Reversal of Streptozotocin-Induced Diabetes in Mice by Cellular Transduction with Recombinant Pancreatic Transcription Factor Pdx1 - A Novel Protein Transduction Domain Based Therapy

Objective: The key pancreatic transcription factor Pdx1, known to control development and maintenance of pancreatic β-cells, possesses a protein transduction domain (PTD) that facilitates its entry into cells. We therefore sought to evaluate the capacity of in vivo-administered recombinant Pdx1 (rPdx1) to ameliorate hyperglycemia in a streptozotocin (Stz)-induced diabetic mice. Research Design and Methods: Cell entry and transcriptional regulatory properties of rPdx1 and its PTD-deletion mutant rPdx1∆, as well as a PTD-GFP reporter protein were evaluated in vitro. After intraperitoneal rPdx1 injection into Stz-diabetic mice, we assessed the its action on blood glucose levels, insulin content, and IPGTT, as well as Pdx1 distribution, pancreatic gene expression, islet cell proliferation, and organ histology. Results: Restoration of euglycemia in Pdx1-treated diabetic mice was evident by improved IPGTT and glucose-stimulated insulin release. Insulin-, glucagon-, and Ki67-immunostaining revealed increased islet cell number and proliferation in pancreata of rPdx1-treated mice. Realtime PCR of pancreas and liver demonstrated up-regulation of INS and PDX1 genes as well as other genes relevant to pancreas regeneration. While the time-course of β-cell gene expression and serum/tissue insulin levels indicated that liverand pancreas-derived insulin contributed to restoration of normoglycemia, near-total pancreatectomy resulted in hyperglycemia, suggesting that β-cell regeneration played the primary role in rPdx1-induced glucose homeostasis. Conclusions: rPdx1 treatment of Stz/diabetic mice promotes β-cell regeneration and liver-cell reprogramming, leading to restoration of normoglycemia. This novel PTD-based protein therapy offers a promising way to treat patients with diabetes, while avoiding potential side-effects associated with the use of viral vectors.