Osteoclastogenesis inhibition by mutated IGSF23 results in human osteopetrosis

Epigenetic control of commensal induced Th2 Responses and Intestinal immunopathology

Understanding the initiation of T-helper (Th)-2 immunity is crucial for addressing allergic diseases that have been linked to the commensal microbiota. However, Th2 responses are notably absent from known host-microbiota intestinal immune circuits. Notably, the commensal protist Tritrichomonas induces a transient innate ILC2 circuit rather than a chronic Th2 circuit. Canonical Th2 responses rely on the induction of IL-4 production by innate cells. This study shows that the absence of Tet2 , a DNA demethylase, reprograms naïve T cells to autonomously produce IL-4 upon T cell receptor stimulation, bypassing the need for IL-4 from innate cells for Th2 differentiation. Loss of this checkpoint induces chronic Th2 responses to Tritrichomonas , associated with IL-25-dependent barrier dysfunction and increased susceptibility to allergic pathology in response to dietary antigens.

Sentence Summary

Regulation of cell autonomous IL-4 in T cells is critical to prevent dysregulated Th2 immunity to commensals and predisposition to allergy.

The genome of African manatee Trichechus senegalensis reveals secondary adaptation to the aquatic environment

Sirenians exhibit unique aquatic adaptations, showcasing both convergent adaptive features shared with cetaceans and unique characteristics such as cold sensitivity and dense bones. Here, we report a chromosome-level genome of the African manatee (Trichechus senegalensis) with high continuity, completeness, and accuracy. We found that genes associated with osteopetrosis have undergone positive selection (CSF1R and LRRK1) or pseudogenized (FAM111A and IGSF23) in the African manatee, potentially contributing to the dense bone formation. The loss of KCNK18 may have increased their sensitivity to cold water temperatures. Moreover, we identified convergent evolutionary signatures in 392 genes among fully aquatic mammals, primarily enriched in skin or skeletal system development and circadian rhythm, which contributed to the transition from terrestrial to fully aquatic lifestyles. The African manatee currently possesses a small effective population size and low genome-wide heterozygosity. Overall, our study provides genetic resources for understanding the evolutionary characteristics and conservation efforts of this species.

Engineering approaches to manipulate osteoclast behavior for bone regeneration

Extensive research has delved into the multifaceted roles of osteoclasts beyond their traditional function in bone resorption in recent years, uncovering their significant influence on bone formation. This shift in understanding has spurred investigations into engineering strategies aimed at leveraging osteoclasts to not only inhibit bone resorption but also facilitate bone regeneration. This review seeks to comprehensively examine the mechanisms by which osteoclasts impact bone metabolism. Additionally, it explores various engineering methodologies, including the modification of bioactive material properties, localized drug delivery, and the introduction of exogenous cells, assessing their potential and mechanisms in aiding bone repair by targeting osteoclasts. Finally, the review proposes current limitations and future routes for manipulating osteoclasts through biological and material cues to facilitate bone repair.

Network pharmacology-based mechanism prediction and pharmacological validation of Bushenhuoxue formula attenuating postmenopausal osteoporosis in ovariectomized mice

BACKGROUND

Bushenhuoxue (BSHX) formula, a ten-compound herbal decoction, is widely used to treat postmenopausal osteoporosis (PMOP) in China. However, the mechanism is not clear yet.

METHODS

The underlying biological processes and signaling pathways were predicted by network pharmacology. In vivo experimental study, 24 female C57BL/6 J mice were randomly divided into sham, ovariectomized (OVX) and BSHX formula groups. Mice in the latter two groups were subjected to bilateral ovariectomy, and mice in the BSHX formula group were extra treated by BSHX formula at an oral dosage of 0.2 mL/10 g for 8 weeks. The femur samples were harvested for tissue analyses including μCT assay, histology and immunohistochemical (IHC) staining of VEGF signaling.

RESULTS

A total of 218 active ingredients and 274 related targets were identified in BSHX formula. After matching with 292 targets of PMOP, 64 overlapping genes were obtained. GO and KEGG enrichment analyses on these 64 genes revealed that angiogenesis and VEGF signaling were considered as the potential therapeutic mechanism of BSHX formula against PMOP. Animal experiments showed that mice in the BSHX formula-treated group presented increased bone mass, microstructural parameters, blood vessel numbers and an activation of VEGF signaling (VEGF, COX2, eNOS and CD31) compared to the OVX mice.

CONCLUSION

This study revealed that BSHX formula exerts anti-PMOP effects possibly through activating VEGF signaling-mediated angiogenesis.

STARD3NL inhibits the osteogenic differentiation by inactivating the Wnt/β‐catenin pathway via binding to Annexin A2 in osteoporosis

Osteoporosis is one of the leading forms of systemic diseases related to bone metabolism in the world. STARD3 N‐terminal like (STARD3NL) showed robust association with osteoporosis‐related traits. Yet, the molecular functional mechanisms of STARD3NL in osteoblasts is still obscure. In this study, we demonstrated a high level of STARD3NL expression in the bone tissues from the patients with low bone mass and ovariectomized (OVX)‐induced osteoporotic mice. We identified Stard3nl as a potent factor that negatively and positively regulates osteoblast differentiation and cell proliferation, respectively. Furthermore, inhibition of Stard3nl induced β‐catenin gene expression and the nuclear translocation of β‐catenin, as well as Wnt signalling activities, contributing to the activation of Wnt/β‐catenin signalling. Mechanistic studies revealed that Stard3nl bound with Annexin A2 (Anxa2) to suppress β‐catenin expression, resulting into the suppression of Wnt signalling and downstream osteogenic differentiation. Moreover, adeno‐associated virus 9 (AAV9)‐mediated silencing of Stard3nl reversed bone loss in OVX‐induced osteoporotic mice by the injection into the knee joints. Collectively, our study revealed that Stard3nl suppressed osteogenesis via binding with Anxa2, resulting into the inactivation of Wnt signalling. It also highlights the preventive and therapeutic potential of STARD3NL as a specific and novel target for osteoporotic patients.

Osteoclastogenesis inhibition by mutated IGSF23 results in human osteopetrosis

OBJECTIVES

Osteopetrosis is a rare inherited skeletal disease characterized by increased bone mineral density due to the loss of osteoclast function or differentiation potential.

MATERIALS AND METHODS

The study involved a Chinese patient with osteopetrosis (the proband) and her immediate family members and 180 controls without osteopetrosis. Bone density of the femoral neck, lumbar spine and total body was measured using dual-energy x-ray absorptiometry. Osteoclast differentiation by the participants' peripheral blood mononuclear cells (PBMCs) was investigated using tartrate-resistant acid phosphatase (TRAP) staining. Osteoblast differentiation was examined with Alizarin Red S staining. Reverse transcription-quantitative PCR was used to amplify immunoglobulin superfamily member 23 (IGSF23), c-FOS and nuclear factor of activated T cells 1 (NFATC1).

RESULTS

We found a homozygous mutation (c.295C>T) in the IGSF23 gene in two osteopetrosis samples. The mutation led to the formation of a stop codon, causing loss of the immunoglobulin-like domain and the whole transmembrane domain. PBMCs from the proband (IGSF23^-/- ) exhibited poor ability for differentiating into mature osteoclasts in vitro. Overexpression of IGSF23 rescued the ability of IGSF23^-/- PBMCs to differentiate into osteoclasts. Moreover, knockdown of IGSF23 reversed the bone loss in OVX mice by injecting AAV-shIGSF23 into mice femoral bone marrow cavity. Furthermore, we also found that the IGSF23 mutation led to decreased c-Fos and NFATC1 expression levels by inhibiting the mitogen-activated protein kinase signalling pathways.

CONCLUSIONS

IGSF23-mediated osteoclast differentiation of PBMCs may serve as a potential target in osteoporosis therapy.