Fibrosis is common after skeletal muscle injury, undermining tissue regeneration and function. The mechanism underlying skeletal muscle fibrosis remains unveiled. Transforming growth factor-β/Smad signaling pathway is supposed to play a pivotal role. However, how microRNAs interact with transforming growth factor-β/Smad-related muscle fibrosis remains unclear. We showed that microRNA (miR)-24-3p and miR-122-5p declined in skeletal muscle fibrosis, which was a consequence of transforming growth factor-β. Upregulating Smad4 suppressed two microRNAs, whereas inhibiting Smad4 elevated microRNAs. Luciferase reporter assay and chromatin immunoprecipitation confirmed that Smad4 directly inhibited two microRNAs. On the other hand, overexpression of these two miRs retarded fibrotic process. We further identified that Smad2 was a direct target of miR-24-3p, whereas miR-122-5p targeted transforming growth factor-β receptor-II. Both targets were important participants in transforming growth factor-β/Smad signaling. Taken together, a positive feedback loop in transforming growth factor-β/Smad4 signaling pathway in skeletal muscle fibrosis was identified. Transforming growth factor-β/Smad axis could be downregulated by microRNAs. This effect, however, was suppressed by Smad4, the downstream of transforming growth factor-β.

Background: Intra-articular steroid injection is a common intervention for frozen shoulder (FS). Purpose: This review aimed to illustrate the effects of intra-articular steroid injection for FS. Study Design: Systematic review and meta-analysis. Methods: PubMed, Embase, and the Cochrane Library were searched for randomized controlled trials (RCTs) comparing intra-articular steroid injection with no injection or sham injections for FS. Visual analog scale (VAS) pain scores were the primary outcome measure. Secondary outcome measures included passive external rotation, abduction, flexion, internal rotation, and functional scores. Complication rates were the safety outcome measure. Comparisons were performed with mean differences (MDs) and 95% confidence intervals (95% CIs). Three time intervals were analyzed: 4 to 6 weeks, 12 to 16 weeks, and 24 to 26 weeks postintervention. Trial sequential analysis was used to verify the pooled results. Line charts were drawn to view the recovery trend in both the intervention and control groups. Results: Eight RCTs with 416 patients were included. Compared with controls, patients who received intra-articular steroid injection had significantly reduced VAS pain scores at 4 to 6 weeks (MD, 1.28 cm [95% CI, 0.75 to 1.82]), 12 to 16 weeks (MD, 1.00 cm [95% CI, 0.47 to 1.52]), and 24 to 26 weeks (MD, 0.65 cm [95% CI, 0.19 to 1.10]) postinjection. Trial sequential analysis confirmed the pooled results at 4 to 6 weeks and 12 to 16 weeks but not at 24 to 26 weeks. Patients who received intra-articular steroid injection had improved passive external rotation, abduction, and flexion and Shoulder Pain and Disability Index (SPADI) scores at all 3 time intervals, as well as improved American Shoulder and Elbow Surgeons (ASES) scores at 12 to 16 weeks (MD, 12.20 [95% CI, 2.55 to 21.85]). No difference was noticed in Constant scores (MD, 5.70 [95% CI, –0.59 to 11.99]) or internal rotation except at 12 to 16 weeks (MD, 0.81° [95% CI, 0.18° to 1.44°]) and 24 to 26 weeks (MD, 3.88° [95% CI, 0.51° to 7.25°]) between steroid injection and placebo. Complication rates were 1.78% for facial flushing, 0.71% for dizziness owing to vasovagal reactions during injection, 1.07% for chest or shoulder pain, and 0.36% for nausea. Line charts improved in both groups. Conclusion: Intra-articular steroid injection is effective and safe for FS and relieves pain, improves functional performance, and increases range of motion. The effects are significant at 4 to 6 and 12 to 16 weeks postintervention and may last as long as 24 to 26 weeks.

Shoulder stiffness (SS) is a common shoulder disease characterized by increasing pain and limited range of motion. SS is considered to be an inflammatory and fibrotic disorder pathologically. However, there is no consensus on the most effective conservative treatment for fibrosis. Given that human Bone Marrow Mesenchymal Stem Cell-derived extracellular vesicles (BMSC-EVs) displayed promising therapeutic effects for various tissues, we investigated the therapeutic effect of BMSC-EVs on fibrosis in a mice immobilization model and two cell models. By conducting a series of experiments, we found that BMSC-EVs can significantly inhibit the fibrogenic process both in vitro and in vivo. In detail, BMSC-EVs suppressed the aberrant proliferation, high collagen production capacity, and activation of fibrotic pathways in TGF-β-stimulated fibroblasts in vitro. Besides, in vivo, BMSC-EVs reduced cell infiltration, reduced fibrotic tissue in the shoulder capsule, and improved shoulder mobility. In addition, via exosomal small RNA sequencing and qPCR analysis, let-7a-5p was verified to be the highest expressed miRNA with predicted antifibrotic capability in BMSC-EVs. The antifibrotic capacity of BMSC-EVs was significantly impaired after the knockdown of let-7a-5p. Moreover, we discovered that the mRNA of TGFBR1 (the membrane receptor of transforming growth factor β) was the target of let-7a-5p. Together, these findings elucidated the antifibrotic role of BMSC-EVs in shoulder capsular fibrosis. This study clarifies a new approach using stem cell-derived EVs therapy as an alternative to cell therapy, which may clinically benefit patients with SS in the future.

The hamstring tendons are commonly harvested for anterior cruciate ligament (ACL) reconstruction with detachment of the tibial insertion. Retaining the insertion may help to preserve vascularity and viability of the graft and bypass the stages of avascular necrosis and revascularization, which might be beneficial to graft maturity. To investigate and compare graft maturity by magnetic resonance imaging (MRI) after ACL reconstruction with preservation or detachment of hamstring tendon tibial insertion at up to 2 years. Randomized controlled trial; Level of evidence, 2. Forty-five patients (age range, 18-45 years) undergoing isolated ACL reconstruction with hamstring tendon were enrolled and randomized to 2 groups. The tibial insertion of the hamstring tendon was preserved in the study group (n = 21) and detached in the control group (n = 24). Patients had follow-up at 3, 6, 12, and 24 months, which consisted of the following: (1) clinical examination and (2) MRI evaluation of graft signal intensity based on signal/noise quotient (SNQ) values. Finally, 18 patients in the study group and 19 in the control group received full follow-up evaluation (ie, at all 4 time points). All knees acquired full range of motion at 24 months without significant laxity. At each time point, the KT-1000 arthrometer revealed no significant difference between groups; the clinical scores significantly improved in both groups, although the difference between groups was not significant. In the control group, the SNQ value increased from 3 months, peaked at 6 months, and then decreased (3 months, 21.4 ± 12.7; 6 months, 25.6 ± 12; 12 months, 18.3 ± 7.7; 24 months, 15.3 ± 6.3). However, the insertion-preserved graft in the study group maintained relatively lower and unchanged signal intensity throughout all time points (3 months, 15.0 ± 11.2; 6 months, 14.9 ± 6.3; 12 months, 12.6 ± 7.0; 24 months, 14.6 ± 7.0). Between groups, there was no significant difference at 3 or 24 months (P = .11 and .75, respectively), while the SNQ values were significantly lower in the study group versus the control group at 6 and 12 months (P = .002 and .02, respectively). The insertion-detached hamstring tendon grafts underwent a significantly increasing change in signal intensity during the first 2 years after ACL reconstruction, while the insertion-preserved grafts kept a relatively lower and unchanged signal intensity. The difference was most significant at 6 and 12 months postoperatively.

Skeletal muscle contusion is among the most common injuries in traumatology and clinics of sports medicine. The injured muscle is vulnerable to re-injury owing to fibrosis formation. Given that the bone marrow stromal cell-derived exosomes (BMSC-Exos) displayed promising therapeutic effect for various tissues, we used BMSC-Exos to treat skeletal muscle contusion and investigated its effects on muscle healing. In this study, the in vivo model of skeletal muscle contusion was established by subjecting the tibialis anterior of young male mice to hit injury, and the in vitro inflammation model was established by lipopolysaccharide treatment on macrophages. Macrophage depletion model was built by intraperitoneal injection with clodronate-containing liposomes. Exosomes were isolated and purified from the supernatant of BMSCs using gradient centrifugation. Nanoparticle tracking analysis, transmission electron microscope, and western blot were used to identify the exosomes. HE stain, Masson stain, immunofluorescence, and biomechanical testing were carried out on the muscle tissue. In addition, enzyme-linked immunosorbent assay (ELISA) assays, real-time qPCR, flow cytometry, and PKH67 fluorescence trace were conducted in vitro. Intramuscular injection of BMSC-Exos to mice after muscle contusion alleviated inflammation level, reduced fibrosis size, promoted muscle regeneration, and improved biomechanical property. After macrophages depletion, the effects of BMSC-Exos were inhibited. In vitro, PKH-67 fluorescence was internalized into macrophages. BMSC-Exos promoted M2 macrophages polarization both in vivo and in vitro. At the same time, BMSC-Exos reduced the production of inflammatory cytokines under the inflammatory microenvironment and upregulated anti-inflammatory factors expression. In conclusion, BMSC-Exos attenuated muscle contusion injury and promoted muscle healing in mice by modifying the polarization status of macrophages and suppressing the inflammatory reaction.