Hyaluronate Uptake and CD-44 Activity in Fetal and Adult Fibroblasts

One of the unique aspects of fetal wounds is the persistence of a high concentration of hyaluronic acid (HA) in the extracellular matrix. Within the wound environment, both the synthesis and breakdown of this complex glycosaminoglycan are regulated predominately by the fibroblast with cell binding mediated by the membrane receptor CD-44. The ability of adult and fetal fibroblasts to incorporate fluorescent-labeled HA (F-HA) was measured, and the effect of a monoclonal antibody to CD-44 to block this uptake was studied. Fetal fibroblasts incorporated significantly greater F-HA than adult fibroblasts at the 4- and 6-hr times ( P < 0.05), while CD-44 blockade reduced the uptake to background levels. These results demonstrate that fetal fibroblasts incorporate F-HA more rapidly than adult fibroblasts and that this uptake is mediated by the membrane protein CD-44.