Over 1 million burn injuries are treated annually in the United States, and current tissue engineered skin fails to meet the need for full-thickness replacement. Bioprinting technology has allowed fabrication of full-thickness skin and has demonstrated the ability to close full-thickness wounds. However, analysis of collagen remodeling in wounds treated with bioprinted skin has not been reported. The purpose of this study is to demonstrate the utility of bioprinted skin for epidermal barrier formation and normal collagen remodeling in full-thickness wounds. Human keratinocytes, melanocytes, fibroblasts, dermal microvascular endothelial cells, follicle dermal papilla cells, and adipocytes were suspended in fibrinogen bioink and bioprinted to form a tri-layer skin structure. Bioprinted skin was implanted onto 2.5 × 2.5 cm full-thickness excisional wounds on athymic mice, compared with wounds treated with hydrogel only or untreated wounds. Total wound closure, epithelialization, and contraction were quantified, and skin samples were harvested at 21 days for histology. Picrosirius red staining was used to quantify collagen fiber orientation, length, and width. Immunohistochemical (IHC) staining was performed to confirm epidermal barrier formation, dermal maturation, vascularity, and human cell integration. All bioprinted skin treated wounds closed by day 21, compared with open control wounds. Wound closure in bioprinted skin treated wounds was primarily due to epithelialization. In contrast, control hydrogel and untreated groups had sparse wound coverage and incomplete closure driven primarily by contraction. Picrosirius red staining confirmed a normal basket weave collagen organization in bioprinted skin-treated wounds compared with parallel collagen fibers in hydrogel only and untreated wounds. IHC staining at day 21 demonstrated the presence of human cells in the regenerated dermis, the formation of a stratified epidermis, dermal maturation, and blood vessel formation in bioprinted skin, none of which was present in control hydrogel treated wounds. Bioprinted skin accelerated full-thickness wound closure by promoting epidermal barrier formation, without increasing contraction. This healing process is associated with human cells from the bioprinted skin laying down a healthy, basket-weave collagen network. The remodeled skin is phenotypically similar to human skin and composed of a composite of graft and infiltrating host cells.

中文翻译：

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生物打印的皮肤概括了全层伤口中正常胶原蛋白的重塑。

在美国，每年要治疗超过一百万的烧伤，并且目前的组织工程皮肤无法满足全厚度置换的需要。生物打印技术已允许制造全层皮肤，并证明了封闭全层伤口的能力。但是，尚未报道用生物打印的皮肤处理过的伤口中胶原重塑的分析。这项研究的目的是证明生物打印的皮肤在全厚度伤口中用于表皮屏障形成和正常胶原重塑的实用性。将人角质形成细胞，黑素细胞，成纤维细胞，真皮微血管内皮细胞，卵泡真皮乳头细胞和脂肪细胞悬浮在纤维蛋白原生物墨水中，并进行生物印刷以形成三层皮肤结构。将生物打印的皮肤植入到2.5×2上。与仅使用水凝胶治疗的伤口或未经治疗的伤口相比，无胸腺小鼠的5厘米全层切除伤口。量化伤口的总闭合，上皮化和收缩，并在第21天收集皮肤样本进行组织学检查。Picrosirius红色染色用于定量胶原纤维的方向，长度和宽度。进行了免疫组织化学（IHC）染色以确认表皮屏障形成，真皮成熟，血管形成和人类细胞整合。与开放对照伤口相比，所有经过生物打印的皮肤处理伤口均在第21天关闭。生物打印的皮肤处理过的伤口中的伤口闭合主要是由于上皮化。相反，对照组水凝胶和未治疗组的伤口覆盖稀疏，并且主要由收缩引起的闭合不完全。Picrosirius红色染色证实了经过生物打印的皮肤处理过的伤口中正常的篮子编织胶原组织，而仅水凝胶和未经处理的伤口中平行胶原纤维。在第21天进行的IHC染色表明，在再生的真皮中存在人类细胞，在生物打印的皮肤中形成了分层的表皮，真皮成熟和血管形成，在对照水凝胶治疗的伤口中均不存在这些细胞。生物印刷的皮肤通过促进表皮屏障的形成而加速了全层伤口闭合，而没有增加收缩。这种愈合过程与来自生物印刷皮肤的人体细胞形成健康的篮状胶原网络有关。重塑的皮肤在表型上与人类皮肤相似，并且由移植和浸润宿主细胞的复合物组成。