Drake Paige M, Franz-Odendaal Tamara A
Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Biology, Mount Saint Vincent University, Halifax, Nova Scotia, Canada.
Dev Dyn. 2025 Jan;254(1):74-93. doi: 10.1002/dvdy.729. Epub 2024 Aug 3.
Conjunctival placodes are a series of placodes that develop into the conjunctival (scleral) papillae and ultimately induce a series of scleral ossicles in the eyes of many vertebrates. This study establishes a hydrocortisone injection procedure (incl. dosage) that consistently inhibits all conjunctival papillae in the embryonic chicken eye. The effects of this hydrocortisone treatment on apoptosis, vasculature, and placode-related gene expression were assessed.
Hydrocortisone treatment does not increase apoptotic cell death or have a major effect on the ciliary artery or vascular plexus in the eye. β-catenin and Eda expression levels were not significantly altered following hydrocortisone treatment, despite the absence of conjunctival papillae. Notably, Fgf20 expression was significantly reduced following hydrocortisone treatment, and the distribution of β-catenin was altered.
Our study showed that conjunctival papillae induction begins as early as HH27.5 (E5.5). Hydrocortisone treatment reduces Fgf20 expression independently of β-catenin and Eda and may instead affect other members of the Wnt/β-catenin or Eda/Edar pathways, or it may affect the ability of morphogens to diffuse through the extracellular matrix. This study contributes to a growing profile of gene expression data during placode development and enhances our understanding of how some vertebrate eyes develop these fascinating bones.
结膜基板是一系列基板，可发育成结膜（巩膜）乳头，并最终在许多脊椎动物的眼睛中诱导出一系列巩膜小骨。本研究建立了一种氢化可的松注射程序（包括剂量），该程序能持续抑制胚胎鸡眼中的所有结膜乳头。评估了这种氢化可的松处理对细胞凋亡、脉管系统和基板相关基因表达的影响。
氢化可的松处理不会增加凋亡细胞死亡，也不会对眼中的睫状动脉或血管丛产生重大影响。尽管没有结膜乳头，但氢化可的松处理后β-连环蛋白和Eda的表达水平没有显著改变。值得注意的是，氢化可的松处理后Fgf20表达显著降低，且β-连环蛋白的分布发生了改变。
我们的研究表明，结膜乳头诱导最早在HH27.5（E5.5）开始。氢化可的松处理独立于β-连环蛋白和Eda降低Fgf20表达，可能反而影响Wnt/β-连环蛋白或Eda/Edar途径的其他成员，或者可能影响形态发生素通过细胞外基质扩散的能力。这项研究有助于增加基板发育过程中的基因表达数据，并增进我们对一些脊椎动物眼睛如何发育出这些迷人骨骼的理解。
