Dynamic chromatin accessibility landscapes of osteoblast differentiation and mineralization

Myocyte-Specific Enhancer Factor 2A Potentiates Osteoclastic Differentiation in Osteoporosis by Inducing Endothelin Receptor Type A

Activation of endothelin receptor type A (EDNRA) has been revealed to induce osteoclastic bone resorption during orthodontic treatment. In this study, we investigated the mechanisms by which EDNRA potentiates osteoclastic differentiation in ovariectomy (OVX)-induced mice with osteoporosis (OP)-like symptoms. The effects of knocking down EDNRA on OP in mice were observed using micro-CT, HE staining, TRAP staining, RT-qPCR, and immunoblotting. The effects of the knockdown of EDNRA in osteoclastic differentiation of bone marrow macrophages (BMs) were investigated by TRAP staining, F-actin staining, RT-qPCR, and immunoblotting. EDNRA was highly expressed in osteoporotic mice, and the knockdown of EDNRA in vivo alleviated osteoporotic phenotypes in OVX-induced mice by inhibiting osteoclast differentiation. BMs with EDNRA knockdown showed repressed MMP1, MMP8, and RANKL protein expression and Nfatc1, Ctsk, C-fos, and Trap mRNA expression. Myocyte-specific enhancer factor 2A (MEF2A) transcriptionally promoted EDNRA expression by binding to the EDNRA promoter. Silencing of MEF2A exerted the same anti-osteoporotic effects, which were reversed by overexpression of EDNRA. Altogether, our findings highlight that MEF2A knockdown alleviates loss of bone mass in the OVX-induced mice by suppressing osteoclast differentiation via inhibition of EDNRA transcription.

Dynamic GelMA/DNA Dual-Network Hydrogels Promote Woven Bone Organoid Formation and Enhance Bone Regeneration

Bone organoids, in vitro models mimicking native bone structure and function, rely on 3D stem cell culture for self-organization, differentiation, ECM secretion, and biomineralization, ultimately forming mineralized collagen hierarchies. However, their development is often limited by the lack of suitable matrices with optimal mechanical properties for sustained cell growth and differentiation. To address this, a dynamic DNA/Gelatin methacryloyl (GelMA) hydrogel (CGDE) is developed to recapitulate key biochemical and mechanical features of the bone ECM, providing a supportive microenvironment for bone organoid formation. This dual-network hydrogel is engineered through hydrogen bonding between DNA and GelMA, combined with GelMA network crosslinking, resulting in appropriate mechanical strength and enhanced viscoelasticity. During a 21-day 3D culture, the CGDE hydrogel facilitates cellular migration and self-organization, promoting woven bone organoid (WBO) formation via intramembranous ossification. These WBOs exhibit spatiotemporal architectures supporting dynamic mineralization and tissue remodeling. In vivo studies demonstrate that CGDE-derived WBOs exhibit self-adaptive properties, enabling rapid osseointegration within 4 weeks. This work highlights the CGDE hydrogel as a robust and scalable platform for bone organoid development, offering new insights into bone biology and innovative strategies for bone tissue regeneration.

Construction of an interactome network among circRNA-miRNA-mRNA reveals new biomarkers in hBMSCs osteogenic differentiation

Human bone marrow mesenchymal stem cells (hBMSCs) are adult stem cells residing in the bone marrow, characterized by their capacity for multi-directional differentiation, self-renewal, migration, and engraftment. Serving as seed cells, BMSCs play a pivotal role in the regeneration of bone defects. Hence, investigating the transcription factors and signaling pathways involved in the regulation of osteogenic differentiation in BMSCs holds significant importance. Recent research has unveiled that certain circular RNAs (circRNAs) can function as molecular sponges, influencing the osteogenic differentiation process of mesenchymal stem cells. However, many circRNAs remain undiscovered, and their precise mechanisms remain elusive. Therefore, the objective of this study is to construct an osteogenic differentiation-related circRNA-miRNA-mRNA network in hBMSCs. Subsequently, through bioinformatics analysis, we constructed a ceRNA network related to the osteogenic differentiation ability of hBMSCs, comprising 22 circRNAs, 17 miRNAs, and 15 mRNAs. The potential circRNA-miRNA-mRNA axes, including the role of hsa_circ_0001600 in promoting the osteogenic differentiation of hBMSCs through the targeted regulation of hsa-miR-542-3p, were validated through in vitro experiments.

Krüppel-like factors family in health and disease

Krüppel-like factors (KLFs) are a family of basic transcription factors with three conserved Cys2/His2 zinc finger domains located in their C-terminal regions. It is acknowledged that KLFs exert complicated effects on cell proliferation, differentiation, survival, and responses to stimuli. Dysregulation of KLFs is associated with a range of diseases including cardiovascular disorders, metabolic diseases, autoimmune conditions, cancer, and neurodegenerative diseases. Their multidimensional roles in modulating critical pathways underscore the significance in both physiological and pathological contexts. Recent research also emphasizes their crucial involvement and complex interplay in the skeletal system. Despite the substantial progress in understanding KLFs and their roles in various cellular processes, several research gaps remain. Here, we elucidated the multifaceted capabilities of KLFs on body health and diseases via various compliable signaling pathways. The associations between KLFs and cellular energy metabolism and epigenetic modification during bone reconstruction have also been summarized. This review helps us better understand the coupling effects and their pivotal functions in multiple systems and detailed mechanisms of bone remodeling and develop potential therapeutic strategies for the clinical treatment of pathological diseases by targeting the KLF family.

Gut microbially produced tryptophan metabolite melatonin ameliorates osteoporosis via modulating SCFA and TMAO metabolism

Osteoporosis (OP) is a severe global health issue that has significant implications for productivity and human lifespan. Gut microbiota dysbiosis has been demonstrated to be closely associated with OP progression. Melatonin (MLT) is an important endogenous hormone that modulates bone metabolism, maintains bone homeostasis, and improves OP progression. Multiple studies indicated that MLT participates in the regulation of intestinal microbiota and gut barrier function. However, the promising effects of gut microbiota-derived MLT in OP remain unclear. Here, we found that OP resulted in intestinal tryptophan disorder and decreased the production of gut microbiota-derived MLT, while administration with MLT could mitigate OP-related clinical symptoms and reverse gut microbiota dysbiosis, including the diversity of intestinal microbiota, the relative abundance of many probiotics such as Allobaculum and Parasutterella, and metabolic function of intestinal flora such as amino acid metabolism, nucleotide metabolism, and energy metabolism. Notably, MLT significantly increased the production of short-chain fatty acids and decreased trimethylamine N-oxide-related metabolites. Importantly, MLT could modulate the dynamic balance of M1/M2 macrophages, reduce the serum levels of pro-inflammatory cytokines, and restore gut-barrier function. Taken together, our results highlighted the important roles of gut microbially derived MLT in OP progression via the "gut-bone" axis associated with SCFA metabolism, which may provide novel insight into the development of MLT as a promising drug for treating OP.