p75NTR optimizes the osteogenic potential of human periodontal ligament stem cells by up-regulating α1 integrin expression

Role of the GRP78-c-Src signaling pathway on osteoblast differentiation of periodontal ligament fibroblasts induced by cyclic mechanical stretch

OBJECTIVES

This study aims to investigate the influence of glucose regulated protein (GRP) 78 on osteoblast differentiation in periodontal ligament fibroblasts (PDLFs) under cyclic mechanical stretch and determine the underlying mechanism.

METHODS

FlexCell 5000 cell mechanical device was applied to simulate the stress environment of orthodontic teeth. GRP78High and GRP78Low subpopulation were obtained by flow sorting. Gene transfection was performed to knockdown GRP78 and c-Src expression and overexpress c-Src. Western blot analysis was used to detect the protein expression of Runt-related gene 2 (RUNX2), Osterix, osteocalcin (OCN), and osteopontin (OPN). Immunoprecipitation assay was used to determine the interaction of GRP78 with c-Src. The formation of cellular mineralized nodules was determined by alizarin red staining.

RESULTS

GRP78 was heterogeneously expressed in PDLFs, and GRP78High and GRP78Low subpopulations were obtained by flow sorting. The osteogenic differentiation ability and phosphorylation level of c-Src kinase in the GRP78High subpopulation were significantly increased compared with those in GRP78Low subpopulation after cyclic mechanical stretch (P<0.05). GRP78 interacted with c-Src in PDLFs. The overexpression c-Src group showed significantly increased osteogenic differentiation ability than the vector group (P<0.05), and the sic-Src group showed significantly decreased osteogenic differentiation ability (P<0.05) after cyclic mechanical stretch.

CONCLUSIONS

GRP78 upregulates c-Src expression by interacting with c-Src kinase and promotes osteogenic differentiation under cyclic mechanical stretch in PDLFs.

p75NTR antibody-conjugated microspheres: an approach to guided tissue regeneration by selective recruitment of endogenous periodontal ligament cells

Repairing defects in alveolar bone is essential for regenerating periodontal tissue, but it is a formidable challenge. One promising therapeutic approach involves using a strategy that specifically recruits periodontal ligament cells (PDLCs) with high regenerative potential to achieve in situ regeneration of alveolar bone. In this study, we have created a new type of microsphere conjugated with an antibody to target p75 neurotrophin receptor (p75NTR), which is made of nano-hydroxyapatite (nHA) and chitosan (CS). The goal of this design is to attract p75NTR+hPDLCs selectively and promote osteogenesis. In vitro experiments demonstrated that the antibody-conjugated microspheres attracted significantly more PDLCs compared to non-conjugated microspheres. Incorporating nHA not only enhances cell adhesion and proliferation on the surface of the microsphere but also augments its osteoinductive properties. Microspheres effectively recruited p75NTR+ cells at bone defect sites in SD rats, as observed through immunofluorescent staining of p75NTR antibodies. This p75NTR antibody-conjugated nHA/CS microsphere presents a promising approach for selectively recruiting cells and repairing bone defects.

Genome-wide analysis of intermuscular bone development reveals changes of key genes expression and signaling pathways in blunt snout bream (Megalobrama amblycephala)

Intermuscular bone (IB) is a hard-boned spicule exist in lower teleost, which brings a lot of detrimental effects on palatability and economic value of blunt snout bream (Megalobrama amblycephala). Masson trichrome staining for ossific IB indicated that some osteoblasts appeared at the edge of the bone matrix and a few osteocytes are present in the center of the mineralized bone matrix. By comparing the orthologous gene families of fish with IBs and without IBs, we screened the key signaling pathways associated with IB formation. Furthermore, the transcriptomic data demonstrated the functional importance of these gene families. The candidate genes involved in chondrocyte development were highly expressed in stage 1 compared with stage 2 and stage 3, suggesting that the development process of IB might mainly involve in intramembranous ossification. Our research reveals the molecular mechanism of IBs formation, and provides molecular evidence for the further study on intermuscular boneless stains.

p75NTR optimizes the osteogenic potential of human periodontal ligament stem cells by up-regulating α1 integrin expression

Human periodontal ligament stem cells (hPDLSCs) are a promising source in regenerative medicine. Due to the complexity and heterogeneity of hPDLSCs, it is critical to isolate homogeneous hPDLSCs with high regenerative potential. In this study, p75 neurotrophin receptor (p75NTR) was used to isolate p75NTR⁺ and p75NTR⁻ hPDLSCs by fluorescence‐activated cell sorting. Differences in osteogenic differentiation among p75NTR⁺, p75NTR⁻ and unsorted hPDLSCs were observed. Differential gene expression profiles between p75NTR⁺ and p75NTR⁻ hPDLSCs were analysed by RNA sequencing. α1 Integrin (ITGA1) small interfering RNA and ITGA1‐overexpressing adenovirus were used to transfect p75NTR⁺ and p75NTR⁻ hPDLSCs. The results showed that p75NTR⁺ hPDLSCs demonstrated superior osteogenic capacity than p75NTR⁻ and unsorted hPDLSCs. Differentially expressed genes between p75NTR⁺ and p75NTR⁻ hPDLSCs were highly involved in the extracellular matrix‐receptor interaction signalling pathway, and p75NTR⁺ hPDLSCs expressed higher ITGA1 levels than p75NTR⁻ hPDLSCs. ITGA1 silencing inhibited the osteogenic differentiation of p75NTR⁺ hPDLSCs, while ITGA1 overexpression enhanced the osteogenic differentiation of p75NTR⁻ hPDLSCs. These findings indicate that p75NTR optimizes the osteogenic potential of hPDLSCs by up‐regulating ITGA1 expression, suggesting that p75NTR can be used as a novel cell surface marker to identify and purify hPDLSCs to promote their applications in regenerative medicine.