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No use, distribution or reproduction is permitted which does not comply with these terms. The common cellular origin between bone marrow adipocytes BMAds and osteoblasts contributes to the intimate link between bone marrow adipose tissue BMAT and skeletal health. An imbalance between the differentiation ability of BMSCs towards one of the two lineages occurs in conditions like aging or osteoporosis, where bone mass is decreased. Here we show that the absence of PiT2 in juveniles leads to an increase in the BMAT that does not originate from an increased adipogenic differentiation of bone marrow stromal cells.
In contrast, the absence of PiT2 does not prevent the increase in BMAT volume in a model of ovariectomy-induced bone loss. Bone marrow adipose tissue BMAT is no longer considered a marrow space filler tissue as the increasing number of studies on its function in the past 20 years has highlighted its important roles in skeletal health or energetic metabolism. However, the underlying cellular and molecular mechanisms involved remain to be determined 1 β 3. In mice, bone marrow adipocytes BMAds first develop in the distal tibia at a very early postnatal age and then appear in the proximal tibia at around 3 months of age 3 , 4.
The proximal and distal BMAT are two distinct tissues mainly because the size and the lipidic components of the adipocytes are different, and both are differentially regulated 5. A growing interest in BMAT and its intimate relationship with skeletal health has emerged in recent years.
Inverse correlation between BMAT volume and bone mass has been described in many situations 5 and also in some genetic mouse models 6 β However, this negative correlation is not always observed and may even be controversial, as in the ovariectomy-induced osteoporosis model 7 , Nevertheless, during puberty, the amount of marrow fat is positively associated with total bone mineral content in girls 18 and, although men have more BMAT mass compared to women, they also have more bone mass These observations highlight a complex relationship between BMAT and bone, which probably cannot be described in all circumstances as a simple inverse correlation.
