title: The efficacy and toxicity of rapamycin in murine islet transplantation. In vitro and in vivo studies.
abstract: We performed an in vivo and in vitro dose-response study of the novel immunosuppressive macrolide antibiotic rapamycin looking at murine islet allograft survival, impact on glucose homeostasis, and possible tissue toxicity. A total of 300 islets were isolated from CBA/J mice (H-2k) and transplanted beneath the renal capsule of streptozotocin-induced diabetic BALB/c (H-2d) recipients. Seven groups of allografted mice received intraperitoneally for 7 days post-transplant: no immunosuppression (n = 8); vehicle only (carboxymethyl-cellulose) (n = 6); or rapamycin at dosages of 0.05 (n = 8), 0.1 (n = 8), 0.3 (n = 8), 1.0 (n = 8), or 5.0 (n = 6) mg/kg/day. Blood glucose was monitored on alternate days, with graft failure defined by the first day of persistently high blood glucose (> 14 mmol/L). The 0.1 and 0.3 mg/kg/day groups showed statistically significant prolongation of diet allograft survival (P < 0.01) when compared to the controls and vehicle-treated mice. Three mice in both the 0.1 and 0.3 mg/kg/day groups and one mouse in the 0.05 mg group reached 100 days normoglycemia and, following nephrectomy of the islet-bearing kidney, returned to hyperglycemia. The 0.05, 1.0, and 5.0 mg/kg/day groups showed no statistically significant prolongation of graft survival. In addition, the higher dosage (1.0 and 5.0 mg/kg/day) groups had erratic blood glucose control. Histologically, there was no evidence of toxicity seen in any of the multiple organ samples. In the in vitro analysis, BALB/c (H-2k) islets cultured in either 0, 10, 30, or 100 ng/ml rapamycin had no significant differences in insulin secretion following a 24-hr culture period; however, there was a significant deterioration in glucose stimulated insulin release after 72 hr culture at high rapamycin concentration (100 ng/ml). Rapamycin significantly prolonged murine islet allograft survival. At doses 10 to 50 times the effective antirejection dosage, we demonstrated adverse impact on glucose homeostasis without histological evidence of end-organ toxicity. We also demonstrated an adverse impact on insulin release in vitro following prolonged culture (72 hr) in a high concentration of rapamycin.
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, Canada.
authors.forename: M C
authors.initials: MC
authors.lastname: Fabian
authors.forename: J R
authors.initials: JR
authors.lastname: Lakey
authors.forename: R V
authors.initials: RV
authors.lastname: Rajotte
authors.forename: N M
authors.initials: NM
authors.lastname: Kneteman
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism; D006085:Graft Survival / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D016381:Islets of Langerhans Transplantation; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D011090:Polyenes / Q000627:therapeutic use* / Q000633:toxicity; D020123:Sirolimus
chemical_list: D007166:Immunosuppressive Agents; D007328:Insulin; D011090:Polyenes; D005947:Glucose; D020123:Sirolimus