Myocutaneous revascularization following graded ischemia in lean and obese mice

Background: Murine models of diabetes and obesity have provided insight into the pathogenesis of impaired epithelialization of excisional skin wounds. However, knowledge of postischemic myocutaneous revascularization in these models is limited. Materials and methods: A myocutaneous flap was created on the dorsum of wild type (C57BL/6), genetically obese and diabetic (ob/ob, db/db), complementary heterozygous (ob⁺/ ob⁻, db⁺/db⁻), and diet-induced obese (DIO) mice (n=48 total; five operative mice per strain and three unoperated mice per strain as controls). Flap perfusion was documented by laser speckle contrast imaging. Local gene expression in control and postoperative flap tissue specimens was determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). Image analysis of immunochemically stained histologic sections confirmed microvascular density and macrophage presence. Results: Day 10 planimetric analysis revealed mean flap surface area necrosis values of 10.8%, 12.9%, 9.9%, 0.4%, 1.4%, and 23.0% for wild type, db⁺/db⁻, ob⁺/ob⁻, db/db, ob/ob, and DIO flaps, respectively. Over 10 days, laser speckle imaging documented increased perfusion at all time points with revascularization to supranormal perfusion in db/db and ob/ob flaps. In contrast, wild type, heterozygous, and DIO flaps displayed expected graded ischemia with failure of perfusion to return to baseline values. RT-PCR demonstrated statistically significant differences in angiogenic gene expression between lean and obese mice at baseline (unoperated) and at day 10. Conclusion: Unexpected increased baseline skin perfusion and augmented myocutaneous revascularization accompanied by a control proangiogenic transcriptional signature in genetically obese mice compared to DIO and lean mice are reported. In future research, laser speckle imaging has been planned to be utilized in order to correlate spatiotemporal wound reperfusion with changes in cell recruitment and gene expression to better understand the differences in wound microvascular biology in lean and obese states.