Biomedical subjects

H Fansa

Publications and source records attributed to H Fansa.

51 records · Page 3Linked to original sources

PubMed2000

[Cultivating human Schwann cells for tissue engineering of peripheral nerves].

Cultivation of human cells is well established. The cultivation of human Schwann cells may offer a new therapeutic approach for treatment of degenerative and traumatic lesions of the peripheral nervous system. Currently, Schwann cells in combination with other biological matrices are used as tissue-engineered biological nerve grafts in animal models. Cultivation of human Schwann cells, however, is more difficult than cultivation of rodent cells. A high cell yield is only achieved by pharmacological stimulation, which should not be used in clinical therapy. Thus, we aimed to establish an easy method of cultivating human Schwann cells from peripheral nerve neuromas that have developed after a complete nerve lesion. As these neuromas have to be resected in any case to allow proper nerve reconstruction, their removal does not lead to additional neurological defects. Schwann cells were cultivated from the neuromas of eleven patients, aged 5 to 75 years. All patients suffered from a complete median nerve lesion at the level of the distal forearm, which could not be treated primarily. Two weeks after trauma, the patients underwent secondary reconstruction by autologous sural nerve grafts. During this operation, the neuromas were resected. Control cultures were established from remaining parts of the sural nerve. Cell yield was determined on the first, third and seventh day in vitro. Schwann cells were stained for S100. Viability was assessed with fluoresceine-fluorescence. The cell count was assessed with regard to the donor age. The growth rate of Schwann cells was found to be donor-age dependent. The highest cell yield was obtained from adult neuromas. By the third day in vitro, they showed a 1.5 fold increased cell count compared with juvenile nerves and neuromas. By the seventh day in vitro, Schwann cells from adult neuromas were increased 2.5 times compared with cells from juvenile nerves and 7 times compared to cells from adult sural nerves. Cultivation of Schwann cells taken from sural nerves of patients older than 65 years was not possible. The utilization of neuromas as a source for human Schwann cells allows an age-independent cultivation within a short time period without any pharmacological treatment. These neuromas are virtually predegenerated and show an activation of Schwann cells implying good adherence and high mitotic activity in culture. Normal nerve tissue as a source for Schwann cells for tissue-engineered nerves is only sufficient in young patients due to its greater proliferative potential. The age-dependent proliferation underlines the need for alternative sources for Schwann cells.

Adolescent↗

PubMed1999

In vivo predegeneration of peripheral nerves: an effective technique to obtain activated Schwann cells for nerve conduits.

In vivo predegeneration of peripheral nerves is presented as a convenient and effective method to obtain activated Schwann cells and an enhanced cell yield following in vitro cultivation. The experiments conducted in rats were aimed at clinical use in gaining Schwann cell suspensions for filling artificial conduits in order to bridge peripheral nerve gaps. The rat sciatic nerve used as a model was transected distally to the spinal ganglia. Predegeneration in vivo was allowed to take place for 1, 2, 3 and 4 days and up to 1, 2 and 3 weeks. The nerve was then resected and prepared for cell cultivation. Schwann cells cultivated from the contralateral untreated nerve served as control. Immunostaining for S100, nerve growth factor receptor and the adhesion molecules N-cadherin and L1 was used to characterize the general state of the cultures. Viability was assessed by fluorescein fluorescence staining, and the proliferation index was determined by bromodeoxyuridine-DNA incorporation. The Schwann cells from predegenerated nerves revealed an increased proliferation rate compared to the control, whereas fibroblast contamination was decreased. Best results were obtained 1 week after predegeneration.

Animals↗

PubMed1999

The effect of the immunosuppressant FK 506 on peripheral nerve regeneration following nerve grafting.

Nerve allografts are highly antigenic and require the continuous use of immunosuppressive drugs. Neurotoxic complications from immunosuppressant therapy with FK 506 have been noted in the central and peripheral nervous system although an increased rate of axonal regeneration has also been noted. Regeneration of peripheral nerve grafts was assessed in a rat model clinically and morphometrically after treatment for 2 and 6 weeks with two different doses of FK 506. Good regeneration was noted in all groups at 6 weeks. A significantly higher axon count was observed in both the FK 506 groups after 2 weeks regeneration compared with controls. This beneficial effect was not evident after 6 weeks of regeneration. Whether this is related to a pruning mechanism or to a down-regulation of regenerative processes in the nerve due to possible neurotoxic effects of FK 506 remains unknown.

Animals↗

PubMed1999

[Stimulation of Schwann cell growth and axon regeneration of peripheral nerves by the immunosuppressive drug FK 506].

BACKGROUND: Nerve allografts are highly antigenic and, thus, require the continuous use of immunosuppressive drugs. The immunosuppressant Cyclosporine A was used in most studies. More recently, the immunosuppressive effect of FK 506 on peripheral nerve allografts and xenografts has been studied, and the drug has been found to prevent rejection successfully. However, neurotoxic complications have been noted in the central and peripheral nervous system although an increased rate of axonal regeneration has also been shown. METHODS: Schwann cells were cultured from the sciatic nerve of the rat. The effect of 100 microM FK 506 administered daily on these cultures was assessed over a period of seven days and compared to an untreated control group of cultures. To visualize a direct effect of FK 506 on Schwann cells, the changes in intracellular calcium were recorded using fluorescence imaging of primary rat Schwann cell cultures loaded with Fluo-3. Regeneration of autologous nerve grafts was assessed in a rat model clinically and morphometrically after daily administration of 0.6 mg FK 506/kg body weight. RESULTS: FK 506 increases the number of Schwann cells in culture significantly compared to the control group, while the fibrocyte population is decreased. FK 506 caused a transient increase of intracellular calcium levels of cultured cells. A significantly higher axon count was observed in the FK 506-treated grafts after two weeks of regeneration compared with controls. Additionally, less myelin debris was evident in the FK 506 treated group after two weeks compared with the control group. Good regeneration was noted in all grafts after six weeks of regeneration. CONCLUSION: The increased axon counts and decreased myelin debris in the FK 506 grafts after two weeks indicate an accelerated Wallerian degeneration and increased axon sprouting into the graft initially. FK 506 promotes axonal regeneration through binding to FKBP-12, thus activating GAP-43 (growth associated protein) and the TGF beta 1-pathway (transforming growth factor). In addition, the increase of the intracellular calcium may induce Schwann cell proliferation via Calmodulin which in turn promotes axonal regeneration.

Animals↗

PubMed1999

[Effect of pre-degeneration of peripheral nerves on plasticity of cultivated Schwann cells and their cell number in vitro].

Predegeneration of peripheral nerve grafts is known to improve axonal regeneration in the sciatic nerve of the rat. Predegeneration involves sectioning the donor nerve in situ for a period of time prior to harvesting in order to allow Wallerian degeneration to take place. It is suggested that proliferating Schwann cells are responsible for this regeneration-promoting effect due to an increased production and accumulation of trophic factors. The aim of this study was to evaluate whether the proliferation of Schwann cells is increased after various predegeneration periods and whether predegeneration does affect the production of trophic factors. The rat's sciatic nerve was transsected distal to the spinal ganglion. Predegeneration was allowed to take place for one, two, three and four days and one, two and three weeks, respectively. The nerve was resected and prepared for Schwann cell cultivation. Cells cultivated from the contralateral untreated nerve served as control. S100 immunostaining, nerve-growth factor (NGF), and N-cadherin were used to characterize Schwann cells. Viability was assessed by fluoresceine fluorescence staining. Proliferation index was determined by BrdU DNA incorporation. Cultivation of cells harvested from predegenerated nerves indicated an increased proliferation of Schwann cells compared to the control. Proliferation effects depended on the period of predegeneration. A higher cell yield was obtained as early as 24 hours and up to three weeks after predegeneration. Optimal proliferation was seen after one week of predegeneration. The rapid expansion of Schwann cell populations oppressed the development of contaminating fibroblasts. NGF and N-cadherin were expressed by all S100-positive cells. Predegeneration did not affect viability. The determined high mitotic activity of predegenerated Schwann cells in combination with an early onset of proliferation may explain the regenerating-promoting effect of predegenerated nerve grafts. The expression of both NGF and N-cadherin in the predegenerated cultures indicates a high level of plasticity with dedifferentiation capacity, which in turn promotes neural regeneration. Predegeneration allows a proliferation of Schwann cells without concomitant pharmacological treatment. Thus, predegeneration of peripheral nerves is considered to be a highly efficacious method if a high yield of activated Schwann cells is desired within a short period of time. This may become relevant in the future of repair of peripheral nerve lesions, when autologous Schwann cells with their capacity to provide neurotrophines and cell adhesion molecules are used as cellular prostheses to bridge nerve gaps.

Animals↗

PubMed1999

Successful implantation of Schwann cells in acellular muscles.

Acellular muscle grafts can support axonal regeneration over short gaps. Due to the lack of viable Schwann cells in the grafts, failure of regeneration is evident with increasing gap lengths. To create a biological nerve conduit, Schwann cells were implanted into acellular muscle. The grafts were then incubated in vitro and assessed histologically and morphometrically. For cultivation of the Schwann cells, rat sciatic nerves were allowed to predegenerate to obtain a high cell yield. Rat gracilis muscles were harvested and made acellular by a liquid nitrogen treatment. After Schwann cell implantation, the muscles were incubated in vitro for 2, 5, and 7 days. S100-immunostaining, NGF, and N-cadherin, characterized the Schwann cells within the muscle. Viability was assessed by fluoresceine-fluorescence staining. Proliferation was determined by BrdU-DNA incorporation. Cell implantation did not to affect Schwann cell viability. Cells were seen throughout the entire length of the muscle basal lamina. They aligned and formed a cell column. Immunostained for S-100, implanted cells showed 100 percent staining. N-cadherin and NGF were expressed by all of the S-100 positive cells. Predegeneration is considered to be a highly efficacious method, if a high yield of activated Schwann cells is required. The successful implantation of the cells into an acellular muscle provides the possibility of a biologic conduit, offering the advantage of large basal lamina tubes serving as a pathway for regenerating axons. It also provides the beneficial effects of viable Schwann cells that produce neurotrophic and neurotropic factors to support axonal regeneration. Functional outcomes require evaluation in further in vivo studies.

Animals↗

PubMed1999

Acellular muscle with Schwann-cell implantation: an alternative biologic nerve conduit.

Denatured or acellular muscle grafts are known to support axonal regeneration. With increasing gap length, failure of regeneration is evident, due to the lack of viable Schwann cells in the graft. The authors created a biologic nerve conduit, in a rat sciatic nerve model, by implanting cultured Schwann cells into an acellular gracilis muscle. Autologous nerve grafts and acellular muscle grafts without Schwann cells served as controls. After 6 weeks, regeneration was assessed clinically, histologically, and morphometrically. Polymerase chain reaction (PCR) analysis showed that the implanted Schwann cells remained viable within the graft. Good regeneration was noted in the muscle-Schwann cell group, while regeneration in the muscle grafts without Schwann cells was significantly impaired. The muscle-Schwann cell graft demonstrated systematic and organized regeneration, including the proper orientation of regenerated fibers. The number of axons regenerating through the muscle-Schwann cell grafts was significantly increased, compared with the acellular muscle without Schwann cells. Implantation of Schwann cells into acellular muscle thus provided a biologic conduit with large basal lamina tubes, as a pathway for regenerating axons. The positive effects of Schwann cells, producing neurotrophic and neurotropic factors, supported axonal regeneration.

Animals↗

PubMed1998

[Artifactual illness in plastic surgery].

The therapy of factitious disorders is a challenge for the treating surgeon. Only a clear understanding of the underlying causes and a good doctor-patient relationship make a successful outcome possible. Discussion about a confrontation of the patient with the diagnosis and the best made of treatment is still in progress. Early diagnosis and the cooperation between surgeons and psychiatrists are the most important parts of dealing with factitious disorders. This article gives an overview of symptoms and therapies. Six case reports demonstrate possibilities of the disorder's appearance.

Adult↗

PubMed1998

[Covering extensive soft tissue defects in infected knee endoprostheses by gastrocnemius flap].

Total knee arthroplasty has become a routine procedure in surgery. Deep infections have an incidence of 2-5%. Major risk factors are large prostheses, rheumatoid arthritis, diabetes mellitus and postoperative wound-healing complications. In large soft-tissue defects with skin necrosis, local wound care shows poor results, especially if loosening of the prosthesis and necrosis of the patellar ligament are evident. In these cases, no standard surgical therapy has been developed yet. Thus, we consider meticulous débridement with synovialectomy to be mandatory. Exchange of the prosthesis may be necessary. Soft-tissue coverage ought to be performed with a gastrocnemius muscle flap covered with a split-thickness skin graft. In the last three years, 11 patients with large soft-tissue defects and necrosis of the ligament were treated according to this concept. In all cases the muscle flap healed primarily and soft tissue coverage was excellent. Two patients who underwent single-stage removal and reimplantation of the prosthesis showed reinfections of the prosthesis. Reconstruction of the ligament was performed with the flap tendon. The patients with two-stage removal and reimplantation of the prosthesis and those who retained their implants had a good functional outcome. The gastrocnemius muscle flap provides easy and reliable soft-tissue reconstruction in large defects. In our patients a two-stage operation for reimplantation of the prosthesis was superior to a single-stage procedure. The reconstructed ligament should be reinforced with autologous material to prevent a secondary rupture. Early reconstruction with sufficient soft-tissue coverage and reconstruction of the ligament offers the patient the best chances of obtaining a good functional result and prevents arthrodesis or amputation. In addition, reconstructive surgery reduces the length of hospital stay and costs.

Aged↗

PubMed1998

Common peroneal nerve palsy caused by a ganglion. Case report.

A common peroneal nerve palsy caused by a ganglion cyst is a rare entity. A 48-year old man was referred with a six year history of intermittent pain that had resulted in a complete palsy of the common peroneal nerve. A magnetic resonance (MR) scan showed compression of the nerve by a ganglion, which was excised and the nerve was released. Three months later the lost muscle function had returned completely.

Ganglia↗

PubMed1998

Treatment of infected median sternotomy wounds with a myocutaneous latissimus dorsi muscle flap.

Infected sternotomy wounds, particularly if accompanied by osteomyelitis, mediastinitis or pericarditis, are associated with significant morbidity, prolonged hospitalization and a mortality of up to 50%. Until the introduction of muscle flaps, the therapy of choice was debridement and open granulation or catheter irrigation. From 1994 to 1996, 9 patients with infected median sternotomy wounds were treated with a single-stage radical debridement and wound closure with a pedicled myocutaneous latissimus dorsi muscle flap (LDM). One patient received, in addition, a rectus abdominis muscle turnover flap. Healing was uneventful in all cases, with no respiratory complications or chest-wall instability. Shoulder strength was also unaffected. Functional and aesthetic outcome was good. The LDM provides a safe flap with little donor site morbidity. Compared to the most local muscle flaps, an intact IMA is not required. At the same time, length and cost of hospital stay are decreased.

Aged↗

PubMed1997

Plasticity and function--the fate of a free, neurovascular muscle graft ten years post-reconstruction.

A 16-year-old female sustained a subtotal amputation of the left thigh. Debridement resulted in a bone and soft-tissue defect of 20 cm in length. The whole quadriceps muscle was lost, and the knee joint was open. The femur was stabilized by transfer of corticocancellous bone grafts. A latissimus dorsi muscle was harvested and transferred to reconstruct the lost quadriceps muscle. The thoracodorsal nerve was coaptated to the motor branch of the femoral nerve. The years after trauma, the muscle provides excellent motor function. EMG evaluation reveals no sign of denervation; macro-electromyography reveals only a moderate enlargement of motor units. There is recruitment of all motor units. Maximum voluntary torque of the transplanted muscle has decreased, compared to the contralateral rectus femoris. Histologic evaluation demonstrates a normal skeletal muscle with typical fiber distribution. These results indicate complete adaptability of the muscle at an atypical site, with a high degree of functional and structural plasticity of the skeletal muscle. The decreased voluntary torque of the transferred latissimus dorsi depends on the lower, total-fiber, cross-sectional area--the result of a parallel fiber structure.

Adolescent↗

PubMed1997

[Surgical decompression of bilateral, compression-induced damage to the posterior interosseous nerve. A case report].

Bilateral posterior interosseous nerve palsy is a rare case of radial nerve entrapment. The patient is unable to extend the fingers in the metacarpophalangeal joints. Extension of the interphalangeal joints is preserved due to the intrinsic muscles. Neither the extensor carpi radialis longus and brevis muscles are affected nor the brachioradialis muscle. However, extension of the wrist may be weak. There is no sensory loss. The neurophysiological examination underlines the clinical findings. In our case compression is caused by the arcade of Frohse and the vessels of the recurrent radial artery. A good recovery of nerve function is seen after surgical decompression.

Decompression, Surgical↗

PubMed1995

Preservation of peripheral nerve grafts: a comparison of normal saline, HTK organ preservation solution, and DMEM Schwann cell culture medium.

The regeneration of peripheral nerve grafts was evaluated in a rat model, after pretreating the grafts with Schwann cell culture medium, HTK organ preservation solution, and normal saline, under cold ischemic conditions for different time periods. Following orthotopic replantation of the grafts into donor animals, the quality of regeneration was assessed after 6 weeks, compared to positive controls (autologous transplantation) and negative controls (acellular grafts). The regenerative quality in the Schwann cell culture groups with ischemic periods of 32 and 72 hr was comparable to normal controls. Significantly minor regeneration was detected in specimens undergoing 14 and 120 hr of ischemia in the Schwann cell culture medium and in the HTK and normal saline groups, regardless of ischemic time. Among the conclusions was that controlled proliferation of Schwann cells seems to be a basic principle for preservation of peripheral nerve grafts.

Animals↗

PubMed1993

Preservation of peripheral nerve grafts with Schwann cell culture medium.

Preservation of peripheral nerves may, in the near future, play an important role in reconstructive surgery, especially if recent advances in immunosuppressive therapy are taken into account. Therefore, it has to be investigated whether peripheral nerves can be stored for some time after harvesting without diminishing their regenerative potential. Previous experiments of our group could demonstrate only little benefit of organ storage solution (HTK) or normal saline (NaCl 0.9%) to peripheral nerves when kept at cold ischaemia of 4 degrees C for 32 and 72 hours. In this presentation, we are reporting the results of peripheral nerve storage in Dulbecco's Modified Eagle Medium which has been used for Schwann cell culture. In 30 adult Sprague-Dawley rats, a 2.5 cm segment of the right sciatic nerve was harvested and kept at 4 degrees C for 14, 32, 72, and 120 hours. It was then reimplanted into the donor animal; regeneration quality was assessed clinically, histologically and morphometrically after 6 weeks. Best regeneration results were obtained in the 32 and 72 hour groups; regeneration here was comparable to the normal controls. These results are explained with the positive effect of nerve predegeneration.

Animals↗