Insulin expressed from endogenously active glucose-responsive EGR1 promoter in bone marrow mesenchymal stromal cells as diabetes therapy.

Advances in islet transplantation have encouraged efforts to create alternative insulin-secreting cells that overcome limitations associated with current therapies. We have recently demonstrated durable correction of murine and porcine diabetes by syngeneic and autologous implantation, respectively, of primary hepatocytes non-virally modified with a glucose-responsive promoter-regulated insulin transgene. As surgical procurement of hepatocytes may be clinically unappealing, we here describe primary bone marrow-derived mesenchymal stromal cells (BMMSC) as alternative insulin-secreting bioimplants. BMMSC are abundant and less invasively procured for clinical autologous transplantation. Electroporation achieved high transgene transfection efficiencies in human BMMSC (HBMMSC) and porcine BMMSC (PBMMSC). We transcriptomically identified an HBMMSC glucose-responsive promoter, EGR1. This endogenously active promoter drove rapid glucose-induced transgene secretions in BMMSC with near-physiological characteristics during static and kinetic induction assays simulating normal human islets. Preparatory to preclinical transplantation, PBMMSC transfected with the circular insulin transgene vector or stably integrated with the linearized vector were evaluated by intrahepatic or intraperitoneal xenotransplantation in streptozotocin-diabetic and non-diabetic NOD-SCID mice. Hyperglycemia, glucose tolerance and body weight were corrected in a dose-responsive manner. Hypoglycemia was not observed even in identically implanted non-diabetic mice. These results establish human EGR1 promoter-insulin construct-modified BMMSC as safe and efficient insulin-secreting bioimplants for diabetes treatment.

Plasmid-electroporated primary hepatocytes acquire quasi-physiological secretion of human insulin and restore euglycemia in diabetic mice.

We describe the durable correction of streptozotocin-induced murine diabetes by in vivo implantation of primary mouse hepatocytes electroporated ex vivo with a human proinsulin cDNA plasmid construct controlled by glucose and zinc regulatory elements. Transfected hepatocytes increased insulin transgene transcription and secretion within 10-20 min of exposure to 25 mM glucose or 60 microM zinc. Insulin release did not occur from secretory granules. Electroporated Rosa26 hepatocytes ( approximately 8 x 10(5) viable cells) were implanted in C57BL/6J diabetic mice in one of three sites: unresected liver, regenerating liver or mesentery. Control diabetic mice were implanted with untransfected hepatocytes. At 30 days after implantation, 8/15 control mice were alive, while 19/19 treated mice were alive. The ratio of body weight on day 30/nadir body weight was significantly higher for all treated groups compared with controls. All eight surviving control mice were hyperglycemic 30 days post-implantation, while 16/19 treated diabetic mice remained normoglycemic. Treated mice had lower mean glucose values (P< or =0.001) without fasting hypoglycemia and better glucose tolerance (P< or =0.0003) than untreated controls. All (6/6) diabetic mice implanted in regenerating liver and 71% (5/7) implanted in unresected liver were alive 77 days after implantation. Engrafted hepatocytes were identified, mainly around central veins, by staining for beta-galactosidase activity and with anti-human insulin antibody.