THE KERATOCYTE DENSITY OF HUMAN DONOR CORNEAS

The cellularity of the human corneal stroma has not been described in the literature. In the present study we calculated the density of keratocytes in human donor corneas using a new method for biochemical measurement of the stromal DNA content (sDNA). The DNA measurements were compared to morphological counts of the number of keratocyte nuclei,per area (KNPA) obtained from histological sections. A significant correlation was found between the data achieved by the two methods (r = +0.52, p < 0.001, n = 46). No significant change in either sDNA or KNPA was found during 28 days of organ culture, and no influence of donor age, sex, or post mortem time was found on either sDNA or KNPA. Both sDNA and KNPA approximated a normal distribution with a mean sDNA of 1.10 +/- 0.25 mu g DNA/mg dry tissue weight and an average KNPA of 200 +/- 53 nuclei/mm(2) (n = 35). Between paired corneas the sDNA were closely correlated (r = +0.83, p < 0.005, n = 11 pairs) with an intra-individual variation of only 0.5%. Using the sDNA data, the keratocyte density in the central region of human donor corneas was calculated to be 129.000 +/- 29.000 per mg dry tissue weight (n = 35). Thus, when corneal grafting is performed (using a 7 mm trephine) an average of 818.000 +/- 186.000 donor keratocytes are transplanted. Assuming a uniform cellularity throughout the stroma, the average number of keratocytes was calculated to be 2.430.000 +/- 551.000 per human donor cornea. These data provide normal values for studying alterations in the cellularity of the human corneal stroma in different pathological conditions.