Background: Adipose stem cell–derived exosomes (ASC-Exos) are reported to effectively prevent muscle atrophy and degeneration of torn rat rotator cuff, but their influence on human samples and their potential mechanism are still unclear. Purpose: We aimed to investigate the effects of ASC-Exos on the metabolic activities of torn human rotator cuff tendons and explore the potential mechanism behind it. Study Design: Controlled laboratory study. Methods: Diseased supraspinatus tendons were harvested from 15 patients with a mean ± SD age of 65.8 ± 3.2 years who underwent reverse shoulder arthroplasty for chronic rotator cuff tears associated with glenohumeral pathological changes. Each tendon was dissected into 3 × 4 × 4–mm explants: the ones derived from the same tendon were placed into 12-well plates and cultured in complete culture media (control) or in complete culture media supplemented with ASC-Exos for 72 hours. Afterward, the concentrations of cytokines secreted into the culture media—including interleukin 1β (IL-1β), IL-6, IL-8, and matrix metalloproteinase 9 (MMP-9)—were measured using enzyme-linked immunosorbent assay (ELISA). Tendons were stained with hematoxylin and eosin and immunohistochemistry (type I and III collagens) for histological analyses. Moreover, the expression of anabolic genes ( TIMP-1 and TIMP-3; type I and III collagen encoding) and catabolic genes ( MMP-9 and MMP-13) in tendons were measured using real-time quantitative polymerase chain reaction. Phosphorylated AMPKα and Wnt/β-catenin pathways were assayed by western blotting to explore the potential mechanism of action of ASC-Exos. Results: Secretion of proinflammatory cytokines, including IL-1β, IL-6, and MMP-9, was significantly reduced in the ASC-Exos group as compared with the control group. Supraspinatus tendons in the ASC-Exos group exhibited superior histological properties, as demonstrated by higher tendon maturing scores and more type I collagen content, but there was no significant difference in type III collagen content between groups. Expression of MMP-9 and MMP-13 genes was decreased in the ASC-Exos group versus the control group. Increased expression of type I and III collagens and an elevated type I/III ratio were found in the ASC-Exos group when compared with the control group. There was no significant difference in the secretion of IL-8 and expression of TIMP-1 and TIMP-3 genes between the ASC-Exos and control groups. Western blotting revealed that ASC-Exos enhanced phosphorylated AMPKα and decreased β-catenin levels to prevent tendon degeneration. Conclusion: ASC-Exos maintained metabolic homeostasis of torn human rotator cuff tendons to improve their histological properties, which might be achieved by enhancing AMPK signaling to suppress Wnt/β-catenin activity. Clinical Relevance: ASC-Exos could be used as an effective biological tool to promote healing in torn human rotator cuff tendons.

Directed differentiation of bone marrow mesenchymal stem cells (BMSCs) toward chondrogenesis plays a predominant role in cartilage repair. However, the uncontrolled inflammatory response to implants is found to impair the stability of scaffolds and the cartilage regeneration outcome. Herein, we fabricated an injectable hydrogel crosslinked by strontium-doped bioglass (SrBG) to modulate both human BMSC (hBMSC) differentiation and the inflammatory response. The results revealed that the introduction of Sr ions could simultaneously enhance the proliferation of hBMSCs, upregulate cartilage-specific gene expression, and improve the secretion of glycosaminoglycan. Moreover, after cultured with SA/ SrBG extracts in vitro, a majority of macrophages were polarized toward the M2 phenotype and subsequently facilitated the chondrogenic differentiation of hBMSCs. Furthermore, after the composite hydrogel was injected into a cartilage defect model, neonatal cartilage-like tissues with a smooth surface and tight integration with original tissues could be found. This study suggests that the synergistic strategy based on an enhanced differentiation ability and a regulated inflammatory response is promising and may lead the way to new anti-inflammatory biomaterials.

Degenerative rotator cuff tendinopathy (RCT) is a chronic tendon disease caused by degeneration and inflammation, which often affects the elderly population. Mesenchymal stem cell senescence is generally recognized as an important pathophysiological mechanism in many age-related skeletal diseases. Herein, we collected human tendon-derived stem/progenitor cells (TSPCs) from degenerative supraspinatus tendons and found that TSPC senescence is closely related to RCT. We further identified that nuclear factor kB (NF-kB) pathway activation is involved in age-related inflammation (inflamm-aging) of degenerative RCT. Moreover, whole genome RNA sequencing revealed that in vitro inhibition of the I kappa B kinase b (IKKb)/NF-kB signaling pathway could reverse the aged TSPC phenotype with decreased TSPC senescence and increased tenogenic potential. To achieve effective in vivo inhibition of IKKb/NF-kB signaling, we fabricated IKKb small interfering RNA (siRNA)-loaded gold nanoclusters (AuNC-siRNA) for efficient and convenient intra-articular delivery of IKKb siRNA. We found that AuNC-siRNA prevented inflamm-aging-induced TSPC senescence and dysfunction in a degenerative RCT aged rat model. Together, these data show that inflamm-aging causes degenerative RCT through inducing TSPC senescence, which can be reversed by blocking the IKKb/ NF-kB pathway in vivo. Thus, our study provides a promising therapeutic strategy for degenerative RCT via intra-articular delivery of IKKb siRNA using AuNCs.