肺臟前驅/幹細胞與間質細胞之蛋白質體分析

Abstract

利用初級肺部組織細胞培養，我們已成功地鑒定出一群肺部的幹細胞/前驅細胞，以下簡稱為colony cells，其表現胚胎幹細胞的細胞標記Oct-4、SSEA-1以及Sca-1與Clara cell的細胞標記CCSP。在細胞培養過程中發現，colony cells的生長與幹性(stemness)的維持需要仰賴周圍的間質細胞(stromal cells)，將colony cells自細胞培養中分離出來至新的培養皿中，將分化成第二型的肺泡細胞(type -2 pneumocytes)，之後繼續分化成第一型的肺泡細胞(type -1 pneumocytes)；此外，若間質細胞的細胞密度過於稀疏，也將導致colony cells的生長停滯並開始進行分化現象。因此，colony cells與間質細胞之間的交互作用(cross-talk)主導著colony cells的生長速度與幹性的維持。首先，本研究欲利用蛋白質體學分析，釐清、鑑定在細胞培養過程中，兩群細胞所釋放出的細胞激素或生長因子。我們在不同的時間點收取細胞培養液，利用細胞激素(cytokine)抗體陣列進行分析，在複雜的細胞激素與生長因子表現中，挑選出候選者，利用反轉錄聚合酶鏈鎖反應確認其在RNA level上的表現，以及利用免疫細胞染色法再加以確認。我們發現，在培養過程中，細胞釋放了大量的細胞激素BLC、LIX與MCP-1，而其相對應受體(receptor)表現在colony cells上。在細胞培養過程中，外加細胞激素BLC、LIX與MCP-1，會加強colony cells潛能性基因的表現，而對於生長方面影響不大。此外，colony cells表現了胚胎幹細胞(embryonic stem cell)潛能性標記Oct-4與Sox2，是否在適合的環境與刺激下，能被誘導成類胚胎幹細胞，也是相當值得探討的重點。

In previously study, we have reported a primary pulmonary cell cultures. In this culture system, the stem/progenitor cells (Oct-4+/SSEA-1+/Sca-1+ and CCSP+) could proliferate and maintain in undifferentiated stage and formed individual colonies with surrounding stromal cells. When the stem/progenitor cells were plucked away from the primary cultures without stromal cells, and transferred to a new culture dishes, the transferred cells were differentiated into type-2 and then type -1 pneumocytes in a sequential fashion. This result suggested that the stromal cells were important for the growth and maintenance the pulmonary stem/progenitor cells in the primary cultures. The aim was to determine the interaction between the stem/progenitor cells and stromal cells. We adopted a proteomic analysis to identify the key factors which regulated the growth of the cells in the culture. Proteomic profiling reveals that colony cells and their neighboring niche cells, stromal cells, produce a number of cytokines and growth factors. We found that stromal cells secrete cytokine BLC, LIX and MCP-1 while colony cells expressed receptor CXCR5, CXCR2 and CCR2. Addition of BLC, LIX and MCP1 could enhance the expression of Oct-4, Sox2 and Nanog in colony cells. Except the paracrine regulation, the autocrine regulation may also play some role. The pulmonary stem/progenitor cells expressed the pluripotency markers of embryonic stem cells, include the Oct-4 and Sox2.They may have potential to become to embryonic-like stem cells after appropriate induction. We also want to evaluate the stemness of the stem/progenitor cells by in vivo assay.