Bone Lining Cells Could Be Sources of Bone Marrow Adipocytes

It was already known that bone lining cells can respond to hormonal signals by transforming into active osteoblasts. Parathyroid hormone and anti-sclerostin antibody have been shown to trigger this process. However, the potential of bone lining cells to differentiate into other cell types, such as bone marrow adipocytes, remained unclear. No prior work had resolved how bone marrow adipocyte formation might be regulated by these same signals. This uncertainty drove the need to explore the role of bone lining cells in adipogenesis. Researchers have long sought to understand the cellular origins of marrow fat and its implications for bone health. The mechanisms of lineage conversion in bone are still not fully understood. This gap motivated the current investigation into the differentiation potential of bone lining cells.

The goal of this research was to determine whether bone lining cells could give rise to bone marrow adipocytes. The study also aimed to assess the impact of anti-sclerostin antibody on this process. Researchers wanted to clarify the role of bone lining cells in marrow adipogenesis. They sought to determine if rosiglitazone could promote this transformation. The study focused on lineage tracing of bone lining cells in mice. The researchers used genetic markers to track cell fate over time. They wanted to understand the relationship between bone formation and marrow fat accumulation. This work aimed to provide new insights into the cellular mechanisms of bone and fat regulation.

The researchers used Dmp1-CreERt2:mTmG mice to label bone lining cells with a fluorescent marker. Mice received 4-hydroxytamoxifen injections to activate the labeling system. They were treated with either vehicle or rosiglitazone for 8 weeks. Some mice also received anti-sclerostin antibody injections twice weekly. Fluorescently labeled cells were tracked from the bone surface to the marrow. Immunohistochemical staining was used to identify adipocyte markers. Serum levels of bone formation markers were measured at multiple time points. Bone mass was assessed using micro-computed tomography at 20 weeks.

Rosiglitazone significantly increased the number of bone marrow adipocytes derived from bone lining cells. The anti-sclerostin antibody reduced this effect when given alongside rosiglitazone. Fluorescently labeled cells in the marrow showed co-expression of perilipin and GFP. Serum P1NP levels indicated active bone formation in response to the antibody. Bone mass was preserved in mice treated with anti-sclerostin antibody. The antibody reversed the bone loss caused by rosiglitazone. Bone lining cells were found to express PPARγ, a key adipogenic factor. These findings suggest a direct link between bone and marrow fat regulation.

The authors suggest that bone lining cells may serve as a source of bone marrow adipocytes. Rosiglitazone appears to promote the differentiation of these cells into adipocytes. Anti-sclerostin antibody may suppress this process, preserving bone mass. The findings support a role for bone lining cells in marrow fat formation. The study highlights the potential for pharmacologic modulation of bone and fat. The results align with prior evidence of bone cell plasticity. The researchers propose that inhibiting sclerostin could enhance bone formation. These conclusions are based on the observed effects in the experimental model.