Chromodomain helicase DNA-binding protein 7 (CHD7), an ATP-dependent eukaryotic chromatin remodeling enzyme, is essential for the development of organs. The mutation of CHD7 is the main cause of CHARGE syndrome, but its function and mechanism in skeletal system remain unclear. Here, we show conditional knockout of Chd7 in bone marrow mesenchymal stem cells (MSCs) and preosteoblasts leads to a pathological phenotype manifested as low bone mass and severely high marrow adiposity. Mechanistically, we identify enhancement of the peroxisome proliferator-activated receptor (PPAR) signaling in Chd7-deficient MSCs. Loss of Chd7 reduces the restriction of PPAR-γ and then PPAR-γ associates with trimethylated histone H3 at lysine 4 (H3K4me3), which subsequently activates the transcription of downstream adipogenic genes and disrupts the balance between osteogenic and adipogenic differentiation. Our data illustrate the pathological manifestations of Chd7 mutation in MSCs and reveal an epigenetic mechanism in skeletal health and diseases.

Introduction: Adipose-derived stem cells (ADSCs) could accomplish neural transdifferentiation with the presence of certain growth factors in vitro . It has been proved that bone marrow stromal cells (BMSCs) can realize neural transdifferentiation only by being co-cultured with Schwann cells...

Introduction: Mechanical forces play critical roles in the development and remodelling process of bone. As an alternative cell source for bone engineering, adipose-derived stem cells (ASCs) should be fully investigated for their responses to mechanical stress and the mechanisms responsible for...

Macrophages have been described as a critical cell population regulating bone regeneration and osseointegration, and their polarization phenotype is of particular importance. Several studies have shown that calcitonin gene-related peptide-α (CGRP) might modulate macrophage polarization in inflammatory response and bone metabolism. This study aimed to investigate the effect of CGRP on macrophage polarization in titanium osseointegration. In vitro, bone marrow-derived macrophages (BMDMs) from C57BL/6 or CGRP^–/– mice were obtained and activated for M1 and M2 polarization. Flow cytometry and real-time PCR were used to evaluate the M1/M2 polarization and inflammatory function. In vivo, mice were divided into 3 groups: wild-type, CGRP^–/–, and CGRP^–/– mice with CGRP lentivirus. After extraction of the maxillary first molar, 0.6 mm × 1.25 mm titanium implants were emplaced. Bone formation and inflammation levels around implants were then observed and analyzed. The results of flow cytometry demonstrated that CGRP deficiency promoted M1 polarization and inhibited M2 polarization in BMDMs, which was consistent with pro-inflammatory and anti-inflammatory cytokine expression levels in real-time PCR. In vivo, compared with the CGRP^–/– group, the CGRP gene transfection group displayed better osseointegration and lower inflammation levels, close to those of the wild-type group. These results revealed that CGRP might play roles in macrophage polarization. In addition, CGRP deficiency could inhibit osseointegration in murine maxillae, while CGRP recovery by lentivirus transfection could improve osseointegration and regulate macrophage phenotype expression.

1α,25-Dihydroxyvitamin D₃ (1,25(OH)₂D₃) is the active form of vitamin D, which is responsible for reducing the risk for diabetes mellitus (DM), decreasing insulin resistance, and improving insulin secretion. Previous studies have shown that 1,25(OH)₂D₃ inhibited the activity of FoxO1, which has been implicated in the regulation of glucose metabolism. However, its function and mechanism of action in DM-induced energy disorders and also in bone development remains unclear. Here, using in vitro and in vivo approaches including osteoblast-specific, conditional FoxO1-knock-out mice, we demonstrate that 1,25(OH)₂D₃ ameliorates abnormal osteoblast proliferation in DM-induced oxidative stress conditions and rescues the impaired glucose and bone metabolism through FoxO1 nuclear exclusion resulting from the activation of PI3K/Akt signaling. Using alizarin red staining, alkaline phosphatase assay, Western blot, and real-time qPCR techniques, we found that 1,25(OH)₂D₃ promotes osteoblast differentiation and expression of osteogenic phenotypic markers (i.e. alkaline phosphatase (1), collagen 1 (COL-1), osteocalcin (OCN), and osteopontin (OPN)) in a high-glucose environment. Moreover, 1,25(OH)₂D₃ increased both total OCN secretion and levels of uncarboxylated OCN (GluOC) by phosphorylating FoxO1 and promoting its nuclear exclusion, indicated by Western blot and cell immunofluorescence analyses. Taken together, our findings confirm that FoxO1 is a key mediator involved in glucose homeostasis and indicate that 1,25(OH)₂D₃ improves glucose metabolism and bone development via regulation of PI3K/Akt/FoxO1/OCN pathway.