The assessment of the in vivo to in vitro cellular transition of human umbilical cord multipotent stromal cells

- Present study focused on human umbilical cord mesenchymal stromal cells (hUC-MSCs).
- Phenotypic changes were examined during two different isolation methods of hUC-MSCs.
- Two cell types were determined in enzymatically or mechanically isolated cells.
- Cytokeratin, vimentin, α-SMA remodelling were differentially regulated.
- The stability of the phenotype represents a critical factor for hUC-MSCs.

IntroductionHuman umbilical cord stroma is a rich source of primitive multipotent stromal cells (hUC-MSCs). However, the methods for hUC-MSC isolation and propagation remain controversial and vary among laboratories. Our group previously demonstrated that two cell types emerge upon enzymatic isolation of hUC-MSCs, which subsequently undergo a transition towards a fibroblastoid phenotype in later passages. The aim of this study was to further analyse cultured hUC-MSCs by evaluating the cytoskeletal and cell adhesion proteins and by comparing the remodelling of those proteins in umbilical cord sections to determine the cell alterations due to enzymatic and explant methods.MethodsTissue sections and cultured cells isolated by enzymatic or explant methods were analysed morphologically and by labelling cytokeratin, vimentin, alpha-smooth muscle actin, E-cadherin and N-cadherin profiles.ResultsThe present observations confirmed that wide, flat cells (type-1) share myofibroblastic features, appear exclusively in enzymatically isolated early cultures; gradually diminish or are replaced by fibroblastoid cells (type-2) in later passages. In contrast, the explant method does not result in the existence of type-1 cells in vitro. Among the tested CK subtypes, CK18 expression is upregulated, whereas CK19 expression is downregulated upon culturing after both protocols. Vimentin and α-SMA, as the major intermediate filaments of hUC-MSCs were found unaltered throughout the culturing period regardless of the cell isolation technique used.DiscussionThe data presented confirm and further elucidate the previously observed phenotypic change in hUC-MSCs as illustrated by alterations in structural proteins during enzymatic isolation and subsequent culturing of cells compared with in situ equivalents.