J. M. Johnson1, M. Orrgren1, M. Auster1, F. W. LoGerfo1, L. K. Pradhan-Nabzdyk1 1Beth Israel Deaconess Medical Center,Vascular And Endovascular Surgery/Surgery,Boston, MA, USA
Introduction: The role of inflammatory cytokines and neuropeptides in peripheral neuropathy and ischemia is not completely understood. These complications of diabetes are known to be major factors in the development of chronic diabetic foot ulcers and non-traumatic limb amputation. This study investigates gene expression of inflammatory cytokines (IL-8, its receptor CXCR1 and IL-6) and neuropeptide receptors (NPY receptors, NPY2R and NPY5R and Substance P receptor, NK1R) in a diabetic rabbit neuroischemic wound healing model.
Methods: New Zealand White rabbits received saline or alloxan monohydrate for the induction of diabetes. 30 days post-alloxan or saline all rabbits underwent wound procedure. In all rabbits, the central and rostral, arteries and nerves in one ear were ligated and resected to induce neuroischemia while in the other ear, arteries and nerves were left intact (sham). Four 6mm full thickness wounds were created in both ears. Rabbits were euthanized at two or ten days post-surgery and wounds were harvested. To confirm diabetes, blood glucose (BG) levels and glycated hemoglobin (HbA1c) were monitored. Rabbits with BG over 250mg/dL and HbA1c levels above 6.5 were considered diabetic. Wound size (% of original wound) was monitored in the 10-day group using computerized planimetry. Using Q-RT-PCR, gene expression was compared between the skin of non-diabetic and diabetic rabbits. Change in gene expression within the sham and neuroischemic wounds (D2 or D10) relative to skin (D0) were also measured and comparisons were made between non-diabetic and diabetic rabbits. All measurements are presented as mean±SEM. N= 3-6 rabbits.
Results: Compared to non-diabetic rabbits, rabbits treated with alloxan had higher BG and HbA1C levels on the day of surgery (112±5.16 mg/dL and 4.65±0.18 vs. 289±22.6 mg/dL and 7.3±0.36). Ten days post-surgery, compared to non-diabetic sham wounds, healing was significantly impaired in diabetic sham wounds (51.74±5.66% vs.62.97±4.65%). Within the neuroischemic wounds, there was no difference in healing between non-diabetic (83.52±3.34) and diabetic (86.49±1.73) rabbits. Gene expression of inflammatory markers, IL-8, CXCR1 and IL-6 was different between non-diabetic and diabetic sham wounds but not neuroischemic wounds, and that of neuropeptide markers, NPY2R, NPY5R and NK1R was significantly different between non-diabetic and diabetic sham and neuroischemic wounds (Figure).
Conclusion: Inflammatory cytokines and neuropeptide markers may play an important role in diabetic wound healing. The rabbit neuroischemic model can be used to study chronic wound-healing impairment in diabetes.
