Gene-expression analysis reveals that embryonic stem cells cultured under osteogenic conditions produce mineral non-specifically compared to marrow stromal cells or osteoblasts

Evans, Nicholas D., Swain, Robin J., Gentleman, Eileen, Gentleman, Molly M. and Stevens, Molly M. (2012) Gene-expression analysis reveals that embryonic stem cells cultured under osteogenic conditions produce mineral non-specifically compared to marrow stromal cells or osteoblasts. European Cells & Materials, 24, 211-223. (PMID:23007907)

Abstract

Pluripotent cells, such as embryonic stem cells (ESCs),
divide indefinitely and can differentiate to form mineralised nodules in response to osteogenic supplements. This suggests that they may be used as a cell source for bone replacement strategies. Here, we related the expression
of osteogenic and chondrogenic genes in cultures of
murine ESCs, marrow stromal cells (MSCs) and calvarial
osteoblasts (OBs) cultured under osteogenic conditions
to the biochemical composition and quantity of mineral
formed. Mineralisation, measured by calcium sequestration,
was >2-fold greater in ESC cultures than in either MSCs
or OBs. Micro-Raman spectroscopy and spectral mapping
revealed a lower mineral-to-matrix ratio and confirmed a
more diffuse pattern of mineralisation in ESCs compared to
MSCs and OBs. Baseline expression of chondrogenic and
osteogenic genes was between 1 and 4 orders of magnitude
greater in MSCs and OBs than in ESCs. Osteogenic culture
of MSCs and OBs was accompanied by increases in
osteogenic gene expression by factors of ~100 compared
to only ~10 in ESCs. Consequentially, peak expression of
osteogenic and chondrogenic genes was greater in MSCs
and OBs than ESCs by factors of 100-1000, despite the fact
that mineralisation was more extensive in ESCs than either
MSCs or OBs. We also observed significant cell death in
ESC nodules. We conclude that the mineralised material
observed in cultures of murine ESCs during osteogenic
differentiation may accumulate non-specifically, perhaps
in necrotic cell layers, and that thorough characterisation
of the tissue formed by ESCs must be achieved before
these cells can be considered as a cell source for clinical
applications.

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Contributors

Author: Nicholas D. Evans

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