Exosomal lncRNA HCP5 derived from human bone marrow mesenchymal stem cells improves chronic periodontitis by miR-24-3p/HO1/P38/ELK1 pathway.

ABSTRACT

Objective: The present study aimed to explore the function of human bone marrow mesenchymal stem cells (hBMMSCs)-derived exosomal long noncoding RNA histocompatibility leukocyte antigen complex P5 (HCP5) in the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) to improve chronic periodontitis (CP). Methods: Exosomes were extracted from hBMMSCs. Alizarin red S staining was used to detect mineralised nodules. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to measure HCP5 and miR-24-3p expression. The mRNA and protein levels of alkaline phosphatase (ALP), osteocalcin, osterix, runt-related transcription factor 2, bone morphogenetic protein 2, osteopontin, fibronectin, collagen 1, heme oxygenase 1 (HO1), P38, and ETS transcription factor ELK1 (ELK1) were detected using RT-qPCR and Western blot. Enzyme-linked immunosorbent assay (ELISA) kits were used to determine the HO1 and carbon monoxide concentrations. Heme, biliverdin, and Fe2+ levels were determined using detection kits. Micro-computed tomography, hematoxylin and eosin staining, ALP staining, tartrate-resistant acid phosphatase staining, ELISA, and RT-qPCR were conducted to evaluate the effect of HCP5 on CP mice. Dual luciferase, RNA immunoprecipitation, and RNA pulldown experiments were performed to identify the interactions among HCP5, miR-24-3p, and HO1. Results: The osteogenic ability of hPDLSCs significantly increased when co-cultured with hBMMSCs or hBMMSCs exosomes. Overexpression of HCP5 and HO1 in hBMMSCs exosomes promoted the osteogenic differentiation of hPDLSCs, and knockdown of HCP5 repressed the osteogenic differentiation of hPDLSCs. HCP5 knockdown enhanced the inflammatory response and repressed osteogenesis in CP mice. MiR-24-3p overexpression diminished the stimulatory effect of HCP5 on the osteogenic ability of hPDLSCs. Mechanistically, HCP5 acted as a sponge for miR-24-3p and regulated HO1 expression, and HO1 activated the P38/ELK1 pathway. Conclusion: HBMMSCs-derived exosomal HCP5 promotes the osteogenic differentiation of hPDLSCs and alleviates CP by regulating the miR-24-3p/HO1/P38/ELK1 signalling pathway.