LOUISIANA COBRE: P2: COMMITMENT OF ADULT STEM CELLS INTO ADIPOCYTE LINEAGE

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 疤痕组织在医学和健康的许多领域中是非常重要的问题。已知皮肤再生发生在两栖动物中，但不在哺乳动物中。哺乳动物中的例外是胎儿和FOXN 1缺陷（裸）小鼠。 我们的长期目标是了解疤痕形成的机制，以及如何控制这些机制以改善成年哺乳动物皮肤和其他器官的愈合。 基质金属蛋白酶（MMPs）与再生和无瘢痕愈合有关：MMPs是两栖动物再生不可或缺的。 哺乳动物胎儿的无瘢痕皮肤愈合与更高水平的MMPs表达相关。 我们已经发现，裸小鼠的完整皮肤组织相对于野生型小鼠表达更高水平的MMP;我们已经表明，裸小鼠的损伤后皮肤组织在愈合的早期和晚期具有独特的MMP 9和MMP 13活性的双峰模式。裸鼠中MMPs表达的这些模式与两栖动物再生过程中发现的MMPs表达模式非常相似。我们的工作模型是，裸鼠中功能性FOXN 1的缺失消除了MMPs的转录抑制，并导致高水平的MMPs，这是模拟两栖动物再生的无瘢痕修复的必要条件。 该模型导致以下可检验的假设： 假设：FOXN 1在正常皮肤修复和瘢痕形成过程中抑制MMP 9和MMP 13的表达。 推论：（a）裸鼠中FOXNl表达的缺失允许MMP 9和MMP 13的上调，伴随皮肤的无瘢痕修复。(b)FOXN 1的抑制将允许MMP 9和MMP 13表达，并导致无瘢痕皮肤愈合。 我们将在裸鼠中检验这一假设及其推论。 我们的目标是确定FOXN 1缺陷如何调节Mmp 9和Mmp 13基因表达，以及MMP 9和MMP 13是否是无瘢痕皮肤修复所必需的。 具体目标1将测试FOXN 1和MMP 9/MMP 13表达之间的相互作用机制。 预测一：FOXN 1通过从角质形成细胞释放可溶性因子来抑制MMP 9/MMP 13表达，所述可溶性因子抑制真皮成纤维细胞中的MMP 13/MMP 9表达（细胞间机制）。 预测二： FOXN 1通过FOXN 1结合结构域和MMP 9启动子区中的应答元件之间的直接作用和/或通过PKC信号传导的转录抑制（细胞内机制）来抑制角质形成细胞中的MMP 9表达。 具体目标2将检验MMP 13和MMP 9表达是无瘢痕皮肤伤口修复的必要条件的假设。 预测1：MMPs活性的抑制消除了裸鼠无瘢痕愈合的能力。 预测2：双突变小鼠FOXN 1/MMP-9和FOXN 1/MMP 13将愈合皮肤损伤并形成瘢痕。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Scar tissue is a problem of great importance in many areas of medicine and health. Skin regeneration is known to occur in amphibians, but not in mammals. The exceptions in mammals are fetuses and FOXN1 deficient (nude) mice. Our long-range objective is to understand the mechanisms of scar formation and how these can be controlled to improve healing of the skin and other organs in adult mammals. Matrix metalloproteinases (MMPs) are implicated in regeneration and in scarless healing: MMPs are indispensable to the regeneration in amphibians. Scarless skin healing in mammalian fetuses is associated with higher levels of MMPs expression. We have found that intact skin tissues from nude mice express higher levels of MMPs relative to wild type mice; and we have shown that post-injury skin tissues in nude mice have distinctive, bimodal patterns of MMP9 and MMP13 activity during early and late stages of healing. These patterns of MMPs expression in nude mice strongly resemble those found to occur in amphibians during regeneration. Our working model is that the absence of functional FOXN1 in nude mice removes the transcriptional suppression of MMPs and leads to high levels of MMPs, an essential, necessary condition for scarless repair that mimics regeneration in amphibians. This models leads to the following testable hypothesis: Hypothesis: FOXN1 suppresses MMP9 and MMP13 expression during normal skin repair and scar formation. Corollaries: (a) Absence of FOXN1 expression in nude mice allows upregulation of MMP9 and MMP13 with concomitant scarless repair of skin. (b) Inhibition of FOXN1 will allow MMP9 and MMP13 expression and result in scarless skin healing. We will test this hypothesis and its corollaries in nude mice. Our goals are to determine how a deficiency in FOXN1 regulates Mmp9 and Mmp13 gene expression, and whether MMP9 and MMP13 are necessary for scarless skin repair. Specific Aim 1 will test mechanisms of interaction between FOXN1 and MMP9/MMP13 expression. Prediction 1: FOXN1 represses MMP9/MMP13 expression through release of soluble factors from keratinocytes that repress MMP13/MMP9 expression in dermal fibroblasts (intercellular mechanism). Prediction 2: FOXN1 represses MMP9 expression in keratinocytes through direct action between FOXN1 binding domain and responsive elements in the promoter region of MMP9 and/or through transcriptional suppression of PKC signaling (intracellular mechanism). Specific Aim 2 will test the hypothesis that MMP13 and MMP9 expression are a necessary condition for scarless skin wound repair. Prediction 1: Suppression of MMPs activities abrogates nude mouse ability for scar-free healing. Prediction 2: Double mutant mice FOXN1/MMP-9 and FOXN1/ MMP13 will heal skin injuries with scar formation.