Transcriptomic profiling reveals a dramatic inflammatory shift in osteal macrophages during colitis-induced osteoporosis.

OBJECTIVE

Colitis disrupts the intestinal barrier, leading to increased permeability and the translocation of harmful microbial components into the circulation and distant organs, including bone. Given that macrophages serve as both frontline immune defenders in tissues and key regulators of bone homeostasis, this study investigates molecular alterations in osteal macrophages (Omacs) and their contribution to bone loss in a murine model of colitis-induced osteoporosis.

METHODS

Colitis-induced osteoporosis was established by administering DSS in drinking water for 5 days. Omacs were isolated from bone tissue and subjected to bulk RNA-seq analysis, phagocytosis assays and co-culture models with osteoblasts or osteoclast precursors.

RESULTS

RNA-seq data of Omcas demonstrated a shift towards an inflammatory phenotype under colitis conditions, which was accompanied by bone loss in mice. The upregulated genes in these cells were most significantly enriched in IL-17, NF-κB, and TNF signaling pathways. Importantly, these cells exhibited decreased phagocytic activity and were able to disrupt osteoblast differentiation and promote osteoclast differentiation in vitro.

CONCLUSIONS

These results indicate that colitis triggers a significant inflammatory response in Omacs, which can contribute to bone metabolic dysfunction. Modulating the activation of inflammatory pathways may offer a potential therapeutic avenue for treating colitis-induced osteoporosis.