Search Results (153)

Trauma-induced heterotopic ossification (tHO) is characterized by aberrant ectopic bone formation in soft tissue following high-energy trauma, affecting >60% of combat-related amputees and >50% of major burn patients. Current prophylactic strategies (including NSAIDs, bisphosphonates, and low-dose radiation) lack mechanistic specificity, carry significant side effects, and surgical excision carries a 27% recurrence rate. This review reframes tHO pathogenesis through the neural–immune axis, arguing that ectopic bone formation is a downstream consequence of dysregulated neuroimmune signaling rather than a primary osteogenic event. Following trauma, nociceptor activation drives nociception-induced neural inflammation (NINI), releasing substance P (SP) and calcitonin gene-related peptide (CGRP), which disrupts the blood–nerve barrier, mobilizes neural crest-derived progenitor cells, and, alongside BMP-2/SMAD1/5/8 signaling and M1-polarized macrophage activation, establishes a permissive osteogenic microenvironment. A BMP-2/CGRP positive feedback loop sustains aberrant osteogenesis, converging on osteogenic transcription factors Runx2, SOX5/6/9, and Osterix. Dysregulated noncoding RNAs represent promising pre-radiographic biomarkers. This neural–immune framework motivates mechanism-based therapeutic strategies targeting CGRP (fremanezumab, erenumab), SP/NK1 signaling (aprepitant), and macrophage polarization (metformin, palovarotene, rapamycin), with multi-node combination approaches tailored to the temporal stages of tHO offering the most promise for precision prophylaxis. Full article

Large bone defects resulting from trauma, tumor resection, infection, or degenerative diseases pose a major clinical challenge in orthopedic surgery and regenerative medicine. Despite advances in biomaterials and surgical techniques, successful outcomes are often compromised by poor vascularization, limited osteoinduction, and donor-site morbidity associated with autografts or allografts. However, conventional delivery systems suffer from burst release, rapid clearance, off-target effects, and supraphysiologic dosing, which can lead to undesirable complications such as ectopic ossification and inflammation, with some reports raising concerns about the long-term tumorigenic risk. Heparin, a naturally highly sulfated glycosaminoglycan structurally related to heparan sulfate, has emerged as a particularly attractive candidate for affinity-based biomaterial systems. It naturally binds over 300 growth factors, including bone morphogenetic proteins. By protecting these proteins from enzymatic degradation, enhancing their bioavailability, and mediating receptor clustering, heparin provides both biochemical stability and biofunctional modulation. This review provides a comprehensive overview of heparin-based delivery strategies in bone tissue engineering. We begin by describing the biological functions of heparin in modulating growth factor activity. We then discuss in detail the different heparin-based biomaterials designed to sustain the release of growth factors for bone tissue engineering, including the heparin–polycation coacervate system; heparin-based supramolecules; and heparin-based hydrogels, nanoparticles, and microspheres for sustained release of bone morphogenic proteins and other growth factors for bone tissue engineering. Finally, we assess the clinical and translational relevance of heparin-based systems, identify key challenges, and outline future perspectives, highlighting the potential of these biomaterials for providing safer and more effective therapies for bone regeneration. Full article

(1) Heterotopic ossification (HO) is a pathological process characterized by ectopic bone formation in soft tissues, often following trauma or neurological injury, and is associated with spasticity and chronic inflammation. Mesenchymal stem cells (MSCs) play a central role in HO by differentiating into osteoblasts through endochondral or intramembranous ossification, while alternative fates such as adipogenesis are suppressed. In this study, we investigated the effects of two commonly used antispastic drugs, baclofen and tizanidine, on MSC differentiation under adipogenic and inflammatory conditions in vitro. (2) Mouse C3H10T1/2 MSCs were cultured and induced toward adipogenesis in the presence of baclofen or tizanidine, and inflammatory stimuli (Interleukin-1β or lipopolysaccharides) were applied where indicated. Gene expressions of adipogenic and osteochondrogenic markers were assessed by RT-qPCR, while osteopontin protein levels were quantified by Simple Western. (3) Baclofen treatment significantly inhibited adipogenic gene expression and promoted osteochondrogenic markers and osteopontin protein under basal conditions, whereas tizanidine had minimal effects. Under inflammatory conditions, baclofen partially suppressed adipogenesis but did not strongly induce osteochondrogenesis. (4) These findings indicate that baclofen can directly modulate MSC fate, potentially contributing to HO risk, while tizanidine may offer a safer alternative for spasticity management in patients at risk of ectopic bone formation. Full article

During aging, bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) shift their lineage commitment away from osteogenesis and towards adipogenesis, resulting in bone loss and marrow fat accumulation. We previously reported that during osteogenesis, BMSCs activate mitochondrial oxidative phosphorylation (OXPHOS) at least in part by downregulating cyclophilin D (CypD) expression and, consequently, mitochondrial permeability transition pore (MPTP) activity. We also reported that in contrast, during adipogenesis, BMSCs upregulate CypD and MPTP, activate glycolysis and inhibit OXPHOS. To further study the role of CypD in BMSC bioenergetics, adipogenesis and bone marrow fat accumulation, we used CypD loss-of-function (LOF) or gain-of-function (GOF) models in osteo-adipoprogenitors in vitro and in vivo. We found that CypD LOF and GOF are associated with impaired and enhanced BMSC adipogenesis, respectively, both in vitro and in ectopic bone grafts in vivo. In addition, bioenergetic profiling and metabolomic analyses show evidence of corresponding metabolic reprogramming in CypD LOF and GOF cells. In summary, our study demonstrates the role of CypD-regulated mitochondrial metabolism during BMSC adipogenesis, facilitating the understanding of stem cell fate determination and the molecular mechanism of age-related bone loss as well as bone marrow fat accumulation. Full article

Background/Objectives: Cells derived from direct chemical reprogramming into osteoblasts represent a promising source for bone regeneration, but the efficiency needs improvement. Here, we systematically evaluated whether the natural compound psoralen (Psr) could enhance this process and explored its therapeutic potential and mechanism of action. Methods: Mouse embryonic fibroblasts (MEFs) were treated with a cocktail of forskolin and phenamil (FP), supplemented with Psr. In vitro differentiation was assessed by alkaline phosphatase and Alizarin Red S staining, reverse transcription quantitative PCR, immunofluorescence and Western blot. The bone-regenerative potential of the derived chemically induced osteoblast-like cells (ciOBs) was evaluated in critical-sized calvarial defects, femoral cortical defects and a subcutaneous ectopic implantation model, using micro-computed tomography and histology. Mechanistic insights of Psr were gained by analyzing the adenylyl cyclase 9 (ADCY9)/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/cAMP response element-binding protein (CREB) axis using inhibitor SQ22536. Results: Psr acted synergistically with the FP cocktail to drive efficient osteogenic reprogramming of MEFs. At an optimal concentration of 25 μM, Psr enabled the most robust induction of early osteogenic markers and generation of mature, mineralizing ciOBs in vitro. In vivo, FP + Psr-induced ciOBs repaired critical-sized calvarial and femoral cortical defects and generated substantial, vascularized bone tissue in ectopic sites. Mechanistically, Psr co-treatment potently activated the ADCY9/cAMP/PKA/CREB pathway, and pharmacological inhibition of this pathway completely abolished the pro-osteogenic effects of Psr. Conclusions: Psr acts as a potent synergistic enhancer of direct chemical reprogramming, generating functional osteoblast-like cells with robust bone-regenerative capacity via activation of the ADCY9/cAMP/PKA/CREB pathway. Full article

Background/Objectives: In humans, diseases such as oral cancer may require surgical amputation of the jaw. This severe disruption causes impairments in eating, swallowing, and speech, leading to a significant decline in quality of life. In contrast, newts, a group of urodele amphibians, can regenerate their jaws even in adulthood. This study explored how adult newts reconstruct lower jaws after substantial loss and clarified how this process contributes to rapid functional recovery when feeding becomes impossible. Methods: Adult Japanese fire-bellied newts (Cynops pyrrhogaster) underwent surgical amputation of the anterior half of their lower jaws. Regeneration was monitored for 64 weeks using histological analyses of bone, cartilage, and dental tissues and micro-computed tomography (micro-CT)-based osteomorphometry to quantify structural changes in the regenerating lower jaw. Results: Histological observations and osteomorphometry revealed the following: epithelial coverage of the amputation margin; ectopic cartilage formation, growth, and regression; bone resorption at the amputation margin prior to bone regeneration; anterior extension of the lower jaw bone along the original dentition position, followed by its thickening; and dental lamina invagination with tooth germ formation. Through these processes, the lower jaw bone, Meckel’s cartilage, and dentition were restored by 64 weeks post-amputation to their pre-amputation states. Conclusions: This study delineates the full sequence of lower jaw regeneration in adult newts, demonstrating complete restoration of bone, cartilage, and teeth after substantial lower jaw loss. These findings provide a detailed framework for understanding urodele jaw regeneration and may inform future strategies for promoting jaw reconstruction in humans. Full article

Background: Silicone chin implants have been widely used is plastic and esthetic surgery of the face being considered as safe and efficient way for chin augmentation. However, complications such as bone resorption, displacement or ectopic bone formation may occur. Methods: The objective of this study was to evaluate complications associated with silicone chin implants and revision surgery protocols. Results: Among 98 patients who received silicone chin implants, 24 (11 males, 13 females) exhibited complications. The most commonly diagnosed issues were displacement (n = 3), bone resorption (n = 9), both conditions (n = 3), and patient dissatisfaction (n = 7). All patients were qualified for revision surgery, which included silicone implant removal followed by sliding genioplasty (n = 7), orthognathic surgery (n = 4), custom-made chin implant placement (n = 7), and repositioning and fixation (n = 1). After revision surgery, no complications occurred. Conclusions: Observations from this revision cohort suggest that careful patient selection and consideration of orthognathic or customized implant-based approaches may reduce the risk of dissatisfaction and revision surgery in patients with dentofacial deformities, or those seeking gender confirmation surgeries, compared to stock silicone implants. Full article

Background: Delayed or non-union fractures comprise 5–10% of cases, indicating the need for biologic interventions. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive agent; yet, collagen carrier-based uncontrolled release causes adverse events. We evaluated the safety and efficacy of a hydroxyapatite (HA) carrier-based rhBMP-2 delivery system for acute traumatic upper and lower fractures exhibiting bone defects. Methods: This prospective, multicenter, single-arm clinical trial enrolled 90 patients who underwent surgery using a hydroxyapatite (HA) carrier-based rhBMP-2 delivery system (Novosis^TM). Radiographically validated union at 6 and 12 months post-surgery and treatment success (union without additional surgery) were used to assess efficacy. The incidence, type, and severity of all device-related adverse events during follow-up were monitored by investigators to evaluate safety. Results: Of the 90 patients enrolled, 81 were included in the full analysis set. The mean age was 58.5 years, and 18.6% (15/81) had open fractures. At 6 months post-surgery, radiographically validated union was achieved in 81.5% (66/81) of patients, increasing to 96.2% (77/81) at 12 months after surgery. Treatment success was 95.0% (76/81). Adverse events were rare (1/81, 1.2%). No ectopic ossification, systemic complications, or severe inflammatory responses were observed. Conclusions: HA-based rhBMP-2 intervention demonstrated favorable union rates and safety with minimal complications in acute upper and lower fractures with bone defects. The biocompatibility and controlled-release properties of HA likely improved efficacy and reduced complications. Results should be interpreted as feasibility data from a heterogeneous case series without a control group. Larger randomized controlled comparative trials are warranted for optimal dosing and evaluating efficacy and cost-effectiveness. Full article

Background: Gout is an inflammatory arthritis associated with increased bone anabolism and a higher risk of ectopic bone formation. Colchicine, used to prevent and treat acute gouty flares, inhibits microtubule polymerization and has been described to promote osteoblastogenesis. In bone disorders such as osteoporosis, disruption of the osteoblast–adipocyte balance contributes to pathology, yet no therapies directly target bone marrow adiposity. Thus, we decided to investigate the impact of colchicine on the osteoblast-adipocyte balance. Methods: C3H10T1/2 mesenchymal stem cells were differentiated to both cell fates in the presence or absence of colchicine. Differentiation was assessed by studying differentiation phenotypes as well as adipocytic and osteoblastic marker genes. Disrupting microtubule homeostasis through stathmin (STMN1) silencing was employed to mimic colchicine effects on differentiation. Proteomic analysis was performed to gain further insight into colchicine’s effects on adipogenesis. Results: Colchicine promoted transcriptional changes consistent with osteoblastogenic commitment and inhibited adipogenesis, as evidenced by reduced intracellular lipid accumulation and downregulation of adipogenic marker genes. These effects were observed following both continuous and transient exposure (median fold change across adipogenic markers 0.41 and 0.59, respectively). Consistent with colchicine-induced microtubule destabilisation, microtubule disruption by STMN1 silencing also suppressed adipogenic differentiation (median fold change = 0.66), suggesting that colchicine’s anti-adipogenic effect may be due to its impact on the cytoskeleton. Conclusions: These findings indicate that colchicine can suppress adipogenic differentiation while favouring osteoblast commitment in mesenchymal stem cells. Although further validation in relevant preclinical models is required, its efficacy following transient exposure supports the exploration of site-specific strategies that limit systemic toxicity. Full article

Reconstruction of large and complex hard tissue defects remains a major clinical challenge, as conventional autografts and allografts are often limited in availability, biological compatibility, and long-term efficacy, particularly for extensive defects or poor bone quality. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive factor capable of initiating the complete cascade of bone formation. However, its clinical use is restricted by dose-dependent complications such as inflammation, ectopic ossification, and osteolysis. This review synthesizes current evidence on the safety profile of rhBMP-2 and examines strategies to enhance its therapeutic index. Preclinical and clinical data indicate that conventional collagen-based carriers frequently cause rapid burst release and uncontrolled diffusion, aggravating adverse outcomes. It is noteworthy that low doses of rhBMP-2 (0.5–0.7 mg/level in anterior cervical discectomy and fusion (ACDF) or 0.5–1.0 mg/level in transforaminal lumbar interbody fusion (TLIF)) provide the optimal balance of efficacy and safety. Advanced biomaterial-based platforms, such as bioceramic–polymer composites, injectable hydrogels, and 3D-printed scaffolds, enable spatially and temporally controlled release while maintaining osteogenic efficacy. Molecular delivery approaches, including chemically modified messenger RNA (cmRNA) and regional gene therapy, provide transient, site-specific rhBMP-2 expression with reduced dosing and minimal systemic exposure. By integrating mechanistic insights with translational advances, this review outlines a framework for optimizing rhBMP-2-based regenerative protocols, emphasizing their potential role in multidisciplinary strategies for reconstructing complex hard tissue defects. Full article

Background/Objectives: Vascular Malformation—Osteolytic Subtype (VMOS) is an exceptionally rare autosomal recessive disorder caused by homozygous pathogenic variants in the ELMO2 gene, with fewer than ten genetically confirmed pediatric cases reported worldwide. This report presents the longitudinal dental management and clinical course of a child with VMOS, emphasizing the challenges of preventive and restorative care in such cases. Methods: A four-year-old child with a confirmed diagnosis of VMOS and a history of urgent bilateral coil embolization and surgical excision of mandibular aneurysmal bone cysts presented for dental care. The patient was followed for three years (2022–2025). Management focused on staged oral rehabilitation, preventive strategies, and restorative interventions adapted to changes across dentition stages. Results: At initial presentation, the child exhibited mandibular swelling, gingival hypertrophy, and a history of spontaneous intraoral bleeding. The postoperative course had been complicated by cerebral abscesses requiring prolonged intravenous antibiotics. During the primary dentition stage, full oral rehabilitation and strict preventive protocols were implemented to minimize caries and infection risk. In the mixed dentition period, the permanent incisors and molars erupted with enamel hypoplasia and developmental defects, necessitating composite restorations. Ectopic eruption and suboptimal oral hygiene, partly related to parental fear of bleeding, were also managed with reinforced preventive counseling. Conclusions: This case highlights the long-term dental implications of VMOS, underscoring the crucial role of the pediatric dentist in early preventive planning and individualized restorative management. Effective multidisciplinary coordination remains essential to preserve oral health and minimize complications in rare vascular syndromes with craniofacial involvement. Full article

Background: Ectopic bone formation models provide useful insights into bone tissue formation and remodeling processes. The use of a subcutaneous site emphasizes the focus on cytokine signaling and cell migration and proliferation while minimizing the effect of mechanical loading and direct interaction with surrounding stem cells. Methods: To study the effect of BMP3 on bone formation and remodeling, Bmp3^-/- mice were subcutaneously implanted with an autologous blood coagulum device containing BMP6, and bone formation was examined at days 7 and 14 post-implantation. Bone marrow cell composition was assessed using FACS. Formation of ectopic bone was analyzed using micro-CT, immunohistochemistry, and RNAseq to obtain transcriptomic data. Results: Bone marrow from Bmp3^-/- mice showed reduced lymphoid-lineage subsets, expanded myeloid lineage, and altered proportions of several osteochondroprogenitor subsets. A limited amount of newly formed bone tissue was seen in the implants after 7 days, while ectopic bone was more evident after 14 days, with significantly more bone in the Bmp3^-/- mice compared to WT mice. Localization of Sox9 and Runx2 showed a more advanced stage of bone tissue remodeling in Bmp3^-/- mice. Transcriptomic analysis showed upregulation of approximately 1700 genes on day 7 and 190 genes on day 14. Conclusions: These results suggest that BMP3 regulates the composition of bone and cartilage progenitor populations in bone marrow and consequently bone formation by arresting the remodeling of cartilage to bone tissue. The lack of BMP3 in ectopic bone accelerates the transition from the cartilaginous template to proper bone tissue. Full article

Heterotopic ossification (HO) is a disease characterized by ectopic bone formation, which can occur following severe traumatic brain injury (TBI). However, the underlying mechanisms remain poorly understood. In this study, we established a stem cell model using adipose-derived stem cells (ADSCs) and skeletal stem cells (SSCs) to examine osteogenic factors present in the sera of TBI patients. Incubation of ADSCs and SSCs with osteoinductive medium supplemented with TBI serum significantly enhanced osteogenic differentiation, particularly in male ADSCs and both female and male SSCs, with male SSCs exhibiting the highest osteogenic potential. Furthermore, we identified TGF-β1 as an important factor involved in these osteogenic processes. Elevated levels of TGF-β1 were detected in the serum of male TBI patients 14 days post-injury. Cellular assays revealed a sexual dimorphism in response to TGF-β1 neutralization: osteogenic differentiation in male SSCs was significantly reduced, while no effect was detectable in female SSCs. These findings, together with the rarity of HO in female patients, suggest that TGF-β1 plays a central role in the development of HO in males. Furthermore, this study highlights the importance of considering sex-specific mechanisms in traumatic HO for the development of sex-specific therapy options. Full article

The intracellular topography of RNA molecules, encompassing ribonucleotides with biochemical modifications, such as N6-methyladenosine (m6A), 5-methylcytosine (m5C), adenosine to inosine (A → I) editing, and isomerization of uridine to pseudouridine (Ψ), as well as of non-coding RNA molecules, is currently studied within the frame of the epigenome. Circulating RNA molecules in the intracellular space that have incorporated information by carrying specific modifications depend on the balanced activity and correct subcellular installation of their modifying enzymes, the “writers”, “readers” and “erasers”. Modifications are critical for RNA translocation from the nucleus to the cytoplasm, for stability and translation efficiency, and for other, still-uncovered functions. Moreover, trafficking of non-coding RNA molecules depends on membrane transporters capable of recognizing signal sequences and RNA recognition-binding proteins that can facilitate their transport to different intracellular locations, guiding the establishment of interconnection possibilities with different macromolecular networks. The potential of long non-coding RNAs to form multilayer molecular connections, as well as the differential topology of micro-RNAs in cell nuclei, compared to cytoplasm, has been recognized by several studies. The study of the intercellular compartmentalization of these molecules has recently become feasible thanks to technological progress; however, a wealth of information has not yet been produced that would lead to safe conclusions regarding non-coding RNA’s contributions to the early steps of pathogenesis and disease progression in hematological malignancies. Both, the bone marrow, as the main hematopoietic tissue, and the lymphoid tissues are composed of cells with highly reactive potential to signals affecting the epigenome and initiating cascade pathways in response. Independently or in combination with coexistent driver genetic mutations, especially mutations of enzymes involved in epigenomic surveillance, intracellular microenvironmental alterations within the cell nuclear, cytoplasmic, and mitochondrial compartments can lead to disorganization of hematopoietic stem cells’ epigenomes, promoting the generation of hematological malignancies. In this review, we discuss the various intracellular processes that, when disrupted, may result in the ectopic placement of RNA molecules, either inducing specific modifications or non-coding molecules or promoting hematological malignant phenotypes. The crosstalk between mitochondrial and nuclear genomes and the complex regulatory effects of mis-localized RNA molecules are highlighted. This research approach may constitute a field for new, more specifically targeted therapies in hematology based on RNA technology. Full article

Extra-osseous calcification refers to the pathological deposition of calcium salts in soft tissues. Its most recognized forms affect the cardiovascular system, leading to vascular and heart valve calcifications. This process is active and regulated, involving the phenotype transition of resident cells into osteo/chondrogenic lineage. Chronic kidney disease (CKD) patients frequently suffer from vascular and other soft tissue calcification. OsteoSense dyes are fluorescent imaging agents developed to visualize calcium deposits during bone formation. In addition to its application in bone physiology, it has been used to detect vascular smooth muscle cell calcification in vitro and to evaluate calcification ex vivo. Here, we investigated CKD-associated soft tissue calcification by applying OsteoSense in vivo. CKD was induced by a diet containing adenine and elevated phosphate. OsteoSense (80 nmol/kg body weight) was injected intravenously through the retro-orbital venous sinus 18 h before the measurement on an IVIS Spectrum In Vivo Imaging System. OsteoSense staining detected calcium deposition in the aorta, kidney, heart, lung, and liver in CKD mice. On the other hand, no calcification occurred in the brain, eye, or spleen. OsteoSense positivity in the calcified soft tissues in CKD mice was associated with increased mRNA levels of osteo/chondrogenic transcription factors. Our findings demonstrate that OsteoSense is a sensitive and effective tool for detecting soft tissue calcification in vivo, and may be particularly valuable for studies of CKD-related ectopic calcification. Full article