Impact of older donor age in kidney transplants in a biopsy-based observational study

Because older donor age is a major concern when considering kidneys for potential transplantation, we explored the actual effect of donor age on the features of kidneys that have been transplanted. We studied the correlations of donor age with molecular injury and rejection scores in 4,502 kidney transplant biopsies assessed by microarrays as well as function and postbiopsy survival. We used multivariable analyses to correct for the correlations of donor age with other predictive variables: recipient age, time of biopsy after transplant, and deceased versus living donors. Older donor age correlated with lower glomerular filtration rate (GFR) and increased acute and chronic injury transcripts but had no effect on rejection, which was anticorrelated with recipient age. Acute injury transcripts peaked immediately after transplant and regressed. Older donor age had little effect on acute molecular injury immediately after transplant but strongly increased molecular injury scores at later times, peaking about 1-year after transplant, indicating that older age does not increase molecular injury but increases failed repair after injury. As expected, older donor age correlated with increased chronic injury and lower GFR, evident from the earliest time after transplant, pretransplant aging. However, despite substantial age-related effects, the quantitative contribution of donor aging to molecular injury, function, and survival was very small.