Competence of In Vitro Cultured Mouse Embryonic Stem Cells for Myogenic Differentiation and Fusion with Myoblasts

Abstract

Pluripotent stem cells are a potential source of various cell types for use in regenerative medicine. Despite accumulating knowledge, there is currently no efficient and reproducible protocol that does not require genetic manipulation for generation of myogenic cells from pluripotent stem cells. Here, we examined whether mouse embryonic stem (ES) cells are able to undergo myogenic differentiation and fusion in response to signals released by differentiating myoblasts. Using ES cells expressing the histone 2B-green fluorescent fusion protein, we were able to detect hybrid myotubes formed by ES cells and differentiating myoblasts. ES cells that fused with myoblasts downregulated the expression of pluripotency markers and induced the expression of myogenic markers, while unfused ES cells did not exhibit this expression pattern. Thus, the signals released by myoblasts were not sufficient to induce myogenic differentiation of ES cells. Although ES cells synthesize many proteins involved in myoblast adhesion and fusion, we did not observe any myotubes formed exclusively by ES cells. We found that ES cells lacked M-cadherin and vascular cell adhesion molecule-1, which may account for the low frequency of hybrid myotube formation in ES cell-myoblast co-cultures and the inability of ES cells alone to form myotubes.

Sdf-1 (CXCL12) induces CD9 expression in stem cells engaged in muscle regeneration

“…In response to Sdf-1 pretreatment, the number of hybrid myotubes increased to 1.13 ± 0.64% (Figure 6 D,E). As we have shown previously, ESCs very rarely fuse with myoblasts [ 42 ]. The observed increase in the fusion index after Sdf-1 treatment was thus an interesting result.…”

From pluripotency to myogenesis: a multistep process in the dish

“…GFP and dystrophin-positive fibers were detected in the muscles of only two out of eight mice transplated with cells, and one of these mice had as few as 30 of these fibers (Bhagavati and Xu 2005 ). Together, these results indicate that the co-culture system is not efficient in the induction of myogenic differentiation of PSCs (Barberi et al 2005 ; Bhagavati and Xu 2005 ; Archacka et al 2014 ). In addition, although the co-culture system yields important information about myogenic potential of stem cells and reciprocal interactions between co-cultured cells, this method is not likely to be clinically suitable.…”

“…As far as PSCs are concerned, analysis of mouse ESCs showed that when co-cultured with myoblasts, they participated in the formation of hybrid myotubes with 1 % frequency (Archacka et al 2014 ). However, ESCs were not able to undergo myogenic differentiation in a fusion-independent way.…”

“…However, ESCs were not able to undergo myogenic differentiation in a fusion-independent way. MRFs were found only in the nuclei of ESCs which fused with myoblasts, but not in those cells only exposed to myoblast-conditioned medium (Archacka et al 2014 ). The presence of MyoD in the nuclei of ESCs cultured in the myoblast-conditioned medium was reported only when these cells were first induced to undergo differentiation by long term co-culture with mouse OP9 stromal cells (Barberi et al 2005 ).…”

“…Examples presented above show that PSCs are able to undergo myogenic conversion only in fusion-dependent manner (Archacka et al 2014 ) or after initial differentiation induced by stromal cell lines and/or myogenic regulators, such as Wnt7a, BMP-4, and RA (Barberi et al 2005 ; Torres et al 2012 ). Differences between PSCs and adipose-derived stem cells or AC133 expressing cells, i.e.…”