocytes is required for growth plate maintenance during juvenile growth, and whether sustained activation of Hh signaling in chondrocytes promotes limb elongation. In this study, we first utilized Hh reporter mice to reveal that Hh signaling was activated in resting and columnar chondrocytes in growth plates of juvenile and adult mice. Next, we genetically modulated Hh signaling by conditionally deleting Smo or Sufu in all or a subpopulation of growth plate chondrocytes, and found that ablation of either Smo or Sufu in chondrocytes of juvenile mice caused premature closure of growth plates and shorter limbs, whereas Osx-Cre-mediated deletion of either of these two genes in prehypertrophic chondrocytes did not lead to obvious growth plate defects, indicating that Hh signaling mainly functions in resting and/or columnar chondrocytes to maintain growth plates at the juvenile stage. At the cellular level, we found that chondrocyte-specific ablation of Smo or Sufu accelerated or suppressed chondrocyte hypertrophy, respectively, whereas both decreased chondrocyte proliferation and survival. Thus, our study provided the first genetic evidence to establish the essential cell-autonomous roles for tightly-regulated Hh signaling in epiphyseal growth plate maintenance and limb elongation during juvenile growth.

Comparative genomics uncovers the evolutionary history, demography, and molecular adaptations of South American canids

The remarkable radiation of South American (SA) canids produced 10 extant species distributed across diverse habitats, including disparate forms such as the short-legged, hypercarnivorous bush dog and the long-legged, largely frugivorous maned wolf. Despite considerable research spanning nearly two centuries, many aspects of their evolutionary history remain unknown. Here, we analyzed 31 whole genomes encompassing all extant SA canid species to assess phylogenetic relationships, interspecific hybridization, historical demography, current genetic diversity, and the molecular bases of adaptations in the bush dog and maned wolf. We found that SA canids originated from a single ancestor that colonized South America 3.9 to 3.5 Mya, followed by diversification east of the Andes and then a single colonization event and radiation of Lycalopex species west of the Andes. We detected extensive historical gene flow between recently diverged lineages and observed distinct patterns of genomic diversity and demographic history in SA canids, likely induced by past climatic cycles compounded by human-induced population declines. Genome-wide scans of selection showed that disparate limb proportions in the bush dog and maned wolf may derive from mutations in genes regulating chondrocyte proliferation and enlargement. Further, frugivory in the maned wolf may have been enabled by variants in genes associated with energy intake from short-chain fatty acids. In contrast, unique genetic variants detected in the bush dog may underlie interdigital webbing and dental adaptations for hypercarnivory. Our analyses shed light on the evolution of a unique carnivoran radiation and how it was shaped by South American topography and climate change.

The miR-548d-5p/SP1 signaling axis regulates chondrocyte proliferation and inflammatory responses in osteoarthritis

Chondrocyte apoptosis and dysfunction play an important role in osteoarthritis (OA), a chronic progressive arthropathy. Non-coding RNAs have been implicated in OA pathogenesis. In this study, microRNA (miR)-548d-5p was found to be downregulated in OA samples and IL-1β-stimulated chondrocytes. miR-548d-5p overexpression partially reversed IL-1β-induced chondrocyte damage in vitro, evidenced by the promotion of cell growth, the inhibition of apoptosis and inflammatory cytokine release, and the improvement in extracellular matrix (ECM) deposition. Furthermore, miR-548d-5p overexpression partially reversed papain-induced damages on OA rat’s knee articular cartilage. Specificity protein 1 (SP1) was inhibited by miR-548d-5p and identified as its direct downstream target. In IL-1β-stimulated chondrocytes, SP1 overexpression significantly attenuated the protective effects of miR-548d-5p overexpression against chondrocyte damage. In conclusion, miR-548d-5p was abnormally downregulated in OA samples and IL-1β-stimulated chondrocytes. miR-548d-5p protects against IL-1β-induced chondrocyte damage via direct inhibition of SP1.

Inactivation of Ihh in Sp7-Expressing Cells Inhibits Osteoblast Proliferation, Differentiation, and Bone Formation, Resulting in a Dwarfism Phenotype with Severe Skeletal Dysplasia in Mice.

Indian hedgehog (Ihh) is an indispensable paracrine factor for proper tissue patterning, skeletogenesis, and cellular proliferation. Recent genetic studies have revealed critical roles of chondrocyte-derived Ihh in regulating chondrocyte proliferation, hypertrophy and cartilage ossification. However, the functions of Sp7-expressing cell-derived Ihh in osteoblast differentiation and bone formation remain unclear. Sp7 is an essential transcription factor for osteoblast differentiation. In the current study, we generated Sp7-iCre; Ihhfl/fl mice, in which the Ihh gene was specifically deleted in Sp7-expressing cells to investigate the roles of Ihh. Ihh ablation in Sp7-expressing cells resulted in a dwarfism phenotype with severe skeletal dysplasia and lethality at birth, but with normal joint segmentation. Sp7-iCre; Ihhfl/fl mice had fewer osteoblasts, almost no cortical and trabecular bones, smaller skulls, and wider cranial sutures. Additionally, the levels of osteogenesis- and angiogenesis-related genes, and of major bone matrix protein genes were significantly reduced. These results demonstrated that Ihh regulates bone formation in Sp7-expressing cells. Ihh deficiency in primary osteoblasts cultured in vitro inhibited their proliferation, differentiation, and mineralization ability, and reduced the expression of osteogenesis-related genes. Moreover, the deletion of Ihh also attenuated the Bmp2/Smad/Runx2 pathway in E18.5 tibial and primary osteoblasts. The activity of primary osteoblasts in mutant mice was rescued after treatment with rhBMP2. In summary, our data revealed that Ihh in Sp7-expressing cells plays an indispensable role in osteoblast differentiation, mineralization, and embryonic osteogenesis, further implicated that its pro-osteogenic role may be mediated through the canonical Bmp2/Smad/Runx2 pathway.

TGF-β1 regulates chondrocyte proliferation and extracellular matrix synthesis via circPhf21a-Vegfa axis in osteoarthritis

BackgroundThe transforming growth factor-beta (TGF-β) signaling pathway is an important pathway associated with the pathogenesis of osteoarthritis (OA). This study was to investigate the involvement of circRNAs in the TGF-β signaling pathway.MethodsCell Counting Kit-8 (CCK-8) assay and 5-ethynyl-2′-deoxyuridine (EdU) assay were used to detect the proliferation of primary mouse chondrocytes (PMCs). RNA-sequencing together with bioinformatics analysis were used to systematically clarify TGF-β1 induced alternations of circRNAs in PMCs. The regulatory and functional role of circPhf21a was examined in PMCs. Downstream targets of circPhf21a were explored by RNA-sequencing after overexpression of circPhf21a and verified by RT-qPCR in PMCs. Finally, the role and mechanism of circPhf21a in OA were explored in mouse models.ResultsWe found that TGF-β1 promoted the proliferation of PMCs. Meanwhile, RT-qPCR and western blotting indicated that TGF-β1 promoted extracellular matrix (ECM) anabolism. RNA-sequencing revealed that a total of 36 circRNAs were differentially expressed between PMCs treated with and without TGF-β1. Of these, circPhf21a was significantly decreased by TGF-β1. Furthermore, circPhf21a knockdown promoted the proliferation and ECM synthesis of PMCs, whereas overexpression of circPhf21a showed the opposite effects. Mechanically, the expression profiles of the mRNAs revealed that Vegfa may be the target of circPhf21a. Additionally, we found that circPhf21a was significantly upregulated in the mouse OA model, and inhibition of circPhf21a significantly relieved the progression of OA.ConclusionsOur results found that TGF-β1 promoted the proliferation and ECM synthesis of PMCs via the circPhf21a-Vegfa axis, which may provide novel therapeutic targets for OA treatment.D41VJr9_D9Fjp__yvtyWkzVideo abstract

Long intergenic non-protein coding RNA 00707 regulates chondrocyte apoptosis and proliferation in osteoarthritis by serving as a sponge for microRNA-199-3p

ABSTRACT It is known that long intergenic non-protein coding RNA 00707 (LINC00707) promotes lipopolysaccharide (LPS)-injury and microRNA-199-3p (miR-199-3p) regulates chondrocyte proliferation and apoptosis. Both processes participate in osteoarthritis (OA). We predicted that LINC00707 and miR-199-3p may interact with each other. Therefore, LINC00707 and miR-199-3p may interact with each other to participate in OA. In this study, the expression of LINC00707 and miR-199-3p in both OA and normal articular cartilage tissues was analyzed using RT-qPCR. The subcellular location of LINC00707 and its direct interaction with miR-199-3p were explored by nuclear fractionation assay, RNA pull-down assay and Luciferase reporter assay, respectively. The role of LINC00707 and miR-199-3p in regulating the expression of each other was analyzed using an overexpression assay, followed by RT-qPCR. The role of LINC00707 and miR-199-3p in regulating OA chondrocyte proliferation and apoptosis was analyzed by BrdU assay and cell apoptosis assay, respectively. OA tissues exhibited increased expression of LINC00707 and decreased expression of miR-199-3p. LINC00707 directly interacted with miR-199-3p in cytoplasm. However, LINC00707 and miR-199-3p overexpression failed to affect each other’s expression. LPS treatment increased LINC00707 expression and decreased miR-199-3p expression in OA chondrocyte. LINC00707 overexpression increased the apoptosis of OA chondrocytes induced by LPS and suppressed the proliferation of OA chondrocytes. Moreover, LINC00707 suppressed the role of miR-199-3p in enhancing cell proliferation and suppressing cell apoptosis. In conclusion, LINC00707 can be detected in cytoplasm and it may sponge miR-199-3p to regulate chondrocyte proliferation and apoptosis in OA.

De novo serine synthesis regulates chondrocyte proliferation during bone development and repair

The majority of the mammalian skeleton is formed through endochondral ossification starting from a cartilaginous template. Cartilage cells, or chondrocytes, survive, proliferate and synthesize extracellular matrix in an avascular environment, but the metabolic requirements for these anabolic processes are not fully understood. Here, using metabolomics analysis and genetic in vivo models, we show that maintaining intracellular serine homeostasis is essential for chondrocyte function. De novo serine synthesis through phosphoglycerate dehydrogenase (PHGDH)-mediated glucose metabolism generates nucleotides that are necessary for chondrocyte proliferation and long bone growth. On the other hand, dietary serine is less crucial during endochondral bone formation, as serine-starved chondrocytes compensate by inducing PHGDH-mediated serine synthesis. Mechanistically, this metabolic flexibility requires ATF4, a transcriptional regulator of amino acid metabolism and stress responses. We demonstrate that both serine deprivation and PHGDH inactivation enhance ATF4 signaling to stimulate de novo serine synthesis and serine uptake, respectively, and thereby prevent intracellular serine depletion and chondrocyte dysfunction. A similar metabolic adaptability between serine uptake and de novo synthesis is observed in the cartilage callus during fracture repair. Together, the results of this study reveal a critical role for PHGDH-dependent serine synthesis in maintaining intracellular serine levels under physiological and serine-limited conditions, as adequate serine levels are necessary to support chondrocyte proliferation during endochondral ossification.

G-Protein-Coupled Estrogen Receptor-1 Positively Regulates the Growth Plate Chondrocyte Proliferation in Female Pubertal Mice.

Estrogen enhances long bone longitudinal growth during early puberty. Growth plate chondrocytes are the main cells that contribute to long bone elongation. The role of G-protein-coupled estrogen receptor-1 (GPER-1) in regulating growth plate chondrocyte function remains unclear. In the present study, we generated chondrocyte-specific GPER-1 knockout (CKO) mice to investigate the effect of GPER-1 in growth plate chondrocytes. In control mice, GPER-1 was highly expressed in the growth plates of 4- and 8-week-old mice, with a gradual decline through 12 to 16 weeks. In CKO mice, the GPER-1 expression in growth plate chondrocytes was significantly lower than that in the control mice (80% decrease). The CKO mice also showed a decrease in body length (crown–rump length), body weight, and the length of tibias and femurs at 8 weeks. More importantly, the cell number and thickness of the proliferative zone of the growth plate, as well as the thickness of primary spongiosa and length of metaphysis plus diaphysis in tibias of CKO mice, were significantly decreased compared with those of the control mice. Furthermore, there was also a considerable reduction in the number of proliferating cell nuclear antigens and Ki67-stained proliferating chondrocytes in the tibia growth plate in the CKO mice. The chondrocyte proliferation mediated by GPER-1 was further demonstrated via treatment with a GPER-1 antagonist in cultured epiphyseal cartilage. This study demonstrates that GPER-1 positively regulates chondrocyte proliferation at the growth plate during early puberty and contributes to the longitudinal growth of long bones.

Role of lincRNA-Cox2 targeting miR-150 in regulating the viability of chondrocytes in osteoarthritis.

Osteoarthritis (OA) is a joint disease characterised by progressive cartilage degradation and inflammation, but the detailed pathogenesis of OA remains unclear. The present study aimed to investigate the role of long intergenic non-coding RNA (lincRNA)-Cox2 in OA progression and the potential mechanism. An OA mouse model was used for in vivo experiments, and IL-1β-induced injury of mouse chondrocytes was conducted for in vitro experiments. Small interfering (si)-Cox2 was transfected into chondrocytes to elucidate the effect of lincRNA-Cox2 on OA. Quantitative reverse transcription PCR assays were conducted to detect the expression of lincRNA-Cox2 and microRNA (miR)-150. Cell proliferation and apoptosis were analysed based on an MTT assay and annexin V/propidium iodide staining, respectively. Western blotting was performed to evaluate the protein expression levels of Ki-67, PCNA, Bax, cleaved (c)-Caspase-3, c-Caspase-9 and Wnt/β-catenin pathway-associated proteins in chondrocytes. High levels of lincRNA-Cox2 were observed in cartilage tissues of the OA mouse model in vivo. In the in vitro experiments, the expression of lincRNA-Cox2 was increased in IL-1β-treated chondrocytes. Knockdown of lincRNA-Cox2 promoted the proliferation and inhibited the apoptosis of chondrocytes. Mechanistically, lincRNA-Cox2 was found to directly target miR-150, acting as a competing endogenous RNA, and the effect of si-Cox2 on the proliferation and apoptosis of chondrocytes was reversed by miR-150 inhibitors. Moreover, lincRNA-Cox2 activated the Wnt/β-catenin pathway to regulate chondrocyte proliferation and apoptosis. The present study demonstrated that silencing lincRNA-Cox2 expression plays a protective role in OA by enhancing the proliferation and suppressing the apoptosis of chondrocytes, which is related to increased miR-150 expression and activation of the Wnt/β-catenin pathway.

De novo serine synthesis regulates chondrocyte proliferation during endochondral ossification

De novo serine synthesis regulates chondrocyte proliferation during endochondral ossification

CircRNA_0092516 regulates chondrocyte proliferation and apoptosis in osteoarthritis through the miR-337-3p/PTEN axis.

The dysregulation of circular RNAs (circRNAs) has been identified in various human diseases. Here, we probed into the potential mechanism of circRNA_0092516 in osteoarthritis (OA). The expression of circRNA_0092516 was tested by quantitative real-time PCR. MTT, flow cytometry and western blot were applied to confirm the functions of circRNA_0092516 in vitro. Besides, RNA pull-down and dual-luciferase reporter gene experiments were applied to probe into the mechanism. circRNA_0092516 was raised in the tissues of OA patients and chondrocytes stimulated by IL-1β. The potential mechanism analysis expounded that circRNA_0092516 bound to miR-337-3p, and the interference with circRNA_0092516 boosted chondrocyte proliferation and restrained cell apoptosis through the miR-337-3p/phosphatase and tensin homolog (PTEN) axis, thereby improving OA. In-vivo experiments expounded that circRNA_0092516 regulated cartilage production through miR-337-3p. Overall, our data expounded that the interference with circRNA_0092516 boosted chondrocyte proliferation and restrained cell apoptosis through the miR-337-3p/PTEN axis, eventually slowed down the progress of OA.

LncRNA NEAT1 regulates chondrocyte proliferation and apoptosis via targeting miR-543/PLA2G4A axis.

Osteoarthritis (OA), which is characterized by articular cartilage degeneration, shows a gradually increasing incidence with age. This study explored the molecular mechanism underlying the proliferation and apoptosis of chondrocytes during OA progression. In this study, chondrocytes were isolated from human knee cartilages. The targeted relationship among nuclear enriched abundant transcript 1 (NEAT1), microRNA-543 (miR-543) and PLA2G4A was predicted on TargetScan V7.2 and starBase and validated by performing dual-luciferase reporter assay. High-expressed NEAT1 was detected in OA cartilage and chondrocytes. NEAT1 was negatively correlated with miR-543 and was low-expressed in OA cartilage and PLA2G4A was negatively correlated with miR-543 and was high-expressed in OA cartilage. In OA chondrocytes, the overexpressed NEAT1 inhibited the expressions of p-Akt1 and Bcl-2 and upregulated that of matrix metalloprotease (MMP)-3, MMP-9, MMP-13, interleukin (IL)-6 and IL-8, but such effects of overexpressed NEAT1 were reversed by miR-543 mimic. SiRNA-NEAT1 exerted an opposite effect to NEAT1 overexpression on OA chondrocytes, but this could be reversed by miR-543 inhibitor. The effect of PLA2G4A overexpression was the opposite to miR-543 mimic on OA chondrocytes. In conclusion, NEAT1 could sponge miR-543 to induce PLA2G4A expression, inhibit chondrocyte proliferation and promote apoptosis.