Functional fibrocartilage regeneration is a bottleneck during bone–tendon healing, and the currently available tissue-engineering strategies for fibrocartilage regeneration are insufficient because of a lack of appropriate scaffold that can load large seeding-cells and induce chondrogenesis of stem cells. The acellular fibrocartilage scaffold (AFS) contains active growth factors as well as tissue-specific epitopes for cell-matrix interactions, which make it a potential scaffold for tissue-engineered fibrocartilage. A limitation to this scaffold is that its low porosity inhibits cells loading and infiltration. Here, inspired by book appearance, we sectioned native fibrocartilage tissue (NFT) into book-shape to improve cells loading and infiltration, and then decellularized with four protocols: (1) 2% SDS for 6-h, (2) 2% SDS for 24-h, (3) 4 SDS for 6-h, (4) 4% SDS for 24-h, followed by nuclease digestion. The optimal protocol was screened with respect to microstructures, DNA residence, native ingredients reservation, and chondrogenic inducibility of the AFS. In vitro studies demonstrated that this screened scaffold is noncytotoxicity and low-immunogenicity, allows adipose-derived stromal cells (ASCs) attachment and proliferation, shows superior chondrogenic inducibility, and stimulates collagen or glycosaminoglycans secretion. The underlying mechanism for this chondrogenic inducibility may be related to hedgehog pathway activating. Additionally, a novel pattern for fabricating tissue-engineered fibrocartilage was developed to enlarge seeding-cells loading, namely, cell-sheets sandwiched by book-shaped scaffold. In-vivo studies indicate that this screened scaffold alone could induce endogenous cells to satisfactorily regenerate fibrocartilage at 16-week, as characterized by fibrocartilaginous extracellular matrix (ECM) deposition and good interface integration. Interleaving this book-shaped AFS with autologous ASCs-sheets significantly enhanced its ability to regenerate fibrocartilage. Cell tracking demonstrated that fibrochondrocytes, osteoblasts, and osteocytes in the healing interface at postoperative 8-week partly originated from the sandwiched ASCs-sheets. On that basis, we propose the use of this book-shaped AFS and cell sheet technique for fabricating tissue-engineered fibrocartilage to improve bone–tendon healing.

The osteogenic differentiation of human bone mesenchymal stromal cells (BMSCs) has been considered as a central issue in fracture healing. Wnt signaling could promote BMSC osteogenic differentiation through inhibiting PPARγ. During atrophic nonunion, Wnt signaling-related factors, WNT5A and FZD3 proteins, were significantly reduced, along with downregulation of Runx2, ALP, and Collagen I and upregulation of PPARγ. Here, we performed a microarray analysis to identify differentially expressed miRNAs in atrophic nonunion tissues that were associated with Wnt signaling through targeting related factors. Of upregulated miRNAs, miR-381 overexpression could significantly inhibit the osteogenic differentiation in primary human BMSCs while increase in PPARγ protein level. Through binding to the 3′UTR of WNT5A and FZD3, miR-381 modulated the osteogenic differentiation via regulating β-catenin nucleus translocation. Moreover, PPARγ, an essential transcription factor inhibiting osteogenic differentiation, could bind to the promoter region of miR-381 to activate its expression. Taken together, PPARγ-induced miR-381 upregulation inhibits the osteogenic differentiation in human BMSCs through miR-381 downstream targets, WNT5A and FZD3, and β-catenin nucleus translocation in Wnt signaling. The in vivo study also proved that inhibition of miR-381 promoted the fracture healing. Our finding may provide a novel direction for atrophic nonunion treatment.

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Osteosarcoma is the most common primary bone malignancy. Recently, studies showed chemokine receptor 4 (CXCR4) played a critical role in osteosarcoma. However, the regulation of CXCR4 is not fully understood. microRNAs are short, non‐coding RNAs that play an important roles in post‐transcriptional regulation of gene expression in a variety of diseases including osteosarcoma. miR‐613 is a newly discovered miRNA and has been reported to function as a tumor suppressor in many cancers. In this study, we confirmed that both Stromal Cell‐Derived Factor (SDF‐1) and CXCR4 could be prognostic markers for osteosarcoma. Meanwhile this study found that SDF‐1/CXCR4 pathway regulated osteosarcoma cells proliferation, migration and reduced apoptosis. Besides, we demonstrated that miR‐613 was significantly downregulated in osteosarcoma patients. Elevated expression of miR‐613 directly suppressed CXCR4 expression and then decreased the proliferation, migration and induced apoptosis of osteosarcoma cells. Moreover, our study found that CXCR4 promoted the development of lung metastases and inhibition of CXCR4 by miR‐613 reduced lung metastases. These data indicated that CXCR4 mediated osteosarcoma cell growth and lung metastases and this effect can be suppressed by miR‐613 through directly downregulating CXCR4.

Most studies concerning to tendon healing and incorporation into bone are mainly based on animal studies due to the invasive nature of the biopsy procedure. The evidence considering tendon graft healing to bone in humans is limited in several case series or case reports, and therefore, it is difficult to understand the healing process. A computerized search using relevant search terms was performed in the PubMed, EMBASE, Scopus, and Cochrane Library databases, as well as a manual search of reference lists. Searches were limited to studies that investigated tendon graft healing to bone by histologic examination after anterior cruciate ligament (ACL) reconstruction with hamstring. Ten studies were determined to be eligible for this systematic review. Thirty-seven cases were extracted from the included studies. Most studies showed that a fibrovascular interface would form at the tendon-bone interface at the early stage and a fibrous indirect interface with Sharpey-like fibers would be expected at the later stage. Cartilage-like tissue at tendon graft-bone interface was reported in three studies. Tendon graft failed to integrate with the surrounding bone in 10 of the 37 cases. Unexpectedly, suspensory type of fixation was used for the above failure cases. An indirect type of insertion with Sharpey-like fibers at tendon-bone interface could be expected after ACL reconstruction with hamstring. Regional cartilage-like tissue may form at tendon-bone interface occasionally. The underlying tendon-to-bone healing process is far from understood in the human hamstring ACL reconstruction. Further human studies are highly needed to understand tendon graft healing in bone tunnel after hamstring ACL reconstruction.

Background: Tendon-bone interface (TBI) injuries are common in sports activities. Owing to the limited regenerative ability of the TBI, its functional healing remains a difficulty in clinical practice. Icariin (ICA) provides strong stimulation for osteogenesis. Platelet-rich plasma (PRP) can be used as a carrier for bioactive molecules, although its ability to provide sustained release for such molecules needs improvement. Hypothesis: Freeze-dried PRP (FD-PRP) as a carrier for ICA can provide sustained release of ICA into the tendon-bone (T-B) healing site, thus accelerating T-B healing. Study Design: Controlled laboratory study. Methods: A total of 84 New Zealand rabbits with partial patellectomy in the hindlimb were randomly allocated into 3 different treatments: ICA incorporated with FD-PRP (ICA/FD-PRP), FD-PRP alone (FD-PRP), or saline control (CTL). The rabbit patella–patellar tendon (PP) interfaces were postoperatively harvested at postoperative week 8 or 16 for gross, radiological, histological, and mechanical evaluations. Results: Our results showed that FD-PRP can act as a carrier for sustained release of ICA into the T-B healing site. Macroscopically, no signs of infection or osteoarthritis were shown in the regenerated PP interfaces, and the area of cartilaginous metaplasia in the FD-PRP and ICA/FD-PRP groups at postoperative week 16 was significantly larger than that of the CTL group ( P < .05 for all). Radiologically, micro–computed tomography showed that new bone which formed at the healing site in the ICA/FD-PRP group was significantly increased, remodeled, and mineralized in comparison with the CTL group ( P < .05 for all). Histologically, the ICA/FD-PRP group exhibited a significant native PP interface, as shown by the enlargement and remodeling of new bone, well-organized collagen fibers, and robust production of proteoglycans in the regenerated fibrocartilage. The mechanical strength of the regenerated PP interface was significantly improved in the ICA/FD-PRP group. Significantly higher failure load and stiffness were shown in the ICA/FD-PRP group compared with the CTL and FD-PRP groups, respectively ( P < .05 for all). Conclusion: FD-PRP is a suitable sustained-release carrier for ICA, and ICA/FD-PRP can provide sustained release of ICA into the T-B healing site, thus effectively accelerating T-B healing. Clinical Relevance: Findings of this study demonstrate the feasibility of using FD-PRP as a carrier for ICA to improve T-B healing and provide a foundation for future clinical application.

Tissue‐engineering approaches have great potential to improve the treatment of tendon injuries which are major musculoskeletal disorders. The purpose of this study was to assess the tissue engineering potential of a novel multilayered decellularized tendon “book” scaffold with bone marrow mesenchymal stem cells (BMSCs) sheets for repair of an Achilles tendon defect in a rabbit model. In this study, we developed a novel book‐shaped decellularized scaffold derived from the extracellular matrix of tendon tissues from New Zealand white rabbits. Hematoxylin and eosin (H&E) staining, 4′, 6‐diamidino‐2‐phenylindole (DAPI) staining, DNA quantitation, and scanning electron microscopy (SEM) confirmed the efficiency of decellularization. After culturing BMSCs on decellularized scaffolds, 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide (MTT) assay, SEM, quantitative real time polymerase chain reaction (qRT‐PCR), and immunofluorescence analysis demonstrated that decellularized scaffolds have the capacity to yield homogeneous distribution and alignment of BMSCs, as well as support their differentiation into tendon. Tenomodulin and Alpha‐1 collagen type I are important indicators for evaluating tenogenic differentiation of BMSCs. When decellularized “book” scaffolds with BMSCs sheets were used to repair a 1 mm Achilles tendon defect, histomorphological analysis, immunohistochemical assessment, and biomechanical testing showed that the book‐shaped decellularized tendon matrix scaffold and BMSCs sheets could promote the regeneration of type I collagen at the wound site during healing, and improve the mechanical properties of the repaired tendon. Therefore, the results of this study suggest that the novel decellularized “book” tendon scaffolds combined with BMSCs sheets have therapeutic effects on improving the healing quality of the Achilles tendon. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1–11, 2019.

Postoperative exercise has been demonstrated to be beneficial for bone-tendon interface (BTI) healing, yet the debate regarding the optimal time to initiate exercise after tendon enthesis repair is ongoing. This study aimed to evaluate the initiation times for exercise after enthesis repair. A total of 192 C57BL/6 mice underwent acute supraspinatus tendon injury repair. The animals were then randomly assigned to four groups: free cage activity after repair (control group); treadmill running started on postoperative day 2 (2-day delayed group); treadmill running started on postoperative day 7 (7-day delayed group), and treadmill running started on postoperative day 14 (14-day delayed group). Mice were euthanized at 4 and 8 weeks postoperatively, and histological, biomechanical, and bone morphometric tests were performed. Higher failure loads and bone volume fractions were found for the 7-day delayed group and the 14-day delayed group at 4 weeks postoperatively. The 7-day delayed group had better biomechanical properties and higher bone volume fractions than the 2-day delayed group at 4 weeks postoperatively. Histologically, the 7-day delayed group exhibited lower modified tendon-to-bone maturity scores than the control group and the 2-day delayed group at 4 and 8 weeks postoperatively.Quantitative reverse-transcription polymerase chain reaction results showed that the 7-day delayed group had higher expressions of chondrogenic-and osteogenicrelated genes. Statement of clinical significance: Postoperative treadmill running initiated on postoperative day 7 had a more prominent effect on BTI healing than other treatment regimens in this study and could accelerate BTI healing and rotator cuff repair.