The Differentiation Potential of Mesenchymal Stem Cells Isolated from EGFP Transgenic Mice in Early Embryogenesis
Date Issued
2010
Date
2010
Author(s)
Yen, Ya-Ping
Abstract
In recent years, many tissue specific stem cells had been successfully isolated and transdifferentiated into lineages other than the tissue of origin. Several studies have reported that bone marrow derived mesenchymal stem cells (MSCs) possess the potency to differentiate into various lineages. Recent study also indicated that a tissue specific stem cell, neural stem cells could contribute to many tissues of the chimera mouse when injected into a blastocyst. Therefore, the object of this study was to investigate the differentiation potential of MSCs in vivo. The ability to contribute to the embryogenesis was determined by introducing them into the early embryonic environment and observing the fate of their progeny.
In this study, type I and type II EGFP-mMSCs were isolated from the femur of transgenic mice carrying s-actin promoter constructed with enhanced green fluorescent protein (EGFP) cDNA serving as a tracing marker. Grouping by cell numbers, EGFP-mMSCs were injected to C57BL/6JNarl blastocysts and injected embryos were transferred to the uterus of the pseudo-pregnant foster mothers to assess the potency of EGFP-mMSCs to integrate into inner cell mass (ICM) during early embryonic development. The results of fluorescence microscopy and polymerase chain reaction analysis showed that EGFP-mMSCs injected embryos failed to give rise to chimeras and EGFP signal could not be observed in conceptuses day 9.5 and day 6.5. In contrast, EGFP embryonic stem (ESCs) could proliferate spontaneously with the ICM and contribute to all cell lineages in vivo. Compared with ESCs, mMSCs don’t have the ability to differentiate in vivo. To test whether mMSCs have the stem cell plasticity via cell aggregation, type I and II EGFP-mMSCs were aggregated with eight-cell or morula stage embryos and further cultured to blastocyst and hatching stages. Analysis on preimplantation embryos by immunofluorescence stain showed that type I and II EGFP-mMSCs could not aggregate with early embryos, suggesting that these somatic stem cells are unable to participate in early embryogenesis.
Results in this thesis revealed that the hypothesis may be false that mMSCs could not integrate into the host embryos during early embryogenesis. The reason injected mMSCs disappear in day 6.5 embryos is required to be clarified, but cell death is a likely answer. Putatively, mMSCs could not aggregate with eight-cell or morula stage embryos which may due to the incompatible cell niche or microenvironment. In addition, the composition of membranous protein of mMSCs and inner cell mass may be enormously different which could be the reason why these cells would not aggregate with each other. Taken together, although mMSCs can differentiate to tri-lineage tissues via in vitro induction, the microenvironment in early embryos might not support for mMSCs survival and differentiation.
Subjects
adult stem cells
embryonic stem cells
mesenchymal stem cells
pluripotent
blastocys
Type
thesis
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