WTAP-mediated N6-methyladenosine modification of circ_PVT1 promotes proliferation and tenogenic differentiation of tendon stem/progenitor cells

Previous studies have shown that the differentiation potential declines with the age of progenitor cells and is linked to altered levels of senescence markers. The purpose of this study was to test whether senescence marker p16 affects age-related tenogenic differentiation in tendon stem/progenitor cells (TSPCs). Young and aged TSPCs were isolated from young/healthy and aged/degenerated human Achilles tendons, respectively. Cellular aging and capacity for tenogenic differentiation were examined. The results showed that the tenogenic differentiation capacity of TSPCs significantly decreases with advancing age. TSPCs from elderly donors showed upregulation of senescence-associated β-galactosidase and p16 and concurrently a decrease in Type I collagen concentration and in the expressions of tendon-related markers: Scx, Tnmd, Bgn, Dcn, Col1, and Col3. Overexpression of p16 significantly inhibited tenogenic differentiation of young TSPCs. Analysis of the mechanism revealed that this effect is mediated by microRNA-217 and its target EGR1. These results indicated that p16 inhibits tenogenic differentiation of TSPCs via microRNA signaling pathways, which may serve as a potential target for the prevention or treatment in the future.

BackgroundTendinopathy is a common musculoskeletal disorder in individuals with diabetes. Tendon stem/progenitor cells (TSPCs) play an essential role in tendon repair, regeneration and homeostasis maintenance. Although studies have demonstrated that diabetic tendinopathy is closely associated with the altered differentiation of TSPCs, the underlying mechanisms remain largely unknown. This study was designed to investigate the role of the HMGB1/RAGE/β-catenin axis in the differentiation imbalance of TSPCs and diabetic tendinopathy.MethodsRat diabetes models were induced with streptozotocin (65 mg/kg). TSPCs were isolated at week 2 and the patellar tendons were isolated at weeks 2 and 4 for histological analysis. The activation of the HMGB1/RAGE/β-catenin axis in TSPCs and diabetic tendons was determined by western blot, ELISA, qRT-PCR and immunohistochemical staining. TSPCs and the diabetic tendons were then treated with lentivirus targeting HMGB1 or glycyrrhizin or FPS-ZM1 or PNU-74654 to demonstrate the role of this axis in TSPCs differentiation and diabetic tendinopathy. Alizarin red staining was performed to evaluate the calcium nodule formation. The mRNA expression of the osteogenic and tenogenic genes in TSPCs and diabetic tendons was examined by qRT-PCR and immunohistochemical staining. Recombinant HMGB1 was injected around the patellar tendons to further study the role of HMGB1 in tendinopathy, the histological changes were evaluated by HE stating and the expression of RAGE, β-catenin and the osteogenic genes in tendons was detected by immunohistochemical staining at weeks 2 and 4.ResultsWe established a rat diabetes model. In diabetic TSPCs, the activity of the HMGB1/RAGE/β-catenin axis was increased. Diabetic TSPCs exhibited increased osteogenic differentiation potential and reduced tenogenic differentiation ability. Blockade of this axis attenuated the differentiation imbalance of diabetic TSPCs. In addition, we also demonstrated the activation of the HMGB1/RAGE/β-catenin axis in diabetic tendons. The expression of tendon-related markers was decreased and the expression of osteogenic markers was increased in diabetic tendons. Inhibition of this axis could ameliorate these non-tenogenic alterations. Furthermore, injection of recombinant HMGB1 promoted the development of tendinopathy, increased the expression of RAGE and β-catenin and upregulated the expression of osteogenic markers in tendon tissue.ConclusionsOur findings revealed the critical role of the HMGB1/RAGE/β-catenin axis in the differentiation imbalance of TSPCs and diabetic tendinopathy, highlighting a novel essential mechanism involved in the pathogenesis of diabetic tendinopathy and providing a promising therapeutic target and approach for diabetic tendinopathy.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13018-025-06572-8.

Previous work suggested that tenogenic differentiation of tendon stem/progenitor cells (TSPCs) was suppressed by upregulated expression of the angiogenic marker vascular endothelial growth factor (VEGF). The purpose of this study was to test the hypothesis that anti-VEGF antibody, bevacizumab, promotes in vitro tenogenic differentiation and maturation of two distinct types of TSPCs, tendon proper-derived cells (TDCs), and paratenon-derived cells (PDCs) originating from rat Achilles tendon. TDCs and PDCs were isolated from the tendon proper and the paratenon of rat Achilles tendons. TDCs and PDCs were cultured for 3 days on plates with or without VEGF. TDCs and PDCs were also cultured in collagen gel matrix, and the blocking effect of VEGF was examined by the addition of 100 ng/mL of bevacizumab. Effects of bevacizumab on tenogenic differentiation were assessed using real-time PCR, immunofluorescent staining, and western blotting. VEGF significantly attenuated expression of the Tnmd gene in both PDCs and TDCs (P<0.05). Expressions of the Scx, Tnmd, and Col1a1 genes were significantly upregulated by the addition of bevacizumab (P<0.05). Immunofluorescent staining showed that the percentage of tenomodulin-positive PDCs and TDCs was significantly higher with bevacizumab treatment than in control cultures (P<0.05). Western blotting showed that bevacizumab suppressed pVEGFR-2 protein expression in both PDCs and TDCs. Bevacizumab promoted the in vitro tenogenic differentiation and maturation of two distinct TSPCs derived from rat Achilles tendon. Since the previous studies demonstrated that TSPCs have a potential to contribute to tendon repair, attenuating VEGF levels in TSPCs by administration of bevacizumab is a novel candidate therapeutic option for promoting tendon repair.

Tendon injury is one of the prevalent disorders of the musculoskeletal system in orthopedics and is characterized by pain and limitation of joint function. Due to the difficulty of spontaneous tendon healing, and the scar tissue and low mechanical properties that usually develops after healing. Therefore, the healing of tendon injury remains a clinical challenge. Although there are a multitude of approaches to treating tendon injury, the therapeutic effects have not been satisfactory to date. Recent studies have shown that stem cell therapy has a facilitative effect on tendon healing. In particular, tendon stem/progenitor cells (TSPCs), a type of stem cell from tendon tissue, play an important role not only in tendon development and tendon homeostasis, but also in tendon healing. Compared to other stem cells, TSPCs have the potential to spontaneously differentiate into tenocytes and express higher levels of tendon-related genes. TSPCs promote tendon healing by three mechanisms: modulating the inflammatory response, promoting tenocyte proliferation, and accelerating collagen production and balancing extracellular matrix remodeling. However, current investigations have shown that TSPCs also have a negative effect on tendon healing. For example, misdifferentiation of TSPCs leads to a “failed healing response,” which in turn leads to the development of chronic tendon injury (tendinopathy). The focus of this paper is to describe the characteristics of TSPCs and tenocytes, to demonstrate the roles of TSPCs in tendon healing, while discussing the approaches used to culture and differentiate TSPCs. In addition, the limitations of TSPCs in clinical application and their potential therapeutic strategies are elucidated.

Quercetin attenuates tendon stem/progenitor cell senescence and promotes aged tendon repair via AKT/NF-κB/NLRP3-mediated mitophagy activation.

Tendinopathy is a tendon disorder characterized by activity-related pain, local edema, focal tenderness to palpation, and decreased strength in the affected area. Tendinopathy is prevalent in both athletes and the general population, highlighting the need to elucidate the pathogenesis of this disorder. Current treatments of tendinopathy are both conservative and symptomatic. The discovery of tendon stem/progenitor cells (TSPCs) and erroneous differentiation of TSPCs have provided new insights into the pathogenesis of tendinopathy. In this review, we firstly present the histopathological characteristics of tendinopathy and explore the cellular and molecular cues in the pathogenesis of tendinopathy. Current evidence of the depletion of the stem cell pool and altered TSPCs fate in the pathogenesis of tendinopathy has been presented. The potential regulatory factors for either tenogenic or nontenogenic differentiation of TSPCs are also summarized. The regulation of endogenous TSPCs or supplementation with exogenous TSPCs as therapeutic targets for the treatment of tendinopathy is proposed. Therefore, inhibiting the erroneous differentiation of TSPCs and regulating the differentiation of TSPCs into tendon cells might be important areas of future research and could provide new clinical treatments for tendinopathy. The current evidence suggests that TSPCs are promising therapeutic targets for the management of tendinopathy.

Patients with diabetes face an increased risk of developing several tendon disorders, such as tendinopathy, tendon rupture, and impaired tendon healing. Tendon stem/progenitor cells (TSPCs) play a crucial role in maintaining tendon tissue homeostasis and facilitating tendon healing. However, under diabetic conditions, TSPC dysfunction contributes to the development and progression of tendinopathy or tendon injury. Despite this, effective treatments remain limited. This study aims to investigate the potential of prim-O-glucosylcimifugin (POG) in preventing high glucose (HG)-induced senescence and restoring the impaired regenerative phenotype of TSPCs. The results reveal that HG stimulation induces TSPC senescence, characterized by impaired self-renewal capacity, increased expression of senescence markers, and reduced tenogenic differentiation potential. Notably, treatment with POG counteracts HG-induced senescence, restoring the impaired tenogenic differentiation capacity through AMP-activated protein kinase (AMPK) pathway activation. To assess the in vivo effect of POG, mesoporous silica nanoparticles are employed for the local delivery of POG. This approach efficiently promotes tendon healing in diabetic mice with partial-cut-induced tendon injury. Moreover, the combination of POG and biomimetic scaffold transplantation functionally rescues endogenous tendon regeneration and repair capacities in diabetic mice. In conclusion, pharmacological intervention with POG can rescue HG-induced TSPC hypofunction and promote tendon healing under diabetic conditions.

The link between tendon stem/progenitor cells (TSPCs) senescence and tendon aging has been well recognized. However, the cellular and molecular mechanisms of TSPCs senescence are still not fully understood. In present study, we investigated the role of Aquaporin 1 (AQP1) in TSPCs senescence. We showed that AQP1 expression declines with age during tendon aging. In aged TSPCs, overexpression of AQP1 significantly attenuated TSPCs senescence. In addition, AQP1 overexpression also restored the age-related dysfunction of self-renewal, migration and tenogenic differentiation. Furthermore, we demonstrated that the JAK-STAT signaling pathway is activated in aged TSPCs, and AQP1 overexpression inhibited the JAK-STAT signaling pathway activation which indicated that AQP1 attenuates senescence and age-related dysfunction of TSPCs through the repression of JAK−STAT signaling pathway. Taken together, our findings demonstrated the critical role of AQP1 in the regulation of TSPCs senescence and provided a novel target for antagonizing tendon aging.

Tendons injuries frequently result in scar-like tissue with poor biochemical structure and mechanical properties. We have recently reported that CD146+ perivascular originated tendon stem/progenitor cells (TSCs), playing critical roles in tendon healing. Here, we identified highly efficient small molecules that selectively activate endogenous TSCs for tendon regeneration.Methods: From a pool of ERK1/2 and FAK agonists, Oxo-M and 4-PPBP were identified, and their roles in tenogenic differentiation of TSCs and in vivo tendon healing were investigated. Controlled delivery of Oxo-M and 4-PPBP was applied via PLGA µS. Signaling studies were conducted to determine the mechanism for specificity of Oxo-M and 4-PPBP to CD146+ TSCs.Results: A combination of Oxo-M and 4-PPBP synergistically increased the expressions of tendon-related gene markers in TSCs. In vivo, delivery of Oxo-M and 4-PPBP significantly enhanced healing of fully transected rat patellar tendons (PT), with functional restoration and reorganization of collagen fibrous structure. Our signaling study suggested that Oxo-M and 4-PPBP specifically targets CD146+ TSCs via non-neuronal muscarinic acetylcholine receptors (AChR) and σ1 receptor (σ1) signaling.Principal conclusions: Our findings demonstrate a significant potential of Oxo-M and 4-PPBP as a regenerative therapeutics for tendon injuries.

Diabetic calcific tendinopathy is the leading cause of chronic pain, mobility restriction, and tendon rupture in patients with diabetes. Tendon stem/progenitor cells (TSPCs) have been implicated in the development of diabetic calcified tendinopathy, but the molecular mechanisms remain unclear. This study found that diabetic tendons have a hyperoxic environment, characterized by increased oxygen delivery channels and carriers. In hyperoxic environment, TSPCs showed enhanced osteogenic differentiation and increased levels of reactive oxygen species (ROS). Additionally, hypoxia-inducible factor-1a (HIF-1a), a protein involved in regulating cellular responses to hyperoxia, was decreased in TSPCs by the ubiquitin-proteasome system. By intervening with antioxidant N-acetyl-L-cysteine (NAC) and overexpressing HIF-1a, we discovered that blocking the ROS/HIF-1a signalling axis significantly inhibited the osteogenic differentiation ability of TSPCs. Animal experiments further confirmed that hyperoxic environment could cause calcification in the Achilles tendon tissue of rats, while NAC intervention prevented calcification. These findings demonstrate that hyperoxia in diabetic tendons promotes osteogenic differentiation of TSPCs through the ROS/HIF-1a signalling axis. This study provides a new theoretical basis and research target for preventing and treating diabetic calcified tendinopathy.

The essential role of aligned architecture in decellularized tendon matrix mediated stem cell tenogenic differentiation and tendon repair

Bone marrow mesenchymal stem cell-derived exosomes promote tendon regeneration by facilitating the proliferation and migration of endogenous tendon stem/progenitor cells

Age-related tendon disorder, a primary motor system disease, is characterized by biological changes in the tendon tissue due to senescence and seriously affects the quality of life of the elderly. The pathogenesis of this disease is not well-understood. Tendon stem/progenitor cells (TSPCs) exhibit multi-differentiation capacity. These cells are important cellular components of the tendon because of their roles in tendon tissue homeostasis, remodeling, and repair. Previous studies revealed alterations in the biological characteristics and tenogenic differentiation potential of TSPCs in senescent tendon tissue, in turn contributing to insufficient differentiation of TSPCs into tenocytes. Poor tendon repair can result in age-related tendinopathies. Therefore, targeting of senescent TSPCs may restore the tenogenic differentiation potential of these cells and achieve homeostasis of the tendon tissue to prevent or treat age-related tendinopathy. In this review, we summarize the biological characteristics of TSPCs and histopathological changes in age-related tendinopathy, as well as the potential mechanisms through which TSPCs contribute to senescence. This information may promote further exploration of innovative treatment strategies to rescue TSPCs from senescence.

3D printing of chemical-empowered tendon stem/progenitor cells for functional tissue repair

The association of tendinopathy with diabetes has been well recognized. Tendon stem/progenitor cells (TSPCs) play critical roles in tendon repair, regeneration, and homeostasis maintenance. Diabetic TSPCs exhibit enhanced erroneous differentiation and are involved in the pathogenesis of diabetic tendinopathy, whereas the underlying mechanism of the erroneous differentiation of TSPCs remains unclear. Here, we showed that high glucose treatment promoted the erroneous differentiation of TSPCs with increased osteogenic differentiation capacity and decreased tenogenic differentiation ability, and stimulated the expression and further secretion of HMGB1 in TSPCs and. Functionally, exogenous HMGB1 significantly enhanced the erroneous differentiation of TSPCs, while HMGB1 knockdown mitigated high glucose-promoted erroneous differentiation of TSPCs. Mechanistically, the RAGE/β-catenin signaling was activated in TSPCs under high glucose, and HMGB1 knockdown inhibited the activity of RAGE/β-catenin signaling. Inhibition of RAGE/β-catenin signaling could ameliorate high glucose-induced erroneous differentiation of TSPCs. These results indicated that HMGB1 regulated high glucose-induced erroneous differentiation of TSPCs through the RAGE/β-catenin signaling pathway. Collectively, our findings suggest a novel essential mechanism of the erroneous differentiation of TSPCs, which might contribute to the pathogenesis of diabetic tendinopathy and provide a promising therapeutic target and approach for diabetic tendinopathy.