P050
Phenotypic Comparison of Epithelial Cells from Thymus and Umbilical Cords

Necef Özbek1, Mehmet Emin Şeker1, Şimal Şenocak1, Şafak Alpat2, Mustafa Yılmaz2, Umutcan Kayıkçı3, Özgür Deren3, Fatima Aerts Kaya1

1 Hacettepe Üniversitesi, Sağlık Bilimleri Enstitüsü, Kök Hücre Bilimleri Anabilim Dalı 2 Hacettepe Üniversitesi, Tıp Fakültesi, Kalp ve Damar Cerrahisi Anabilim Dalı
3 Hacettepe Üniversitesi, Tıp Fakültesi, Kadın Hastalıkları ve Doğum Anabilim Dalı

Background/Aim: The thymus is a primary lymphoid organ for T lymphocyte development and maturation. Absence of functional T cells results in severe immune deficiency. Thymic epithelial and stromal cells play an important role in the maturation of T cells, but lack of sufficient thymus material makes it difficult to generate functional thymus organoids. The umbilical cord (UC) stroma contains both epithelial and stromal stem cells. To assess the potential use of these cells to generate thymus organoids, we compared thymus and UC epithelial cells.

Materials and Methods: Thymic cells were isolated from pediatric donors. Thymi were washed with PBS, minced and run through 40 um cell strainers to obtain a single cell suspension. UCs were rinsed with PBS, the amnionic membrane was removed and cut in small pieces and cultured in M-171 medium with supplement. Cells were grown and expanded until passage 3. Total thymic stromal cells and umbilical cord epithelial cells were assessed for presence of the cell surface markers CD29, CD31, CD44, CD54, CD73, CD90, CD105, CD200 and HLA-DR.

Results: The thymic epithelial and stromal cell mixture expressed high levels of CD29, CD31 and CD44 (>70%), medium expression of HLA-DR (50%) and showed low expression of the mesenchymal markers CD73, CD90 and CD105 and epithelial markers CD54 and CD200 (<3%). In contrast, UC ep- ithelial cells showed high expression of CD29, CD44, CD73 and CD105 (>90%), medium expression of CD54 and CD200 (>50%), and low expression of CD31 and HLA-DR.

Conclusion: Analysis showed the presence of mixed stromal populations in whole, thymic cell prepa- rations, consisting of endothelial, epithelial and stromal cells, whereas culture of UC epithelial cells resulted in the isolation of CD54 and CD200 expressing epithelial cells, that also co-express mesen- chymal cell markers. Further purification of thymic cell populations will allow better comparison of the epithelial cell contents.

Keywords: Thymic cells, Umbilical cord epithelial cells, Mesenchymal stem cells