Recipient age and weight affect chronic renal allograft rejection in rats.

Nephron doses and immune responses change with age. Therefore, age is a potential risk factor for graft survival after kidney transplantation. The aim of this study was to determine whether age-related differences are of importance for long-term outcomes after renal transplantation. Kidneys from Fisher 344 rats were orthotopically transplanted into nephrectomized Lewis rats. Kidneys were transplanted using donors and recipients of three age levels, 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 observed between donor kidney weight on the day of transplantation and morphologic results. Advanced recipient age was associated with reduced creatinine clearance, more severe histologic injuries, including extended glomerular sclerosis, interstitial fibrosis, and vascular lesions, more pronounced cellular 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 transplantation and morphologic results was observed, there was a significant correlation 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 deteriorate in old recipients, suggesting effects of recipient functional demand on long-term outcomes.