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.