异种器官再造有望彻底解决临床器官供体不足和免疫排斥的问题。在异种器官再造过程中，还不清楚异种干细胞在宿主体内经历了何种分化命运、如何参与器官构建。鹿茸是哺乳动物中罕见的能够完全再生的器官，前期研究证实鹿茸再生是一个依赖于干细胞的过程。我们通过移植鹿茸干细胞在裸鼠体内构建了异种鹿茸，初步分析证实异种鹿茸是鹿/鼠细胞的嵌合体。初步检测推断鹿茸干细胞的外泌因子是招募宿主细胞构建异种鹿茸的关键。经过多组学筛选和初步功能分析我们提出：细胞迁移和血管形成的调控因子S100A4，是鹿茸干细胞招募宿主细胞构建异种鹿茸的关键因子。本课题拟通过双色荧光标记及单细胞测序全面解析异种鹿茸中鹿源/鼠源细胞分布；体外验证S100A4及其上下游调控因子对宿主细胞的作用；体内分析S100A4及相关调控因子对异种鹿茸形成及细胞分布的影响。我们相信揭示结构相对简单的异种鹿茸的形成机制，对于再造复杂的异种器官具有重要借鉴意义。

Generation of xenogeneic organs is arguably the most effective alternative to xenografts for solving the problems of donor organ shortage and immune rejection. However, it is still not clear how the grafted stem cells initiate the process of xenogeneic organ construction in the host environment, experience differentiation fate, and interact with the host cells. Deer antlers are the unique mammalian appendages capable of full regeneration, our previous studies found that antler regeneration is a stem cell-based process. Based on this finding, we have generated xenogeneic antlers in nude mice by transplanting antler stem cells. The xenogeneic antlers were found to be chimeras of mouse- and deer-derived cells. Our preliminary work demonstrated that the secretory cytokines from antler stem cells containing key factors that could recruit host cells to participate in formation of the xenogeneic antler. Based on the results of multi-omics screening and preliminary functional analysis, we propose that S100A4, which plays a key role in cell migration and angiogenesis, is a key factor of antler stem cells for the recruit of host cells to participate the construction of xenogeneic antlers. In this applicaiton, we will systematically analyze distribution of the deer/mice-derived cells in the generated xenogeneic antler using the techniques of two-color fluorescent labeling and single-cell sequencing. We will also determine the effects of S100A4 and related regulatory factors on the recruitment, proliferation and differentiation of the host cells in vitro; and the effects of S100A4 and related regulatory factors on the formation and cell distribution of xenogeneic antler in vitro. We believe that revealing the distribution of deer/mouse-derived cells in the xenogeneic antlers and underlying mechanism, will provide novel insights into generation of complex xenogeneic organs in clinics.