Caveolin-1 expression is a distinct feature of chronic rejection-induced transplant capillaropathy

Peritubular capillary basement membrane multilayering (PTCBMML) is a pathological landmark of chronic rejection-induced transplant capillaropathy (TC), but its cellular mechanisms are not fully understood. We observed de novo caveolae formation in endothelial cells in TC under electron microscopy. To examine the role of caveolae and their structural components in TC, biopsy samples from cases of chronic rejection were double-immunostained for Caveolin-1 (Cav-1) and Pathologische Anatomie Leiden-endothelium (PAL-E; a marker of peritubular capillary [PC]). Thirty-two cases of chronic rejection (group I) were compared with 18 cases of interstitial fibrosis and tubular atrophy with no evidence of any specific etiology (IF/TA; group II) and eight cases of peritubular capillaritis (group III). The Cav-1/PAL-E immunoreactivities in groups I-III (%Cav-1/PAL-E) were 41.8+/-23.1%, 8.1+/-7.3% (p < 0.01 vs. group I) and 12.7+/-7.4% (p < 0.01 vs. group I), respectively. Furthermore, multiple linear regression models demonstrated that %Cav-1/PAL-E was independently associated with the PTCBMML grade and reduced PC number. No correlation was observed between %Cav-1/PAL-E and PC C4d deposition in group I. We conclude that de novo caveolae formation in PC endothelia is involved in TC in chronic rejection.