Objective: Aim of this study was to de-differentiate the haematopoietic stem cells (HSCs) that originated from the umbilical cord blood. One of the ways to do it is to use a co-cultivation system. Design: Prospective experimental study. Setting: Laboratory study - Institute of reproductive medicine and endocrinology, Pilsen. Methods: HSCs were co-cultivated with mouse embryonic stem cells (mESC) with and without feeder cells. After co-cultivation HSCs were analyzed using flow-cytometry for presence of haematopoietic markers (CD34, CD45, CD133) and using immunohistochemistry for presence of embryonic stem cell markers (SSEA-4, Tra-1-60, Tra-1-81). Results: No de-differentiation was detectable in any our experiment, only the intensity of the HSC cell markers decreased. Conclusion: We suppose that there were two major reasons for the experiment failure: there was no direct cell to cell contact and there was a mixture of cell types that originated from two different species. To reach our goal of in vitro de-differentiation we will need to change our strategy towards a pure human culture system without any animal additives and with cell to cell contact.

        Key words: haematopoietic stem cells (HSCs), mouse embryonic stem cells (mESC), umbilical cord blood (UCB), flow cytometry (FACS), immunohistochemistry