Abstract
Purpose: :
Proliferative diabetic retinopathy (PDR) results from the proliferation of retinal capillary endothelial cells. In many tissues, estrogen induced proliferation of cells is well documented. We hypothesized that 17β estradiol (E2) induces proliferation in retinal capillary endothelial cells and that this estrogen effect is mediated by PEDF.
Methods: :
Monkey retinal capillary endothelial cells (mREC) in culture were exposed to 1nM E2 for 1, 3, 5 and 7 days to study the effect of E2 on the change in the total number of mREC in culture. mREC were also exposed to 1 nM E2, 1 nM E2 + 1nM tamoxifen (TM) and 1 nM E2 + 1nM raloxifene (RA) for 6 days. The numbers of viable mREC were counted using a hemocytometer and trypan blue method. Conditioned media were collected and assayed for PEDF levels by ELISA.
Results: :
The total number of mREC in culture increased from 17k (day 0) to 70k (day 7) in a control media of MEMα-1X with 10% charcoal-stripped FBS. When exposed to E2, the number of mREC in culture increased at all sampling points (90k cells on day 7). In a subsequent experiment, E2 treatment of mREC increased the viable cell number from 130k (control) to 260k in 6d. However, the addition of TM and RA reduced cell proliferation counts to 120k and 133k, respectively. E2 treatment also reduced the level of PEDF in the conditioned media from 0.2 pg/10k viable cells in control media to 0.1 pg/10k viable cells. The addition of TM and RA returned the PEDF level in the conditioned media to 0.2 pg/10k viable cells.
Conclusions: :
E2 (1 nM) induced a significant increase in the number of mREC in culture, suggesting a possible role of E2 in the development of PDR. Selective estrogen receptor modulators TM and RA were effective modulators of this estrogen effect on mREC proliferation. E2 also induced a significant decrease in PEDF in the conditioned media and this effect of estrogen was modulated by TM and RA. Since PEDF is known to inhibit the proliferation of endothelial cells, the estrogen-induced mREC proliferation we observed may well be mediated by PEDF.
Keywords: drug toxicity/drug effects • diabetic retinopathy • receptors