Dead muscle tissue promotes dystrophic calcification by lowering circulating TGF-β1 level

Bu Yang Huan Wu Prevents Osteogenic Effect of Muscle-Derived Stromal Cells via Regulating JAK/STAT Pathway

Heterotopic ossification (HO) is a crucial pathological process in which bone or calcification develop in skeletal muscle and surrounding soft tissues. Muscle-derived stromal cells (MDSC) are important muscle-resident mesenchymal progenitor cells and macrophage-derived oncostatin M (OSM) can induce osteogenic differentiation. Bu Yang Huan Wu (BYHW), which has a long history of use in restraining inflammation, can prevent osteogenic differentiation and HO formation while underlying mechanism is still unclear. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway is an important pathway to regulate osteogenic differentiation of related cells. In this study, we investigated whether BYHW could inhibit osteogenesis effect of MDSC through OSM mediated by macrophages, and whether JAK/STAT pathway regulated this biological process. We found that activated macrophages promoted osteogenic differentiation of MDSC through OSM and BYHW could decrease the level of OSM and osteogenic activity of MDSC. Further, we confirmed the regulatory effect of JAK/STAT pathway, blocking this pathway could suppress the level of OSM and osteogenic differentiation of MDSC. We showed that BYHW could suppress osteogenic differentiation of MDSC through JAK/STAT signalling. These findings expand the application scope of traditional Chinese medicine and provide a basis for the further investigation of the potential therapeutic role of HO.

Incidence and Risk Factors of Heterotopic Ossification in the Knee After Reamed Tibial Nailing

INTRODUCTION

Heterotopic ossification (HO) in the knee after tibial intramedullary nailing (IMN) has yet to be thoroughly investigated. Our aim was to assess frequency and associated factors for HO in the knee after tibial IMN.

METHODS

This is a retrospective review at a single level 1 urban trauma center of 213 patients who underwent reamed tibial IMN. Plain radiographs were reviewed postoperatively and on final follow-up (≥6 weeks). Chart review was performed for surgical approach (suprapatellar versus infrapatellar), demographics, injury characteristics, and clinical follow-up. The primary outcome was frequency of HO.

RESULTS

HO on final follow-up (mean: 41.43 weeks) was recorded in 15% cases. Postsurgical retroinfrapatellar reaming debris (odds ratio [OR], 4.73), Injury Severity Score (OR, 1.05), intensive care unit admission (OR, 2.89), chest injury (OR, 3.4), and ipsilateral retrograde femoral IMN (OR, 5.08) showed a notable association with HO development. No association was observed in HO formation between surgical approach, knee pain, or range-of-motion deficits.

DISCUSSION

Radiographic evidence of HO in the knee after reamed tibial IMN is not uncommon and is associated with retained reaming debris, Injury Severity Score, chest injury, intensive care unit admission, and ipsilateral retrograde femoral nailing. No differences were noted in HO formation between approaches. HO was not associated with knee pain or range-of-motion deficits.

Calcification of the pump pouch in patients receiving ITB therapy: A rare complication affecting refill procedure - Analysis of two cases

BACKGROUND

Intrathecal baclofen therapy (ITB) is an effective treatment for reducing spasticity but can be associated with various complications, including infection and implant malfunction.

METHODS

This retrospective cohort study analyzed refill reports, complications, and functional outcomes in 40 consecutive patients with intractable spasticity or dystonia undergoing ITB.

RESULTS

Among the 40 patients, 8 experienced complications, including two cases of calcification of the baclofen pump pouch and surrounding tissue, a rare complication not extensively described in the literature.

DISCUSSION

Calcification, in addition to port access difficulties, could lead to drug delivery failure. We hypothesize that calcification may result from microtrauma or needlestick injury to the subcutaneous tissue and muscle fascia. The length of time the pump stays in the pocket could also contribute to favoring this phenomenon.

CONCLUSION

As the number of patients receiving ITB increases, physicians must be aware of potential life-threatening complications. The risk of pouch calcification should be further investigated and considered in managing patients undergoing ITB, as it could significantly impact patient care.

Pathogenesis of acquired heterotopic ossification: Risk factors, cellular mechanisms, and therapeutic implications

Heterotopic ossification (HO), including hereditary and acquired HO, is the formation of extraskeletal bone in skeletal muscle and surrounding soft tissues. Acquired HO is often caused by range of motion, explosion injury, nerve injury or burns. Severe HO can lead to pain and limited joint activity, affecting functional rehabilitation and quality of life. Increasing evidence shows that inflammatory processes and mesenchymal stem cells (MSCs) can drive HO. However, explicit knowledge about the specific mechanisms that result in HO and related cell precursors is still limited. Moreover, there are no effective methods to prevent or reduce HO formation. In this review, we provide an update of known risk factors and relevant cellular origins for HO. In particular, we focus on the underlying mechanisms of MSCs in acquired HO, which follow the osteogenic program. We also discuss the latest therapeutic value and implications for acquired HO. Our review highlights the current gaps in knowledge regarding the pathogenesis of acquired HO and identifies potential targets for the prevention and treatment of HO.

BRD4 promotes heterotopic ossification through upregulation of LncRNA MANCR

Aims

Acquired heterotopic ossification (HO) is a debilitating disease characterized by abnormal extraskeletal bone formation within soft-tissues after injury. The exact pathogenesis of HO remains unknown. It was reported that BRD4 may contribute to osteoblastic differentiation. The current study aims to determine the role of BRD4 in the pathogenesis of HO and whether it could be a potential target for HO therapy.

Methods

Achilles tendon puncture (ATP) mouse model was performed on ten-week-old male C57BL/6J mice. One week after ATP procedure, the mice were given different treatments (e.g. JQ1, shMancr). Achilles tendon samples were collected five weeks after treatment for RNA-seq and real-time quantitative polymerase chain reaction (RT-qPCR) analysis; the legs were removed for micro-CT imaging and subsequent histology. Human bone marrow mesenchymal stem cells (hBMSCs) were isolated and purified bone marrow collected during surgeries by using density gradient centrifugation. After a series of interventions such as knockdown or overexpressing BRD4, Alizarin red staining, RT-qPCR, and Western Blot (Runx2, alkaline phosphatase (ALP), Osx) were performed on hBMSCs.

Results

Overexpression of BRD4 enhanced while inhibition of Brd4 suppressed the osteogenic differentiation of hBMSCs in vitro. Overexpression of Brd4 increased the expression of mitotically associated long non-coding RNA (Mancr). Downregulation of Mancr suppressed the osteoinductive effect of BRD4. In vivo, inhibition of BRD4 by JQ1 significantly attenuated pathological bone formation in the ATP model (p = 0.001).

Conclusion

BRD4 was found to be upregulated in HO and Brd4-Mancr-Runx2 signalling was involved in the modulation of new bone formation in HO.

Cite this article: Bone Joint Res 2021;10(10):668–676.