Svitina H. Comparative characterization of rat and human placental mesenchymal stromal cells and influence of their transplantation on cancerogenesis of colon tumors.

Transplantation of placenta-derived multipotent cells (PDMCs) is one of the most promising approaches of cell therapy for inflammation-associated colon diseases. However, the effect of PDMCs on colon cancer remains unknown. The aim of this study was to characterize PDMCs obtained from human and rat placentas and to evaluate their impact on colon cancer progression in rats. PDMCs were obtained from human and rat placentas by tissue explant culturing. Stemness- and trophoblast-related gene expression was studied by RT-PCR. Surface markers and intracellular proteins were detected, using flow cytometry and immunofluorescent analysis respectively. Experimental colon carcinogenesis was induced in male albino Wistar rats by injecting 20 mg/kg of dimethylhydrazine (DMH) once per week for 20 consecutive weeks. The administation of the rat and human PDMCs was performed when T2-stage tumors had been formed. The number and size of each tumor lesion were calculated. The type of tumor was determined by standard histological methods. Cell engraftment was monitored by PCR and immunofluorescence, after rats were sacrificed. The mammalian placenta is composed of both fetal and maternal components. The fetal origin of rat and human PDMCs was confirmed by the presence of the Y chromosome via FISH analysis. Flow cytometry analysis of rat PDMCs at 3rd passage showed that all cells were CD90+ and CD45- and heterogeneous for CD29 and CD44. Human PDMCs were positive for CD90, CD44, partially positive for CD29, and negative for CD45. Rat PDMCs expressed vimentin but not pan-cytokeratin, whereas expression of both was detected in human PDMCs. Transcription factors EOMES and CDX2, which are critical for trophoblast as well as for mesoderm development, were detected in PDMCs of both origins. Our results revealed presence of CDX2, EOMES, ID2 and POU5F1 at mRNA level in both, rat and human PDMCs by RT-PCR, whereas Nanog expression was not detected in rat PDMCs. Moreover, the syncytial trophoblast and trophoblast giant cell gene (Prl3b1) and spongiotrophoblast-specific gene (Tpbpa) expression were not discovered in rPDMCs. Absence of specific-for-differentiated-trophoblast-cells mRNAs indicates that the rat PDMCs were not contaminated with trophoblast cell populations. Human PDMCs expressed both genes of stemness and trophoblast specific genes CGB and ERVW-1. Allogeneic and xenogeneic transplantation of PDMCs to rats at middle phase of DMH induced colon cancerogenesis does not influence the number of neoplasms and the mean diameter of single tumour or total tumours area. Allogeneic transplantation leads to increase in tumour size at the fourth degree of invasion. Intravenous allogeneic transplantation of PDMCs reduces survival of rats bearing colon cancer by 17 days. Rat PDMCs engrafted in animals, could be found in intestine, lung, liver, and spleen in case when healthy rats were used and even in tumour site when rats with colon adenocarcinomas were used. Thus, rat and human PDMCs possess immunophenotype and differentiation potential inherent with MSCs. However, in contrast to hPDMCs have low expression of CD44 and do not express trophoblast-associated genes. Our data suggest that PDMCs can engraft in different tissues but do not significantly affect DMH-induced tumor growth during short-term observations.