Human diploid MRC-5 cells exhibit several critical properties of human umbilical cord-derived mesenchymal stem cells

MRC-5 is the most common human diploid cell line used in production of viral vaccines; mesenchymal stem cells (MSCs) is a type of adult multipotent stem cells. Both cell types share the same fibroblast-like morphology and maintain a normal diploid karyotype over long in vitro expansion. However, other than these similarities, very little is known about MRC-5 in terms of biological properties possessed by MSCs. In this study, we compared MRC-5 with human umbilical cord-derived MSCs (hUC-MSCs), which serves as a representative of human MSCs, in expression of cell surface markers, abilities to differentiate into multiple cell lineages, inhibition of lymphocyte proliferation and promotion of Regulatory T lymphocytes (Treg), and IDO1 expression in response to inflammatory cytokines, all of which are critical properties of MSCs. It was revealed that MRC-5 was almost identical to hUC-MSCs in expression of both positive and negative surface markers of MSCs. Similar to hUC-MSCs, MRC-5 was also able to differentiate into osteocytes and chondrocytes, effectively inhibit mitogen-activated lymphocyte proliferation and promote Tregs, and express IDO1 in response to inflammatory cytokines IFN-gamma and TNF-alpha. In addition, both MRC-5 and hUC-MSCs were non-tumorigenic with an extremely low telomerase activity. Moreover, both cells demonstrated a similar sensitivity to infection by EV71 and rubella viruses, which served as model viruses, in a virus infectivity assay. Therefore, this study suggests that MRC-5 is very likely a previously undefined MSC cell line, thus suggesting the feasibility of developing MSCs of at least umbilical cord origin as new cell substrates to be used in production of viral vaccines. (C) 2014 Elsevier Ltd. All rights reserved.