Factors controlling skeletal muscle stem cell self-renewal and regeneration

Supervisors: Professor Jennifer Morgan and Dr Silvia Torelli

The objectives of the proposed investigation:
Our goal is to improve the engraftment efficiency of donor satellite cells transplanted into dystrophic muscles.

Project background:
Satellite cells are the principal stem cells of skeletal muscle [1]. We have shown that only some satellite cells are capable of regenerating muscle fibres and functionally reconstituting the satellite cell compartment and that modulation of the host muscle environment is critical for optimal donor satellite cell engraftment [1, 2]. In our in vivo model system, donor satellite cell self-renewal and muscle regeneration act in concert, as one does not occur without the other.

Recently, we have focussed on the influence of the host satellite cell niche (the myofibre, its attendant satellite cells and basal lamina) on donor cell engraftment [3].

We hypothesise that factors driving self-renewal, rather than differentiation, of donor satellite cells are the critical factors influencing their engraftment efficiency.

A detailed plan of the research to be undertaken by the student, including a broad timeline:
We will determine:

1. Whether satellite cells can be driven towards self-renewal rather than regeneration
2. The mechanism by which the niche within irradiated host muscle signals to incoming donor satellite cells
3. The fate of donor satellite cells if they do not contribute to skeletal muscle fibres or to satellite cells

This will be done using in vitro models of satellite cell activation, proliferation, differentiation and self-renewal and in vivo models to quantify contribution of satellite cells to skeletal muscle regeneration [3, 4].

MicroRNA arrays and qPCR, will be used to determine whether any key microRNAs [5] are the means by which the niche controls satellite cell function.

Timeline:
Year 1: Investigation of the effect of modulating signalling pathways on satellite cell function
Year 2-3: The mechanism by which the host cell niche signals to incoming satellite cells
Year 3: The fate of satellite cells that do not contribute to muscle regeneration.

The relevance of the proposed project to the interface between basic and clinical science:
The proposed project is basic science, but will address an important bottleneck in the translation of stem cell therapies for muscular dystrophies into the clinic.

References:
1) Collins, C.A., et al., Stem cell function, self-renewal, and behavioral heterogeneity of cells from the adult muscle satellite cell niche. Cell, 2005. 122(2): p. 289-301.
2) Boldrin, L., et al., Mature adult dystrophic mouse muscle environment does not impede efficient engrafted satellite cell regeneration and self-renewal. Stem Cells (Dayton, Ohio), 2009. 27(10): p. 2478-2487.
3) Boldrin, L., et al., Donor Satellite Cell Engraftment is Significantly Augmented When the Host Niche is Preserved and Endogenous Satellite Cells are Incapacitated. Stem cells, 2012.
4) Neal, A., L. Boldrin, and J.E. Morgan, The satellite cell in male and female, developing and adult mouse muscle: distinct stem cells for growth and regeneration. PloS one, 2012. 7(5): p. e37950.
5) Roberts, T.C., et al., Expression Analysis in Multiple Muscle Groups and Serum Reveals Complexity in the MicroRNA Transcriptome of the mdx Mouse with Implications for Therapy. Mol Ther Nucleic Acids, 2012. 1: p. e39.