Pyogenic granuloma, an impaired wound healing process, linked to vascular growth driven by FLT4 and the nitric oxide pathway.

Pyogenic granuloma, also called lobular capillary hemangioma, is a condition usually occurring in skin or mucosa and often related to prior local trauma or pregnancy. However, the etiopathogenesis of pyogenic granuloma is poorly understood and whether pyogenic granuloma being a reactive process or a tumor is unknown. In an attempt to clarify this issue, we performed genome-wide transcriptional profiling of laser-captured vessels from pyogenic granuloma and from a richly vascularized tissue, placenta, as well as, from proliferative and involutive hemangiomas. Our study identified a gene signature specific to pyogenic granuloma. In the serial analysis of gene expression (SAGE) database, this signature was linked to 'white blood cells monocytes'. It also demonstrated high enrichment for gene ontology terms corresponding to 'vasculature development' and 'regulation of blood pressure'. This signature included genes of the nitric oxide pathway alongside genes related to hypoxia-induced angiogenesis and vascular injury, three conditions biologically interconnected. Finally, one of the genes specifically associated with pyogenic granuloma was FLT4, a tyrosine-kinase receptor related to pathological angiogenesis. All together, these data advocate for pyogenic granuloma to be a reactive lesion resulting from tissue injury, followed by an impaired wound healing response, during which vascular growth is driven by FLT4 and the nitric oxide pathway.