CRABP2 upregulation in perichondral stem cells is associated with microtia

Microtia is a common congenital craniofacial malformation characterized by the partial or complete absence of the external ear structure. Despite its relatively high incidence, the pathogenesis of microtia remain poorly understood. In this study, we analyzed both single-cell and bulk RNA sequencing data from microtia cases and identified a population of COL1 + HES1+mesenchymal stem cell in perichondrium with significantly higher expression of the CRABP2 gene, a gene that encodes a nuclear transporter of retinoic acid. Gene expression analysis further confirmed that the RA signaling intensity and stemness are both higher in COL1 + HES1+ perichondral stem cells from microtia patients, possibly due to elevated CRABP2 levels. Through histological verification we further confirmed the presence of this cell population with high CRABP2 expression in the perichondrium. Mechanistically, the elevated CRABP2 expression in perichondral stem cells seen in microtia patients may cause dysregulated RA signaling and disrupt the regulation of stem cell differentiation during auricular development. Histological analysis further revealed higher KLF2 expression as well as cartilage hypoplasia in microtia samples. Our study identified that the CRABP2-induced RA dysregulation in COL1 + HES1+ perichondral stem cells may contribute to microtia. These findings offer new insights into the etiology of microtia and provide potential directions for prenatal prevention and tissue engineering treatments.