Bone marrow sinusoidal endothelium: damage and potential regeneration following cancer radiotherapy or chemotherapy.

It is very well known that bone marrow (BM) microvasculature may possess a crucial role in the maintenance of homeostasis of BM due to mutual interactions between BM microvascular system and other physiological functions including haematopoiesis and osteogenesis. Chemotherapy and radiotherapy are known as main approaches for cancer treatment and also are known as the main cause of damage to the BM microvascular system. However, despite the importance of BM microvasculature in orchestrating various biological functions, less attention has been drawn to address the underlying mechanisms for the damage and to explore cellular and molecular mechanisms by which the recovery/regeneration of chemotherapy- and/or radiotherapy-induced BM microvascular system damage can occur. Therefore, in this review we firstly discuss the ultra-/structure and biological characteristics of BM microvascular system (sinusoids). Secondly, potential contribution of BM sinusoids is discussed in pathophysiological circumstances (bone remodelling, haematopoiesis, cancer bone metastasis, and haematological cancers). Thirdly, we address previous preclinical and clinical studies regarding chemotherapy- and irradiation-induced BM microvasculature damage. Finally, potential cellular and molecular mechanisms are discussed for the recovery/regeneration of damaged BM microvascular system, including the potential roles of endothelial progenitor cells, haematopoietic stem/progenitor cells, and stimulation of VEGF/VEGFR and Ang-1/Tie-2 signalling pathways.