Introduction-Recent studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Previous research using regional magnetic resonance spectroscopy methods to measure BMAT has reported inconsistent findings on the relationship between BMAT and dual-energy absorptiometry (DXA)-measured bone mineral density (BMD).

Summary The relationship between bone marrow adipose tissue and bone mineral density is different between African Americans and Caucasians as well as between men and women. This suggests that the mechanisms that regulate the differentiation and proliferation of bone marrow stromal cells may differ in these populations. Introduction It has long been established that there are ethnic and sex differences in bone mineral density (BMD) and fracture risk. Recent studies suggest that bone marrow adipose tissue (BMAT) may play a role in the pathogenesis of osteoporosis. It is unknown whether ethnic and sex differences exist in the relationship between BMAT and BMD. Methods Pelvic BMAT was evaluated in 455 healthy African American and Caucasian men and women (age 18–88 years) using whole-body T1-weighted magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry. Results A negative correlation was observed between pelvic BMAT and total body BMD or pelvic BMD (r=−0.533, −0.576, respectively; P<0.001). In multiple regression analyses with BMD as the dependent variable, ethnicity significantly entered the regression models as either an individual term or an interaction with BMAT. Menopausal status significantly entered the regression model with total body BMD as the dependent variable. African Americans had higher total body BMD than Caucasians for the same amount of BMAT, and the ethnic difference for pelvic BMD was greater in those participants with a higher BMAT. Men and premeno-pausal women had higher total body BMD levels than postmenopausal women for the same amount of BMAT. Conclusions An inverse relationship exists between BMAT and BMD in African American and Caucasian men and women. The observed ethnic and sex differences between BMAT and BMD in the present study suggest the possibility that the mechanisms regulating the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

Our results suggest that the herein introduced simple measure of irregularities in vertebral alignment could provide useful supplement to the currently used diagnostic tools of fracture prediction in elderly women.

Diversities in cancers pose difficulties in identifying effective therapies. Currently, it is unknown how the cell of origin influences the characteristics of melanoma, a highly heterogeneous and most dangerous cancer in the skin. Here, we introduced melanoma-forming mutations in two distinct populations of stem cells in adult mouse skin. Lineage tracing reveals that melanocyte stem cells harbored in the hair follicle possess the potential to form pigmented epidermal melanoma. In contrast, nestin positive multipotent stem cells residing in the skin dermis produce amelanotic dermal melanoma. Upon transplantation into the same microenvironment, they produce distinct melanoma tumors of consistent phenotype. Furthermore, they respond differently to the modulation of signaling pathways that dictate proliferation and differentiation of melanocytic cells. These results demonstrate that the distinct cell of origin confers inherent differences to melanoma, providing a new mechanism why melanoma tumors with the same genetic mutations are divergent in phenotypes and responsiveness to therapies.