m6A methylation modification and immune infiltration analysis in osteonecrosis of the femoral head

Injectable hydrogel regulates immune infiltration through physical and chemical synergy in the treatment of steroid-induced osteonecrosis of the femoral head

The incidence of steroid-induced osteonecrosis of the femoral head (SONFH) is increasing annually; however, the underlying pathological mechanism remains unclear, which is an obstacle to its effective treatment. The negative effect of immune infiltration on the physiological activity of focal stem cells is one potential mechanism that has attracted attention. It is difficult to simulate the complex regulation of the interaction system between immune cells and stem cells using a single regulation method. In this study, we demonstrated that the immune infiltration of T helper 17 (Th17) cells plays an important role in the progression of SONFH. Based on this finding, we developed an injectable hydrogel system with both physical and chemical synergistic regulatory properties to enhance the activity of stem cells using electrical stimulation. This treatment was designed to prevent the infiltration of Th17 cells by regulating the physiological function of stem cells and blocking the negative effect of Th17 cells on stem cells pharmacologically. Thus, the dual synergistic regulation of immune infiltration at the lesion site of SONFH enhanced the physiological activity and function of the stem cells, thereby improving the therapeutic effect of SONFH. This hydrogel system provides insight for the future development of multifactorial regulatory systems and provides a strategy for the treatment of SONFH.

YTHDF2-Mediated m6A methylation inhibition by miR27a as a protective mechanism against hormonal osteonecrosis in BMSCs

BACKGROUND

With the increasing incidence of steroid-induced necrosis of the femoral head (SNFH), numerous scholars have investigated its pathogenesis. Current evidence suggests that the imbalance between lipogenesis and osteoblast differentiation in bone marrow mesenchymal stem cells (BMSCs) is a key pathological feature of SNFH. MicroRNAs (miRNAs) have strong gene regulatory effects and can influence the direction of cell differentiation. N6-methyladenosine (m6A) is a prevalent epigenetic modification involved in diverse pathophysiological processes. However, knowledge of how miRNAs regulate m6A-related factors that affect BMSC differentiation is limited.

OBJECTIVE

We aimed to investigate the role of miR27a in regulating the expression of YTHDF2 in BMSCs.

METHODS

We compared miR27a, YTHDF2, and total m6A mRNA levels in SNFH-affected and control BMSCs. CCK-8 and TUNEL assays were used to assess BMSC proliferation and apoptosis. Western blotting and qRT‒PCR were used to measure the expression of osteogenic (ALP, RUNX2, and OCN) and lipogenic (PPARγ and C/EBPα) markers. Alizarin Red and Oil Red O staining were used to quantify osteogenic and lipogenic differentiation, respectively. miR27a was knocked down or overexpressed to evaluate its impact on BMSC differentiation and its relationship with YTHDF2. Bioinformatics analyses identified YTHDF2 as a differentially expressed gene in SNFH (ROC analysis) and revealed potential signaling pathways through GSEA. The effects of YTHDF2 silencing on the lipogenic and osteogenic functions of BMSCs were assessed.

RESULTS

miR27a downregulation and YTHDF2 upregulation were observed in the SNFH BMSCs. miR27a knockdown/overexpression modulated YTHDF2 expression, impacting BMSC differentiation. miR27a silencing decreased m6A methylation and promoted osteogenic differentiation, while YTHDF2 silencing exerted similar effects. GSEA suggested potential signaling pathways associated with YTHDF2 in SNFH.

CONCLUSION

miR27a regulates BMSC differentiation through YTHDF2, affecting m6A methylation and promoting osteogenesis. This finding suggests a potential therapeutic target for SNFH.