Recipient age and weight affect chronic renal allograft rejection in rats

Nephron doses and immune responses change with age. Therefore, age is a pot ential risk factor for graft survival after kidney transplantation. The aim of this study was to determine whether age-related differences are of impo rtance for long-term outcomes after renal transplantation. Kidneys from Fis her 344 rats were orthotopically transplanted into nephrectomized Lewis rat s. Kidneys were transplanted using donors and recipients of three age level s, i.e., young (8 wk of age), adult (16 wk of age), and old (40 wk of age). Rats were killed 24 wk after transplantation, and functional, morphologic, and molecular evaluations were performed. Recipient age, rather than donor age, determined graft survival rates. No significant correlation was obser ved between donor kidney weight on the day of transplantation and morpholog ic results. Advanced recipient age was associated with reduced creatinine c learance, more severe histologic injuries, including extended glomerular sc lerosis, interstitial fibrosis, and vascular lesions, more pronounced cellu lar infiltration, and greater expression of transforming growth factor-beta and platelet-derived growth factor A and B chains. Although no significant correlation between donor age or kidney weight on the day of transplantati on and morphologic results was observed, there was a significant correlatio n between recipient body weight on the day of transplantation and allograft injury. It is concluded that recipient age and weight affect chronic renal rejection. Renal allografts may benefit from young recipient age but may d eteriorate in old recipients, suggesting effects of recipient functional de mand on long-term outcomes.