Indoleamine 2,3-dioxygenase (IDO) expression induction as gene therapy in experimental pancreatic islet transplantation

Abstract

Purpose: The blockade of allograft rejection is essential to a successful pancreatic islet (PI) transplantation. An attractive alternative arises from the immunological paradox during pregnancy, when the mother does not reject the allogeneic fetus. This protection may be due to the IDO production in the placenta. Purpose: To isolate the IDO cDNA, to construct a vector expression for IDO and to analyze the effect of the IDO expression into PI in an experimental model of PI transplantation. Methods: The IDO cDNA was isolated from rat placenta and inserted in the pcDNA 3.1 vector. PI were transfected using Lipofectamine and different concentrations of the IDO-vector were analyzed. The IDO expression was confirmed by RT-PCR, immunohistochemistry and functional analysis. Lewis rats with streptozotocin-induced diabetes (glycemia >300mg/dL) received islets under the kidney capsule and they were distributed among groups: SYN Tx (syngeneic), Lewis recipients transplanted with islets from Lewis rats; ALLO Tx (allogeneic), Lewis recipients of islets from Sprague-Dawley rats; and ALLO+IDO Tx, Lewis recipients of IDO-transfected islets from Sprague-Dawley rats. Results: The SYN Tx rats presented permanent normoglycemia, while the ALLO Tx rats returned to hyperglycemia (>300mg/dl) few days after transplantation (11+1 days). In contrast, ALLO+IDO Tx rats presented glycemia <300mg/dL during a longer-term follow-up. At day 45, the SYN Tx group presented normal levels of serum insulin (0.55+0.13 ng/mL), while the ALLO Tx group presented a significantly reduction (0.14+0.02 ng/mL; p<0.05). The ALLO+IDO Tx group presented significantly higher levels than the ALLO Tx group (0.33+0.04 ng/mL;p<0.05). Conclusion: The induction of IDO expression protects the islets, increasing islets survival and improving the metabolic control.