E. D. Stamper1, P. Matheson2,3, A. Clarke1, J. Smith2, R. N. Garrison2,3, C. D. Downard4 1University Of Louisville,School Of Medicine,Louisville, KY, USA 2University Of Louisville,Department Of Surgery,Louisville, KY, USA 3Robley Rex Veterans Affairs Medical Center,Surgery,Louisville, KY, USA 4University Of Louisville,Pediatric Surgery,Louisville, KY, USA
Introduction: Relaxin (RLXN) supplementation in experimental necrotizing enterocolitis (NEC) decreases severity of disease by mechanisms that include increased ileal blood flow via microvascular vasodilation. However, RLXN also stimulates angiogenesis in adults, at least partially by up-regulating the platelet-derived growth factor (PDGF) family and analogous receptors. Thus, we hypothesized that oral RLXN given with diet gavage might alter PDGF and PDGF receptor expression in experimental NEC in rats as compared to Controls or NEC rats alone.
Methods: We induced NEC in Sprague-Dawley rats by premature delivery, formula feeds, oral LPS, and episodic hypoxia/hypothermia. NEC groups (n=12/group), randomized by litter, were: 1) NEC only, 2) NEC + 1x oral RLXN supplement (at 44 hours), and 3) NEC + oral RLXN supplement in All Feeds. Controls (n=12) were vaginally delivered, dam fed, and time-matched. At 48 hours, collected ileum sections were mounted in paraffin, and stained with either H&E or immunohistochemistry (IHC). IHC staining was performed using rabbit anti-rodent polyclonal antibodies for PDGF-A, PDGF-B, PDGF-Rα , or PDGF-Rβ .
Results: Table 1 describes the intensity of IHC staining in mucosal epithelial cells and severity of NEC in the ileum. Briefly, PDGF-A, B, Rα , and Rβ were present in Controls. PDGF-B and PDGF-Rα staining was increased in NEC, while PDGF-A and PDGF-Rβ were decreased. RLXN supplementation in the diet gavage in NEC rats increased PDGF-B expression and PDGF-Rα was maintained.
Conclusion: RLXN supplementation increased PDGF-B expression, which is the primary isoform of the PDGF family involved in angiogenesis, and PDGF-Rα , while decreasing the severity of NEC. These data suggest that the RLXN-mediated increase in angiogenic PDGF might play a role in the improvement of NEC and provide therapeutic direction for future studies with relaxin supplementation in NEC.
