d) Immunostaining of heart sections for N2.261 and MEF2 in 5 dpci ppargc1a+/+ and ppargc1a-/- animals; magnified view of area in white boxes shown below; arrowheads point to N2.261+ CMs; white dashed lines mark the wound border; percentage of N2.261+ CMs in the border zone shown on the right (n = 4-6 ventricles of each genotype). 