High-dose erythropoietin inhibits apoptosis and stimulates proliferation in neonatal rat intestine.

BACKGROUND: Erythropoietin (Epo) receptors are widely expressed in the small bowel of neonatal rats and evidence suggests Epo has important trophic effects in developing bowel. OBJECTIVE: To compliment in vitro data, we directly examine in vivo the hypotheses that systemic Epo treatment can promote cell division and enterocyte migration, and arrest apoptosis in the ileum of neonatal rats. DESIGN: Epo (5000 U/kg s.c.) or vehicle treatments were given to one week old Sprague-Dawley rats (n = 86) along with timed injections of the thymidine analog 5-bromo-2-deoxyuridine (BrdU, 50mg/kg s.c.) to label DNA synthesis and track newly proliferating cells. To characterize the time course of effects, animals were killed at scheduled times from 30 min to 24 h after treatment. BrdU-containing cells were immunostained and counted in intestinal crypts, villi, and muscle wall of ileum. Effects of Epo on apoptosis were analyzed by TUNEL staining. Calibrated measurements were made to determine the density or relative proportion of BrdU- and TUNEL-positive cells. RESULTS: Systemic high-dose Epo promoted cell division in intestinal smooth muscle and enterocytes, stimulated migration of intestinal epithelial cells, and arrested apoptosis of enterocytes at the villous tips. CONCLUSION: These data provide in vivo evidence that Epo functions trophically in developing intestine tissues.