A New Model for Specific Visualization of Skin Graft Neoangiogenesis Using Flt1-tdsRed BAC Transgenic Mice

Background: Neovascularization plays a critical role in skin graft survival. Up to date, the lack of specificity to solely track the newly sprouting blood vessels has remained a limiting factor in skin graft transplantation models. Therefore, the authors developed a new model by using Flt1-tdsRed BAC transgenic mice. Flt1 is a vascular endothelial growth factor receptor expressed by sprouting endothelial cells mediating neoangiogenesis. The authors determined whether this model reliably visualizes neovascularization by quantifying tdsRed fluorescence in the graft over 14 days. Methods: Cross-transplantation of two full-thickness 1 x 1-cm dorsal skin grafts was performed between 6- to 8-week-old male Flt1 mice and KSN/Slc nude mice (n = 5). The percentage of graft area occupied by tdsRed fluorescence in the central and lateral areas of the graft on days 3, 5, 9, and 14 was determined using confocal-laser scanning microscopy. Results: Flt1(+) endothelial cells migrating from the transgenic wound bed into the nude graft were first visible in the reticular dermis of the graft center on day 3 (0.5 +/- 0.1; p < 0.05). Peak neovascularization was observed on day 9 in the lateral and central parts, increasing by 2- to 4-fold (4.6 +/- 0.8 and 4.2 +/- 0.9; p < 0.001). Notably, some limited neoangiogenesis was displayed within the Flt grafts on nude mice, particularly in the center. No neovascularization was observed from the wound margins. Conclusion: The ability of the Flt1-tdsRed transgenic mouse model to efficiently identify the origin of the skin-graft vasculature and visualize graft neovascularization over time suggests its potential utility for developing techniques that promote graft neovascularization.

背景：新生血管形成在皮肤移植物存活中起着关键作用。到目前为止，在皮肤移植物移植模型中，缺乏专门追踪新生血管的特异性仍然是一个限制因素。因此，作者利用Flt1 - tdsRed BAC转基因小鼠开发了一种新模型。Flt1是一种由介导新生血管形成的新生内皮细胞表达的血管内皮生长因子受体。作者通过对14天内移植物中的tdsRed荧光进行定量，来确定该模型是否能可靠地观察到新生血管形成。 方法：在6 - 8周龄的雄性Flt1小鼠和KSN/Slc裸鼠之间进行两块1×1厘米的全层背部皮肤移植物交叉移植（n = 5）。使用共聚焦激光扫描显微镜测定在第3、5、9和14天移植物中心和周边区域中tdsRed荧光所占移植物面积的百分比。 结果：从转基因创面上迁移到裸鼠移植物中的Flt1（+）内皮细胞在第3天首次在移植物中心的网状真皮中可见（0.5 ± 0.1；p < 0.05）。在第9天，在周边和中心部位观察到新生血管形成达到峰值，增加了2 - 4倍（4.6 ± 0.8和4.2 ± 0.9；p < 0.001）。值得注意的是，在裸鼠的Flt1移植物内显示出一些有限的新生血管形成，特别是在中心部位。在创面边缘未观察到新生血管形成。 结论：Flt1 - tdsRed转基因小鼠模型能够有效地识别皮肤移植物血管的来源，并随时间推移观察到移植物新生血管形成，这表明它在开发促进移植物新生血管形成的技术方面具有潜在的实用性。