Tenocyte-like Cells Research Articles

Effectiveness of Injection Strategies on Patients With Patellar Tendonitis (Jumpers' Knee): A Network Meta-analysis of Randomized Controlled Trials.

Patellar tendonitis (PT) is a common degenerative disease of the patellar tendon that seriously affects the sports careers of elite athletes and activities of daily living of sports enthusiasts. Injection therapy is a prevalent invasive treatment for PT. This work comprehensively analyzes various injection treatments for PT that consider agent type and characteristics, frequency, and assessment timepoints by meta-analysis. PubMed, Embase, and the Cochrane Library were sources of data. Randomized controlled trials (RCTs) analyzing the effect of various injection strategies on the treatment of patients with PT were considered. Systematic review and meta-analysis. Level 2. First author, year of publication, research location, registration information, patient type, sample size, age, sex, intervention, control treatment, and follow-up period in each study were extracted. Nineteen RCTs were included in the analysis. In the network meta-analysis of Victorian Institute of Sports Assessment-Patellar (VISA-P) outcomes, polidocanol (standardized mean difference (SMD), 6.52; 95% CI 4.75, 8.30; P < 0.01), tenocyte-like cells (SMD, 4.08; 95% CI 2.92, 5.25; P < 0.01), and leukocyte-poor platelet-rich plasma (LP-PRP) plus high-volume image-guided injection (HVIGI) (SMD, 1.56; 95% CI 0.62, 2.50; P < 0.01) were significantly superior to noninjection conservative treatment, mainly at the 6-month follow-up timepoint. For visual analog scale results, multiple dry needling (DN) (SMD, -1.78; 95% CI -2.56, -1.00; P < 0.01), LP-PRP (SMD, -0.71; 95% CI -1.31, -0.12; P = 0.02), and LP-PRP plus HVIGI (SMD, -1.31; 95% CI -2.22, -0.39; P < 0.01) were significantly superior to blank, which was also mainly at the 6-month timepoint. Injection-related treatments: polidocanol, tenocyte-like cells, LP-PRP, and multiple DN showed potential short (1-3 months) or medium (6 months)-term treatment benefits. There is still no evidence for injection interventions with long-term therapeutic benefit.

Nonoperative and Operative Soft-Tissue, Cartilage, and Bony Regeneration and Orthopaedic Biologics of the Elbow and Upper Extremity: An Orthoregeneration Network Foundation Review

Orthoregeneration is defined as a solution for orthopaedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and, optimally, provide an environment for tissue regeneration. Options include drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electromagnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the elbow and upper extremity, including the tendons (lateral epicondylitis, medial epicondylitis, biceps tendonitis, triceps tendonitis), articular cartilage (osteoarthritis, osteochondral lesions), and bone (fractures, nonunions, avascular necrosis, osteonecrosis). Promising and established treatment modalities include hyaluronic acid; botulinum toxin; corticosteroids; leukocyte-rich and leukocyte-poor platelet-rich plasma; autologous blood; bone marrow aspirate comprising mesenchymal stromal cells (alternatively termed medicinal signaling cells and frequently mesenchymal stem cells [MSCs]) and bone marrow aspirate concentrate; MSCs harvested from adipose and skin (dermis) sources; vascularized bone grafts; bone morphogenic protein scaffold made from osteoinductive and conductive β-tricalcium phosphate and poly-ε-caprolactone with hydrogels, human MSCs, and matrix metalloproteinases; and collagen sponge. Autologous blood preparations such as autologous blood injections and platelet-rich plasma show positive outcomes for nonresponsive tendinopathy. In addition, cellular therapies such as tissue-derived tenocyte-like cells and MSCs show a promising ability to regulate degenerative processes by modulating tissue response to inflammation and preventing continuous degradation and support tissue restoration.

ANIMAL COMPONENT-FREE WORKFLOWS TO DERIVE TENOCYTE-LIKE CELLS FROM HUMAN MESENCHYMAL STROMAL CELLS AND PLURIPOTENT STEM CELLS

Cell-based therapies offer a promising strategy to treat tendon injuries and diseases. Both mesenchymal stromal cells (MSCs) and pluripotent stem cells (PSCs) are good candidates for such applications due to their self-renewing and differentiation capacity. However, the translation of cell-based therapies from bench to bedside can be hindered by the use of animal-derived components in ancillary materials and by the lack of standardised media and protocols for in vitro tenogenic differentiation. To address this, we have optimized animal component-free (ACF) workflows for differentiating human MSCs and PSCs to tenocyte-like cells (TLCs) respectively. MSCs isolated from bone marrow (n = 3) or adipose tissue (n = 3) were expanded using MesenCult™-ACF Plus Culture Kit for at least 2 passages, and differentiated to TLCs in 21 days using a step-wise approach. Briefly, confluent cultures were treated with an ACF tenogenic induction medium for 3 days, followed by treatment with an ACF maturation medium for 18 days. Monolayer cultures were maintained at high density without passaging for the entire duration of the protocol, and the medium was changed every 2 – 3 days. In a similar fashion, embryonic (n = 3) or induced PSCs (n = 3) were first differentiated to acquire a mesenchymal progenitor cell (MPC) phenotype in 21 days using STEMdiff™ Mesenchymal Progenitor Kit, followed by the aforementioned tenogenic protocol for an additional 21 days. In all cases, the optimized workflows using ACF formulations consistently activated a tenogenic transcriptional program, leading to the generation of elongated, spindle-shaped tenomodulin-positive (TNMD+) cells and deposition of an extracellular matrix predominantly composed of collagen type I. In summary, here we describe novel workflows that can robustly generate TLCs from MSCs and hPSC-derived MPCs for potential translational applications.

Synergistic effects of growth factor-based serum-free medium and tendon-like substrate topography on tenogenesis of mesenchymal stem cells

Addressing clinical challenges for tendon injuries requires a deeper understanding of the effects that biological and biophysical cues have on tenogenesis. Although prior studies have identified tenogenic growth factors (GFs) or elucidated the effects of substrate topography on tenocyte behavior, few have characterized their combined effect in the presence of a tendon-like substrate. In this study, we assessed the effect of biological (GFs) and biophysical (substrate topography) cues on tenogenic proliferation and differentiation under defined, serum-free conditions. Specifically, human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured in a serum-free culture medium containing a GF cocktail comprised of fibroblast growth factor-2 (FGF-2), transforming growth factor-beta 3 (TGF-β3), and insulin-like growth factor-1 (IGF-1), either alone or in combination with tendon-like substrate topography produced by replica casting of tendon tissue sections. Our data demonstrated that the use of serum-free GF cocktail medium alone promoted hMSC proliferation, as shown via DNA staining as well as Ki67 protein levels and gene expression. In particular, gene expression of Ki67 was increased by 8.46-fold in all three donors relative to serum-free medium control. Also, serum-free GF cocktail promoted tenogenic differentiation, on the basis of expression of tendon-associated gene and protein markers, scleraxis (SCX), tenascin C (TNC), and collagen type I (COL1A1) including increased normalized collagen production by 1.4-fold in two donors relative to serum-free medium control. Interestingly, hMSCs cultured on a tendon-like substrate exhibited highly oriented cell morphology and extracellular matrix (ECM) alignment reminiscent of tendon. In particular, when this GF cocktail was combined with tendon-like topography, they showed a synergistically increased expression of tendon-related markers and anisotropic organization of ECM proteins with moderate-to-large effect sizes. Together, in addition to showing the utility of a GF cocktail for expansion and differentiation of tenocyte-like cells, our findings clearly demonstrate the synergistic relationship between GF-mediated and substrate topography-related effects on hMSC tenogenic differentiation. This information provides insights into the design of strategies that combine biological and biophysical cues for ex vivo tenocyte production and tendon tissue engineering.

A myogenic niche with a proper mechanical stress environment improves abdominal wall muscle repair by modulating immunity and preventing fibrosis

Volumetric muscle loss (VML) healing is often complicated by fibrosis, which impairs muscle regeneration and function. Adjusting mechanical stress in the repair environment may modulate immunity and reduce fibrosis. In this study, we aimed to create a biomaterial with suitable tension conditions and bidirectional tissue-inducing abilities to prevent fibrosis thus promote muscle regeneration and induce aponeurosis-like structures to restore muscle force transmission. A protocol was developed to manufacture decellularized muscle aponeurosis (D-MA) patches with an intact extracellular matrix (ECM) and low cytotoxicity. D-MA optimized the mechanical stress distribution in muscle injury sites and decreased the number of proinflammatory macrophages and myofibroblasts, thereby attenuating muscle fibrosis. Muscle and aponeurosis ECM environments had different microstructures and mechanical properties, which specifically enhanced stem cell differentiation into muscle-like cells on muscle ECM and tenocyte-like cells on aponeurosis ECM in vitro. Four weeks after orthotopic implantation, the biphasic muscle-aponeurosis-like tissue was successfully regenerated by the D-MA scaffold. The regenerated muscle fibers in D-MA were more abundant than those in the fibrotic decellularized muscle (D-M) scaffold. D-MA can be used to repair abdominal defects, which significantly improves the repair outcomes. Our results suggest D-MA as a promising material for VML repair.

Stem cell therapy for the management of lateral elbow tendinopathy: A systematic literature review

Summary Purpose Lateral elbow tendinopathy is the most common cause of lateral elbow pain with a lifetime prevalence of approximately 40% in the general population. The purpose of this study was to complete a systematic review to identify the potential of stem cell therapy based on the current evidence in the treatment of lateral elbow tendinopathy. Methodology A systematic review through the Ovid, Medline, and Cochrane Review databases was performed with the search terms of lateral epicondylitis, tendinopathy, tennis elbow, stem cell, bone marrow, treatment, and therapy. Results The systematic review initially identified 816 articles from three databases. Five studies met the inclusion criteria. The five studies evaluated four different stem cell preparations including autologous tenocytes, skin-derived tenocyte-like cells, allogeneic adipose-derived mesenchymal stem cells, and bone marrow aspirate. Conclusion While a majority of lateral elbow tendinopathy cases resolve in a timely manner with no or limited intervention, recovery can be a delayed process for a small percentage of patients. The role of emerging treatment options has not been established. Stem cell therapy is an option for refractory cases, but current evidence is poor. Early findings demonstrated significant improvements in imaging and functional outcomes, but findings were limited by lack of control arms or other treatment arms for comparison. Further large, controlled studies are needed to evaluate safety, efficacy in order to establish the role of stem cell therapy in the management of lateral elbow tendinopathy.

Induced pluripotent stem cell-derived tenocyte-like cells promote the regeneration of injured tendons in mice

Tendons are dense fibrous structures that attach muscles to bones. Healing of tendon injuries is a clinical challenge owing to poor regenerative potential and scarring. Here, we created reporter mice that express EGFP, driven by the promoter of the tendon-specific Scleraxis (Scx) transcription-factor gene; we then generated induced pluripotent stem cells (iPSCs) from these mice. Utilising these fluorescently labelled iPSCs, we developed a tenogenic differentiation protocol. The iPSC-derived EGFP-positive cells exhibited elevated expression of tendon-specific genes, including Scx, Mohawk, Tenomodulin, and Fibromodulin, indicating that they have tenocyte-like properties. Finally, we demonstrated that these cells promoted tendon regeneration in mice after transplantation into injured tendons reducing scar formation via paracrine effect. Our data demonstrate that the tenogenic differentiation protocol successfully provided functional cells from iPSCs. We propose that pluripotent stem cell-based therapy using this protocol will provide an effective therapeutic approach for tendon injuries.

The Effectiveness of Minimally Invasive Techniques in the Treatment of Patellar Tendinopathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

The aim was to determine the effectiveness of minimally invasive techniques (MIT) in patients with patellar tendinopathy. Database searches were performed for randomized controlled trials (RCTs) in electronic databases (WOS, Cochrane Central, SportDiscus, and Medline via PubMed and PEDro). The inclusion criteria used were published in English or Spanish and involving adults with patellar tendinopathy (pain on the inferior pole of the patella for a minimum of 3 months), with at least one group receiving MIT. The quality of the relevant RCTs was evaluated using the PEDro scale. The primary outcome was functionality using the VISA-p questionnaire. Secondary outcome was focused on pain. A total of 1164 studies were screened for possible inclusion in our systematic review. Finally, 10 RCTs were included with a total of 326 individuals. Five RCTs were included in the meta-analysis. The quality assessment revealed that all the studies included were considered to possess high methodological quality. All studies analyzing MIT such as platelet-rich plasma (PRP), dry needling, or skin-derived tenocyte-like cells, when combined with exercise, proved to be effective for patellar tendinopathy. Moreover, the PRP technique with doses greater than 4 mL together and combined with an exercise program lasting over 6 weeks obtained better results in functionality and pain than other treatments in the short term. However, in the long term, dry needling and skin-derived tenocyte-like cells are more effective than PRP. Although the infiltration of drugs was effective at posttreatment, these improvements were not maintained over time and may have secondary effects. Although there are no RCTs analyzing the effectiveness of MIT like percutaneous needle electrolysis, there has been an increasing number of publications achieving excellent results in the last years. However, it is necessary to develop RCTs analyzing not only the effect but also comparing the effectiveness between different MIT such as dry needling and percutaneous needle electrolysis.

Rotator Cuff Tenocytes Differentiate into Hypertrophic Chondrocyte-Like Cells to Produce Calcium Deposits in an Alkaline Phosphatase-Dependent Manner

Calcific tendonitis is a frequent cause of chronic shoulder pain. Its cause is currently poorly known. The objectives of this study were to better characterize the cells and mechanisms involved in depositing apatite crystals in human tendons. Histologic sections of cadaveric calcified tendons were analyzed, and human calcific deposits from patients undergoing lavage of their calcification were obtained to perform infrared spectroscopy and mass spectrometry-based proteomic characterizations. In vitro, the mineralization ability of human rotator cuff cells from osteoarthritis donors was assessed by alizarin red or Von Kossa staining. Calcifications were amorphous areas surrounded by a fibrocartilaginous metaplasia containing hypertrophic chondrocyte-like cells that expressed tissue non-specific alkaline phosphatase (TNAP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which are two key enzymes of the mineralization process. Calcific deposits were composed of apatite crystals associated with proteins involved in bone and cartilage development and endochondral bone growth. In vitro, tenocyte-like cells extracted from the rotator cuff were able to mineralize in osteogenic cultures, and expressed TNAP, type X COLLAGEN, and MMP13, which are hypertrophic chondrocytes markers. The use of a TNAP inhibitor significantly prevented mineral deposits. We provide evidence that tenocytes have a propensity to differentiate into hypertrophic chondrocyte-like cells to produce TNAP-dependent calcium deposits. We believe that these results may pave the way to identifying regulating factors that might represent valuable targets in calcific tendonitis.

Tenogenic differentiation protocol in xenogenic-free media enhances tendon-related marker expression in ASCs.

Adipose-derived stem cells (ASCs) are multipotent and immune-privileged mesenchymal cells, making them ideal candidates for therapeutic purposes to manage tendon disorders. Providing safe and regulated cell therapy products to patients requires adherence to good manufacturing practices. To this aim we investigated the in vitro tenogenic differentiation potential of ASCs using a chemically defined serum-free medium (SF) or a xenogenic-free human pooled platelet lysate medium (hPL) suitable for cell therapy and both supplemented with CTGF, TGFβ-3, BMP-12 and ascorbic acid (AA) soluble factors. Human ASCs were isolated from 4 healthy donors and they were inducted to differentiate until 14 days in both hPL and SF tenogenic media (hPL-TENO and SF-TENO). Cell viability and immunophenotype profile were analysed to evaluate mesenchymal stem cell (MSC) characteristics in both xenogenic-free media. Moreover, the expression of stemness and tendon-related markers upon cell differentiation by RT-PCR, protein staining and cytofluorimetric analysis were also performed. Our results showed the two xenogenic-free media well support cell viability of ASCs and maintain their MSC nature as demonstrated by their typical immunophenototype profile and by the expression of NANOG, OCT4 and Ki67 genes. Moreover, both hPL-TENO and SF-TENO expressed significant high levels of the tendon-related genes SCX, COL1A1, COL3A1, COMP, MMP3 and MMP13 already at early time points in comparison to the respective controls. Significant up-regulations in scleraxis, collagen and tenomodulin proteins were also demonstrated at in both differentiated SF and hPL ASCs. In conclusion, we demonstrated firstly the feasibility of both serum and xenogenic-free media tested to culture ASCs moving forward the GMP-compliant approaches for clinical scale expansion of human MSCs needed for therapeutical application of stem cells. Moreover, a combination of CTGF, BMP-12, TGFβ3 and AA factors strongly and rapidly induce human ASCs to differentiate into tenocyte-like cells.

PEDF-derived peptide promotes tendon regeneration through its mitogenic effect on tendon stem/progenitor cells

BackgroundTendon stem/progenitor cells (TSPC) exhibit a low proliferative response to heal tendon injury, leading to limited regeneration outcomes. Exogenous growth factors that activate TSPC proliferation have emerged as a promising approach for treatment. Here, we evaluated the pigment epithelial-derived factor (PEDF)-derived short peptide (PSP; 29-mer) for treating acute tendon injury and to determine the timing and anatomical features of CD146- and necleostemin-positive TSPC in the tendon healing process.MethodsTendon cells were isolated from rabbit Achilles tendons, stimulated by the 29-mer and analyzed for colony-forming capacity. The expression of the TSPC markers CD146, Oct4, and nestin, induced by the 29-mer, was examined by immunostaining and western blotting. Tendo-Achilles injury was induced in rats by full-thickness insertion of an 18-G needle and immediately treated topically with an alginate gel, loaded with 29-mer. The distribution of TSPC in the injured tendon and their proliferation were monitored using immunohistochemistry with antibodies to CD146 and nucleostemin and by BrdU labeling.ResultsTSPC markers were enriched among the primary tendon cells when stimulated by the 29-mer. The 29-mer also induced the clonogenicity of CD146+ TSPC, implying TSPC stemness was retained during TSPC expansion in culture. Correspondingly, the expanded TSPC differentiated readily into tenocyte-like cells after removal of the 29-mer from culture. 29-mer/alginate gel treatment caused extensive expansion of CD146+ TSPC in their niche on postoperative day 2, followed by infiltration of CD146+/BrdU− TSPC into the injured tendon on day 7. The nucleostemin+ TSPC were located predominantly in the healing region of the injured tendon in the later phase (day 7) and exhibited proliferative capacity. By 3 weeks, 29-mer-treated tendons showed more organized collagen fiber regeneration and higher tensile strength than control tendons. In culture, the mitogenic effect of the 29-mer was found to be mediated by the phosphorylation of ERK2 and STAT3 in nucleostemin+ TSPC.ConclusionsThe anatomical analysis of TSPC populations in the wound healing process supports the hypothesis that substantial expansion of resident TSPC by exogenous growth factor is beneficial for tendon healing. The study suggests that synthetic 29-mer peptide may be an innovative therapy for acute tendon rupture.

Optimization of Tenocyte Lineage-Related Factors from Mesenchymal Stem Cells

Category: Basic Sciences/Biologics Introduction/Purpose: Researchers should consider various potential factors that affect tenogenic differentiation of MSCs. Numerous experimental settings are associated with high cost and time. Response surface methodology (RSM), a component in the design of experiments (DOE), is gaining recognition as a powerful tool in optimizing conditions for the production of industrially important products such as chemicals and enzymes. The purpose of this study was to access the differential effects of transforming growth factor beta 3 (TGF-β3) on the tenogenesis of tonsil-derived mesenchymal stem cells (T-MSCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) using RSM. Methods: Bone marrow was collected from four patients (mean age: 79.0±2.2) and mononuclear cells were separated. The tonsillar tissues were collected from four patients (mean age: 7.6±0.6). After isolation of MSCs, they were treated with 5ng/ml and 10ng/ml of TGF-β3 with vehicle control. The full-factorial experimental design was employed to study the effect of tension based on T-MSCs. The design was composed of three levels being coded as -1, 0 and +1 and a total of 18 runs were carried out in duplicates to optimize the level of chosen variables, such as days and amount. A total of 84 trials were utilized and fitted with RSM; they were then used to obtain mathematical prediction models. Results: Exposure of TGF-β3 to T-MSCs and BM-MSCs resulted in an increase in the expression of SCX, TNMD, decorin, collagen I, and tenacin C. Most tenocyte lineage-related factors from T-MSCs and BM-MSCs presented a maximum increase in 2- 3 day treatment. Considering all of tenocyte lineage-related factors that we assessed, the predicted value of the factors was significantly induced at 2.7 ng/mL of TGF-β3 (p &lt; 0.001) on 2.5-day culture (p = 0.001). (Fig A) Considering all of tenocyte lineage-related factors that we assessed, the predicted value of the factors was significantly induced on 2.3-day culture (p = 0.004) regardless of the concentration of TGF-β3. (Fig B) Conclusion: We demonstrated that tenocyte-like cells can be successfully differentiated from T-MSCs and BM-MSCs under TGF- β3 stimulation. This study demonstrated that T-MSCs and BM-MSCs in tenogenic stimulation with TGF-β3 have a similar tenogenic differentiation potential using RSM.

Comparative Analysis of Different Platelet Lysates and Platelet Rich Preparations to Stimulate Tendon Cell Biology: An In Vitro Study.

The poor healing potential of tendons is still a clinical problem, and the use of Platelet Rich Plasma (PRP) was hypothesized to stimulate healing. As the efficacy of PRPs remains unproven, platelet lysate (PL) could be an alternative with its main advantages of storage and characterization before use. Five different blood products were prepared from 16 male donors: human serum, two PRPs (Arthrex, (PRP-ACP); RegenLab (PRP-BCT)), platelet concentrate (apheresis, PC), and PL (freezing-thawing destruction of PC). Additionally, ten commercial allogenic PLs (AlloPL) from pooled donors were tested. The highest concentration of most growth factors was found in AlloPL, whereas the release of growth factors lasted longer in the other products. PRP-ACP, PRP-BCT, and PC significantly increased cell viability of human tenocyte-like cells, whereas PC and AlloPL increased Col1A1 expression and PRP-BCT increased Col3A1 expression. MMP-1, IL-1β, and HGF expression was significantly increased and Scleraxis expression decreased by most blood products. COX1 expression significantly decreased by PC and AlloPL. No clear positive effects on tendon cell biology could be shown, which might partially explain the weak outcome results in clinical practice. Pooled PL seemed to have the most beneficial effects and might be the future in using blood products for tendon tissue regeneration.

An investigation of BMP-7 mediated alterations to BMP signalling components in human tenocyte-like cells

The incidence of tendon re-tears post-surgery is an ever present complication. It is suggested that the application of biological factors, such as bone morphogenetic protein 7 (BMP-7), can reduce complication rates by promoting tenogenic characteristics in in vitro studies. However, there remains a dearth of information in regards to the mechanisms of BMP-7 signalling in tenocytes. Using primary human tenocyte-like cells (hTLCs) from the supraspinatus tendon the BMP-7 signalling pathway was investigated: induction of the BMP associated Smad pathway and non-Smad pathways (AKT, p38, ERK1/2 and JNK); alterations in gene expression of BMP-7 associated receptors, Smad pathway components, Smad target gene (ID1) and tenogenic marker scleraxis. BMP-7 increases the expression of specific BMP associated receptors, BMPR-Ib and BMPR-II, and Smad8. Additionally, BMP-7 activates significantly Smad1/5/8 and slightly p38 pathways as indicated by an increase in phosphorylation and proven by inhibition experiments, where p-ERK1/2 and p-JNK pathways remain mainly unresponsive. Furthermore, BMP-7 increases the expression of the Smad target gene ID1, and the tendon specific transcription factor scleraxis. The study shows that tenocyte-like cells undergo primarily Smad8 and p38 signalling after BMP-7 stimulation. The up-regulation of tendon related marker genes and matrix proteins such as Smad8/9, scleraxis and collagen I might lead to positive effects of BMP-7 treatment for rotator cuff repair, without significant induction of osteogenic and chondrogenic markers.

The Role of Scleraxis in Fate Determination of Mesenchymal Stem Cells for Tenocyte Differentiation.

Mesenchymal stem cells (MSCs) are pluripotent cells that primarily differentiate into osteocytes, chondrocytes, and adipocytes. Recent studies indicate that MSCs can also be induced to generate tenocyte-like cells; moreover, MSCs have been suggested to have great therapeutic potential for tendon pathologies. Yet the precise molecular cascades governing tenogenic differentiation of MSCs remain unclear. We demonstrate scleraxis, a transcription factor critically involved in embryonic tendon development and formation, plays a pivotal role in the fate determination of MSC towards tenocyte differentiation. Using murine C3H10T1/2 pluripotent stem cells as a model system, we show scleraxis is extensively expressed in the early phase of bone morphogenetic protein (BMP)-12-triggered tenocytic differentiation. Once induced, scleraxis directly transactivates tendon lineage-related genes such as tenomodulin and suppresses osteogenic, chondrogenic, and adipogenic capabilities, thus committing C3H10T1/2 cells to differentiate into the specific tenocyte-like lineage, while eliminating plasticity for other lineages. We also reveal that mechanical loading-mediated tenocytic differentiation follows a similar pathway and that BMP-12 and cyclic uniaxial strain act in an additive fashion to augment the maximal response by activating signal transducer Smad8. These results provide critical insights into the determination of multipotent stem cells to the tenocyte lineage induced by both chemical and physical signals.

Do Matrix Metalloproteases and Tissue Inhibitors of Metalloproteases in Tenocytes of the Rotator Cuff Differ with Varying Donor Characteristics?

An imbalance between matrix metalloproteases (MMPs) and the tissue inhibitors of metalloproteases (TIMPs) may have a negative impact on the healing of rotator cuff tears. The aim of the project was to assess a possible relationship between clinical and radiographic characteristics of patients such as the age, sex, as well as the degenerative status of the tendon and the MMPs and TIMPs in their tenocyte-like cells (TLCs). TLCs were isolated from ruptured supraspinatus tendons and quantitative Real-Time PCR and ELISA was performed to analyze the expression and secretion of MMPs and TIMPs. In the present study, MMPs, mostly gelatinases and collagenases such as MMP-2, -9 and -13 showed an increased expression and protein secretion in TLCs of donors with higher age or degenerative status of the tendon. Furthermore, the expression and secretion of TIMP-1, -2 and -3 was enhanced with age, muscle fatty infiltration and tear size. The interaction between MMPs and TIMPs is a complex process, since TIMPs are not only inhibitors, but also activators of MMPs. This study shows that MMPs and TIMPs might play an important role in degenerative tendon pathologies.

Well-aligned chitosan-based ultrafine fibers committed teno-lineage differentiation of human induced pluripotent stem cells for Achilles tendon regeneration

Physical property of substrates such as stiffness and topography have been reported to induce mesenchymal stem cells differentiation into bone, muscle and neuron lineages. Human-induced pluripotent stem cells (hiPSCs) are a highly promising cell source for regenerative medicine. However, physical properties have not yet been reported to successfully induce pluripotent stem cells into specific lineages. This study aimed to develop a robust, stepwise topographic strategy to induce hiPSCs differentiate into teno-lineage. A novel spinning approach termed stable jet electrospinning (SJES), is utilized to fabricate continuous well-aligned ultrafine fibers (891 ± 71 nm), which mimic the native tendon's microstructure and mechanical properties. hiPSCs are first differentiated into MSCs on smooth plastic surface as confirmed by the differentiations into three mesenchymal lineages and expression of characteristic MSC surface markers through an EMT (Epithelial–Mesenchymal Transition) process. Subsequently, the hiPSC derived MSCs are seeded onto well-aligned fibers to differentiate into tenocyte-like cells through activating mechanic-signal pathway. The in situ tendon repair study further confirms that aligned fiber scaffold with hiPSC-MSCs had significant effect on improving the structural and mechanical properties of tendon injury repair. These findings indicate that the stepwise physical substrate change strategy can be adopted to induce hiPSCs differentiation for tendon tissue regeneration.

Thyroid hormones increase collagen I and cartilage oligomeric matrix protein (COMP) expression in vitrohuman tenocytes

we previously demonstrated the presence of high levels of thyroid hormones (THs) receptors isoforms in healthy tendons, their protective action during tenocyte apoptosis, and the capability to enhance tenocyte proliferation in vitro. In the present study we tested the ability of THs to influence ECM protein tenocyte secretion in an in vitro system. primary tenocyte-like cells were cultivated for 1, 7 and 14 days in the presence of T3 or T4 individually or in combination with ascorbic acid (AA). THs (T3 or T4) in synergism with AA increase significantly the total collagen production after 14 days. THs in synergism with AA increase significantly the expression of collagen I,biglycan and COMP, after some days. THs play a role on the extra cellular matrix of tendons, enhancing in vitro the production of several proteins such as collagen I, biglycan and COMP. THs receptors are active on human tenocytes, and can play a role in tendon ailments.

Correction: Characteristics and Stimulation Potential with BMP-2 and BMP-7 of Tenocyte-Like Cells Isolated from the Rotator Cuff of Female Donors

Correction: Characteristics and Stimulation Potential with BMP-2 and BMP-7 of Tenocyte-Like Cells Isolated from the Rotator Cuff of Female Donors

Relationship between muscle fatty infiltration and the biological characteristics and stimulation potential of tenocytes from rotator cuff tears

The healing after rotator cuff surgery is still dissatisfying, and increased muscle fatty infiltration even more impairs the healing success. To achieve sufficient healing after rotator cuff reconstructions, the use of growth factors may be one possibility. The aim of the study was to identify a possible relationship between fatty infiltration of the supraspinatus muscle and cellular biological characteristics and stimulation potential of tenocyte-like cells (TLCs). TLCs of 3 donor groups differing in grade of muscle fatty infiltration were analyzed for their cellular characteristics and were stimulated with BMP-2 or BMP-7 in a 3D scaffold culture. The cell count and potency for self-renewal were significantly decreased in TLCs from donors with high muscle fatty infiltration compared to the lower fatty infiltration groups. Cell count and collagen-I expression as well as protein synthesis were stimulated by growth factors. Interestingly, TLCs of the high fatty infiltration group exhibited a weaker stimulation potential compared to the other groups. TLCs from donors with high muscle fatty infiltration generally revealed inferior characteristics compared to cells of lower fatty infiltration groups, which may be one reason for a weaker healing potential and may represent a possible starting point for the development of future treatment options.