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.

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.

Reactive changes in dorsal roots and dorsal root ganglia after C7 dorsal rhizotomy and ventral root avulsion/replantation in rabbits

Current surgical treatment of spinal root injuries aims at reconnecting ventral roots to the spinal cord while severed dorsal roots are generally left untreated. Reactive changes in dorsal root ganglia (DRGs) and in injured dorsal roots after such complex lesions have not been analysed in detail. We studied dorsal root remnants and lesioned DRGs 6 months after C7 dorsal rhizotomy, ventral root avulsion and immediate ventral root replantation in adult rabbits. Replanted ventral roots were fixed to the spinal cord with fibrin glue only or with glue containing ciliary neurotrophic factor and/or brain-derived neurotrophic factor. Varying degrees of degeneration were observed in the deafferented dorsal spinal cord in all experimental groups. In cases with well-preserved morphology, small myelinated axons extended into central tissue protrusions at the dorsal root entry zone, suggesting sprouting of spinal neuron processes into the central dorsal root remnant. In lesioned DRGs, the density of neurons and myelinated axons was not significantly altered, but a slight decrease in the relative frequency of large neurons and an increase of small myelinated axons was noted (significant for axons). Unexpectedly, differences in the degree of these changes were found between control and neurotrophic factor-treated animals. Central axons of DRG neurons formed dorsal root stumps of considerable length which were attached to fibrous tissue surrounding the replanted ventral root. In cases where gaps were apparent in dorsal root sheaths, a subgroup of dorsal root axons entered this fibrous tissue. Continuity of sensory axons with the spinal cord was never observed. Some axons coursed ventrally in the direction of the spinal nerve. Although the animal model does not fully represent the situation in human plexus injuries, the present findings provide a basis for devising further experimental approaches in the treatment of combined motor/sensory root lesions.

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.

Effects of root replantation and neurotrophic factor treatment on long-term motoneuron survival and axonal regeneration after C7 spinal root avulsion

In order to determine the effect of nerve root replantation on motoneuron survival and regeneration, we have avulsed and replanted C7 ventral rootlets in adult rabbits under various conditions. Intraspinal alterations and exact positions of ventrolateral replantations were studied in each animal, and the effects of BDNF and/or CNTF administration during replantation investigated in different experimental groups. Six months after lesion, about 70% of motoneurons were lost on the lesioned sides in the C7 segment, without significant differences between groups. Retrograde fluorescent tracing and histological analysis documented that many axons had regrown through the original ventral exit zones or had exited the spinal cord at the lateral replantation site. However, many laterally exiting axons had not grown out directly from the ventral horn through the lateral white matter but had elongated vertically before leaving the spinal cord. The mean axonal diameter was significantly higher in regenerated axons that had exited through the original ventral exit zones in comparison with axons which had grown out laterally. Application of BDNF and/or CNTF did not show any effects on the pathways of regeneration into the replanted root. The results indicate that motoneuron survival cannot be significantly improved by a single dose of neurotrophic factors applied to a ventrolateral replantation site. However, a significant number of myelinating axons are found in replanted roots, and regeneration may be more efficient when outgrowth through the original ventral exit zone is supported.

Engineered Adipose Tissue Supplied by Functional Microvessels

A volume-persistent culture of adipose tissue under in vivo conditions can be achieved only by early vascularization after cell transplantation. Cotransplantation of autologous preadipocytes with endothelial cells may enable the early formation of a capillary network. Investigations were performed in vivo in a specially adapted chorioallantoic membrane (CAM) model. Fertilized White Leghorn eggs were incubated and opened on day 3 of incubation and human dermal microvascular endothelial cell (HDMVEC) spheroids and preadipocytes were transferred in a fibrin matrix to the CAM. On day 7 after incubation the composites were explanted and immunohistologically investigated. Numerous vessels consisting of HDMVECs could be detected and the lumena of these vessels were perfused by chick erythrocytes. These results show the formation of a capillary network consisting of transplanted HDMVECs. The microcirculation of chick erythrocytes in vessels consisting of human endothelial cells proves the continuity of a newly formed capillary system to the host vessel system. The experiments demonstrate the first patent connection of tissue-engineered microvessels in adipose tissue to a host vessel system without applying exogenous angiogenic growth factors or transient transfection. The cotransplantation of endothelial cell spheroids with angiogenic mesenchymal cells may lead to the engineering of complex three-dimensional implants.

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.

The effect of sevoflurane on implicit memory: a double-blind, randomised study

Forty-eight gynaecological patients were randomly allocated to three groups (target end-tidal sevoflurane concentration 1.2, 1.5 or 2%), and into subgroups for positive or neutral suggestion. Anaesthesia was induced by inhalation of sevoflurane in oxygen. When the target concentration was achieved, the bispectral index, computed from a bi-frontal electroencephalogram, was noted. One of two eight-word lists was then played to prime implicit memory, followed by a positive or neutral suggestion. After surgery, each patient tried to identify 24 words obscured by background noise. Priming increased the likelihood of identifying words in the 1.2% group only, i.e. there was evidence of implicit memory in this group. There was no evidence of a therapeutic effect of positive suggestion (p = 0.3), but the power of this part of the study was low. The bispectral index did not achieve statistical significance as an indicator of susceptibility to priming.

Comparison of performance in materials-based occupation, imagery-based occupation, and rote exercise in nursing home residents

Materials-based occupation, imagery-based occupation, and rote exercise have been examined individually by several researchers. The present study compares all three approaches with one another (i.e., kicking a balloon, imagining kicking a balloon, and a control rote exercise) in nursing home residents. The dependent variable was the number of exercise repetitions. The subjects were 12 women and 3 men between 56 and 93 years of age residing in two nursing homes. All subjects experienced the three approaches but in different orders. One-way analysis of variance for related measures indicated a significant difference among conditions (p = .004). The Tukey procedure (Stevens, 1986) determined that the materials-based occupation condition elicited significantly more repetitions than the other two conditions. The difference between the imagery-based occupation and rote exercise was not statistically significant. These findings support our profession's historical emphasis on the use of physical materials to enhance performance.

Serological evidence of herpesvirus infection in captive Asian elephants (Elephas maximus)

In mid 1988 a 3-yr-old Asian elephant (Elephas maximus) from a circus in Switzerland died following generalized manifestation of a herpesvirus infection. In an effort to determine prevalence of infection with the herpesvirus, and due to lack of a corresponding virus isolate, it was decided to evaluate contact animals and elephants from a second herd for antibody to bovine herpesvirus 1 (BHV1) and bovine herpesvirus 2 (BHV2). Of 15 sera tested four displayed low neutralizing antibody titers to BHV2. None of the sera neutralized BHV1. However, as evidenced by protein A-mediated immunoprecipitation of metabolically radio-labeled virus-infected and mock-infected cell antigens, followed by separation of precipitation products in SDS-polyacrylamide gels, the 15 sera precipitated multiple antigens from both viruses. Similar results were obtained when using BHV4 antigens. The extent of reaction was most distinct with respect to BHV2 antigens, less prominent with BHV1 antigens, and least with BHV4 antigens. The respective protein patterns, although less marked, matched well with those obtained with bovine reference sera. Additional evaluation of sera from six elephants from two zoos in the Federal Republic of Germany gave essentially identical results. It was concluded that at least one herpesvirus, immunologically related to BHV2, may be widely distributed among captive Asian elephants, and that this virus apparently does not cause overt disease in the majority of animals.

[Realtime sonography of intrascrotal space-occupying lesions]

In 848 examinations of the testes in 317 patients, including 253 follow-up and/or multiple follow-up examinations and 36 unilateral testicle examinations (e.g., orchidectomy, aplasia or nondescent) it was shown that sonography is a diagnostic method which is on the one hand capable of clearly differentiating cystic from solid space-occupying processes, and on the other hand also offers certain possibilities for evaluating the status of solid findings. Histologic identification of malignant tumors was only achieved with teratomas. The differential diagnostic problem was in differentiating scrotal tumors from focal orchitis, chronic epididymitis, testicular torsion and contusion, and in differentiation between paratesticular neoplasms and epididymitides. The testicular findings included testicular neoplasms, cicatrization and cysts of the tunic, sequelae of trauma, orchitis, cryptorchism, hypoplasia, aplasia, and testicular cysts. Paratesticular findings included hydroceles, spermatoceles, varicoceles, paratesticular neoplasms, epididymitides, paratesticular scars, and thickening of the testicular coat.