Endothelial Cell Progenitors and Homocysteine

This article [Zhu et al., 2006: (http://www.ncbi.nlm.nih.gov/pubmed/16624647)] shows that the numbers of circulating endothelial progenitor cells vary inversely with serum homocysteine levels (are reduced in people with elevated homocysteine and more numerous in people with low homocysteine). That and similar articles are interesting, but I thought it was interesting to think about the way this type of thing might tie in with something like vitamin A toxicity or other factors that have been causally associated with venous sinus thrombosis and thrombogenic conditions in the cerebral blood vessels. There are almost no articles discussing the mechanisms leading to venous sinus thrombosis. As far as vitamin A and hematopoiesis are concerned, some tiny, basal amount is required to maintain the red blood cell count and to allow the proliferation and differentiation of other bone marrow-derived cells to proceed normally. But a higher vitamin A intake, past that minimal level, doesn't really promote erythrocyte differentiation or have an "antianemic" effect. High intakes tend to cause those derangements of differentiation of bone marrow-derived cells and increase mast cell densities in different tissues, etc. I tend to think that an increase in granulocytic differentiation would tend to be thrombogenic, and there's all the research associating improvements in vitamin D status with reductions in thrombogenicity or antiatherogenicity.

I don't know much about those different markers for endothelial progenitor cells, but this article [Liu et al., 2004: (http://bloodjournal.hematologylibrary.org/cgi/content/full/103/12/4449) (http://www.ncbi.nlm.nih.gov/pubmed/14976050?dopt=Abstract)] discusses CD34+KDR+ cells as being an important class of "hemangioblasts" that are endothelial progenitor cells and can differentiate, in response to epidermal growth factor and vascular endothelial growth factor, into endothelial cells. It looks like Zhu et al. (2006) defined endothelial progenitor cells as those cells that showed AC133 and KDR coexpression (AC133+KDR+ cells). I wonder if those are also CD34+ cells. I can't access the full text of the article by Zhu et al. (2006). This article [Peichev et al., 2000: (http://www.ncbi.nlm.nih.gov/pubmed/10648408?dopt=Abstract)] discusses the fact that the function of AC133 is unknown, but some CD34+AC133+ cells are evidently endothelial cell progenitors.