Traumatic injuries resulting in peripheral nerve lesions often require a graft to bridge the gap.Although autologous nerve graft is still the first choice strategy in reconstructions, it has thesevere disadvantage of the sacrifice of a functional nerve. Cell transplantation in a bioartificialconduit is an alternative strategy to create a favourable environment for nerveregeneration. Among adult stem cells, adipose-derived stem cells (ASC) are a useful tool inregenerative medicine as they can be induced towards multiple mesodermal and nonmesodermal lineages, being recently differentiated into cells showing Schwann cell-likemorphology, glial cell markers and increased neurotrophic potential. The first two chapters ofthis work describe in vivo applications of Schwann cell-like differentiated ASC (dASC),seeded into biodegradable nerve guides made of fibrin, investigating both brief (2 weeks) andlong (4 months) term effects on the regenerating nerves. Comparison was carried out withsimilarly differentiated bone marrow mesenchymal stem cells (dMSC), Schwann cells (SC)and empty fibrin conduits, as well as with autologous nerve grafts. Regeneration wasevaluated in a 1cm gap total axotomy sciatic nerve injury model on rats. Results showed thatdASC could improve regeneration distance in a similar manner to other regenerative cells inthe brief term. This effect was maintained and strengthened in the long term, where nervemorphology, spinal motoneurons regeneration, protection from muscle atrophy andelectrophysiological performances of regenerated nerves were analysed. dASC positiveeffects lasted in the long term with functional results comparable to the autologous nervegrafts, which served as controls. The third chapter focuses on the possibility to furtherimprove dASC regenerative performances using fibronectin and laminin, two keyextracellular matrix (ECM) molecules involved in nerve regeneration, with the future aim tooptimize cell host, directional cues and neurotrophism of tissue engineered conduits.Fibronectin and laminin protected dASC from stress-induced cell death in vitro, significantlyincreasing cell adhesion and viability. Laminin significantly improved neurotrophic propertiesof dASC enhancing neurite outgrowth of both primary sensory neurons and NG108-15neurons co-cultured with dASC, suggesting a further activation of the neurotrophic effect ofdASC by ECM molecules. These improved effects were increased when a direct contact wasestablished between the laminin substrate, dASC and neurons, suggesting a primary role oflaminin in contact signalling, finally boosting the neurotrophic potential of dASC.Further studies will be needed to clarify the interactions between dASC and the complexniche of peripheral nerve regeneration, including the ECM molecules. However, theneurotrophic potential of dASC expressed in both in vitro and in vivo experiments opens wideperspectives in tissue engineering applications among new methods to enhance peripheralnerve repair.
|Date of Award||31 Dec 2012|
- The University of Manchester
|Supervisor||Giorgio Terenghi (Supervisor)|
- adipose-derived stem cells, regenerative cells, peripheral nerve regeneration, extracellular matrix, sciatic nerve, nerve conduits, fibrin