血管管壁是一種相當複雜的組織，在生理的功能上，被各種細胞和細胞間的交互作用所調控，例如細胞激素(cytokine)的分泌或者細胞和細胞之間的直接接觸(cell-cell direct contact)。在以下的研究裡，我們以血管細胞共同培養(vascular cell co-culture)的方式，試圖釐清內皮細胞(endothelial cells)和平滑肌細胞(smooth muscle cells)經由direct contact後對血管生理環境所帶來的影響。在共同培養的模式下，我們發現內皮細胞和平滑肌細胞間的交互作用造成內皮細胞的-catenin蛋白在tyrosine 142和serine 45/threonine 41兩種位置的磷酸化現象。而平滑肌細胞conditional medium的刺激只能造成Ser45/Thr41的活化，且將平滑肌細胞替換為纖維母細胞(fibroblast)的結果無法活化beta-catenin的磷酸化。另外，利用阻斷性胜肽(blocking peptide)和小干擾RNA (small interfering RNA, siRNA)技術我們證實connexin 43經由影響Fer kinase的活化調節beta-catenin的Tyr142的磷酸化。經由Cx43 siRNA和beta-catenin mutant plasmid的實驗，我們發現內皮細胞的vascular adhesion molecule-1 (VCAM-1)的基因表現和內皮細胞對於單核球的吸附(monocyte adhesion)能力也受到此訊息途徑的調控。本論文的研究結果證實內皮細胞和平滑肌細胞的直接接觸經由Cx43, Fer kinase和beta-catenin-Tyr142的磷酸化進而調節內皮細胞的發炎反應。關於解釋beta-catenin磷酸化現象，我們的研究也提出了其在調節血管細胞生理中其嶄新的腳色。

The blood vessel wall is a complex structure and is highly modulated by homo- or heterocellular communications, such as cytokine release or cell-cell direct contact. In this study, I aim to elucidate the influence of direct heterocellular contact between endothelial cells (ECs) and smooth muscle cells (SMCs) by using a vascular cell co-culture model that is composed of monolayers of ECs and SMCs on opposite sides of a membrane. Under this co-culture system, the interaction between ECs and SMCs resulted in the phosphorylation of beta-catenin at tyrosine 142 (Tyr142) and serine 45/threonine 41 (Ser45/Thr41). ECs treated with SMC conditional medium induced beta-catenin phosphorylation at Ser45/Thr41 but not at Tyr142. The co-culture with fibroblasts (FBs) did not induce any beta-catenin phosphorylation. Moreover, by pre-treating cells with blocking peptides and using specific siRNA transfection, I demonstrated that connexin 43 modulated the phosphorylatin of beta-catenin-Tyr142 via Fer kinase. Transfecting ECs with siRNA specific for Cx43 or beta-catenin or beta-catenin-Tyr142 constitutive negative mutants inhibited vascular adhesion molecule-1 (VCAM-1) gene expression and thus modulated EC monocyte adhesion. These results indicate that vascular heterocellular communication regulates EC inflammation by inducing beta-catenin-Tyr142 phosphorylation through Cx43/Fer signaling via direct contact effects. My findings provide insights into the complexities of beta-catenin phosphorylation signaling in vascular cells, the mechanisms underlying the EC-SMC cross interaction in modulating signaling and gene expression in ECs and the consequent modulation of their inflammatory functions.

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