Bone Marrow Adipose Tissue

Abstract

Bone marrow (BM) acts as a dynamic organ within the bone cavity, responsible for hematopoiesis, skeletal remodeling, and immune system control. Bone marrow adipose tissue (BMAT) was long simply considered a filler of space, but now it is known that it instead constitutes an essential element of the BM microenvironment that participates in homeostasis, influences bone health and bone remodeling, alters hematopoietic stem cell functions, contributes to the commitment of mesenchymal stem cells, provides effects to immune homeostasis and defense against infections, and participates in energy metabolism and inflammation. BMAT has emerged as a significant contributor to the development and progression of various diseases, shedding light on its complex relationship with health. Notably, BMAT has been implicated in metabolic disorders, hematological malignancies, and skeletal conditions. BMAT has been shown to support the proliferation of tumor cells in acute myeloid leukemia and niche adipocytes have been found to protect cancer cells against chemotherapy, contributing to treatment resistance. Moreover, BMAT's impact on bone density and remodeling can lead to conditions like osteoporosis, where high levels of BMAT are inversely correlated with bone mineral density, increasing the risk of fractures. BMAT has also been associated with diabetes, obesity, and anorexia nervosa, with varying effects on individuals depending on their weight and health status. Understanding the interaction between adipocytes and different diseases may lead to new therapeutic strategies.

Keywords: bone marrow adipocytes; bone marrow disorder; bone marrow microenvironment.

Figure 1

Bone marrow adipose tissue trephine of a 50-year-old woman. Adipocytes are shown as holes in the biopsy. Original magnification ×10, scale bar 20 μm.

Figure 2

A Transmission Electron Microscopy of human normal bone marrow. Left: an adipocyte is surrounded by different types of hematopoietic cells. The squared area is enlarged in the right panel showing the nucleus of the adipocyte and the close connection with hematopoietic cells. Bar: 3 mm in left panel and 0.5 mm in right panel.