Tiam Mana Saffari

124 CHAPTER 6 repaired with a nerve graft results in immunotrophic changes locally, and also in the peripheral environment. Extracellular matrix (ECM) Collagen is found in most connective tissues and plays a key role in each phase of healing after injury 37 . In vitro , high levels of ECM-related gene expression profiles demonstrate cell adhesion and cell-to-cell communication abilities 17 . In rat skin, type III collagen is associated with early increase in collagen synthesis and may function in supporting healing 37 . These studies are consistent with our observation that ECM related gene expression is increased in SIEF nerve tissue. Strengths and limitations Evaluation of gene expression profiles in a surgical nerve repair model in which a pedicled adipofascial flap supports vascularization of nerve allografts represents a new approach to understand how vascularization alters the local healing environment. Molecular results can support the assessment of functional outcomes and provide mechanistic answers to success or failure of nerve repair strategies by elucidating effects of surgical angiogenesis on nerve allografts. Unfortunately, the set-up of these experiments did not allow for functional recovery outcomes. Future animal studies will focus on combining molecular results with functional motor outcomes to describe the effect of surgical angiogenesis on nerve regeneration in more detail. Another limitation of the current in vivo study is the lack of gene expression profiles evaluation over time. Gene expression may vary over time and following these profiles over a time course may provide more information. One obstacle remains the experimental logistics, the cost of surgery and animal maintenance to obtain longitudinal results that permit assessment of nerve vascularization over time. We also appreciate the limitation that gene expression profiles may be altered due to the trauma or inflammation caused at time of surgery, and that some growth factors and EMC proteins in the healing environment are triggered in vivo only and cannot be recapitulated in vitro .