From Invaginating Site to Deep Lesion: Spatial Transcriptomics Unravels Ectopic Endometrial Penetration Features in Adenomyosis

Abstract Adenomyosis, characterized by clinical intractability, significantly impacts female fertility and life quality due to the absence of definitive diagnostic markers and effective treatment options. The invagination theory is a primary hypothesis for adenomyosis, but the underlying molecular mechanisms remain unclear. In this study, a spatial transcriptional landscape of adenomyosis with an evident invagination structure is mapped from the endometrial invaginating site to ectopic lesions utilizing spatial transcriptomics and single‐cell RNA sequencing. In addition, the authors employ bulk RNA sequencing deconvolution to assess the significance of core spatial ecotypes, use histological techniques to target specific cell types, and conduct in vitro experiments for validation. At the invagination site, SFRP5 + epithelial cells promote endometrial proliferation and angiogenesis through secretion of IHH. During the invading process, ESR1 + smooth muscle cells (SMCs) facilitate invasion by creating migratory tracts via collagen degradation. Within deep lesions, CNN1 + stromal fibroblasts induce fibrosis by undergoing a fibroblast‐to‐myofibroblast transition (FMT) in response to pathologic profibrogenic signals in the microenvironment of lesions. This work offers an in‐depth understanding of the molecular mechanisms underlying the pathological processes of adenomyosis with invagination. Furthermore, this work introduces the first transcriptomics web source of adenomyosis, which is expected to be a valuable resource for subsequent research.