Evaluation of influence of 24-hour cold preservation on endothelin production and on endothelin receptors in the bone vasculature

Vascularized bone allotransplantation: current state and implications for future reconstructive surgery

This article focuses on current advances in musculoskeletal tissue allotransplantation, including strategies for maintaining tissue viability in the face of histocompatibility mismatch and resulting acute and chronic rejection responses. In particular, it introduces a novel concept developed in the authors' laboratory and currently under evaluation that may obviate the problem of chronic rejection. The authors have used therapeutic angiogenesis to develop a host-derived neoangiogenic circulation that maintains blood flow regardless of rejection. The replacement of the allogeneic vessels together with bone remodeling from host-derived cells eventually may largely replace the allogeneic osteocytes and bone with native bone.

Cold ischemia induces endothelin gene upregulation in the preserved kidney

BACKGROUND

Prolonged cold ischemia time (CIT) can lead to posttransplant renal dysfunction; however, the pathophysiology remains unclear. Endothelin (ET), a potent vasoconstrictive peptide, may play a role in this injury. The purpose of this study was to determine if cold ischemia could induce renal ET-1 gene upregulation and to localize ET-1 peptide expression in the hypothermic kidney.

MATERIALS AND METHODS

Kidneys from Lewis rats were perfused with Viaspan, harvested, and stored at 4 degrees C for varying periods of CIT: 0, 6, 24, and 48 h. Preproendothelin-1 (ppET-1) gene upregulation was measured using a reverse-transcription polymerase-chain reaction. ET-1 peptide expression was localized using immunohistochemistry.

RESULTS

Control kidneys (0 h CIT) had 0. 56 +/- 0.22 DU of ppET-1 mRNA. After 6 h of CIT, a 2.3-fold increase in this level was noted. Following 24 h of CIT, ppET-1 mRNA was significantly upregulated to 1.96 +/- 0.38 DU (P < 0.05). Immunohistochemistry revealed typical vascular ET-1 staining in control kidneys. At 6 h of CIT, a significant increase in the expression of ET-1 was noted in the peritubular capillaries and vasa recta. After 24 h, intense staining for ET-1 was seen in the medullary collecting ducts. After 48 h of CIT, early cellular necrosis was present along with global decreases in ET-1 expression and ppET-1 mRNA levels.

CONCLUSIONS

This study demonstrates that 24 h of cold preservation can induce significant upregulation of the renal ET-1 gene and increase expression of the ET-1 peptide localized to both vascular endothelial and tubular epithelial surfaces of the kidney. Consequently, prolonged cold ischemia prior to transplantation may lead to delayed renal function following revascularization via endothelin-induced vasoconstriction and/or tubular impairment.

Endothelin induces vasoconstriction in the bone vasculature in vitro: an effect mediated by a single receptor population

The aim of this study was to define the types of endothelin receptors present in the canine tibial vasculature. Endothelin receptor agonists and antagonists were used in two different models: isolated nutrient tibial arteries in organ bath and in vitro-perfused canine tibial bones. In isolated nutrient tibial arteries, endothelin-1 caused concentration-dependent contractions of rings with and without endothelium. BQ-123, a selective endothelin-A antagonist, induced a significant rightward shift of endothelin-1 concentration-response curves. No contractions were observed with sarafotoxin S6c, a selective endothelin-B agonist. The responses of endothelin-1 were not affected by the presence of NG-monomethyl-L-arginine acetate plus indomethacin or by removal of the endothelium. In perfused tibial bones, endothelin-1 was more potent than endothelin-3 in causing concentration-dependent contractions. Neither endothelin-1, endothelin-3, nor sarafotoxin S6c caused relaxations. Neither the inhibition of nitric oxide nor the inhibition of prostaglandins significantly altered contractions to endothelin-1. These concordant data indicate that endothelin is a vasoconstrictor in the bone vasculature, an effect that appears to be mediated only through endothelin-A receptors.