Expression of CD44 in kidney after acute ischemic injury in rats

De novo CD44 and ligand expression at wound margins accompanies cellular pr oliferation and migration that effect repair of injured mucosal and vascula r endothelial tissues. To determine whether CD44 could play a role in recov ery from acute ischemic renal injury, we characterized its renal. expressio n and those of two of its ligands, hyaluronic acid and osteopontin. Althoug h no expression is detectable in nonischemic kidneys, several mRNAs for CD4 4 are present within 1 day after injury. CD44 mRNA is expressed in proximal tubules undergoing repair. CD44 peptide is present in basal and lateral ce ll membranes. Hyaluronic acid is normally expressed in the interstitium of the renal papilla only. By 1 day postischemia, hyaluronic acid can be detec ted, in addition, in the interstitium surrounding regenerating tubules. Ost eopontin, not normally expressed in the renal proximal tubule, is expressed in regenerating tubules by 3 days after induction of acute ischemic injury . Immunoreactive osteopontin peptide continues to be localized in those tub ules still undergoing repair for as long as 7 days after the injury. Our da ta are consistent with a role for CD44-ligand interactions in the regenerat ing proximal tubule participating in the process of recovery after ischemic injury.