Long noncoding RNA H19 accelerates tenogenic differentiation by modulating miR-140-5p/VEGFA signaling

Rotator cuff tear (RCT) is a common tendon injury, but the mechanisms of tendon healing remain incompletely understood. Elucidating the molecular mechanisms of tenogenic differentiation is essential to develop novel therapeutic strategies in clinical treatment of RCT. The long noncoding RNA H19 plays a regulatory role in tenogenic differentiation and tendon healing, but its detailed mechanism of action remains unknown. To elucidate the role of H19 in tenogenic differentiation and tendon healing, tendon-derived stem cells were harvested from the Achilles tendons of Sprague Dawley rats and a rat model of cuff tear was established for the exploration of the function of H19 in promoting tenogenic differentiation. The results showed that H19 overexpression promoted, while H19 silencing suppressed, tenogenic differentiation of tendon-derived stem cells (TDSCs). Furthermore, bioinformatic analyses and a luciferase reporter gene assay showed that H19 directly targeted and inhibited miR-140-5p to promote tenogenic differentiation. Further, inhibiting miR-140-5p directly increased VEGFA expression, revealing a novel regulatory axis between H19, miR-140-5p, and VEGFA in modulating tenogenic differentiation. In rats with RTC, implantation of H19-overexpressing TDSCs at the lesion promoted tendon healing and functional recovery. In general, the data suggest that H19 promotes tenogenic differentiation and tendon-bone healing by targeting miR-140-5p and increasing VEGFA levels. Modulation of the H19/miR-140-5p/VEGFA axis in TDSCs is a new potential strategy for clinical treatment of tendon injury.

Hepatocyte Growth Factor-Induced Tendon Stem Cell Conditioned Medium Promotes Healing of Injured Achilles Tendon

Tendon repair is a medical challenge. Our present study investigated the effectiveness of acellular therapy consisting of conditioned medium (CM) of tendon stem cells (TSCs) induced with hepatocyte growth factor (HGF) in promoting the healing of injured Achilles tendon in a rat model. Proteomic analysis of soluble substances in the CM was performed using an array chip, and bioinformatic analysis was carried out to evaluate interactions among the factors. The effects of CM on viability and migratory capacity of tendon fibroblasts derived from rats with ruptured Achilles tendon were evaluated with the Cell Counting Kit 8 and wound healing assay, respectively. The expression of extracellular matrix (ECM)-related protein was assessed by western blotting. Rats with Achilles tendon injury were treated with CM by local injection for 2 weeks, and the organization of tendon fibers at the lesion site was evaluated by hematoxylin and eosin and Masson's trichrome staining of tissue samples. The deposition and degradation of ECM proteins and the expression of inflammatory factors at the lesion site were evaluated by immunohistochemistry and immunofluorescence. Biomechanical testing was carried out on the injured tendons to assess functional recovery. There were 12 bioactive molecules in the CM, with HGF as the hub of the protein-protein interaction network. CM treatment enhanced the viability and migration of tendon fibroblasts, altered the expression of ECM proteins, promoted the organization of tendon fibers, suppressed inflammation and improved the biomechanics of the injured Achilles tendon. These results suggest that HGF stimulates the secretion of soluble secretory products by TSCs and CM promotes the repair and functional recovery of ruptured Achilles tendon. Thus, HGF-induced TSC CM has therapeutic potential for the treatment of tendinopathy.

A Novel Approach for Meniscal Regeneration Using Kartogenin-Treated Autologous Tendon Graft

BACKGROUND

The meniscus is one of the most commonly injured parts of the body, and meniscal healing is difficult.

HYPOTHESIS

Kartogenin (KGN) induces tendon stem cells (TSCs) to differentiate into cartilage cells in vitro and form meniscus-like tissue in vivo. A damaged meniscus can be replaced with a KGN-treated autologous tendon graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

In the in vitro experiments, TSCs were isolated from rabbit patellar tendons and cultured with various concentrations of KGN, from 0 to 1000 µM. The effect of KGN on the chondrogenesis of TSCs in vitro was investigated by histochemical staining and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The in vivo experiments were carried out on 6 New Zealand White rabbits by removing a meniscus from the rabbit knee and implanting an autologous tendon graft treated with KGN or saline. The meniscus formation in vivo was examined by histological analysis and immune staining.

RESULTS

The proliferation of TSCs was promoted by KGN in a concentration-dependent manner. Both histochemical staining and qRT-PCR showed that the chondrogenic differentiation of TSCs was increased with KGN concentration. After 3 months of implantation, the tendon graft treated with KGN formed a meniscus-like tissue with a white and glistening appearance, while the saline-treated tendon graft retained tendon-like tissue and appeared yellowish and unhealthy. Histochemical staining showed that after 3 months of implantation, the KGN-treated tendon graft had a structure similar to that of normal meniscus. Many cartilage-like cells and fibrocartilage-like tissues were found in the KGN-treated tendon graft. However, no cartilage-like cells were found in the saline-treated tendon graft after 3 months of implantation. Furthermore, the KGN-treated tendon graft was positively stained by both anti-collagen type I and type II antibodies, but the saline-treated tendon graft was not stained by collagen type II.

CONCLUSION

The findings indicated that KGN can induce the differentiation of TSCs into cartilage-like cells in vitro and in vivo. The results suggest that KGN-treated tendon graft may be a good substitute for meniscal repair and regeneration.

CLINICAL RELEVANCE

This study revealed the direct effects of KGN on the chondrogenic differentiation of TSCs in vitro and in vivo. A KGN-treated autologous tendon graft induced formation of a meniscus-like tissue in vivo. This study provides a new cartilage regenerating technology for the treatment of damaged meniscus.

Moderate treadmill running exercise prior to tendon injury enhances wound healing in aging rats

The effect of exercise on wound healing in aging tendon was tested using a rat moderate treadmill running (MTR) model. The rats were divided into an MTR group that ran on a treadmill for 4 weeks and a control group that remained in cages. After MTR, a window defect was created in the patellar tendons of all rats and wound healing was analyzed. We found that MTR accelerated wound healing by promoting quicker closure of wounds, improving the organization of collagen fibers, and decreasing senescent cells in the wounded tendons when compared to the cage control. MTR also lowered vascularization, increased the numbers of tendon stem/progenitor cells (TSCs) and TSC proliferation than the control. Besides, MTR significantly increased the expression of stem cell markers, OCT-4 and Nanog, and tenocyte genes, Collagen I, Collagen III and tenomodulin, and down-regulated PPAR-γ, Collagen II and Runx-2 (non-tenocyte genes). These findings indicated that moderate exercise enhances healing of injuries in aging tendons through TSC based mechanisms, through which exercise regulates beneficial effects in tendons. This study reveals that appropriate exercise may be used in clinics to enhance tendon healing in aging patients.