Fig. 3.

In vivo gene therapy restores impaired regeneration in CAPN3-KO muscle

Schematic diagram of single stranded AAV9.CAPN3 vector (a). In between the 5′ and 3′ single strand ITRs (inverted terminal repeats), muscle creatine kinase (MCK) promoter (563 bp) drives the expression of CAPN3 open reading frame (2466 bp). Also labeled is polyadenylation site (Poly A, 53 bp). Tibialis anterior (TA) muscles from CAPN3-KO mice were first injected with CTX, and 2 weeks later with 1 × 10¹¹ vg of AAV.CAPN3 to left TA (b) or PBS to right TA (c). Four weeks after gene injection the muscle diameter increased and the lobulated fibers were less common compared to the untreated CAPN3-KO muscle. d Lobulated fibers with a pattern of subsarcolemmal organelle, mitochondria distribution (arrows) suggesting partial myotube fusion in the untreated CAPN3-KO muscle at higher magnification. Scale bar = 20 μm for B-D. e The muscle fiber size distribution histograms (mean ± SEM/square millimeter area; derived from 3 mice in each group) of the treated and untreated TA muscle from CAPN3-KO mice showing a shift to larger diameter fibers with treatment; an increase in the small diameter subpopulation is present in the untreated group. f STO fiber size distribution histograms show excessive number of small fibers in the untreated CAPN3-KO muscle.