Rosin Nicole L, Agabalyan Natacha, Olsen Katherine, Martufi Giampaol, Gabriel Vincent, Biernaskie Jeff, Di Martino Elena S
Department of Comparative Biology and Regenerative Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada.
Biomedical Engineering Graduate Program, University of Calgary, Calgary, AB, Canada.
Wound Repair Regen. 2016 Mar;24(2):263-74. doi: 10.1111/wrr.12402. Epub 2016 Feb 16.
The gold standard treatment for full thickness injuries of the skin is autologous split-thickness skin grafting. This involves harvesting the epidermis and superficial dermis from healthy skin and transplanting it onto the prepared wound bed. The donor site regenerates spontaneously, but the appendages and cellular components from the dermal layer are excluded from the graft. As a result, the new tissue is inferior; the healed graft site is dry/itchy, has decreased elasticity, increased fragility, and altered sensory function. Because this dermal layer is composed of collagen and other extracellular matrix proteins, the aim was to characterize the changes in the dermal collagen after split thickness grafting that could contribute to a deficit in functionality. This will serve as a baseline for future studies designed to improve skin function using pharmacological or cell-based therapies for skin repair. A xenograft model whereby human split-thickness grafts were implanted into full-thickness defects on immunocompromised (athymic Nu/Nu) mice was used. The grafts were harvested 4 and 8 weeks later. The collagen microstructure was assessed with second harmonic generation with dual-photon microscopy and light polarization analysis. Collagen fiber stiffness and engagement stretch were estimated by fitting the results of biaxial mechanical tensile tests to a histo-mechanical constitutive model. The stiffness of the collagen fibril-proteoglycan complex increased from 682 ± 226 kPa/sr to 1016 ± 324 kPa/sr between 4 and 8 weeks postgrafting. At the microstructural level there were significant decreases in both thickness of collagen fibers (3.60 ± 0.34 μm vs. 2.10 ± 0.27 μm) and waviness ratio (2.04 ± 0.17 vs. 1.43 ± 0.08) of the collagen fibers postgrafting. The decrease of the macroscopic engagement stretch from 1.19 ± 0.11 to 1.09 ± 0.08 over time postgrafting mirrored the decrease in waviness measured at the microscopic level. This suggested that the integrity of the collagen fibers was compromised and contributed to the functional deficit of the skin postgrafting.
皮肤全层损伤的金标准治疗方法是自体中厚皮片移植。这包括从健康皮肤获取表皮和浅表真皮，并将其移植到准备好的创面床。供皮区可自发再生，但真皮层的附属器和细胞成分不包含在移植皮片中。因此，新组织质量较差；愈合后的移植部位干燥/瘙痒，弹性降低，脆性增加，感觉功能改变。由于该真皮层由胶原蛋白和其他细胞外基质蛋白组成，目的是表征中厚皮片移植后真皮胶原蛋白的变化，这些变化可能导致功能缺陷。这将作为未来旨在使用药理学或基于细胞的疗法改善皮肤修复功能的研究的基线。使用了一种异种移植模型，即将人中厚皮片植入免疫缺陷（无胸腺裸鼠）小鼠的全层缺损处。4周和8周后收获移植皮片。用双光子显微镜二次谐波产生和光偏振分析评估胶原蛋白微观结构。通过将双轴机械拉伸试验结果拟合到组织力学本构模型来估计胶原纤维刚度和接合拉伸。移植后4至8周，胶原原纤维 - 蛋白聚糖复合物的刚度从682±226 kPa/sr增加到1016±324 kPa/sr。在微观结构水平上，移植后胶原纤维的厚度（3.60±0.34μm对2.10±0.27μm）和胶原纤维的波纹率（2.04±0.17对1.43±0.08）均显著降低。移植后随时间推移，宏观接合拉伸从1.19±0.11降低到1.09±0.08，这反映了微观水平上测量的波纹度的降低。这表明胶原纤维的完整性受到损害，并导致移植后皮肤的功能缺陷。
