利用人類胚胎幹細胞探討PM2.5在心臟發育時期和心 臟細胞引起之毒性

Abstract

空氣中懸浮微粒2.5(PM2.5)是一種心血管疾病的致病因子，同時也是先天性心臟病的致病因子之一。動物研究證實PM2.5可以引發心血管疾病以及先天性心臟病。然而PM2.5造成心臟疾病的致病機轉仍未知。本研究利用人類胚胎幹細胞以及人類胚胎幹細胞衍化之心肌細胞探討PM2.5對其影響。我發現PM2.5會降低人類胚胎幹細胞的多能基因表現(NANOG, OCT4)，進而造成中胚層基因(MESP1)表現量下降和降低心肌前驅細胞相關基因(NKX2.5, HAND, HAND2, GATA4 and GATA6 )的表現，最後導致心肌細胞的分化效率下降。同時在人類胚胎幹細胞曝曬PM2.5後其衍生之心肌細胞呈現肌節構造排列不規則以及細胞變大的現象。此外我也發現不論長期或是短期的PM2.5曝曬皆會造成心肌細胞跳動頻率下降，以及無法自行恢復的肌節構造排列不規則。整體而言，本研究首次證明PM2.5造成人類胚胎幹細胞分化成心肌細胞的效率下降，同時這些心肌細胞有肌節構排列不整齊以及細胞變大的狀況，其原因可能為幹細胞多功能基因表現量下降，導致中胚層基因以及心臟前驅細胞基因表現量降低，我更進一步發現PM2.5會直接造成心肌細胞的肌節構排列不整齊以及跳動頻率下降

Particulate matter 2.5 (PM2.5) is a risk factor for cardiovascular disease (CVD) and congenital heart disease (CHD). Animal studies show that PM2.5 induces CVD and CHD. However, the underlying mechanisms of PM2.5-induced CVD and CHD remain unknown. In this thesis study, I used human embryonic stem cells (hESCs) and human embryonic stem cell-derived cardiomyocytes (hESC-derived CMs) to investigate the effects of PM2.5 on hESC pluripotent stemness and hESC-derived CMs. PM2.5 treatment decreased the expression of pluripotency markers NANOG and OCT4 and lowered the efficiency of cardiomyocyte differentiation in hESCs. Moreover, PM2.5 treatment down-regulated the mesoderm marker MESP1 and cardiac progenitor genes (NKX2.5, HAND1, HAND2, GATA4, and GATA6) during directed cardiac differentiation. Interestingly, these PM2.5-pretreated hESC-derived CMs exhibited disorganized sarcomeric structures and larger cell size. In addition, PM2.5-treated hESC-derived CMs showed a slower beating rate and disorganized sarcomeric structures. Taken together, PM2.5 may affect directed cardiomyocyte differentiation by down-regulating the expression of the mesoderm marker MESP1 and cardiac progenitors NKX2.5, HAND, HAND2, GATA4, and GATA6 and disorganizing sarcomeric structures.