H. Albadawi1,3, R. Oklu2,3, T. P. Uong1, J. D. Milner1, H. Yoo1, M. T. Watkins1,3 1Massachusetts General Hospital,Department Of Surgery, Division Of Vascular And Endovascular Surgery,Boston, MA, USA 2Massachusetts General Hospital,Department Of Imaging, Division Of Interventional Radiology,Boston, MA, USA 3Harvard School Of Medicine,Brookline, MA, USA
Introduction: The polygenic mouse model of diabetes is believed to better simulate the human adult type-2 diabetes compared to the monogenic models (i.e. db/db or Ob/Ob). This model exhibits a maturity-onset transition from impaired glucose tolerance to a stable non-fasting hyperglycemia when fed a 10% high fat diet after 16 weeks. Wound healing experiments using these mice show substantial impairment in wound healing processes involving the skin. The aim of this study was to assess acute skeletal muscle injury in the polygenic mouse model of diabetes following hind limb ischemia reperfusion (IR).
Methods: The recombinant polygenic diabetic mice (NONcNZO10/LtJ, n=6) and its non-diabetic control strain (NON/ShiLtJ, n=5) were subjected to unilateral moderate hind limb tourniquet ischemia for 1.5 hours followed by 24 hours of reperfusion. To confirm their diabetic state, fasting blood glucose levels were measured prior to ischemia. After 24 hours of reperfusion, mice were sacrificed and muscle samples were processed for histological quantitative assessment of muscle fiber injury and inflammatory cell infiltration (Ly6G, marker of neutrophils, or Mac-3, marker of monocytes lineage) using immunohistochemistry. The protein levels of pro-inflammatory chemokine KC (CXCL1) in the serum and solubilized muscle protein extracts were measured using ELISA. Data were expressed as mean±SEM and statistical analysis was performed using student’s t-test.
Results: The fasting blood glucose levels in the diabetic mice were significantly greater than in the non-diabetic mice (472±32 vs. 165±28 mg/dL, p<0.000001). There was no significant difference in the degree of muscle fiber injury between the diabetic vs. non-diabetic mice (15±2 vs. 16±2 average injured fiber per high power field, p=0.6). The accumulation of Ly6G+ (41±10 vs. 48±15 average positive cells per field, p=0.7) and Mac3+ (42±6 vs. 33±5 average positive cells per field, p=0.7) cells in skeletal muscle following IR was similar in the diabetic vs. non-diabetic mice. Furthermore, levels of muscle KC (17±2 vs. 14±2 pg/mg protein, p=0.2) and serum KC (103±6 vs. 73±15 pg/ml, p=0.09) were also not statistically different between the two groups.
Conclusion: While excessive IR injury and increased inflammation is believed to play a major role in defective wound healing models, the pattern of acute skeletal muscle IR in the polygenic diabetic mouse does not appear to be worse than that of the non-diabetic mouse following 1.5 hours of ischemia. Further studies in these polygenic diabetic mice subjected to severe periods of ischemia (i.e. ≥3 hours) and characterization of the regenerative phase (i.e. healing) in the limb muscle is warranted.