The role of endothelial-mesenchymal transition in heterotopic ossification

A bioactive composite scaffold enhances osteochondral repair by using thermosensitive chitosan hydrogel and endothelial lineage cell-derived chondrogenic cell

Articular cartilage regeneration is a major challenge in orthopedic medicine. Endothelial progenitor cells (EPCs) are a promising cell source for regenerative medicine applications. However, their roles and functions in cartilage regeneration are not well understood. Additionally, thermosensitive chitosan hydrogels have been widely used in tissue engineering, but further development of these hydrogels incorporating vascular lineage cells for cartilage repair is insufficient. Thus, this study aimed to characterize the ability of EPCs to undergo endothelial-mesenchymal stem cell transdifferentiation and chondrogenic differentiation and investigate the ability of chondrogenic EPC-seeded thermosensitive chitosan-graft-poly (N-isopropylacrylamide) (CEPC-CSPN) scaffolds to improve healing in a rabbit osteochondral defect (OCD) model. EPCs were isolated and endothelial-to-mesenchymal transition (EndMT) was induced by transforming growth factor-β1 (TGF-β1); these EPCs are subsequently termed transdifferentiated EPCs (tEPCs). The stem cell-like properties and chondrogenic potential of tEPCs were evaluated by a series of in vitro assays. Furthermore, the effect of CEPC-CSPN scaffolds on OCD repair was evaluated. Our in vitro results confirmed that treatment of EPC with TGF-β1 induced EndMT and the acquisition of stem cell-like properties, producing tEPCs. Upon inducing chondrogenic differentiation of tEPCs (CEPCs), the cells exhibited significantly enhanced chondrogenesis and chondrocyte surface markers after 25 days. The TGF-β1-induced differentiation of EPCs is mediated by both the TGF-β/Smad and extracellular signal-regulated kinase (Erk) pathways. The CEPC-CSPN scaffold reconstructed well-integrated translucent cartilage and repaired subchondral bone in vivo, exhibiting regenerative capacity. Collectively, our results suggest that the CEPC-CSPN scaffold induces OCD repair, representing a promising approach to articular cartilage regeneration.

A rare mass with atypical localization: Heterotopic ossification associated with flexor hallucis longus

Heterotopic ossification (HO), characterized by the formation of ectopic bone, is a benign mass observed in soft tissues. Depending on its location, it can cause symptoms beyond compression, such as mechanical blockage when associated with joints, leading to limitations in joint movements. In the majority of cases, involvement of the hip and elbow joints is common, while HO can sometimes be observed in atypical locations. Trauma, head injury, and spinal cord injuries are well-recognized risk factors for HO development. However, on rare occasions, in non-traumatic cases are identified without any known risk factors. Herein, we present a rare non-traumatic HO case associated with the flexor hallucis longus (FHL) tendon in a 58-year-old female patient. She complained of pain under the first toe of her right foot while wearing shoes for a year, and a mass was detected on the plantar surface of the foot along with limitation of movement in the first metatarsophalangeal joint. Further examinations revealed that the identified mass was a mature HO lesion. Surgical treatment was performed, and during one-year follow-up, the pain subsided, and joint movements returned to normal, resulting in a satisfactory outcome. In conclusion, although many cases of HO are associated with traumatic injuries, it can sometimes be idiopathic, as in our case, and rarely it is accompanied tendon such as FHL in the foot.

Role of the NF-kB signalling pathway in heterotopic ossification: biological and therapeutic significance

Heterotopic ossification (HO) is a pathological process in which ectopic bone develops in soft tissues within the skeletal system. Endochondral ossification can be divided into the following types of acquired and inherited ossification: traumatic HO (tHO) and fibrodysplasia ossificans progressiva (FOP). Nuclear transcription factor kappa B (NF-κB) signalling is essential during HO. NF-κB signalling can drive initial inflammation through interactions with the NOD-like receptor protein 3 (NLRP3) inflammasome, Sirtuin 1 (SIRT1) and AMP-activated protein kinase (AMPK). In the chondrogenesis stage, NF-κB signalling can promote chondrogenesis through interactions with mechanistic target of rapamycin (mTOR), phosphatidylinositol-3-kinase (PI3K)/AKT (protein kinase B, PKB) and other molecules, including R-spondin 2 (Rspo2) and SRY-box 9 (Sox9). NF-κB expression can modulate osteoblast differentiation by upregulating secreted protein acidic and rich in cysteine (SPARC) and interacting with mTOR signalling, bone morphogenetic protein (BMP) signalling or integrin-mediated signalling under stretch stimulation in the final osteogenic stage. In FOP, mutated ACVR1-induced NF-κB signalling exacerbates inflammation in macrophages and can promote chondrogenesis and osteogenesis in mesenchymal stem cells (MSCs) through interactions with smad signalling and mTOR signalling. This review summarizes the molecular mechanism of NF-κB signalling during HO and highlights potential therapeutics for treating HO.

Suppression of Overactive Insulin-Like Growth Factor 1 Attenuates Trauma-Induced Heterotopic Ossification in Mice

Heterotopic ossification (HO) is the ectopic bone formation in soft tissues. Aside from hereditary HO, traumatic HO is common after orthopedic surgery, combat-related injuries, severe burns, or neurologic injuries. Recently, mammalian target of rapamycin (mTOR) was demonstrated to be involved in the chondrogenic and osteogenic processes of HO formation. However, its upstream signaling mechanism remains unknown. The current study used an Achilles tendon puncture-induced HO model to show that overactive insulin-like growth factor 1 (IGF-1) was involved in the progression of HO in mice. Micro-computed tomography imaging showed that IGF-1 not only accelerated the rate of osteogenesis and increased ectopic bone volume but also induced spontaneous ectopic bone formation in undamaged Achilles tendons. Blocking IGF-1 activity with IGF-1 antibody or IGF-1 receptor inhibitor picropodophyllin significantly inhibited HO formation. Mechanistically, IGF-1/IGF-1 receptor activates phosphatidylinositol 3-kinase (PI3K)/Akt signaling to promote the phosphorylation of mTOR, resulting in the chondrogenic and osteogenic differentiation of tendon-derived stem cells into chondrocytes and osteoblasts in vitro and in vivo. Inhibitors of PI3K (LY294002) and mTOR (rapamycin) both suppressed the IGF-1-stimulated mTOR signal and mitigated the formation of ectopic bones significantly. In conclusion, these results indicate that IGF-1 mediated the progression of traumatic HO through PI3K/Akt/mTOR signaling, and suppressing IGF-1 signaling cascades attenuated HO formation, providing a promising therapeutic strategy targeting HO.

Peri-articular bone formation involving the temporomandibular joint: a narrative summary and Delphi consensus of a new classification system

Heterotopic ossification (HO) is defined as 'bone where it does not belong'. Given the historical variety of nomenclature and eponyms, there is significant confusion about the etiology, pathogenesis, classification, and treatment of HO related to the temporomandibular joint (TMJ). The existing classifications for TMJ HO have shortcomings: they relate to specific populations, use differing imaging studies and demographic data, do not universally include alloplastic/autologous replacements, are based variously on radiological and/or clinical presentations that cannot always be combined, and were largely developed to assist oral and maxillofacial surgeons in surgical management. These deficiencies make it problematic to compare studies, draw valid conclusions, and pursue research. The aim of this study was to develop a new, more inclusive classification for TMJ HO. Currently available classifications were evaluated and a Delphi-type system used to build consensus from clinicians and researchers to develop a new system. Fourteen unique classifications for TMJ ankylosis/HO were identified. In light of the biological specifics related to heterotopic calcification of extracellular matrix versus heterotopic formation of actual bone, the group recommends a more unambiguous term - peri-articular bone formation - and proposes a new classification. This will help clinicians and researchers to study, describe, and manage various types of ectopic bone associated with the TMJ.

Enthesis repair - State of play

The fibrocartilaginous enthesis is a highly specialised tissue interface that ensures a smooth mechanical transfer between tendon or ligament and bone through a fibrocartilage area. This tissue is prone to injury and often does not heal, even after surgical intervention. Enthesis augmentation approaches are challenging due to the complexity of the tissue that is characterised by the coexistence of a range of cellular and extracellular components, architectural features and mechanical properties within only hundreds of micrometres. Herein, we discuss enthesis repair and regeneration strategies, with particular focus on elegant interfacial and functionalised scaffold-based designs.

Melatonin as a therapeutic agent for alleviating endothelial dysfunction in cardiovascular diseases: Emphasis on oxidative stress

The vascular endothelium is vital in maintaining cardiovascular health by regulating vascular permeability and tone, preventing thrombosis, and controlling vascular inflammation. However, when oxidative stress triggers endothelial dysfunction, it can lead to chronic cardiovascular diseases (CVDs). This happens due to oxidative stress-induced mitochondrial dysfunction, inflammatory responses, and reduced levels of nitric oxide. These factors cause damage to endothelial cells, leading to the acceleration of CVD progression. Melatonin, a natural antioxidant, has been shown to inhibit oxidative stress and stabilize endothelial function, providing cardiovascular protection. The clinical application of melatonin in the prevention and treatment of CVDs has received widespread attention. In this review, based on bibliometric studies, we first discussed the relationship between oxidative stress-induced endothelial dysfunction and CVDs, then summarized the role of melatonin in the treatment of atherosclerosis, hypertension, myocardial ischemia-reperfusion injury, and other CVDs. Finally, the potential clinical use of melatonin in the treatment of these diseases is discussed.

Characterization of Fibrodysplasia Ossificans Progessiva relevant Acvr1/Acvr2 Activin receptors in medaka (Oryzias latipes)

Activin and Bone Morphogenetic Protein (BMP) signaling plays crucial roles in vertebrate organ formation, including osteo- and angiogenesis, and tissue homeostasis, such as neuronal maintenance. Activin and BMP signaling needs to be precisely controlled by restricted expression of shared receptors, stoichiometric composition of receptor-complexes and presence of regulatory proteins. A R206H mutation in the human (hs) BMP type I receptor hsACVR1, on the other hand, leads to excessive phosphorylation of Sons of mothers against decapentaplegic (SMAD) 1/5/8. This in turn causes increased inflammation and heterotopic ossification in soft tissues of patients suffering from Fibrodysplasia Ossificans Progressiva (FOP). Several animal models have been established to understand the spontaneous and progressive nature of FOP, but often have inherent limitations. The Japanese medaka (Oryzias latipes, ola) has recently emerged as popular model for bone research. To assess whether medaka is suitable as a potential FOP animal model, we determined the expression of Activin receptor type I (ACVR1) orthologs olaAcvr1 and olaAcvr1l with that of Activin type II receptors olaAcvr2ab, olaAcvr2ba and olaAcvr2bb in embryonic and adult medaka tissues by in situ hybridization. Further, we showed that Activin A binding properties are conserved in olaAcvr2, as are the mechanistic features in the GS-Box of both olaAcvr1 and olaAcvr1l. This consequently leads to FOP-typical elevated SMAD signaling when the medaka type I receptors carry the R206H equivalent FOP mutation. Together, this study therefore provides experimental groundwork needed to establish a unique medaka model to investigate mechanisms underlying FOP.

Higher Improvement of Cardiac Function Following Myocardial Infarction using Menstrual Blood Stromal/Stem Cells (MenSCs) Suspended in Conditioned Medium versus Conditioned Medium Alone in Rat Model

Background

To evaluate the efficiency of Menstrual blood Stromal/Stem Cells (MenSCs) administration in Myocardial Infarction (MI), the effects of MenSCs and their derived conditioned Medium (CM) on cardiac function in MI rat model was assessed.

Methods

Animals were divided into four groups including sham group, MI group, MenSCs derived CM group (CM group), and MenSCs suspended in CM (MenSCs+CM) group. The injection of different groups was carried out 30 min after ligation of left anterior descending coronary artery into the infarct border zone.

Results

The results showed a significant reduction in scar size after injection of MenSCs+CM compared to MI group. Ejection fraction and fractional shortening of MenSCs+CM group were higher than CM and MI group at day 28. Administration of MenSCs+CM led to much more survival of cardiomyocytes, and prevention of meta-plastic development. Moreover, human mitochondrial transfer from MenSCs to cardiomyocytes was seen in group treated by MenSCs+CM. Indeed, MenSCs+CM treatment evoked nuclear factor-κB (NF-κB) down-regulation more than other treatments.

Conclusion

MenSCs+CM treatment could significantly ameliorate cardiac function by different mechanisms including inhibition of cartilaginous metaplasia, inhibition of NF-κB and mitochondrial transfer.

Differential expression profiles and functional prediction of circRNA in mice with traumatic heterotopic ossification

Background

Traumatic heterotopic ossification (HO) is an intractable sequela incited by inflammatory insult. To date, the exact molecular mechanisms of traumatic HO formation remain unclear. Recent studies have indicated that circular RNAs (circRNAs) participate in various human skeletal diseases. Although the formation of HO recapitulates many programs during bone development and remodeling, few data are available concerning whether circRNAs could participate in this pathological osteogenesis.

Methods

To investigate the differentially expressed circRNAs (DE-circRNAs) in HO formation, microarray assay was performed to analyze the circRNA expression profile in four pairs of mice HO tissues and normal tissues. Then, qRT-PCR was applied to verify the microarray data. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed the biological functions of the differentially expressed circRNAs target genes. Cytoscape software was used to construct the circRNA-miRNA-mRNA network for circRNAs with different expression levels as well as the target genes.

Results

We demonstrated that 491 circRNAs were significantly differentially expressed in mouse HO tissues by a fold-change ≥ 2 and p-value ≤ 0.05. Among them, the expressions of 168 circRNAs were increased, while 323 were decreased. The expression levels of 10 selected circRNAs were verified successfully by qRT-PCR. GO analysis exhibited that these DE-circRNAs participated in a series of cellular processes. KEGG pathway analysis revealed that multiple upregulated and downregulated pathways were closely related to the DE-circRNAs in HO mice. The circRNA-miRNA-mRNA networks demonstrated that DE-circRNAs may be involved in the pathological osteogenesis of HO through the circRNA-targeted miRNA-mRNA axis.

Conclusion

Our study first demonstrated the expression profiles and predicted the potential functions of DE-circRNAs in mice traumatic HO, which may shed new light on the elucidation of mechanisms as well as provide novel potential peripheral biological diagnostic markers and therapeutic targets for traumatic HO.

Post-traumatic heterotopic ossification in front of the ankle joint for 23 years: A case report and review of literature

BACKGROUND

Heterotopic ossification (HO) refers to the formation of new bone in non-skeletal tissues such as muscles, tendons or other soft tissues. Severe muscle and soft tissue injury often lead to the formation of HO. However, anterior HO of the ankle is rarely reported.

CASE SUMMARY

We report a patient with massive HO in front of the ankle joint for 23 years. In 1998, the patient was injured by a falling object on the right lower extremity, which gradually formed a massive heterotopic bone change in the right calf and dorsum of the foot. The patient did not develop gradual ankle function limitations until nearly 36 mo ago, and underwent resection of HO. Even after 23 years and resection of HO, the ankle joint was still able to move.

CONCLUSION

It is recommended that the orthopedist should be aware of HO and distinguish it from bone tumor.

Contemporary perspectives on heterotopic ossification

Heterotopic ossification (HO) is the formation of ectopic bone that is primarily genetically driven (fibrodysplasia ossificans progressiva [FOP]) or acquired in the setting of trauma (tHO). HO has undergone intense investigation, especially over the last 50 years, as awareness has increased around improving clinical technologies and incidence, such as with ongoing wartime conflicts. Current treatments for tHO and FOP remain prophylactic and include NSAIDs and glucocorticoids, respectively, whereas other proposed therapeutic modalities exhibit prohibitive risk profiles. Contemporary studies have elucidated mechanisms behind tHO and FOP and have described new distinct niches independent of inflammation that regulate ectopic bone formation. These investigations have propagated a paradigm shift in the approach to treatment and management of a historically difficult surgical problem, with ongoing clinical trials and promising new targets.

Case Report: Unable to Jump Like a Kangaroo Due to Myositis Ossificans Circumscripta

A male 10-year-old captive red kangaroo (Macropus rufus) was presented with a chronic progressive pelvic limb lameness and reluctance to jump. The general examination revealed a palpable induration of the lumbar epaxial muscles. Magnetic resonance imaging performed under general anesthesia revealed bilateral almost symmetric, well-circumscribed mass lesions in superficial erector spinae muscles. The lesions had irregular to multilobulated appearance with hyper-, hypo-, and isointense areas in T2- and T1-weighted (w) sequences without contrast enhancement. On computed tomography, a peripheral rim of mineralization was apparent. Histopathological analysis of a muscle biopsy showed osseous trabeculae with rare clusters of chondrocytes indicating metaplasia of muscle tissue to bone. No indications of inflammation or malignancy were visible. The clinical, histopathological, and imaging workup of this case was consistent with myositis ossificans circumscripta. This disorder is particularly well-known among human professional athletes such as basketball players, where excessive, chronic-repetitive force or blunt trauma causes microtrauma to the musculature. Metaplasia of muscle tissue due to abnormal regeneration processes causes heterotopic ossification. The kangaroo's clinical signs improved with cyto-reductive surgery, cage rest, weight reduction, and meloxicam without further relapse.

Clinical significance of pancreatic calcifications: a 15-year single-center observational study

Objectives

Pancreatic calcifications (PC) are considered specific for chronic pancreatitis (CP), but PC may also be present in non-CP diseases. The aims are to understand the pattern of calcifications in different diseases and to determine they were related to malignant diseases.

Methods

A retrospective study was performed including patients with PC or CP undergoing surgery in the Department of General Surgery of Ruijin Hospital from January 2003 to June 2018.

Results

PC were observed in 168 (4.5%) of the 3755 patients with pancreatic lesions treated during the study period. The majority of patients with PC had three kinds of CP (73.2%) while 26.8% had other five kinds of non-CP diseases. In patients with non-CP diseases, the incidence of PC in malignant intraductal papillary mucinous neoplasm (IPMN) was significantly higher than benign IPMN (8.3% vs. 0.7%, p = 0.004). In patients of CP with pancreatic mass (n = 81), PC (Odds ratio = 28.6, p = 0.000), advanced age (> 55 years) and parenchymal atrophy were independent predictors for malignancy. In patients of CP without pancreatic mass (n = 110), there were 82 cases (74.5%) with PC and 5 cases (4.5%) with pancreatic ductal adenocarcinoma. The regression model of risk factors was not successful.

Conclusions

The disease spectrum with PC was very diverse. PC may be related to malignant IPMN in non-CP diseases and is related to malignancy in the patients of CP with pancreatic mass and indications for resection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40001-022-00725-9.

Sustained local ionic homeostatic imbalance caused by calcification modulates inflammation to trigger heterotopic ossification

Heterotopic ossification (HO) is a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues. Despite being a frequent complication of orthopedic and trauma surgery, brain and spinal injury, the etiology of HO is poorly understood. The aim of this study is to evaluate the hypothesis that a sustained local ionic homeostatic imbalance (SLIHI) created by mineral formation during tissue calcification modulates inflammation to trigger HO. This evaluation also considers the role SLIHI could play for the design of cell-free, drug-free osteoinductive bone graft substitutes. The evaluation contains five main sections. The first section defines relevant concepts in the context of HO and provides a summary of proposed causes of HO. The second section starts with a detailed analysis of the occurrence and involvement of calcification in HO. It is followed by an explanation of the causes of calcification and its consequences. This allows to speculate on the potential chemical modulators of inflammation and triggers of HO. The end of this second section is devoted to in vitro mineralization tests used to predict the ectopic potential of materials. The third section reviews the biological cascade of events occurring during pathological and material-induced HO, and attempts to propose a quantitative timeline of HO formation. The fourth section looks at potential ways to control HO formation, either acting on SLIHI or on inflammation. Chemical, physical, and drug-based approaches are considered. Finally, the evaluation finishes with a critical assessment of the definition of osteoinduction. STATEMENT OF SIGNIFICANCE: The ability to regenerate bone in a spatially controlled and reproducible manner is an essential prerequisite for the treatment of large bone defects. As such, understanding the mechanism leading to heterotopic ossification (HO), a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues, would be very useful. Unfortunately, the mechanism(s) behind HO is(are) poorly understood. The present study reviews the literature on HO and based on it, proposes that HO can be caused by a combination of inflammation and calcification. This mechanism helps to better understand current strategies to prevent and treat HO. It also shows new opportunities to improve the treatment of bone defects in orthopedic and dental procedures.

Giant nontraumatic myositis ossificans in a child: A case report

BACKGROUND

Nontraumatic myositis ossificans is a rare disease whose specific pathogenesis is unclear. Early diagnosis of this disease is very difficult in children because of difficulties in determining medical history and nonspecific early clinical manifestations, which may lead to the failure of timely and effective diagnosis and treatment in some patients. We report the diagnosis and treatment of a child with nontraumatic myositis ossificans and summarize the clinical characteristics and diagnosis and treatment of the disease.

CASE SUMMARY

An 8-year-old girl first came to our hospital for more than a week with pain in the right lower limb. There was no history of trauma or strenuous activities. On physical examination, no mass on the right thigh was found, and the movement of the right lower extremity was limited. Ultrasonography showed synovitis of the hip, and bed rest was recommended. Three days later, the child’s pain persisted and worsened, accompanied by fever and other discomforts. She came to our hospital again and a mass was found on the right thigh with redness and swelling on the surface. The images showed a soft tissue tumor on the right thigh with calcification. Routine blood tests revealed that the inflammation index was significantly increased. In case of infection, the patient was given antibiotics, and the pain was relieved soon after, without fever. However, the right thigh mass persisted and hardened. The patient underwent incision biopsy more than 1 mo later, and the postoperative pathology showed nontraumatic myositis ossificans. After approximately 9 mo of observation, the tumor still persisted, which affected the life of the child, and then resection was performed. Since follow-up, there has been no recurrence.

CONCLUSION

Due to the difficulty in discerning a child's medical history and the diverse early manifestations, it is difficult to diagnose nonossifying muscle disease in children in its early stage. Measures such as timely follow-up and periodic image monitoring are conducive to early diagnosis of the disease. The disease has a certain degree of self-limitation, and it can be observed and treated first. If the tumor persists in the later stage or affects functioning, then surgery is considered.

Giant nontraumatic myositis ossificans in a child: A case report

BACKGROUND

Nontraumatic myositis ossificans is a rare disease whose specific pathogenesis is unclear. Early diagnosis of this disease is very difficult in children because of difficulties in determining medical history and nonspecific early clinical manifestations, which may lead to the failure of timely and effective diagnosis and treatment in some patients. We report the diagnosis and treatment of a child with nontraumatic myositis ossificans and summarize the clinical characteristics and diagnosis and treatment of the disease.

CASE SUMMARY

An 8-year-old girl first came to our hospital for more than a week with pain in the right lower limb. There was no history of trauma or strenuous activities. On physical examination, no mass on the right thigh was found, and the movement of the right lower extremity was limited. Ultrasonography showed synovitis of the hip, and bed rest was recommended. Three days later, the child’s pain persisted and worsened, accompanied by fever and other discomforts. She came to our hospital again and a mass was found on the right thigh with redness and swelling on the surface. The images showed a soft tissue tumor on the right thigh with calcification. Routine blood tests revealed that the inflammation index was significantly increased. In case of infection, the patient was given antibiotics, and the pain was relieved soon after, without fever. However, the right thigh mass persisted and hardened. The patient underwent incision biopsy more than 1 mo later, and the postoperative pathology showed nontraumatic myositis ossificans. After approximately 9 mo of observation, the tumor still persisted, which affected the life of the child, and then resection was performed. Since follow-up, there has been no recurrence.

CONCLUSION

Due to the difficulty in discerning a child's medical history and the diverse early manifestations, it is difficult to diagnose nonossifying muscle disease in children in its early stage. Measures such as timely follow-up and periodic image monitoring are conducive to early diagnosis of the disease. The disease has a certain degree of self-limitation, and it can be observed and treated first. If the tumor persists in the later stage or affects functioning, then surgery is considered.

Return to play after treating acute muscle injuries in elite football players with radial extracorporeal shock wave therapy

Background

To compare lay-off times achieved by treating acute muscle injuries in elite football players with a multimodal therapy approach that includes a specific protocol of almost daily radial extracorporeal shock wave therapy (rESWT) with corresponding data reported in the literature.

Methods

We performed a retrospective analysis of treatments and recovery times of muscle injuries suffered by the players of an elite football team competing in the first/second German Bundesliga during one of the previous seasons.

Results

A total of 20 acute muscle injuries were diagnosed and treated in the aforementioned season, of which eight (40%) were diagnosed as Type 1a/muscular tightness injuries, five (25%) as Type 2b/muscle strain injuries, four (20%) as Type 3a/partial muscle tear injuries and three (15%) as contusions. All injuries were treated with the previously mentioned multimodal therapy approach. Compared with data reported by Ekstrand et al. (Br J Sports Med 47:769–774, 2013), lay-off times (median/mean) were shortened by 54% and 58%, respectively, in the case of Type 1a injuries, by 50% and 55%, respectively, in the case of Type 2b injuries as well as by 8% and 21%, respectively, in the case of Type 3a injuries. No adverse reactions were observed.

Conclusions

Overall, the multimodal therapy approach investigated in this study is a safe and effective treatment approach for treating Type 1a and 2b acute muscle injuries amongst elite football players and may help to prevent more severe, structural muscle injuries.

Exosomes for gene therapy effectively inhibit the endothelial-mesenchymal transition in mouse aortic endothelial cells

Background

Heterotopic ossification (HO) can limit joint activity, causes ankylosis and impairs the function and rehabilitation of patients. Endothelial to mesenchymal transition (EndMT) plays an important role in the pathogenesis of HO, and high expression of SMAD7(Mothers Against Decapentaplegic Homolog 7) in endothelial cells can effectively reverse the TGF-β1 mediated EndMT. This article studied an appropriately engineered exosome with high biocompatibility and good targeting property to administrate SMAD7 gene therapy to inhibit the EndMT.

Methods

Exosomes from mouse aortic endothelial cells were cultured and harvested. DSPE-PEG and antibody CD34 were combined to exosomes to synthesize the endothelial cell targeting exosome vector (Exosome-DSPE-PEG-AbCD34). The biocompatibility, stability, targeting and cell internalization of exosome vector were tested, then the Exosome-DSPE-PEG-AbCD34 was loaded with Smad7 plasmid and administrated to MAECs to examine its therapeutic effect on EndMT of MAEC mediated by TGF-β1.

Results

The Exosome-DSPE-PEG-AbCD34 has no impact on MAEC cell viability at high concentration, and exosome-DSPE-PEG-Ab_CD34 could be stably stored at 4°C and 37°C for at least 8 days. Exosome-DSPE-PEG-Ab_CD34 has better targeting property to MAEC cells and can enter into the cells more effectively. The Exosome-DSPE-PEG-Ab_CD34-Smad7 could significantly increase the level of SMAD7, decrease the expression of TGF-β1, and effectively reverse the EndMT of MAEC mediated by TGF- β1 in MAEC cells.

Conclusions

The synthesized Exosome-DSPE-PEG-AbCD34-Smad7 has good biological properties and can effectively reverse the EndMT of MAEC mediated by TGF-β1. Thus, Exosome-DSPE-PEG-AbCD34-Smad7 may has the potential for the prevention and treatment of HO.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04896-0.

Macrophages in heterotopic ossification: from mechanisms to therapy

Heterotopic ossification (HO) is the formation of extraskeletal bone in non-osseous tissues. It is caused by an injury that stimulates abnormal tissue healing and regeneration, and inflammation is involved in this process. It is worth noting that macrophages are crucial mediators of inflammation. In this regard, abundant macrophages are recruited to the HO site and contribute to HO progression. Macrophages can acquire different functional phenotypes and promote mesenchymal stem cell (MSC) osteogenic differentiation, chondrogenic differentiation, and angiogenesis by expressing cytokines and other factors such as the transforming growth factor-β1 (TGF-β1), bone morphogenetic protein (BMP), activin A (Act A), oncostatin M (OSM), substance P (SP), neurotrophin-3 (NT-3), and vascular endothelial growth factor (VEGF). In addition, macrophages significantly contribute to the hypoxic microenvironment, which primarily drives HO progression. Thus, these have led to an interest in the role of macrophages in HO by exploring whether HO is a "butterfly effect" event. Heterogeneous macrophages are regarded as the "butterflies" that drive a sequence of events and ultimately promote HO. In this review, we discuss how the recruitment of macrophages contributes to HO progression. In particular, we review the molecular mechanisms through which macrophages participate in MSC osteogenic differentiation, angiogenesis, and the hypoxic microenvironment. Understanding the diverse role of macrophages may unveil potential targets for the prevention and treatment of HO.

Rapamycin prevents heterotopic ossification by inhibiting the mTOR pathway and oxidative stress

Rapamycin (RAPA), which was first described as an anti-fungal agent, is a potent immunosuppressant that suppresses tumors and inhibits the mTOR signaling pathway. Heterotopic ossification (HO) is abnormal bone formation outside the skeletal system (e.g., in muscles, tendons, articular capsules and other soft tissues), often due to trauma or injury. There are currently no drugs available to treat traumatic HO, largely due to limited understanding of the disease. In this study, we focused on the role of oxidative stress (OS) in the early stage of traumatic HO, and explored the underlying mechanism of traumatic HO by using RAPA to specifically inhibit the mTOR pathway, which is known to play a role in the pathogenesis of HO. To assess the effects of RAPA in traumatic HO, we used an NSE-BMP4 transgenic mouse model that develops ossification in response to traumatic injury and intramuscular injection of cardiotoxin to initiate injury. These mice were then treated with RAPA or vehicle intraperitoneally every other day for 2 weeks. Our results demonstrate that RAPA can inhibit HO through a number of different mechanisms. We show that OS and a strong inflammatory response contribute to the hypoxia associated with the early stages of HO, and that RAPA inhibits these responses. Furthermore, RAPA reduces the vascularization triggered by mTOR signaling that leads to HO formation. Therefore, we believe that RAPA could be an effective treatment for the early stages of HO.

Are open surgery and total resection good choices for traumatic myositis ossificans in children?

BACKGROUND

Traumatic myositis ossificans is a self-limited, non-neoplastic, ectopic bone formation in the soft tissues caused by trauma. Conservative treatment is the mainstay of management. However, open surgery and complete resection should be considered in patients with limited joint function and constant pain. Herein, we retrospectively analyzed the outcome of open surgical resection in children with myositis ossificans (MO).

METHODS

The data of patients diagnosed with MO between February 2010 and May 2019 were retrospectively analyzed. The clinical data included medical history, physical examination, and laboratory, imaging, and pathological findings. All patients underwent an open surgery and total resection. Radiography findings and joint function were evaluated. Patients with developing complications, such as recurrence and assessing joint function, were followed up. In total, 20 patients (sex, 15 male and 5 female patients; age, 8.1 ± 2.5 years) were included.

RESULTS

MO was located around the elbow, wrist, proximal humerus, and thigh in 13, one, one, and five patients, respectively. All patients were followed up for > 12 months. Two patients had partial recurrence after surgery. One patient with forearm MO had poor elbow function (Broberg-Morrey score of 70). Nineteen patients had good functional outcomes according to the Broberg-Morrey and Cooney methods.

CONCLUSION

Open surgical resection is an effective method for children with MO. The recurrence rate was low when the surgery was performed after the acute stage (1.5 months from disease presentation).

Colloid carcinoma derived from intraductal papillary mucinous neoplasm of the pancreatic head with calcification: A case report and literature review

Background

Colloid carcinoma derived from intraductal papillary mucinous neoplasm (IPMN) of the pancreatic head with prominent calcification is exceedingly rare. Only a few studies about this entity have been reported in the literature. Therefore, its biological behavior, appropriate treatment modalities, and overall patient prognosis remain largely unclear. In this report, we present a case of a resected colloid carcinoma derived from IPMN with prominent calcification. In addition, we review the relevant literature and discuss the clinical management of colloid carcinoma derived from IPMN with prominent calcification, including the histopathological features.

Case presentation

A 75-year-old man presented with a pancreatic tumor measuring 58 mm on the head of the pancreas that was incidentally detected by abdominal ultrasonography. Abdominal computed tomography and endosonography revealed a multilobular cystic lesion with a 17 mm mural nodule in the pancreatic head. Furthermore, prominent calcification was observed on part of the cyst wall. Magnetic resonance cholangiopancreatography showed a multilobular cyst in the branch duct lacking communication between the cystic lesion and the main pancreatic duct. Thus, the lesion was diagnosed as intraductal papillary mucinous carcinoma (IPMC) with a preoperative classification of T1N0M0 stage IA according to the 8th Union for International Cancer Control (UICC) guidelines, and the patient underwent conventional pancreatoduodenectomy. The resected specimen was microscopically found to contain colloid carcinoma, probably derived from IPMN. In addition, marked calcification was confirmed in the partition wall of the cystic mass. The postoperative course was uneventful, and no evidence of recurrence or metastasis was observed after 10 months of follow-up.

Conclusions

We consider that colloid carcinoma derived from IPMN should be differentially diagnosed as a pancreatic multilobular cystic lesion with prominent calcification that shows no sign of systemic chronic pancreatitis.

LncRNA AERRIE Is Required for Sulfatase 1 Expression, but Not for Endothelial-to-Mesenchymal Transition

Endothelial cells can acquire a mesenchymal phenotype through a process called Endothelial-to-Mesenchymal transition (EndMT). This event is found in embryonic development, but also in pathological conditions. Blood vessels lose their ability to maintain vascular homeostasis and ultimately develop atherosclerosis, pulmonary hypertension, or fibrosis. An increase in inflammatory signals causes an upregulation of EndMT transcription factors, mesenchymal markers, and a decrease in endothelial markers. In our study, we show that the induction of EndMT results in an increase in long non-coding RNA AERRIE expression. JMJD2B, a known EndMT regulator, induces AERRIE and subsequently SULF1. Silencing of AERRIE shows a partial regulation of SULF1 but showed no effect on the endothelial and mesenchymal markers. Additionally, the overexpression of AERRIE results in no significant changes in EndMT markers, suggesting that AERRIE is marginally regulating mesenchymal markers and transcription factors. This study identifies AERRIE as a novel factor in EndMT, but its mechanism of action still needs to be elucidated.

Burn-induced heterotopic ossification from incidence to therapy: key signaling pathways underlying ectopic bone formation

Burn injury is one of the potential causes of heterotopic ossification (HO), which is a rare but debilitating condition. The incidence ranges from 3.5 to 5.6 depending on body area. Burns that cover a larger percentage of the total body surface area (TBSA), require skin graft surgeries, or necessitate pulmonary intensive care are well-researched risk factors for HO. Since burns initiate such complex pathophysiological processes with a variety of molecular signal changes, it is essential to focus on HO in the specific context of burn injury to define best practices for its treatment. There are numerous key players in the pathways of burn-induced HO, including neutrophils, monocytes, transforming growth factor-β1-expressing macrophages and the adaptive immune system. The increased inflammation associated with burn injuries is also associated with pathway activation. Neurological and calcium-related contributions are also known. Endothelial-to-mesenchymal transition (EMT) and vascularization are known to play key roles in burn-induced HO, with hypoxia-inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) as potential initiators. Currently, non-steroidal anti-inflammatory drugs (NSAIDs) and radiotherapy are effective prophylaxes for HO. Limited joint motion, ankylosis and intolerable pain caused by burn-induced HO can be effectively tackled via surgery. Effective biomarkers for monitoring burn-induced HO occurrence and bio-prophylactic and bio-therapeutic strategies should be actively developed in the future.

Post-traumatic myositis ossificans: a benign lesion that simulates malignant bone and soft tissue tumours

Myositis ossificans (MO) is a benign bone formation in an extra-skeletal location. The most common subtype of MO, the post-traumatic, usually develops in young males after a traumatic event or sports injury.MO may simulate malignant bone lesions such as extra-skeletal or surface osteosarcomas, or soft tissue sarcomas such as synovial sarcoma or undifferentiated pleomorphic sarcoma. In the early phase the diagnosis of MO is challenging because imaging and histopathological findings may be non-characteristic.Detailed medical history as well as clinical examination, follow-up imaging studies and histological assessment are crucial for a proper diagnosis. Early and accurate differential diagnosis between MO and malignant soft tissue and bone tumours is important to maximize. Cite this article: EFORT Open Rev 2021;6:572-583. DOI: 10.1302/2058-5241.6.210002.

Tissue interactions are indispensable for cavity formation and disc separation in the temporomandibular joint

Purpose: Our previous study found that in the temporomandibular joint (TMJ) of the K14-cre; Ctnnb1^ex3f mouse embryo, the morphogenesis of glenoid fossa was interrupted by the dislocated condyle. This observation suggested that the formation of the glenoid fossa required tissue interactions with condylar mesenchyme. The purpose of this study was to clarify if the interactions between other components are essential for TMJ morphogenesis.Materials and methods: We examined the gross morphology, histology, cell proliferation, and gene expression in the developing TMJ of K14-cre; Ctnnb1^ex3f mice by whole-mount bone and cartilage staining, Azon staining, BrdU labeling, and in situ hybridization, respectively.Results: In K14-cre; Ctnnb1^ex3f mice, the zygomatic arch was misconnected to the mandibular bone by ectopic bone formation, which disrupted the attachment of temporalis to the mandibular bone and joint capsule formation. Although the initiation and differentiation of the condylar cartilage were slightly impacted, the K14-cre; Ctnnb1^ex3f TMJ lacked joint cavities and separated disc, suggesting that the tissue interactions between the joint capsule and the TMJ were indispensable for the cavity formation and disc separation. The ectopic activation of Gli2 in the cells occupying the cavities, and the enhanced PTHrP transcription in the condylar perichondrium of the K14-cre; Ctnnb1^ex3f TMJ suggested that the disrupted interactions between the joint capsule and the TMJ impaired cavity formation and disc separation by altering Hh signaling.Conclusion: Joint capsule formation was essential for cavity formation and disc separation during TMJ development.

Inhibition of IL-17 prevents the progression of traumatic heterotopic ossification

Traumatic heterotopic ossification (HO) is the abnormal formation of bone in soft tissues as a consequence of injury. However, the pathological mechanisms leading to traumatic HO remain unknown. Here, we report that aberrant expression of IL-17 promotes traumatic HO formation by activating β-catenin signalling in mouse model. We found that elevated IL-17 and β-catenin levels are correlated with a high degree of HO formation in specimens from patients and HO animals. We also show that IL-17 initiates and promotes HO progression in mice. Local injection of an IL-17 neutralizing antibody attenuates ectopic bone formation in a traumatic mouse model. IL-17 enhances the osteoblastic differentiation of mesenchymal stem cells (MSCs) by activating β-catenin signalling. Moreover, inhibition of IL-17R or β-catenin signalling by neutralizing antibodies or drugs prevents the osteogenic differentiation of isolated MSCs and decreases HO formation in mouse models. Together, our study identifies a novel role for active IL-17 as the inducer and promoter of ectopic bone formation and suggests that IL-17 inhibition might be a potential therapeutic target in traumatic HO.

Myositis ossificans causing ulnar neuropathy: a case report

Myositis ossificans (MO) can compress peripheral nerves and cause neuropathy. We herein describe a patient with ulnar neuropathy caused by MO at the medial elbow. A 28-year-old man with a drowsy mentality and multiple organ damage following a traffic accident was admitted to our hospital. After 3 weeks of postoperative care, the patient’s mental status recovered. However, he complained of severe sharp pain in his left medial forearm and fourth and fifth fingers. He exhibited weak fifth finger abduction and wrist adduction. Severe elbow joint pain was elicited during range-of-motion testing of his left elbow. Ultrasound also showed an edematous, enlarged, hypoechoic ulnar nerve lying above the MO, and the MO outwardly displaced the ulnar nerve. Elbow radiographic examination, computed tomography, and magnetic resonance imaging revealed MO development and compression of the left ulnar nerve. The patient underwent surgery; the following day, his left medial forearm pain completely disappeared with slight improvement in the motor weakness of fifth finger abduction. Ultrasound is a useful tool to easily evaluate the presence of MO and compression of peripheral nerves caused by MO.

Chondrogenesis mediates progression of ankylosing spondylitis through heterotopic ossification

Ankylosing spondylitis (AS) is chronic inflammatory arthritis with a progressive fusion of axial joints. Anti-inflammatory treatments such as anti-TNF-α antibody therapy suppress inflammation but do not effectively halt the progression of spine fusion in AS patients. Here we report that the autoimmune inflammation of AS generates a microenvironment that promotes chondrogenesis in spine ligaments as the process of spine fusion. Chondrocyte differentiation was observed in the ligaments of patients with early-stage AS, and cartilage formation was followed by calcification. Moreover, a large number of giant osteoclasts were found in the inflammatory environment of ligaments and on bony surfaces of calcified cartilage. Resorption activity by these giant osteoclasts generated marrow with high levels of active TGF-β, which induced new bone formation in the ligaments. Notably, no Osterix+ osteoprogenitors were found in osteoclast resorption areas, indicating uncoupled bone resorption and formation. Even at the late and maturation stages, the uncoupled osteoclast resorption in bony interspinous ligament activates TGF-β to induce the progression of ossification in AS patients. Osteoclast resorption of calcified cartilage-initiated ossification in the progression of AS is a similar pathologic process of acquired heterotopic ossification (HO). Our finding of cartilage formation in the ligaments of AS patients revealed that the pathogenesis of spinal fusion is a process of HO and explained why anti-inflammatory treatments do not slow ankylosing once there is new bone formation in spinal soft tissues. Thus, inhibition of HO formation, such as osteoclast activity, cartilage formation, or TGF-β activity could be a potential therapy for AS.

The Surgical Management of the Rare Neurogenic Myositis Ossificans of the Hip: A Report of 3 Cases

Introduction:

Myositis ossificans (MO) is a benign non-neoplastic condition in which heterotopic bone formation occurs in soft tissues. Neurogenic MO is one variant of MO where the lesion is a result of neurological disorders, including brain and spinal cord injuries, especially when followed by immobility and spasticity. MO can also be a result of direct trauma or even genetic mutations.

Case Report:

We present three cases of young men (16, 37, and 22-year-old) who developed MO of the hip joint following brain or spinal cord injuries. One of them had also sustained a direct trauma to the affected hip joint at the time of the accident. All three patients presented with inability to walk independently due to diminished range of motion at the affected joint. X-rays and computerized tomography (CT) scans with 3-dimentional (3D) reconstruction suggested the diagnosis of MO, but the serum alkaline phosphatase was within normal limits at the time of presentation. The first case had bilateral involvement with unmistakable separation between the heterotopic bone formation and the frank hip joints on CT. This patient underwent successful staged excision of the ossifications. The second patient had unilateral hip joint involvement with the absence of clear separation between the heterotopic bone formation and the hip joint, thus, underwent total hip replacement for the affected side as excision was not possible. The third patienthad unilateral hip joint involvement and underwent excision of the ossification with dynamic hip screw insertion after sustaining a stable intertrochanteric fracture intraoperatively. Postoperatively, all three patients received physiotherapy and oral indomethacin. Upon recovery, they were able to walk independently with a near-normal range of motion at the hip joint. There was no evidence of recurrence upon follow-up visits, and CT scans in patients I and II. Follow-ups for patient III were not possible as the patient died 1 month after surgery due to pulmonary embolism.

Conclusion:

The surgical management of MO is indicated when non-operative methods fail to provide an adequate range of motion around the hip joint. Pre-operative assessment utilizing 3D-CT scans proved to be essential in dictating the appropriate surgical approach. During post-operative follow-ups, the physiotherapy and oral indomethacin provided additional improvement in outcome and patients’ satisfaction.

Melatonin Promotes Heterotopic Ossification Through Regulation of Endothelial-Mesenchymal Transition in Injured Achilles Tendons in Rats

Although heterotopic ossification (HO) has been reported to be a common complication of the posttraumatic healing process, the underlying mechanism remains unknown. Endothelial-mesenchymal transition (EndMT) is known to play a role in HO, and our recent study observed that neuroendocrine signals can promote HO by modulating EndMT. Melatonin, a neuroendocrine hormone secreted mainly by the pineal gland, has been documented to perform its function in the skeletal system. This study aimed at describing the expression of melatonin during the formation of HO in rat models of Achilles tendon injury and to further investigate its role in regulating EndMT in HO. Histological staining revealed the expression of melatonin throughout the formation of heterotopic bone in injured Achilles tendons, and the serum melatonin levels were increased after the initial injury. Double immunofluorescence showed that the MT2 melatonin receptor was notably expressed at the sites of injury. Micro-CT showed the enhancement of heterotopic bone volume and calcified areas in rats treated with melatonin. Additionally, our data showed that melatonin induced EndMT in primary rat aortic endothelial cells (RAOECs), which acquired traits including migratory function, invasive function and EndMT and MSC marker gene and protein expression. Furthermore, our data exhibited that melatonin promoted the osteogenic differentiation of RAOECs undergoing EndMT in vitro. Importantly, inhibition of the melatonin-MT2 pathway by using the MT2 selective inhibitor 4-P-PDOT inhibited melatonin-induced EndMT and osteogenesis both in vivo and in vitro. In conclusion, these findings demonstrated that melatonin promoted HO through the regulation of EndMT in injured Achilles tendons in rats, and these findings might provide additional directions for the management of HO.

Neurological heterotopic ossification: novel mechanisms, prognostic biomarkers and prophylactic therapies

Neurological heterotopic ossification (NHO) is a debilitating condition where bone forms in soft tissue, such as muscle surrounding the hip and knee, following an injury to the brain or spinal cord. This abnormal formation of bone can result in nerve impingement, pain, contractures and impaired movement. Patients are often diagnosed with NHO after the bone tissue has completely mineralised, leaving invasive surgical resection the only remaining treatment option. Surgical resection of NHO creates potential for added complications, particularly in patients with concomitant injury to the central nervous system (CNS). Although recent work has begun to shed light on the physiological mechanisms involved in NHO, there remains a significant knowledge gap related to the prognostic biomarkers and prophylactic treatments which are necessary to prevent NHO and optimise patient outcomes. This article reviews the current understanding pertaining to NHO epidemiology, pathobiology, biomarkers and treatment options. In particular, we focus on how concomitant CNS injury may drive ectopic bone formation and discuss considerations for treating polytrauma patients with NHO. We conclude that understanding of the pathogenesis of NHO is rapidly advancing, and as such, there is the strong potential for future research to unearth methods capable of identifying patients likely to develop NHO, and targeted treatments to prevent its manifestation.

The role of bone morphogenetic protein signaling in vascular calcification

Vascular calcification is associated with atherosclerosis, chronic kidney disease, and diabetes, and results from processes resembling endochondral or intramembranous ossification, or from processes that are distinct from ossification. Bone morphogenetic proteins (BMP), as well as other ligands, receptors, and regulators of the transforming growth factor beta (TGFβ) family regulate vascular and valvular calcification by modulating the phenotypic plasticity of multipotent progenitor lineages associated with the vasculature or valves. While osteogenic ligands BMP2 and BMP4 appear to be both markers and drivers of vascular calcification, particularly in atherosclerosis, BMP7 may serve to protect against calcification in chronic kidney disease. BMP signaling regulators such as matrix Gla protein and BMP-binding endothelial regulator protein (BMPER) play protective roles in vascular calcification. The effects of BMP signaling molecules in vascular calcification are context-dependent, tissue-dependent, and cell-type specific. Here we review the current knowledge on mechanisms by which BMP signaling regulates vascular calcification and the potential therapeutic implications.

Myositis ossificans mimicking sarcoma: a not so rare bioptic diagnostic pitfall

Background

Myositis ossificans (MO) is a heterotopic bone formation in soft tissues, usually caused by traumas or neuropathies. Although the aetiology remains unclear, MO is supposed to be an osteoblast metaplasia with a benign and self-limiting course. Remarkably, at onset MO can be clinically, radiologically and histologically indistinguishable to soft tissue malignancies, especially in cases lacking a history of trauma, leading to misdiagnoses and improper treatments.

Case presentation

A 13-year-old male was referred to the Oncology Department because of a previous diagnosis of osteogenic sarcoma of his left thigh. The diagnosis was made upon a history of isolated thigh pain in the absence of traumas, the evidence of a contrast-enhanced soft tissue mass on magnetic resonance imaging and the histological findings of atypical nuclei and mitotic figures. The lesion was eventually radiologically unchanged after five cycles of chemotherapy; thus, the child was referred for radical surgery. At admission, endorsing the child well-appearance, together with the evidence of a reduced calcified lesion on a further magnetic resonance, a clinical suspicion of myositis ossificans was raised. Hence, the excisional biopsy confirmed the pathognomonic zonal pattern of myositis ossificans.

Conclusions

This case highlights some frequent diagnostic pitfalls facing myositis ossificans. A lacking history of traumas, along with a too early radiological and histological evaluation can lead to a misdiagnosis of soft tissue malignancies. Even in the absence of a clear history of trauma, a painful soft tissue swelling with a benign clinical course should raise the suspicion of myositis ossificans.

Bone Marrow Microvasculature

The skeleton is highly vascularized due to the various roles blood vessels play in the homeostasis of bone and marrow. For example, blood vessels provide nutrients, remove metabolic by-products, deliver systemic hormones, and circulate precursor cells to bone and marrow. In addition to these roles, bone blood vessels participate in a variety of other functions. This article provides an overview of the afferent, exchange and efferent vessels in bone and marrow and presents the morphological layout of these blood vessels regarding blood flow dynamics. In addition, this article discusses how bone blood vessels participate in bone development, maintenance, and repair. Further, mechanical loading-induced bone adaptation is presented regarding interstitial fluid flow and pressure, as regulated by the vascular system. The role of the sympathetic nervous system is discussed in relation to blood vessels and bone. Finally, vascular participation in bone accrual with intermittent parathyroid hormone administration, a medication prescribed to combat age-related bone loss, is described and age- and disease-related impairments in blood vessels are discussed in relation to bone and marrow dysfunction. © 2020 American Physiological Society. Compr Physiol 10:1009-1046, 2020.

Stimulating Factors and Origins of Precursor Cells in Traumatic Heterotopic Ossification Around the Temporomandibular Joint in Mice

The contributing factors and the origins of precursor cells in traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ), which causes obvious restriction of mouth opening and maxillofacial malformation, remain unclear. In this study, our findings demonstrated that injured chondrocytes in the condylar cartilage, but not osteoblasts in the injured subchondral bone, played definite roles in the development of THO-TMJ in mice. Injured condylar chondrocytes without articular disc reserves might secrete growth factors, such as IGF1 and TGFβ2, that stimulate precursor cells, such as endothelial cells and muscle-derived cells, to differentiate into chondrocytes or osteoblasts and induce THO-TMJ. Preserved articular discs can alleviate the pressure on the injured cartilage and inhibit the development of THO-TMJ by inhibiting the secretion of these growth factors from injured chondrocytes. However, the exact molecular relationships among trauma, the injured condylar cartilage, growth factors such as TGFβ2, and pressure need to be explored in detail in the future.

The Survey of Cells Responsible for Heterotopic Ossification Development in Skeletal Muscles-Human and Mouse Models

Heterotopic ossification (HO) manifests as bone development in the skeletal muscles and surrounding soft tissues. It can be caused by injury, surgery, or may have a genetic background. In each case, its development might differ, and depending on the age, sex, and patient's conditions, it could lead to a more or a less severe outcome. In the case of the injury or surgery provoked ossification development, it could be, to some extent, prevented by treatments. As far as genetic disorders are concerned, such prevention approaches are highly limited. Many lines of evidence point to the inflammatory process and abnormalities in the bone morphogenetic factor signaling pathway as the molecular and cellular backgrounds for HO development. However, the clear targets allowing the design of treatments preventing or lowering HO have not been identified yet. In this review, we summarize current knowledge on HO types, its symptoms, and possible ways of prevention and treatment. We also describe the molecules and cells in which abnormal function could lead to HO development. We emphasize the studies involving animal models of HO as being of great importance for understanding and future designing of the tools to counteract this pathology.

The effect of celecoxib in traumatic heterotopic ossification around temporomandibular joint in mice

OBJECTIVE

In this study, the role of inflammation in traumatic heterotopic ossification around temporomandibular joint (THO-TMJ), as well as the preventive and treatment effect of celecoxib in THO-TMJ both in vivo and in vitro were explored.

DESIGN

A surgically-induced THO-TMJ mouse model and a co-culture model of ATDC-5 or MC3T3-E1 and RAW-264.7 cells were used in this study for in vivo and in vitro research.

RESULTS

A series of inflammatory factors, such as CD3, CD68, CD20, IL-10, IL-6 and TNF-α, were activated 48 h after trauma in a THO-TMJ model. Local trauma initiated systemic inflammatory responses as well as T cell- and macrophage-mediated local inflammatory responses around TMJ. In addition, expression of COX-2 was significantly elevated. The findings also showed that local injection of celecoxib could effectively alleviate the inflammatory response around TMJ at the early stage of trauma and inhibit the formation of THO-TMJ in vivo. Meanwhile, celecoxib could inhibit chondrogenic differentiation of ATDC-5 and osteogenic differentiation of MC3T3-E1 under inflammatory condition in vitro. Furthermore, celecoxib could inhibit the expression of Bmpr1b in the injured condylar cartilage at the initiation stage of THO-TMJ, which implied that Bmpr1b expressed by the residual condylar cartilage might be related to the pathogenesis of THO-TMJ.

CONCLUSIONS

Inflammation played a crucial role in the pathogenesis of THO-TMJ, and anti-inflammation might be a possible choice to inhibit THO-TMJ, which provided scientific clues for the mechanisms, pharmacotherapy and molecular intervention of THO-TMJ.

Development of Bilateral Heterotopic Ossification After Survival of Life Threatening Purpura Fulminans

Heterotopic ossification has been reported in patients who have undergone traumatic amputations, burn injuries, and total hip arthroplasty; however, the incidence of heterotopic ossification following purpura fulminans has only been reported in one case with unilateral involvement. Here we present a bilateral lower extremity case of heterotopic ossification as sequelae of purpura fulminans. 

A 34-year-old male smoker with a past medical history of stab wounds to the chest and abdomen requiring emergent exploratory laparotomy, diaphragmatic repair, and splenectomy 15 years ago presented to the emergency department with a rapid onset of high fevers, chills and myalgia. He did not receive post-splenectomy prophylactic vaccinations for Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. The patient presented clinically in septic shock with disseminated intravascular coagulation. The patient was admitted to the Medical Intensive Care Unit and subsequent workup suggested Streptococcus pneumoniae bacteremia. Over the next 48 hours, the patient developed extensive necrosis of the bilateral upper and lower extremities concerning for purpura fulminans. The decision was made to perform a right transradial forearm amputation as well as bilateral transtibial amputations. He tolerated these procedures and was discharged to an inpatient rehabilitation facility. Approximately four months following his bilateral below knee amputations, the patient had difficulty wearing the prosthetics secondary to pain and eventually discontinued use altogether. At home, he continued to ambulate by bearing weight on his knees while wearing kneepads. He continued to report significant tenderness and pain along the bilaterally, below knee amputation stumps. His physical examination was concerning for significant distal bone formation in his bilateral amputation stump sites without evidence of skin breakdown. Intraoperatively, extensive bony formation was found bilaterally within his soleus muscle flaps, concerning for heterotopic ossification. Postoperatively, the patient was refitted for lower extremity prosthetics. 

Similar to burns and trauma, the development of heterotopic ossification in patients with purpura fulminans may be directly related to the inflammatory process and amount of tissue damage. In some cases, heterotopic ossification could be caused from daily living activities, so the timing of diagnostic imaging techniques and clinical intervention is crucial.

Molecular and Cellular Mechanisms that Induce Arterial Calcification by Indoxyl Sulfate and P-Cresyl Sulfate

The protein-bound uremic toxins, indoxyl sulfate (IS) and p-cresyl sulfate (PCS), are considered to be harmful vascular toxins. Arterial media calcification, or the deposition of calcium phosphate crystals in the arteries, contributes significantly to cardiovascular complications, including left ventricular hypertrophy, hypertension, and impaired coronary perfusion in the elderly and patients with chronic kidney disease (CKD) and diabetes. Recently, we reported that both IS and PCS trigger moderate to severe calcification in the aorta and peripheral vessels of CKD rats. This review describes the molecular and cellular mechanisms by which these uremic toxins induce arterial media calcification. A complex interplay between inflammation, coagulation, and lipid metabolism pathways, influenced by epigenetic factors, is crucial in IS/PCS-induced arterial media calcification. High levels of glucose are linked to these events, suggesting that a good balance between glucose and lipid levels might be important. On the cellular level, effects on endothelial cells, which act as the primary sensors of circulating pathological triggers, might be as important as those on vascular smooth muscle cells. Endothelial dysfunction, provoked by IS and PCS triggered oxidative stress, may be considered a key event in the onset and development of arterial media calcification. In this review a number of important outstanding questions such as the role of miRNA’s, phenotypic switching of both endothelial and vascular smooth muscle cells and new types of programmed cell death in arterial media calcification related to protein-bound uremic toxins are put forward and discussed.

The Vicious Cycle of Arterial Stiffness and Arterial Media Calcification

Arterial media calcification and arterial stiffness are independent predictors of cardiovascular mortality. Both processes reinforce one another, creating a vicious cycle in which transdifferentiation of endothelial cells and vascular smooth muscle cells play a central role. Physiological functioning of vascular smooth muscle cells in the arterial medial layer greatly depends on normal endothelial cell behavior. Endothelial or intimal layer cells are the primary sensors of pathological triggers circulating in the blood during, for example, ageing or inflammation, and often can be seen as initiators of this vicious cycle. As such, the search for treatment of arterial media calcification, which until now has been mainly concentrated at the level of the vascular smooth cell, may need to be expanded to intimal layer targets.

Molecular Pathophysiology of Ossification of the Posterior Longitudinal Ligament (OPLL)

Ossification of the posterior longitudinal ligament (OPLL) can be defined as an ectopic ossification in the tissues of spinal ligament showing a hyperostotic condition. OPLL is developed mostly in the cervical spine and clinical presentations of OPLL are majorly myelopathy and/or radiculopathy, with serious neurological pathology resulting in paralysis of extremities and disturbances of motility lowering the quality of life. OPLL is known to be an idiopathic and multifactorial disease, which genetic factors and non-genetic factors including diet, obesity, physical strain on the posterior longitudinal ligament, age, and diabetes mellitus, are involved into the pathogenesis. Up to now, surgical management by decompressing the spinal cord is regarded as standard treatment for OPLL, although there might be the risk of development of reprogression of ossification. The molecular pathogenesis and efficient therapeutic strategy, especially pharmacotherapy and/or preventive intervention, of OPLL has not been clearly elucidated and suggested. Therefore, in this review, we tried to give an overview to the present research results on OPLL, in order to shed light on the potential pharmacotherapy based on molecular pathophysiologic aspect of OPLL, especially on the genetic/genomic factors involved into the etiology of OPLL.

Endothelial to Mesenchymal Transition: Role in Physiology and in the Pathogenesis of Human Diseases

Numerous studies have demonstrated that endothelial cells are capable of undergoing endothelial to mesenchymal transition (EndMT), a newly recognized type of cellular transdifferentiation. EndMT is a complex biological process in which endothelial cells adopt a mesenchymal phenotype displaying typical mesenchymal cell morphology and functions, including the acquisition of cellular motility and contractile properties. Endothelial cells undergoing EndMT lose the expression of endothelial cell-specific proteins such as CD31/platelet-endothelial cell adhesion molecule, von Willebrand factor, and vascular-endothelial cadherin and initiate the expression of mesenchymal cell-specific genes and the production of their encoded proteins including α-smooth muscle actin, extra domain A fibronectin, N-cadherin, vimentin, fibroblast specific protein-1, also known as S100A4 protein, and fibrillar type I and type III collagens. Transforming growth factor-β1 is considered the main EndMT inducer. However, EndMT involves numerous molecular and signaling pathways that are triggered and modulated by multiple and often redundant mechanisms depending on the specific cellular context and on the physiological or pathological status of the cells. EndMT participates in highly important embryonic development processes, as well as in the pathogenesis of numerous genetically determined and acquired human diseases including malignant, vascular, inflammatory, and fibrotic disorders. Despite intensive investigation, many aspects of EndMT remain to be elucidated. The identification of molecules and regulatory pathways involved in EndMT and the discovery of specific EndMT inhibitors should provide novel therapeutic approaches for various human disorders mediated by EndMT.

Identification of reference genes for quantitative PCR during C3H10T1/2 chondrogenic differentiation

C3H10T1/2, a mouse mesenchymal stem cell line, is a well-known in vitro model of chondrogenesis that can be easily employed to recapitulate some of the mechanisms intervening in this process. Moreover, these cells can be used to validate the effect of candidate molecules identified by high throughput screening approaches applied to the development of targeted therapy for human disorders in which chondrogenic differentiation may be involved, as in conditions characterized by heterotopic endochondral bone formation. Chondrogenic differentiation of C3H10T1/2 cells can be monitored by applying quantitative polymerase chain reaction (qPCR), one of the most sensitive methods that allows detection of small dynamic changes in gene expression between samples obtained under different experimental conditions. In this work, we have used qPCR to monitor the expression of specific markers during chondrogenic differentiation of C3H10T1/2 cells in micromass cultures. Then we have applied the geNorm approach to identify the most stable reference genes suitable to get a robust normalization of the obtained expression data. Among 12 candidate reference genes (Ap3d1, Csnk2a2, Cdc40, Fbxw2, Fbxo38, Htatsf1, Mon2, Pak1ip1, Zfp91, 18S, ActB, GAPDH) we identified Mon2 and Ap3d1 as the most stable ones during chondrogenesis. ActB, GAPDH and 18S, the most commonly used in the literature, resulted to have an expression level too high compared to the differentiation markers (Sox9, Collagen type 2a1, Collagen type 10a1 and Collagen type 1a1), therefore are actually less recommended for these experimental conditions. In conclusion, we identified nine reference genes that can be equally used to obtain a robust normalization of the gene expression variation during the C3H10T1/2 chondrogenic differentiation.

Neurotrophin-3 acts on the endothelial-mesenchymal transition of heterotopic ossification in rats

Despite the fact that extensive studies have focused on heterotopic ossification (HO), its molecular mechanism remains unclear. The endothelial-mesenchymal transition (EndMT), which may be partially modulated by neuroendocrine cytokines is thought to play a major role in HO. Neurotrophin-3 (NT-3), which has neuroendocrine characteristics is believed to promote skeletal remodeling. Herein, we suggest that that NT-3 may promote HO formation through regulation of EndMT. Here, we used an in vivo model of HO and an in vitro model of EndMT induction to elucidate the effect and underlying mechanism of NT-3 on EndMT in HO. Our results showed that heterotopic bone and cartilage arose from EndMT and NT-3 promoted HO formation in vivo. Our in vitro results showed that NT-3 up-regulated mesenchymal markers (FSP-1, α-SMA and N-cadherin) and mesenchymal stem cell (MSC) markers (STRO-1, CD44 and CD90) and down-regulated endothelial markers (Tie-1, VE-cadherin and CD31). Moreover, NT-3 enhanced a chondrogenesis marker (Sox9) and osteogenesis markers (OCN and Runx2) via activation of EndMT. However, both EndMT specific inhibitor and tropomyosin-related kinase C (TrkC) specific inhibitor rescued NT-3-induced HO formation and EndMT induction in vivo and in vitro. In conclusion, our findings demonstrate that NT-3 promotes HO formation via modulation of EndMT both in vivo and in vitro, which offers a new potential target for the prevention and therapy of HO.