Diabetic Microangiopathy in the Bone Marrow Causes Hypoperfusion and Depletion of the Stem Cell Niche.

Diabetes mellitus [DM], with its burden of premature morbidity and mortality, represents one of the major threats to human health in the 21st century (Zimmet 2001). Accelerated atherosclerosis affecting arteries that supply the heart, brain and lower extremities is responsible for an increased risk of acute ischemic events. DM is also associated with microvascular disease, which is a leading cause of blindness, renal failure and debilitating neuropathies. Endothelial dysfunction, increased vascular permeability and microvascular cell loss by apoptosis are all hallmarks of diabetic microangiopathy. Diabetic patients not only incur cardiovascular complications more frequently, but also experience worse outcomes due to attenuation of vascular repair mechanisms. This impairment includes quantitative and qualitative abnormalities of bone marrow [BM]-derived progenitor cells (Emanueli 2002&2004; Loomans 2004; Krankel 2005; Fadini 2006). The mechanisms underlying BM dysfunction remain however enigmatic, especially when considering the privileged location that protects stem cells [SC] and progenitor cells [PC] of the marrow from external insults (Kopp 2008 and Kiel 2008). BM endothelial cells [EC] are instead an obvious target of DM, because they are directly exposed to blood glucose and incapable to regulate glucose influx. Strangely enough, little is known about the impact of diabetes on BM microvasculature. We hypothesize that damage induced by DM might start at the microvascular level, in a similar fashion to microangiopathy, which occurs in kidney, retina, heart and brain. We also propose that enduring microvascular cell loss might result in marrow hypo-perfusion and destabilization of SC homeostasis.

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