Bishop, Allen T.

Background: Mesenchymal stem cells have the potential to produce neurotrophic growth factors and establish a supportive microenvironment for neural regeneration. The purpose of this study was to determine the effect of undifferentiated and differentiated mesenchymal stem cells dynamically seeded onto decellularized nerve allografts on functional outcomes when used in peripheral nerve repair. Methods: In 80 Lewis rats, a 10-mm sciatic nerve defect was reconstructed with (1) autograft, (2) decellularized allograft, (3) decellularized allograft seeded with undifferentiated mesenchymal stem cells, or (4) decellularized allograft seeded with mesenchymal stem cells differentiated into Schwann cell–like cells. Nerve regeneration was evaluated over time by cross-sectional tibial muscle ultrasound measurements, and at 12 and 16 weeks by isometric tetanic force measurements, compound muscle action potentials, muscle mass, histology, and immunofluorescence analyses. Results: At 12 weeks, undifferentiated mesenchymal stem cells significantly improved isometric tetanic force measurement and compound muscle action potential outcomes compared to decellularized allograft alone, whereas differentiated mesenchymal stem cells significantly improved compound muscle action potential outcomes. The autografts outperformed both stem cell groups histologically at 12 weeks. At 16 weeks, functional outcomes normalized between groups. At both time points, the effect of undifferentiated versus differentiated mesenchymal stem cells was not significantly different. Conclusions: Undifferentiated and differentiated mesenchymal stem cells significantly improved functional outcomes of decellularized allografts at 12 weeks and were similar to autograft results in the majority of measurements. At 16 weeks, outcomes normalized as expected. Although differences between both cell types were not statistically significant, undifferentiated mesenchymal stem cells improved functional outcomes of decellularized nerve allografts to a greater extent and had practical benefits for clinical translation by limiting preparation time and costs.

Background Intraosseous ganglia of the carpal bones are uncommon with sparse publications to guide treatment. The purpose of this study was to review a single-institution experience to determine the outcomes of patients with surgically treated intraosseous carpal ganglia. Methods Skeletally mature patients with intraosseous carpal ganglia between 1995 and 2016 treated operatively were identified. Demographic information, clinical data, and radiographic studies were evaluated. Results Thirty-three ganglia in 31 patients were identified. Intraosseous ganglia were located in the lunate (23), scaphoid (9), and trapezoid (1). Patients who presented with pathologic fracture or collapse had larger intraosseus ganglia than those presenting with pain alone. Surgery significantly improved pain. Patients treated with debridement with autograft bone graft had a higher consolidation rate compared with allograft bone but no difference in pain. Conclusions Patients with large or symptomatic lesions can be treated successfully with curettage and debridement, which leads to relief of pain. The use of bone grafting remains controversial.

AbstractBackgroundIn nerve allograft development, currently used subjective histological scoring systems to evaluate nerve structure in experimental studies are not uniform and have not been validated.The aim of this study was to describe and validate a simple, fast and inexpensive method to compare structural properties of nerve allografts on a histological level.Materials and methodsA total of 113 histological sections of rat (sciatic nerves) and human peripheral nerve segments (thoracodorsal and long thoracic nerve for motor and sural for sensory nerve) treated with various decellularization protocols were analyzed. Slides were stained with Hematoxylin & Eosin (H&E), Toluidine Blue and Laminin. A subjective scoring system using a 5‐point scale was used to score each nerve section by four independent researchers. For validation of this score both inter‐ and intra‐rater reliability were calculated using the Intraclass Correlation Coefficient (ICC).ResultsOverall, an excellent correlation between the different observers was found for the Toluidine Blue (ICC = 0.919, 95% CI: 0.891–0.941), H&E (ICC = 0.9, 95% CI: 0.865–0.927) and Laminin staining (ICC = 0.897, 95% CI: 0.860–0.926). Intra‐rater reliability was good for all three staining techniques (ICC >0.8).ConclusionThis study demonstrates the validity of this simple scoring system to evaluate nerve structure after different processing protocols. All three evaluated staining techniques can reliably be used for both rat and human nerve tissue. We believe this method is suitable to compare different processing techniques to create processed nerve allografts, especially when the average scores of multiple raters are used.

AbstractPurposeAdipose derived mesenchymal stem cells (MSCs) are hypothesized to supplement tissues with growth factors essential for regeneration and neovascularization. The purpose of this study was to determine the effect of MSCs with respect to neoangiogenesis when seeded onto a decellularized nerve allograft in a rat sciatic nerve defect model.MethodsAllograft nerves were harvested from Sprague–Dawley rats and decellularized. MSCs were obtained from Lewis rats. 10 mm sciatic nerve defects in Lewis rats were reconstructed with reversed autograft nerves, decellularized allografts, decellularized allografts seeded with undifferentiated MSC or decellularized allografts seeded with differentiated MSCs. At 16 weeks, the vascular surface area and volume were evaluated.ResultsThe vascular surface area in normal nerves (34.9 ± 5.7%), autografts (29.5 ± 8.7%), allografts seeded with differentiated (38.9 ± 7.0%) and undifferentiated MSCs (29.2 ± 3.4%) did not significantly differ from each other. Unseeded allografts (21.2 ± 6.2%) had a significantly lower vascular surface area percentage than normal nonoperated nerves (13.7%, p = .001) and allografts seeded with differentiated MSCs (17.8%, p = .001). Although the vascular surface area was significantly correlated to the vascular volume (r = .416; p = .008), no significant differences were found between groups concerning vascular volumes. The vascularization pattern in allografts seeded with MSCs consisted of an extensive nonaligned network of microvessels with a centripetal pattern, while the vessels in autografts and normal nerves were more longitudinally aligned with longitudinal inosculation patterns.ConclusionsNeoangiogenesis of decellularized allograft nerves was enhanced by stem cell seeding, in particular by differentiated MSCs. The pattern of vascularization was different between decellularized allograft nerves seeded with MSCs compared to autograft nerves.

Background: Processed nerve allografts are a promising alternative to nerve autografts, providing an unlimited, readily available supply and avoiding donor-site morbidity and the need for immunosuppression. Currently, clinically available nerve allografts do not provide satisfactory results for motor reconstruction. This study evaluated motor recovery after reconstruction of a long nerve gap using a processed nerve allograft and the influence of storage techniques. Methods: Nerve allografts were decellularized using elastase and detergents and stored at either 4° or −80°C. In 36 New Zealand White rabbits, a 3-cm peroneal nerve gap was repaired with either an autograft (group 1, control) or a cold-stored (group 2) or frozen-stored (group 3) processed nerve allograft. Nerve recovery was evaluated using longitudinal ultrasound measurements, electrophysiology (compound muscle action potentials), isometric tetanic force, wet muscle weight, and histomorphometry after 24 weeks. Results: Longitudinal ultrasound measurements showed that the cold-stored allograft provided earlier regeneration than the frozen-stored allograft. Furthermore, ultrasound showed significantly inferior recovery in group 3 than in both other groups (p < 0.05). Muscle weight and isometric tetanic force showed similar outcomes in the autograft and cold-stored allograft groups [p = 0.096 (muscle weight) and p = 0.286 (isometric tetanic force)], and confirmed the inferiority of the frozen-stored allograft to the autograft [p < 0.01 (muscle weight) and p = 0.02 (isometric tetanic force)]. Conclusions: Frozen storage of the nerve allograft significantly impairs functional recovery and should be avoided. The cold-stored optimized nerve allograft yields functional recovery similar to the gold standard autograft in the reconstruction of a 3-cm motor nerve defect. Future studies should focus on further improvement of the nerve allograft.

Management of hand and wrist avascular necrosis with osteochondral fragmentation or focal arthritis can be a challenging problem with a variety procedures described for its treatment. Osteochondral autograft transplantation systems have been utilized in various focal defects of the knee, ankle, elbow, and wrist. The same principle for the treatment of focal defects of the proximal scaphoid, proximal capitate as well as metacarpal head as an alternative treatment is described. The main indication for this treatment is to address focal or partial osteochondral defects where the size of the defect is smaller than the isthmus of the involved bone to accommodate a cylindrical osteochondral graft that can be press fit. Larger and complete defects are contraindications to this treatment. We discuss the surgical technique as well as its main indications and expected outcomes

Abstract Background An adipofascial flap in the rat may provide new options for adding vascularization to scarred or nonvascularized beds for a variety of research studies. Current literature lacks sufficient description for a simple reproducible flap model for a vascularized pedicled flap in rats, in particular for neovascularization of allograft nerves for the reconstruction of sciatic nerve defects. The purpose of this study was to describe a surgical technique and determine long-term survivability for the pedicled superficial inferior epigastric artery fascial (SIEF) flap in the rat to meet requirement for a tunneled adipofascial flap to add vascularization to the sciatic nerve area. Methods The technique and use of a 4 × 3-cm SIEF flap are described. Twenty Lewis rats underwent the technique to determine feasibility. The flap was wrapped around processed allograft nerve reconstructions and viability of the flap was evaluated after 12 and 16 weeks. To visualize vessels, nerve grafts were harvested at 12 weeks and stained with hematoxylin-eosin and an antibody against microvessels (CD-34). Results All flaps remained viable after survival of 12 and 16 weeks. Complications included one hematoma formation and two lymphocele formations that did not have any impact on the flap. Immunohistochemistry confirmed an increase in microvessels and Schwann cell nuclei in the SIEF group compared with nerve samples from the unoperated, contralateral side. Conclusion A pedicled adipofascial flap model in the rat to provide a vascular bed for sciatic nerve reconstruction is detailed with long-term survivability evaluation of the flap. This flap is technically simple to be harvested and is suitable for revascularization procedures of various tissues in the lower abdomen, genital area, thigh, or upper limb of the rat.

Background: The purpose of this study was to evaluate the molecular mechanisms underlying nerve repair by a decellularized nerve allograft seeded with adipose-derived 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.