Tubular CD44 expression in renal allograft biopsies

CD44 is a type I transmembrane glycoprotein serving as a cell adhesion receptor, whose main ligand is hyaluronic acid, but also may interact with collagen, laminin, fibronectin, and osteopontin. This marker is involved in cell migration, homing, activation, metastasis, and inflammation. Tubular CD44 expression has been shown to correlate with scarring in renal diseases, but there is little data on allograft biopsies. This deficiency is important since experimental studies have shown that blockade of the CD44-hyaluronic acid interaction may prolong allograft survival. In an attempt to clarify the role of tubular CD44 expression in renal allografts, CD44 expression was determined immunohistochemically in 37 allograft and 10 implantation biopsies, as the percentage of tubules expressing this marker. For implantation biopsies the mean tubular CD44 expression was 6% +/- 14%; for allograft biopsies, 13% +/- 20% (P =.17, Mann-Whitney U). By the Spearman correlation test, CD44 expression did not correlate with Banff scores, but was moderately correlated with serum creatinine values at the time of biopsy (P =.017, r =.4). These findings suggest an important role of tubular CD44 expression in renal allografts. It appears to be induced by more than one pathway, resulting in a pattern of expression that correlated with renal function. However larger series are required before recommending the routine use of this marker.