ABSTRACT
The identity of BMSCs in situ has long remained elusive. Morphological data point to cells with ill-defined morphology and multiple names: adventitial cells, reticular cells, stromal fibro blasts, preadipocytes, undifferentiated mesenchymal cells, Westen-Bainton cells. In the post-natal marrow, these cells form both an adventitial (outer) coating of the sinusoid wall and branching extravascular meshwork that provides the physical substrate for myelopoiesis. Westen-Bainton cells are characterized by extensive, elongated and attenuated cell processes with membrane-bound alkaline phosphatase activity.61 They express low levels of collagen types I and III and osteonectin, indicative of their partial fibroblastic character.8,51 In human post-natal marrow, Weston-Bainton cells also demonstrate characteristics of preadipocytes.5 In different animal species, varying proportions of these cells survive mechanical dissociation and plating in vitro. Of those that survive and attach to the culture vessels, the great majority begin to proliferate to form BMSC colonies, and are likely CFU-Fs, at least in part.
