Complex causal association between genetically predicted 731 immunocyte phenotype and osteonecrosis: a bidirectional two-sample Mendelian randomization analysis

Purpose: Previous studies have explored the role of immune cells on osteonecrosis. This Mendelian randomization (MR) study further assessed 731 immunocyte phenotypes on osteonecrosis whether a causal relationship exists and provides some evidence of causality. Methods: The 731 immunocyte phenotypes and osteonecrosis data used in this study were obtained from their respective genome-wide association studies (GWAS). We used inverse variable weighting (IVW) as the primary analysis method. In addition, we simultaneously employed multiple analytical methods, including MR-Egger, weighted mode, simple mode, and weighted median, to strengthen the final results. Finally, sensitivity analyses were conducted to verify the stability and feasibility of the data. Results: The results of the IVW method of MR analysis showed that 8 immunocyte phenotypes were positively associated with osteonecrosis ( P <0.05, OR > 1); 18 immunocyte phenotypes were negatively associated with osteonecrosis ( P <0.05, OR<1), none of which were heterogeneous or horizontally pleiotropic ( P > 0.05) or reverse causality. In addition to this, in reverse MR, osteonecrosis was positively associated with 10 additional immunocyte phenotypes ( P <0.05, OR > 1) and negatively associated with 14 immunocyte phenotypes ( P <0.05, OR<1). And none of them had heterogeneity and horizontal pleiotropy ( P > 0.05) or reverse causality. Conclusions: We demonstrated a complex causal relationship between multiple immune phenotypes and osteonecrosis through a comprehensive two-way two-sample MR analysis, highlighting the complex pattern of interactions between the immune system and osteonecrosis.