Upregulation of MT1-MMP Expression by Hyaluronic Acid Enhances Homing-Related Responses of Hematopoietic CD34⁺ Cells to an SDF-1 Gradient.

Hyaluronic acid (HA), the bone marrow (BM) extracellular matrix microenvironment (ECM) component, not only supports cell adhesion but also promotes migration and homing of hematopoietic stem/progenitor cells (HSPC) by interacting with its cell surface receptor CD44. CD44 has been shown to co-localize with matrix metalloproteinases (MMPs), particularly membrane-type (MT)-1 MMP and MMP-9, at the leading edge of migrating tumor cells, and the cleavage of CD44 by MT1-MMP is critical for tumor cell migration and invasion. MT1-MMP has strong pericellular proteolytic activity and also activates latent forms of MMP-2 and MMP-9. In this study we examined the effect of HA on MT1-MMP expression and migration of BM, peripheral blood and cord blood CD34⁺ cells. We found that HA upregulates mRNA for MT1-MMP and MMP-9, increases MT1-MMP protein (as evaluated by Western blotting) and stimulates MMP-9 and MMP-2 activity (as determined by zymography) in CD34⁺ cells. In chemotaxis assays HA alone did not show any chemotactic activity but primed the chemotaxis of CD34⁺ cells to a low SDF-1 gradient (10 ng/mL) and their trans-Matrigel chemoinvasion to a low SDF-1 gradient. Similarly, SDF-1 besides stimulating MMP-2 and MMP-9 (as we previously described in