Type-2 diabetic Lepr(db/db) mice show a defective microvascular phenotype under basal conditions and an impaired response to angiogenesis gene therapy in the setting of limb ischemia

Front Biosci. 2007 Jan 1:12:2003-12. doi: 10.2741/2205.

Abstract

Diabetes mellitus is associated with macro- and micro-angiopathy, leading to increased risk of peripheral ischemia. In the present study, we have characterized the microvascular phenotype at the level of limb muscles and the spontaneous angiogenesis response to surgically-induced unilateral limb ischemia in a murine model of type-2 diabetes, the obese C57BL/KsOlaHsd-Lepr(db/db) mice (Lepr(db/db)), and in non-diabetic heterozygous Lepr(db/+). Wild type C57BL mice (WT) were used as controls. The basal microvascular phenotype was determined in mice aged 3 or 5 months, while the response to limb ischemia was studied only in 5-month old mice. Moreover, in 5-month old ischemic Lepr(db/db) and Lepr(db/+), we have tested the therapeutic potential of local angiogenesis gene therapy with human tissue kallikrein (hTK) or constitutively-activated Akt kinase (Myr-Akt). We found that in the muscles of 3- or 5-month old Lepr(db/db), apoptosis of endothelial cells was enhanced and the densities of capillary and arteriole were reduced. Arterioles of Lepr(db/db) showed hypertrophic remodelling and, occasionally, lumen occlusion. Following ischemia, Lepr(db/db) showed a defective reparative angiogenesis in ischemic muscle, delayed blood flow recovery, and worsened clinical outcome as compared with controls. Five-month old Lepr(db/+) displayed an increase in endothelial cell apoptosis under basal conditions, while capillary and arteriole densities were normal. Lepr(db/+) mounted a proper reparative angiogenesis response to limb ischemia and regained blood flow to the ischemic limb, regularly. Local gene therapy with hTK or Myr-Akt induced angiogenesis in ischemic muscles of Lepr(db/+) and Lepr(db/db). However, in the Lepr(db/db) neither gene therapy approach improved the blood flow recovery and the clinical outcome from ischemia. In contrast, either hTK or Myr-Akt gene transfer improved the post-ischemic recovery of Lepr(db/+). Type-2 diabetes has a negative impact on the basal microvascular phenotype and severely impairs post-ischemic recovery of limb muscles. Gene therapy-induced stimulation of neovascularization might not suffice as a sole therapeutic strategy to combat type-2 diabetes-related vascular complications. In type-2 diabetic patients, therapeutic angiogenesis may need to be further optimized before being recommended for clinical applications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Capillaries / pathology
  • Diabetes Mellitus, Type 2 / complications*
  • Diabetic Angiopathies / pathology
  • Diabetic Angiopathies / physiopathology
  • Diabetic Angiopathies / therapy*
  • Genetic Therapy*
  • Humans
  • Ischemia / pathology
  • Ischemia / physiopathology
  • Ischemia / therapy*
  • Lower Extremity / blood supply
  • Mice
  • Mice, Inbred C57BL
  • Mice, Obese
  • Muscle, Skeletal / blood supply
  • Muscle, Skeletal / metabolism
  • Neovascularization, Physiologic*
  • Nitric Oxide Synthase Type III / metabolism
  • Phenotype
  • Proto-Oncogene Proteins c-akt / genetics
  • Receptors, Cell Surface / genetics
  • Receptors, Leptin
  • Tissue Kallikreins / genetics
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Receptors, Cell Surface
  • Receptors, Leptin
  • Vascular Endothelial Growth Factor A
  • Nitric Oxide Synthase Type III
  • Proto-Oncogene Proteins c-akt
  • Tissue Kallikreins