维生素D受体在胆道闭锁胆管上皮细胞损伤中的作用及机制研究

Bile duct epithelial injury is very important in the occurrence and development of biliary atresia (BA). There is a wide range of 1,25(OH)2D3 deficiency in children with BA. The normal expression level and function of vitamin D receptor (VDR) is a prerequisite for normal biological effects of 1,25(OH)2D3. VDR predominantly expressed in biliary epithelial cells in the liver, has been shown to play a significant role in maintaining innate immune homeostasis and integrity of bile duct epithelium. Our previous study found that BA patients with reduced expression of VDR in biliary epithelial cells tended to have shorter autologous liver survival and more frequent recurrent cholangitis after the Kasai operation, but their serum 1,25-(OH) 2D3 levels were not significantly lower than other BA children. Based on these findings, this project intends to use Vdr-/- and wild C57BL/6 neonatal mice to build the murine model of biliary atresia and murine experimental model of bile duct obstruction and recanalization to study the role and mechanism of VDR in bile duct epithelial injury during biliary atresia in vivo and in vitro. In addition, the value of VDR agonist for the individualized treatment of BA with reduced expression of VDR in biliary epithelial cells will be preliminarily evaluated through the clinical observation and research. This study may provide a new therapeutic target for the treatment of BA and provide a theoretical basis for individualized treatment of BA.

胆管上皮损伤是胆道闭锁（BA）发病及进展过程中的重要环节。临床上BA患儿存在广泛的1,25(OH)2D3缺乏。维生素D受体（VDR）的表达水平及功能正常是1,25(OH)2D3正常发挥生物学效应的前提，在肝内主要表达在胆管上皮细胞和非实质细中。VDR在维持胆管上皮细胞免疫及完整性中扮演重要角色。我们预实验发现肝组织内VDR表达降低的BA患儿Kasai术后自体肝生存时间较对照组更短，术后出现难治性胆管炎的比例更大，但血清1,25(OH)2D3水平与对照组相比无统计学差异。本项目拟利用Vdr-/-及野生C57BL/6新生鼠构建BA及胆管梗阻再通动物模型，模拟BA发病及Kasai术后胆管炎病理过程，通过体内外研究，深入探讨VDR在BA胆管上皮细胞损伤中的作用及机制。初步评估VDR激动剂用于治疗肝内VDR降低的BA患儿的价值。该研究将可能为BA治疗提供新的干预靶点，为BA个体化治疗提供理论依据。

50%以上的先天性胆道闭锁（BA）患儿因肝门-空肠吻合术(Kasai术)后仍存在肝内持续炎症和进行性纤维化而预后不良，其发病及进展机制尚未阐明。围产期病毒感染导致的胆管上皮细胞（BDECs）损伤被认为BA发生及进展的主要原因和源头之一，但机制不明。我们通过聚肌胞苷酸Poly(I:C)模拟细胞外双链RNA(dsRNA)病毒的作用，干预IBDECs，首次发现自噬是dsRNA病毒引起IBDECs损伤的重要原因，且通过干预VD3/VDR抑制自噬可以缓解这种损伤作用。临床上BA患儿存在广泛的1,25(OH)2D3缺乏。我们前期发现肝内胆管上皮细胞（IBDECs）中维生素D受体（VDR）表达显著降低的BA患儿Kasai术后出现难治性胆管炎的比例更大，自体肝生存时间更短。本课题在前期临床发现的基础上，进一步通过临床标本和体外细胞实验首次发现：IBDECs中VDR表达水平显著下降可能是BA预后不良的标志物。我们通BA新生鼠模型和临床上BA患儿Kasai术后口服骨化三醇（VDR激活剂）辅助治疗，初步证实了通过干预VD3/VDR辅助治疗BA的可能性。最后我们进一步研究发现干预VD3/VDR 可能通过 PLA2/PKC/ERK 通路减轻 dsRNA病毒对IBDECs的损伤作用。为丰富BA发病进展机制及寻找新的治疗靶点提供了重要理论依据。受本项目资助已发表SCI收录论文2篇，中华系列核心期刊论文1篇；2次应邀在国内会议作大会发言；培养并毕业博士研究生1名、硕士研究生2名。