探討皮質類固醇對SSEA-1+肺部幹細胞類器官發育的影響

Abstract

因為肺部發育不全併發嚴重的呼吸窘迫症是造成早產兒死亡的主要原因之一，產前類固醇目前已被廣泛運用在有早產風險的孕婦身上。然而，僅有少數的證據能說明產前類固醇促進胎兒肺部成熟的詳細機制，且皮質類固醇對於肺部幹細胞的影響仍不清楚。因此，本研究主旨在探討皮質類固醇對SSEA1+肺部幹細胞及其發育而成的類器官的影響。我們結果顯示持續給予SSEA1+肺部類器官dexamethasone的刺激，會顯著增加細支氣管外分泌細胞(club)標誌Scgb1a1，伴隨著CCSP分泌到類器官的空腔。相反地，dexamethasone會減少纖毛(ciliated)及杯狀(goblet)細胞的標誌，分別是Foxj1及Muc5ac。螢光染色也發現在dexamethasone刺激後的類器官中纖毛(ciliated)細胞會消失。更重要的是，我們發現給予dexamethasone也會增加第一型及第二型肺泡細胞的標誌基因及蛋白表達。從機制上來看，我們發現dexamethasone顯著減少轉錄因子Sox2與Sox9的表達，這兩個基因分別主要表達在氣道與肺泡的先驅細胞中。與in vitro的數據相同的是，in vivo dexamethasone注射也傾向減少SSEA1+細胞數量，但增加基底(basal)及第二型細胞的標誌，這些效果可能同樣是透過抑制Sox2及Sox9來達成。綜合來說，這些結果表明皮質類固醇可以促進SSEA1+幹細胞分化成似肺泡(alveolar-like)的肺部類器官且從機制上來加速肺部幹細胞的成熟。這些發現也強調了皮質類固醇對於胎兒肺部發育成熟的益處且更深入了其對肺部幹細胞分化的影響。本研究最終可能有助於改善早產兒的臨床表現與整體健康狀況。

The immaturity of the lung is a leading cause of mortality in preterm infants with severe pulmonary complication such as respiratory distress syndrome (RDS). Antenatal corticosteroids have been widely used to treat women at risk of preterm delivery. However, there is limited evidence elucidating the detailed mechanisms of antenatal corticosteroids on fetal lung maturation, and their impact on lung stem cells remains unclear. In this study, we aimed to investigate the influence and mechanism of corticosteroids on pulmonary SSEA-1+ stem/progenitor cells and the lung organoid model generated from SSEA1+ cells. Our results indicated that sustained dexamethasone stimulation significantly increased the gene expression of club cell marker Scgb1a1, accompanied by the secretion of CCSP into the organoid lumen. In contrast, dexamethasone decreased the ciliated and goblet cell markers, Foxj1 and Muc5ac, respectively. Immunofluorescence staining also revealed an absence of ciliated cells in dexamethasone-treated organoids. Importantly, dexamethasone treatment upregulated the expression of type I and type II alveolar cell markers at both the mRNA and protein levels. Mechanistically, dexamethasone decreased the expression of the transcription factors Sox2 and Sox9, which are typically expressed in airway and alveolar progenitor cells, respectively. Consistent with in vitro data, in vivo dexamethasone injection appeared to reduce SSEA1+ cell population while increasing the expression of basal and AT2 cell markers, likely through the suppression of Sox2 and Sox9. Together, these results demonstrated that dexamethasone promoted the differentiation of SSEA1+ stem cells into alveolar-like lung organoids and mechanistically accelerated their maturation. These findings highlight the beneficial effects of corticosteroids on lung development and provide further insight into their impact on pulmonary stem cell differentiation. Ultimately, this study might contribute to improving outcomes and health in preterm infants.