Nerve Reconstruction: Improving outcome using allografts and stem cells in motor nerve repair

The overarching aim of this thesis is to improve nerve reconstruction using an off the shelf peripheral nerve allograft that is unlimited in supply and can be individualized to each patient using stem cells, providing functional recovery comparable to autograft nerve. In the first part, studies on the current clinical use of nerve grafts are presented. The clinical focus of this part is on brachial plexus injury, as these injuries typically require large amounts of donor nerve material that is frequently not available. The availability of an off the shelf alternative would be very beneficial in this field. Before implementing new nerve reconstruction strategies in vivo in animal models, we recognized there was a need for non-invasive follow-up methods. Therefore, in the second part of this thesis, we aimed to develop an ultrasound based evaluation technique to measure muscle recovery after nerve reconstruction in animal models. In the third part of this thesis, studies are presented that focus on the implementation and further improvement of the processed nerve allograft. Our previously optimized nerve allograft was implemented in different animal models. Results were promising, but did show there was further room for improvement. We hypothesized the need for a source of supportive and stimulating growth factors since allografts are devoid of cells that would provide this stimulus in autografts. We hypothesized that patient own adipose derived stem cells (MSCs) added to the nerve allograft could potentially produce these growth factors to further improve outcomes. A simple technique to deliver stem cells to the nerve allograft was developed. Finally, the interaction between MSCs and our optimized nerve allograft was evaluated with regard to growth factor production and gene expression. With this work, we have taken a promising path by using allografts and stem cells on our mission to improve nerve reconstruction

Posterior interosseous nerve palsy after closed proximal forearm fractures

Although rare, posterior interosseous nerve (PIN) palsy can occur in patients with a closed proximal forearm fracture and may present in a delayed fashion after initial trauma. In this case series, three cases of posterior interosseous nerve (PIN) injury following proximal forearm fractures are presented and discussed. Our literature search yielded six studies concerning PIN injury in radial head/neck fractures and proximal forearm fractures. Out of a total of 8 patients, 7 patients were treated non-operatively and in one patient a PIN release was performed. One patient was lost to follow-up, all other 7 patients showed successful recovery. A treatment algorithm for PIN palsy after proximal forearm fractures is provided. Based on our experience and what we found in literature, it seems safe to treat PIN palsies conservatively

Gene expression and growth factor analysis in early nerve regeneration following segmental nerve defect reconstruction with a mesenchymal stromal cell-enhanced decellularized nerve all

Background: The purpose of this study was to evaluate the molecular mechanisms underlying nerve repair by a decellularized nerve allograft seeded with adiposederived mesenchymal stromal cells (MSCs) and compare it to the unseeded allograft and autograft nerve. Methods: Undifferentiated MSCs were seeded onto decellularized nerve allografts and used to reconstruct a 10 mm gap in a rat sciatic nerve model. Gene expression profiles of genes essential for nerve regeneration and immunohistochemical staining (IHC) for PGP9.5, NGF, RECA-1, and S100 were obtained 2 weeks postoperatively. Results: Semi-quantitative RT-PCR analysis showed that the angiogenic molecule VEGFA was significantly increased in seeded allografts, and transcription factor SOX2 was downregulated in seeded allografts. Seeded grafts showed a significant increase in immunohistochemical markers NGF and RECA-1, when compared with unseeded allografts. Conclusions: MSCs contributed to the secretion of trophic factors. A beneficial effect of the MSCs on angiogenesis was found when compared with the unseeded nerve allograft, but implanted MSCs did not show evidence of differentiation into Schwann cell-like cells

Recipient-derived angiogenesis with short term immunosuppression increases bone remodeling in bone vascularized composite allotransplantation: A pilot study in a swine tibial defect model

Current vascularized composite allotransplantation (VCA) transplantation protocols rely upon life-long immune modulation to maintain tissue perfusion. Alternatively, bone-only VCA viability may be maintained in small animal models using surgical angiogenesis from implanted autogenous vessels to develop a neoangiogenic bone circulation that will not be rejected. This study tests the method's efficacy in a large animal model as a bridge to clinical practice, quantifying the remodeling and mechanical properties of porcine tibial VCAs. A segmental tibial defect was reconstructed in Yucatan miniature swine by transplantation of a matched tibia segment from an immunologically mismatched donor. Microsurgical repair of nutrient vessels was performed in all pigs, with simultaneous intramedullary placement of an autogenous arteriovenous (AV) bundle in Group 2. Group 1 served as a no-angiogenesis control. All received 2 weeks of immunosuppression. After 16 weeks, micro-CT and histomorphometric analyses were used to evaluate healing and remodeling. Axial compression and nanoindentation studies evaluated bone mechanical properties. Micro-CT analysis demonstrated significantly more new bone formation and bone remodeling at the distal allotransplant/recipient junction and on the endosteal surfaces of Group 2 tibias (p = 0.03). Elastic modulus and hardness were not adversely affected by angiogenesis. The combination of 2 weeks of immunosuppression and autogenous AV-bundle implantation within a microsurgically transplanted tibial allotransplant permitted long-term allotransplant survival over the study period of 16 weeks in this large animal model. Angiogenesis increased bone formation and remodeling without adverse mechanical effects. The method may allow future composite-tissue allotransplantation of bone without the risks associated with long-term immunosuppres