Ultrastructural study of human umbilical cord blood Buffy coat and Wharton's Jelly cells

ABSTRACT

Human umbilical cord [UC] has been a tissue of increasing interest in recent years. Umbilical cord blood [UCB] was used in the treatment of several hematological diseases. New potential uses of cord blood in nonhematopoietic applications are now proposed. Lately, the Wharton's jelly [WJ], the embryonic mucuos connective tissue of the UC, with its mesenchymal stromal cells represents a promising source of cells for several regenerative therapies. This study aims to highlight the morphological ultrastustural characteristics of the UCB buffy coat and the WJ stromal cells in situ. Tiny specimens from the UCB buffy coat and the WJ were double-fixed with glutaraldehyde and osmium tetroxide, dehydrated, and embedded in epoxy resin. Ultrathin sections were cut and stained with uranyl acetate and lead citrate. Transmission electron microscopic examination [TEM] of the UCB buffy coat cells showed immature cellular constituents and few changes in the ultrastructural morphology of cord blood platelets. These ultrastructural changes may clarify the specific cultural, immunological and regenerative properties attributed to cord blood in comparison to bone marrow or peripheral blood. Wharton's Jelly TEM showed stromal cells exhibiting morphological resemblance with both fibroblasts and smooth muscle cells. In addition, cells resembling stellate cells exhibiting intracytoplasmic lipid globules and ultrastructural properties related to protein synthesis were discerned. Also, oval cells with primitive nuclear and cytoplasmic features pointing to a subpopulation with stem cell potency were seen. We suggest that the WJ contains several distinct populations of stromal cells with different potentials including a primitive subpopulation. We propose that the nomenclature of these cells should not only be linked to their morphological appearance but also to their specific functional properties. Extensive in situ and in vitro molecular, immunohistochemical and immuno electron microscopic studies are necessary to clearly identify these cell populations with different potentials