Abstract
Purpose :
The extraocular muscles (EOMs) are hypothesized to be responsive to exogenous factors due to an increased satellite cell abundance and more regular myonuclear addition and myofiber remodeling relative to limb skeletal muscle. Past studies from our lab show that eye alignment and EOM properties of animal models can be manipulated by varying types of neurotrophic factor treatment. However, the effects of these factors on the proliferation and differentiation of EOM satellite cell subpopulations are unclear, and more studies on their effects in vitro and in vivo must be done to evaluate their pharmacological value towards the treatment of ocular motor disorders, such as idiopathic childhood onset strabismus.
Methods :
Wild type mouse EECD34 myogenic precursor cells (mpcs) from dissected EOM and tibialis anterior (TA) were isolated via cell sorting using the following cell markers: CD34+/CD31-/CD45-/Sca1-. These cells were plated on 8 well chamber slides and stained for their proliferation or differentiation states following treatment with fibroblast growth factor 2 (FGF2) treated media at 10 ng/ml or 40 ng/ml, or control media. Counts for proliferating and non-proliferating cells were averaged for each well. Counts for non-differentiating myocytes, differentiating mononuclear myocytes (desmin+, single nuclei), and fused myocytes (desmin+, multi-nuclei) were averaged for each well. One-way ANOVAs were used to assess significant differences.
Results :
FGF2 treatment of EOM-derived EECD34 cells showed no significant difference in proliferation compared to controls. However, FGF2 caused a significant increase in the proportion of differentiating EOM-derived mononuclear cells relative to naïve control.
Conclusions :
EECD34 myogenic precursors showed no change in proliferation in the presence of FGF2 and responded to increased FGF2 concentrations by increased differentiation in the absence of fusion. This result indicates that FGF2 may reduce the fusion of differentiating muscle precursor cells into fibers thus reducing myonuclear turnover in these fibers. These data correlate with studies of children with Apert syndrome. Further work must be done to evaluate fully the role of neurotrophic factors in EOM satellite cell proliferation and fusion behaviors. Such work will utilize a wider range of concentrations for FGF2 and other growth factors and the isolation of Pax7+ satellite cells for similar experiments.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.