Comparison of Schwann cells and olfactory ensheathing cells for peripheral nerve gap bridging.

INTRODUCTION: Previously, we introduced the biogenic conduit (BC) as a novel autologous nerve conduit for bridging peripheral nerve defects and tested its regenerative capacity in a short- and long-term setting. The aim of the present study was to clarify whether intraluminal application of regeneration-promoting glial cells, including Schwann cells (SC) and olfactory ensheathing cells (OEC), displayed differential effects after sciatic nerve gap bridging. MATERIAL AND METHODS: BCs were generated as previously described. The conduits filled with fibrin/SC (n = 8) and fibrin/OEC (n = 8) were compared to autologous nerve transplants (NT; n = 8) in the 15-mm sciatic nerve gap lesion model of the rat. The sciatic functional index was evaluated every 4 weeks. After 16 weeks, histological evaluation followed regarding nerve area, axon number, myelination index and N ratio. RESULTS: Common to all groups was a continual improvement in motor function during the observation period. Recovery was significantly better after SC transplantation compared to OEC (p < 0.01). Both cell transplantation groups showed significantly worse function than the NT group (p < 0.01). Whereas nerve area and axon number were correlated to function, being significantly lowest in the OEC group (p < 0.001), both cell groups showed lowered myelination (p < 0.001) and lower N ratio compared to the NT group. DISCUSSION: SC-filled BCs led to improved regeneration compared to OEC-filled BCs in a 15-mm-long nerve gap model of the rat.

The long-term functional recovery of repair of sciatic nerve transection with biogenic conduits.

INTRODUCTION: The aim of this study was to evaluate long-term regenerative capacity over a 15-mm nerve gap of an autologous nerve conduit, the biogenic conduit (BC), 16 weeks after sciatic nerve transection in the rat. METHODS: A 19-mm long polyvinyl chloride (PVC) tube was implanted parallely to the sciatic nerve. After implantation, a connective tissue cover developed around the PVC-tube, the so-called BC. After removal of the PVC-tube the BCs filled with fibrin (n = 8) were compared to autologous nerve grafts (n = 8). Sciatic functional index (SFI) was evaluated every 4 weeks, histological evaluation was performed at 16 weeks postimplantation. Regenerating axons were visualized by retrograde labelling. RESULTS: SFI revealed no significant differences. Nerve area and axon number in the BC group were significantly lower than in the autologous nerve group (P < 0.05; P < 0.01). Analysis of myelin formation showed no significant difference in both groups. Analysis of N-ratio revealed lower values in the BC group (P < 0.001). CONCLUSION: This study reveals the suitability of BC for nerve gap bridging over a period of 16 weeks with functional recovery to comparable extent as the autologous nerve graft despite impaired histomorphometric parameters.

An in vivo engineered nerve conduit--fabrication and experimental study in rats.

BACKGROUND: Several types of nerve conduits have been used for peripheral nerve gap bridging. This study investigated the in vivo engineering of a biological nerve conduit and its suitability for nerve gap bridging. MATERIAL AND METHODS: A 19-mm long polyvinyl chloride (PVC) tube was implanted parallely to the sciatic nerve. After implantation, a connective tissue cover developed around the PVC-tube, the so-called biogenic conduit. Histological cross-sections were performed after 1, 2, 3, and 4 weeks. Wall thicknesses were measured and all vessels per cross-section were counted. The biogenic conduit filled with fibrin was used to bridge a 15-mm long nerve gap in the sciatic lesion model of the rat (n = 8). The results of nerve repair with the conduit were compared to the autologous nerve graft (n = 8). Sciatic functional index (SFI), nerve area, axon count, myelination index, and ratio of total myelinated fiber area/nerve area (N-ratio) were analyzed after 4 weeks. RESULTS: The wall thickness of biogenic conduits increased over the 4 weeks implantation time. Biogenic conduits revealed highest number of vessels per cross-section after 4 weeks. The results of SFI analysis did not show significant difference between the repairs with biogenic conduit and autologous nerve graft. Nerve area and axon count in the biogenic conduit group were significantly lower than in the autologous nerve group (P < 0.001). The biogenic conduit group showed significant higher myelination values, but lower N-ratio when compared to the nerve graft group (P < 0.001). CONCLUSIONS: The in vivo engineered conduits allow nerve gap bridging of 15 mm. However, quality of regeneration after 4 weeks observation time is not comparable to autologous nerve grafts. Whether biogenic conduits might be a suitable alternative to artificial and biological conduits for gap bridging will have to be evaluated in further studies.

Single-dose application of CNTF and BDNF improves remyelination of regenerating nerve fibers after C7 ventral root avulsion and replantation.

Although axonal regeneration has been observed after replantation of avulsed ventral roots (VR) into the spinal cord, the functional outcome of this treatment in terms of motor reinnervation is unsatisfactory. In the present study, effects of single-dose ciliary and/or brain-derived neurotrophic factor (CNTF, BDNF) application on axon regeneration after C7 VR avulsion and replantation in adult rabbits were morphologically assessed by analysis of numbers, calibers, and myelination of axons in replanted VRs. Electromyography (EMG) was carried out to document the time course of de- and reinnervation in individual animals. After 3 weeks, replanted C7 VRs were almost devoid of myelinated axons. At week 8, active EMG-denervation was confirmed in affected muscles, but was less pronounced in neurotrophic factor (NF)-treated animals than in controls. Reinnervation potentials were identified in paraspinal muscles in more NF-treated animals than in controls. After 6 months, the number of myelinated axons in replanted VRs was approximately 45% of that in unlesioned roots in all groups, with small-sized axons constituting the majority of axons. At this time, more NF-treated animals than controls featured reinnervation. Moreover, myelination deficits of regenerated axons in controls were less pronounced in NF-treated animals. Especially in CNTF + BDNF-treated animals, myelination of regenerated axons of specific sizes was significantly increased compared to regenerated controls. In summary, NFs stimulated reinnervation early after the lesion and, for the first time, our morphological data quantitatively indicate positive effects of CNTF + BDNF on remyelination.

Chorioallantoic membrane angiogenesis model for tissue engineering: a new twist on a classic model.

Tissue-engineering (TE) applications include the isolation, culture, and seeding of cells into a suitable matrix or scaffold before in vivo transplantation. After transplantation, vascularization of the scaffold is a principal limiting factor for cell viability for the first 6-8 days posttransplantation. A model for systematic analysis of this process has been developed. Fertilized White Leghorn eggs were incubated (at 37.8 degrees C in 60% relative humidity) and opened on day 3 of incubation. Preadipocyte-seeded fibrin constructs were implanted in a specially designed plastic cylinder and placed through the opening on the surface of the chorioallantoic membrane (CAM) on day 8 of incubation. Vascularization of the constructs by chorioallantoic blood vessels was assessed for up to 8 days posttransplantation. The survival rate for embryos receiving transplanted constructs was about 90%. Histology confirmed transplant cell viability at day 4 posttransplantation and vascularization of the constructs by avian endothelial cells began at this time. A new in vivo model to study the effect of angiogenesis in TE constructs, including assessments of viability, proliferation, and differentiation of transplanted cells and biomaterial properties, is presented. Advantages include easy access to the vascular network of the CAM, lack of immunocompetence, low costs, and avoidance of animal experiments.

Rho kinase inhibitors Y27632 and H1152 augment neurite extension in the presence of cultured Schwann cells.

BACKGROUND: RhoA and Rho kinase inhibitors overcome the inhibition of axonal regeneration posed by central nervous system (CNS) substrates. METHODS: To investigate if inhibition of the Rho pathway augments the neurite extension that naturally occurs in the peripheral nervous system (PNS) following nerve damage, dorsal root ganglion neurons and Schwann cell co-cultures were incubated with culture medium, C3 fusion toxin, and the Rho kinase (ROCK) inhibitors Y27632 and H1152. The longest neurite per neuron were measured and compared. Incubation with Y27632 and H1152 resulted in significantly longer neurites than controls when the neurons were in contact with Schwann cells. When separated by a porous P.E.T. membrane, only the group incubated with H1152 developed significantly longer neurites. This work demonstrates that Rho kinase inhibition augments neurite elongation in the presence of contact with a PNS-like substrate.

Biobrane in the treatment of burn and scald injuries in children.

Eighty-four children with a burn (n = 7) or scald injury (n = 77), treated with Biobrane, were investigated in a retrospective and clinical study. In most patients (n = 71), the Biobrane was adherent and without any reactions or infections. An infection was seen in 10.7% (9 from 84 patients). Twenty-one of 49 patients of the follow-up had limited scar areas. In scarless healed areas, 54.3% had normopigmentation and 39.1% were hypopigmented. The skin quality of the scars was mostly hypopigmented with a softness between minimal and middle resistance, under 2-mm high, and of normal to pink skin color. Compared with other dressings, Biobrane is no more expensive than others. We conclude that when used on properly selected wounds, Biobrane is an effective and, for the children, less traumatic therapy for superficial partial-thickness burns without increasing the cost of outpatient burn care.

Motoneuron survival after C7 nerve root avulsion and replantation in the adult rabbit: effects of local ciliary neurotrophic factor and brain-derived neurotrophic factor application.

BACKGROUND: The authors investigated the extent and time course of motoneuron cell death after C7 ventral nerve root avulsion under conditions resembling the trauma mechanism in clinical situations. In addition, they evaluated the effect on motoneuron survival of locally applied ciliary neurotrophic factor and brain-derived neurotrophic factor, with the aim of improving preconditions for successful regeneration of peripheral motor innervation. METHODS: Forty-four New Zealand White rabbits were operated on using a dorsal approach. The dorsal spinal nerve roots of segment C7 were cut, and the ventral roots were completely pulled out from the spinal cord. In seven experimental groups, ciliary neurotrophic factor, brain-derived neurotrophic factor, or both were applied to the lesion site using different application methods and compared with two control groups. One or 3 weeks after the operation, the animals were euthanized and segments C6 to C8 were studied histologically. In group 9, the avulsed rootlets were replanted into the ventrolateral spinal cord and the effect of replantation on motoneuron survival was assessed at 3 weeks postoperatively. RESULTS: The results indicated that within a period of 7 days, 54.4 +/- 12.1 percent of the motoneurons in segments C6 to C8 died without any therapy. Local application of ciliary neurotrophic factor or brain-derived neurotrophic factor lowered motoneuron loss significantly to 16.9 +/- 14.3 percent and 28.0 +/- 11.4 percent, respectively (p < 0.05). The reduction in motoneuron loss persisted after 3 weeks' survival time (23.1 +/- 4.3 percent in ciliary neurotrophic factor-treated animals, and 22.3 +/- 8.4 percent in brain-derived neurotrophic factor-treated animals, p < 0.05). Survival rates were not significantly higher after treatment with a combination of both factors (motoneuron loss, 33.5 +/- 7.1 percent). CONCLUSION: The authors conclude that the early application of neurotrophic factors appears to be a promising technique to improve motoneuron survival after nerve root avulsion.