we propose that this organization involves a spectrum of microenvironmental complexity concomitant with changing cellular requirements , that it is achieved by the extracellular matrix produced by marrow stromal cells , and that its specificity is conferred by the heterogeneity intrinsic in the conformation of proteoglycans and their constituent glycosaminoglycans .
C0015350
extracellular matrix
C0033692
proteoglycans