Introduction and Aims: Although skeletal muscles have remarkable potential for adaptation, the amount of muscle length increase during gradual limb lengthening is always less than the amount of bone lengthening. The purpose of this study was to analyse gene expression in skeletal muscle undergoing adaptation to limb lengthening.

Method: Ten adult goats were randomly divided into two groups of five animals. Group 1 underwent 20% (43–47mm) standard Ilizarov tibial lengthening and group 2 served as un-operated control. Muscle tissues from proximal myotendenous junctions of Peroneus Longus were harvested from the lengthened limb in the distraction group and corresponding limb in the control group and immediately snap frozen in liquid nitrogen. To screen for genes potentially associated with sarcomerogenesis, microarray technology was employed. Biotin labeled cRNA was hybridised to Affymetrix HU133A GeneChips, containing 22,284 gene transcripts. All created data files were analysed using computer software GeneSpring 5.0.

Results: In both groups, 5092 (23%) gene transcripts flagged present. Thirty-two of these transcripts were differentially expressed between distracted and control groups (p < 0.05). Represented by these transcripts were 12 known and three unknown genes, which were up-regulated in lengthened muscles by more than 2.0 fold. The substantially up-regulated genes identified were MYOZ2 (myozenin 2), MYL4 (embryonic myosin alkali light chain), MYL6 (myosin light polypeptide 6), CRYAB (crystalline), PFN2 (profiling 2), ARPP-19 (cyclic AMP phosphorprotein), TUBB2 (tubulin beta 2), PPP1R12 (protein phosphatase 1), RCOR (REST corepressor), LIM (LIM protein), FN1 (fibronectin 1), ACTC (alpha-actin), and hypothetical protein FLJ10111. Among the genes found to be up-regulated are genes involved in the myogenesis pathway. Myozenin 2 gene is associated with the signalling and activity of Calcineurin/Calsarcin that plays a significant role in muscle cell proliferation and myofiber type differentiation. Crystallin gene may be involved in promoting muscle survival during differentiation. The functionality of the remaining genes range from cytoskeletal organisation (TUBB2), cyto-skeletal structure (PFN2, MYL4, MYL6), cell adhesion and motility (FN1), muscle development and differentiation (FHL1 and LIM), intercellular adhesion and intermediate filament organisation (PNN), muscle contraction and relaxation (PPP1R12A), neuronal-specific gene silencing (RCOR), and PKA-dependent intracellular messaging (ARPP-19).

Conclusion: The findings suggest that tension stress observed during gradual limb lengthening using standard Ilizarov distraction protocol activates expression of genes involved in skeletal muscle growth, differentiation, and neogenesis. On-going studies involving immunohistochemistry, RT-PCR, and in situ hybridisation to confirm cellular localisation of up-regulated genes are underway.