Background: The biologic responses to transforming growth factor-beta (TGF-beta) suggest many potential therapeutic applications; however, in the only clinical trial to examine the effect of the systemic administration of a TGF-beta isoform, patients experienced significant but reversible declines in renal function. We studied the effects of administering human recombinant TGF-beta2 to adult mice.
Methods: The effect of daily administration of TGF-beta2 on tissue vasoconstriction, tissue levels of endothelin and angiotensin II, tissue hypoxia, and renal fibrosis were examined.
Results: Daily administration of TGF-beta2 at 10 or 100 microg/kg caused apparent tissue vasoconstriction that was visualized by vascular casting, with the largest impact seen in the kidney. Tissue levels of endothelin 1 and angiotensin II were significantly elevated in kidneys of treated mice, as was urinary thromboxane beta2. Renal fibrosis was observed in the cortical tubular interstitium and vasculature, particularly at the cortical-medullary junction and medullary vasa recta; however, glomerular sclerosis was not observed. Fibrosis was correlated to focal tissue hypoxia as determined by immunohistochemical detection of tissue bound pimondazole.
Conclusion: We conclude that there are significant histopathologic consequences, focused in the kidney, resulting from the daily administration of high doses of human recombinant TGF-beta2, and we propose that selective vascular constriction with consequent tissue hypoxia is a contributing factor.