Floor plan - 2013 Annual Meeting - American Association for Hand ...

Caspase 3 Knockout Mice Show Partial Protection of Skeletal Muscle Atrophy following
Denervation
Institution where the work was prepared: McMaster University, Hamilton, ON, Canada
James Bain, MD, MSc1; Jane AE Batt, MD, PhD, FRCPC2; Pam Plant2; Minna Woo2; (1)Hamilton Health Sciences and
McMaster University, (2)University Health Network, University ofToronto
Early functional reinnervation is the goal following peripheral nerve injury and denervation. However, profound and eventually irreversible
muscle denervation atrophy is a barrier to this goal. The ubiquitin proteasomal pathway is the predominant protein degradation
pathway activated following denervation that results in denervation muscle atrophy. However, the proteasome is not able to
degrade intact actinomyosin myofibrils. Capsase-3 has been purported to be a key enzyme that degrades intact actinomyosin complexes,
into substrates upon which the ubiquitin proteasome subsequently acts.
HYPOTHESIS:
The absence of the caspase-3 protein will protect muscle from denervation atrophy.
PURPOSE:
To explore the muscle denervation atrophy in caspase-3 knockout mice and evaluate both the downstream ubiquitination pathways,
and apoptotic pathways in this animal model.
METHODS/MATERIALS:
Caspase-3 knockout mice and heterozygote and wild type controls were anesthetized and had the sciatic nerve transected under institutionally
guided ethics approval. Animals were sacrificed after 2 or 4 weeks of denervation. Animal and wet Gastrocnemius muscle
weights were recorded for experimental and contralateral sides. Muscle was then either snap frozen in liquid nitrogen and maintained
at ñ80, or fixed in paraformaldehyde for subsequent histological analysis. RNA and protein were isolated. Real time RT PCR and western
blotting determine mRNA and protein expression levels respectively of key mediators of the ubiquitin proteasome pathways.
RESULTS:
Although experimental and control animals demonstrated muscle atrophy, significantly less muscle loss was observed in the homozygous
animals at both 2 weeks and 4 weeks (p