Single-Cell Transcriptome Analysis Reveals Mesenchymal Stem Cells in Cavernous Hemangioma

Abstract

A cavernous hemangioma, well-known as vascular malformation, is present at birth, grows proportionately with the child, and does not undergo regression. Although a cavernous hemangioma has well-defined histopathological characteristics, its origin and formation remain unknown. In the present study, we characterized the cellular heterogeneity of cavernous hemangioma using single-cell RNA sequencing (scRNA-seq). The main contribution of the present study is the discovery of mesenchymal stem cells (MSCs) that cause cavernous hemangioma formation during embryonic development. MSCs in the cavernous hemangioma exhibit characteristics of tumors, the over-expression of MKI67, GAPDH and EGFR. Other new findings include the responsive ACKR1 positive endothelial cell (ACKR1+EC) and BTNL9 positive endothelial cell (BTNL9+EC) and the BTNL9-caused checkpoint blockade enhanced by the CXCL12-CXCR4 signalling. The activated CD8+T and NK cells may highly express CCL5 for their infiltration in cavernous hemangiomas, independent on the tumor cell-derived CCL5-IFNG - CXCL9 pathway. The plasmacytoid dendritic cells (pDCs) function for anti-tumour as CD8+T cells in cavernous hemangiomas. The oxidised low-density lipoprotein (OxLDL) and scavenger receptors (SRs) may play an important role in the immune responses in the tumour microenvironment of cavernous hemangiomas. Notably, we propose that OxLDL induces the OxLDL-OLR1-NLRP3 pathway in M1-like macrophages via the over-expression of OLR1, whereas OxLDL induces the OxLDL-SRs-C1q pathway in M2-like macrophages via the over-expression of many SRs (LILRB5, etc) except OLR1. The highly expressed EREG in M1-like macrophages and the highly expressed EGFR in MSCs may cause MSC proliferation. The present study revealed the origin of cavernous hemangiomas and reported the marker genes, cell types and molecular mechanisms, which are associated with the origin, formation, progression, diagnosis or therapy of cavernous hemangiomas. Our discoveries facilitate the development of gold standards for molecular diagnosis and effective drugs for treatment, and enrich the fundamental knowledge in the research field of immune, cancer and even cell biology.