腫瘤內皮標誌1屬於第一型穿膜醣蛋白質，被歸類在C型凝集素家族中，此蛋白分子是由6個功能區所構成，分別是類凝集素功能區(TEM1D1)、類壽司功能區(TEM1D2)、三重複類表皮生長因子功能區(TEM1D3)、黏液素功能區(TEM1D4)、穿膜功能區(TEM1D5)和細胞質內功能區(TEM1D6)。腫瘤內皮標誌1主要表現在基質細胞上，包括纖維母細胞和週細胞。纖維母細胞除了能分泌且調控細胞外基質的平衡外亦會影響表皮細胞的分化、發炎反應以及傷口癒合。在先前的文獻中指出，降低纖維母細胞對於腫瘤內皮標誌1的表現同時也會使纖維母細胞增生和爬行的能力下降。而目前關於腫瘤內皮標誌1的研究多是集中在探討內源性腫瘤內皮標誌1的功能，對於外源性或水溶性腫瘤內皮標誌1的功能目前尚未清楚。因此我們利用哺乳類表現系統純化出重組腫瘤內皮標誌1的細胞外功能區蛋白 (rTEM1D1-4)，並用以模擬外源性腫瘤內皮標誌1的功能。纖維母細胞在重組腫瘤內皮標誌1的細胞外功能區蛋白的處理下，其生長狀況顯著增加。重組腫瘤內皮標誌1的細胞外功能區蛋白亦具有吸引纖維母細胞爬行的功能。在重組腫瘤內皮標誌1的細胞外功能區蛋白刺激下，纖維母細胞的訊息傳遞分子ERK、JNK、p38會被活化。在共同處理抑制劑後發現重組腫瘤內皮標誌1的細胞外功能區蛋白促進纖維母細胞的增生是透過p38的活化。另一方面，由於在傷口癒合過程中纖維母細胞是影響癒合的重要細胞之一，因此我們利用鏈脲佐菌素 (Streptozotocin) 誘導的糖尿病小鼠進行皮膚傷口癒合實驗。結果顯示，給予重組腫瘤內皮標誌1的細胞外功能區蛋白對於傷口癒合有些微促進效果。綜合以上結果，我們發現腫瘤內皮標誌1細胞外功能區蛋白對於纖維母細胞有顯著提升細胞增生的效果，且能吸引纖維母細胞的爬行，但是在糖尿病傷口治療上尚未發現有顯著的療效。

Fibroblasts are the major cells in the stroma tissue. Fibroblasts in the epidermal region play an important role in regulating extracellular matrix (ECM) homeostasis, epithelial differentiation, inflammation and wound healing. Tumor endothelial marker 1 (TEM1), also known as CD248 or endosialin, belongs to the C-type lectin protein family 14. It is composed of 6 domains, including an N-terminal C-type lectin-like domain (D1), a sushi-like domain (D2), a three-repeated epidermal growth factor (EGF)-like domain (D3), a mucin-like domain (D4), a transmembrane domain (D5), and a cytoplasmic domain (D6). Previous studies demonstrated that TEM1 is expressed on the surface of stromal cells such as fibroblasts and pericytes. In previous study, it was reported that silencing of endogenous TEM1 in fibroblasts could reduce cell viability. However, the function of soluble exogenous TEM1 remains largely undetermined. Hence, we want to identify the biological function of soluble form TEM1 through the treatment of recombinant extracellular domain of TEM1 (rTEM1D1-4) on fibroblasts. First, rTEM1D1-4 was prepared using mammalian expression system. Treatment of purified rTEM1D1-4 can increase fibroblasts viability and attracts fibroblasts migration. In addition, we also exam the ability of rTEM1D1 and rTEM1D3 which were prepared using pichia expression system. Results showed that only rTEM1D1-4 but not rTEM1D1 and rTEM1D3 can significantly promote fibroblasts viability. Further, the signaling molecules in fibroblasts, including ERK, JNK and p38, were activated by treatment with rTEM1D1-4. By co-treatment with inhibitors, we found that rTEM1D1-4 promotes fibroblasts viability via activation of p38. To show the therapeutic effects of rTEM1D1-4, we use streptozotocin (STZ)-induced diabetic mice to perform cutaneous wound healing experiments. Local administration of rTEM1D1-4 to the wound site slightly improved wound healing in STZ-induced diabetic mice. In summary, we found that rTEM1D1-4 significantly improved fibroblasts viability and attracted fibroblasts migration in vitro, but its effects on wound healing in diabetic mice needs to be further investigated.

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