Expression of embryonic stem cell markers in pyogenic granuloma

Background Recent description of hemangioblastic blood islands within pyogenic granuloma ( PG ) has led us to investigate the expression of embryonic stem cell (ESC) markers in this tumor. Methods In this study we examined the expression of ESC markers, OCT4 , SOX2 , STAT3 and NANOG in PG samples from 11 patients, by immunohistochemical ( IHC ) staining, NanoString analysis and in situ hybridization ( ISH ). Results IHC staining demonstrated the expression of pSTAT3 , OCT4 , SOX2 and NANOG by the endothelium of the microvessels in PG whilst pSTAT3 , SOX2 and NANOG were also expressed by cells in the interstitium, outside of the microvessels. NanoString and ISH analysis showed mRNA expression for STAT3 , OCT4 and NANOG in PG . Conclusions The expression of the ESC markers, OCT4 , SOX2 , pSTAT3 and NANOG , suggests the endothelium of PG displays a primitive phenotype. Cells in the interstitium expressing pSTAT3 , SOX2 and NANOG may represent a more downstream derivative of the primitive endothelium, or a separate population. The primitive nature of the endothelium and cells in the interstitium reveals novel insights into the biology of PG . To the best of our knowledge, this is the first demonstration of the expression of ESC markers in PG , implying the presence of a hematopoietic stem cell population.