Expression of CD44 adhesion molecules on human placentae

Objective: This study was performed to characterize CD44 expression in human placentae. Study design: We conducted reverse transcriptase polymerase chain reaction (RT-PCR) analyses of CD44H (hematopoietic form, also called CD44s) and CD44R1 (epithelial form) in 14 normal term placentae, and immunohistochemical analysis of CD44H and CD44v6 in 31 placentae (25 term and 6 first-trimester). Results: All 14 term placentae expressed CD44H (double bands) suggesting expression of alternative isoforms on the placentae. CD44R1 was expressed on 3 of 14 (21.4%) term placentae. Immunohistochemical analysis revealed expression of CD44H in all the placentae examined. However, positive staining for CD44v6 was observed in 3 of 6 (50%) first-trimester and only 6 of 25 (24%) term placentae showing decreased expression on term placentae. Positive staining for CD44v6 was observed on the trophoblast surface of immature villi especially in the sub-chorionic area where hypoxic conditions prevail. Conclusion: These results suggest that CD44 splicing variants might play a role in the invasion of trophoblast into maternal tissue in early pregnancy.