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The article discusses a study on targeted pathological collagen delivery of sustained-release rapamycin to prevent heterotopic ossification. It mentions that tendon stem/ progenitor cells do not undergo osteochondrogenic differentiation when mTOR signaling is inactivated by gene knockout or rapamycin (RAPA) treatment.

The regenerative process of injured muscle is dependent on the fusion and differentiation of myoblasts derived from muscle stem cells. Hsp70 is important for maintaining skeletal muscle homeostasis and regeneration, but the precise cellular mechanism remains elusive. In this study, we found that Hsp70 was upregulated during myoblast differentiation. Depletion or inhibition of Hsp70/Hsc70 impaired myoblast differentiation. Importantly, overexpression of p38 mitogen-activated protein kinase (p38MAPK) but not AKT1 rescued the impairment of myogenic differentiation in Hsp70- or Hsc70-depleted myoblasts. Moreover, Hsp70 interacted with MK2, a substrate of p38MAPK, to regulate the stability of p38MAPK. Knockdown of Hsp70 also led to downregulation of both MK2 and p38MAPK in intact muscles and during cardiotoxin-induced muscle regeneration. Hsp70 bound MK2 to regulate MK2-p38MAPK interaction in myoblasts. We subsequently identified the essential regions required for Hsp70-MK2 interaction. Functional analyses showed that MK2 is essential for both myoblast differentiation and skeletal muscle regeneration. Taken together, our findings reveal a novel role of Hsp70 in regulating myoblast differentiation by interacting with MK2 to stabilize p38MAPK. [ABSTRACT FROM AUTHOR]

Osteonecrosis of the femoral head (ONFH) is a common but intractable disease. In this study, we investigated the mechanisms regulating alterations in mesenchymal stem cell (MSC) differentiation in ONFH. Five patients who were diagnosed with ONFH were enrolled in this study. Bone MSCs (BMSCs) were isolated from the osteonecrotic zone in the femoral head (FH-pMSCs) and from the normal zone in the pelvis (hMSCs) of the same patient. Morphology, cell proliferation and expression of mediators of the Wnt signalling pathway were evaluated. There were significant differences in cell proliferation and expression of surface markers between the two populations of cells. FH-pMSCs exhibited significantly lower osteogenic differentiation compared with hMSCs (P50.0001). Dissection of the Wnt pathway showed that FH-pMSCs had significantly higher GSK3β expression compared with hMSCs (P50.001). Addition of LiCl, a GSK3β inhibitor, significantly increased osteogenic differentiation in FH-pMSCs, suggesting a relationship between the microenvironment and regulation of stem cell behaviour in ONFH. FH-pMSCs also exhibited significant downregulation of other mediators of the Wnt signalling pathway, including runx2 and b-catenin. Our data suggested that mediators of the Wnt signalling pathway, such as GSK3β could be important therapeutic targets for early-stage ONFH. [ABSTRACT FROM AUTHOR]

Background: Mesenchymal stem cell therapy for osteoarthritis (OA) has been widely investigated, but the mechanisms are still unclear. Exosomes that serve as carriers of genetic information have been implicated in many diseases and are known to participate in many physiological processes. Here, we investigate the therapeutic potential of exosomes from human embryonic stem cell-induced mesenchymal stem cells (ESC-MSCs) in alleviating osteoarthritis (OA). Methods: Exosomes were harvested from conditioned culture media of ESC-MSCs by a sequential centrifugation process. Primary mouse chondrocytes treated with interleukin 1 beta (IL-1β) were used as an in vitro model to evaluate the effects of the conditioned medium with or without exosomes and titrated doses of isolated exosomes for 48 hours, prior to immunocytochemistry or western blot analysis. Destabilization of the medial meniscus (DMM) surgery was performed on the knee joints of C57BL/6 J mice as an OA model. This was followed by intra-articular injection of either ESC-MSCs or their exosomes. Cartilage destruction and matrix degradation were evaluated with histological staining and OARSI scores at the post-surgery 8 weeks. Results: We found that intra-articular injection of ESC-MSCs alleviated cartilage destruction and matrix degradation in the DMM model. Further in vitro studies illustrated that this effect was exerted through ESC-MSC-derived exosomes. These exosomes maintained the chondrocyte phenotype by increasing collagen type II synthesis and decreasing ADAMTS5 expression in the presence of IL-1β. Immunocytochemistry revealed colocalization of the exosomes and collagen type II-positive chondrocytes. Subsequent intra-articular injection of exosomes derived from ESC-MSCs successfully impeded cartilage destruction in the DMM model. Conclusions: The exosomes from ESC-MSCs exert a beneficial therapeutic effect on OA by balancing the synthesis and degradation of chondrocyte extracellular matrix (ECM), which in turn provides a new target for OA drug and drug-delivery system development. [ABSTRACT FROM AUTHOR]