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Biomedical subjects

G B Stark

Publications and source records attributed to G B Stark.

At least 19 recordsLinked to original sources
PubMed2005

Tissue engineering of skin substitutes.

Cultivated epithelial autografts as multilayered thin sheets represent common standard in clinically applied tissue engineering substitutes, outnumbering all experimental alternatives. However, the unsatisfying short and long term results concerning mechanical stability and scarring demand for alternatives. Our group investigated cultivation and transplantation of cultured autologous keratinocytes as a single cell suspension in a fibrin sealant matrix in athymic mice in combination with allogenic skin grafting. We observed reliable wound reepithialization after a cultivation period of only 2 weeks. Additionally, we could allocate successful combination of a keratinocyte fibrin sealant suspension and acellular dermis in an attempt to regenerate full thickness skin defects in a pig animal model. The potential clinical implication of subconfluently cultured keratinocytes is enhanced by the possibility of co-transplantation with decellularized dermis.

Animals↗
PubMed2004

[Angiogenesis investigations in tissue engineering. The cylinder model on the chorioallantois membrane].

INTRODUCTION: Tissue engineering (TE) applications include the isolation, culture, and seeding of cells into a suitable matrix or scaffold prior to in vivo transplantation. After transplantation, vascularization of the scaffold is a principal factor limiting cell viability for the first 6-8 days post transplantation. A model has been developed for systematic analysis of this process. METHODS: Fertilized white Leghorn eggs were incubated and opened at day 3 of incubation. Preadipocyte-seeded fibrin constructs were implanted in a specially designed plastic cylinder and placed through the opening onto the surface of the chorioallantoic membrane (CAM) at day 8 of incubation. Vascularization of the constructs by chorioallantoic blood vessels was assessed for up to 8 days post transplantation. RESULTS: The survival rate for embryos receiving constructs was about 90%. Histology confirmed transplant cell viability at day 4 post transplantation, and vascularization of the constructs by avian endothelial cells progressively increased thereafter. CONCLUSION: 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 CAM vascular network, lack of immunocompetence, low cost, and avoidance of animal experiments.

Adipocytes↗
PubMed2004

Fibrin/Schwann cell matrix in poly-epsilon-caprolactone conduits enhances guided nerve regeneration.

The goal of this study was to investigate if a three dimensional matrix, loaded homogeneously with Schwann cells and the neurotrophic factor LIF (leukemia inhibitory factor), enhances regeneration in a biodegradable nerve guidance channel as compared to non-structured cell suspensions. Therefore a 10 mm nerve gap in the buccal branch of the rat's facial nerve was bridged with tubular PCL (poly-epsilon-caprolactone) conduits filled with no matrix, Schwann cells, the three dimensional fibrin/Schwann cell matrix or the fibrin/Schwann cell matrix added with LIF Four weeks after the nerve defects were bridged histological and morphometric analyses of the implants were performed. In conclusion, the three dimensional fibrin/Schwann cells matrix enhanced the quantity and the quality of peripheral nerve regeneration through PCL conduits. The application of LIF prevented hyperneurotization. Therefore, tissue engineered fibrin/Schwann cells matrices are new invented biocompatible and biodegradable devices for enhancing peripheral nerve regeneration as compared to non-structured cell suspensions without neurotrophic factors.

Analysis of Variance↗
PubMed2004

Y chromosome detection of three-dimensional tissue-engineered skeletal muscle constructs in a syngeneic rat animal model.

Surgical reconstruction of muscle tissue lost by trauma or tumor ablation is limited by the lack of availability of functional native tissue substitution. Moreover, so far most inherited or acquired muscle diseases are lacking sufficient treatment, because only few alternatives exist to provide functional restoration of lost muscle tissues. Engineering those tissues and transplantation into sites of dysfunction may be an alternative approach and may allow replacement of such damaged or failing skeletal muscle tissues. Techniques attempting reconstruction of some human tissues and organs (tissue engineering) have been introduced into clinical practice recently. One major problem that previous transplantation studies were facing is the ability of detection of transplanted cells after integration. Using the Y chromosome in situ hybridization technique in a syngeneic rat model allows transplantation of cell constructs orthotopically, without manipulation of the cells, with no rejection or immunosuppression being implied, but providing a nondilutable genetic marker to identify transplanted cells. The purpose of our study was to create functional skeletal muscle tissue in vivo using the transplantation of primary myoblasts precultivated within a three-dimensional (3D) fibrin matrix and to determine the fate of the transplanted cells using the Y chromosome detection technique. 3D myoblast cultures were established derived from male donor rats and after 7 days of cultivation we performed an orthotopic transplantation of 3D cell constructs into a created muscle defect within the gracilis muscle of syngeneic female rats. Anti-desmin immunostaining and Y chromosome in situ hybridization indicated the survival and integration of transplanted male myoblasts into the female recipient animal, thus demonstrating the feasibility of this approach in tissue engineering and the research of cell transplantation in general.

Animals↗
PubMed2003

Expression of Trisk 51, agrin and nicotinic-acetycholine receptor epsilon-subunit during muscle development in a novel three-dimensional muscle-neuronal co-culture system.

The purpose of our study was to create functional muscle tissue in vitro and to investigate the influence of organotypic neuronal slice cultures from rat spinal cord on the differentiation and function of primary rat myoblasts in a novel three-dimensional culture system. Three-dimensional muscle-neuronal cultures were established by co-cultivating primary rat skeletal muscle cells of newborn rats with organotypic slice cultures of the spinal cord prepared from isogenic rats in a fibrin matrix. These constructs were cultured for up to 4 weeks. Differentiation and fusion of the myoblasts to myofibers was evaluated by analyzing the expression pattern and localization of muscle- and neuron-specific markers. The fibrin matrix provided a suitable environment for three-dimensional myoblast culture. Co-culturing of organotypic spinal cord slices with myoblasts induced the formation of spontaneously contracting multinuclear and parallel-aligned myofibers. Pharmacological tests suggested the formation of neuromuscular junctions. The analysis of neural agrin expression and myogenic desmin, myogenin, MyoD, Trisk 51, and nicotinic-acetycholine receptor (nACh-receptor) epsilon-subunit expression revealed the differentiation of the myoblasts to myofibers. The presented novel three-dimensional co-culture system allows the in vitro investigation of myoblast differentiation and neuron-myoblast interaction. Our results suggest the existence of an alternative pathway for the maturation of the nAChR gamma-subunit to the epsilon-subunit without neural agrin activity.

Agrin↗
PubMed2003

[Skin tissue engineering].

Cultivated epithelial autografts as multilayered, thin sheets represent a common standard in clinically applied tissue engineering substitutes, outnumbering all experimental alternatives. However, the unsatisfying short- and long-term results concerning mechanical stability and scarring require alternatives. The cultivation and transplantation of cultured autologous keratinocytes as a single cell suspension in a fibrin matrix, combined with allogenic skin grafting, has been investigated extensively in athymic nude mice. Wounds can be reliably reepithelialized after a cultivation period of only 14 days. Moreover, the successful combination of keratinocyte fibrin suspension and acellular dermis in an attempt to regenerate full thickness skin defects in a pig model has been demonstrated. The usefulness of subconfluently cultured keratinocytes-which can be harvested very early and are easy to handle-is enhanced by cotransplantation with decellularized dermis.

Animals↗
PubMed2003

Skin tissue engineering.

The coverage of extensive wounds with viable autologous keratinocytes remains the only option of treatment if autologous donor skin is not obtainable. There is evidence that proliferating keratinocytes, as suspended cells or as a single layer, are adequate for wound closure. Understanding keratinocyte-matrix interactions not only allows us to influence keratinocyte outgrowth, adhesion, and migration, but may also guide us to modify matrix molecules for enhancing keratinocyte take. Further approaches may include the generation of genetically manipulated keratinocytes, which allow the use of an off-the-shelf epidermal replacement. As surgeons, our goal is to help burn patients with the best quality of skin in the shortest time possible. As tissue engineers, we have not achieved the goal of a universal skin product. By continually reviewing the options and using them, we can at least use the proper material in the adequate situation. Because of the limited resources, the need for comparisons of clinical effectiveness and cost are ever more important. As anatomy and physiology of engineered skin substitutes improve, they will become more similar to native skin autografts. Improvement of skin substitutes will result from inclusion of additional cell types (eg, melanocytes) and from modifications of culture media and scaffolds. Skin-substitute materials may be able to stimulate regeneration rather than repair, and tissue-engineered skin may match the quality of split-skin autografts, our present gold standard.

Animals↗
PubMed2003

Engineering of muscle tissue.

The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in health care. Tissue engineering and regenerative medicine is an emerging interdisciplinary field that applies the principles of biology and engineering to the development of viable substitutes that restore, maintain, or improve the function of human tissues and organs. Tissue engineering science has provided critical new knowledge that will deepen our understanding of the phenotype of an important category of cell types-the muscle cells-and this knowledge may enable meaningful advances in musculoskeletal tissue engineering. There are two principle strategies for the replacement of impaired muscle tissues. One approach uses the application of isolated and differentiated cells (in vivo tissue engineering), using a transport matrix for the cell delivery; the other uses in vitro-designed and pre-fabricated tissue equivalents (in vitro tissue engineering). Future developments and the decision regarding which approach is more promising depend on the elucidation of the relationships among cell growth and differentiation, the three-dimensional environment, the architecture of the cells, and gene expression of the developmental process and the survival of the cells and integration in the host in in vivo experiments. As the techniques of tissue engineering become more sophisticated and as issues such as vascularization and innervation are addressed, the usefulness of these methods for reconstructive surgery may grow significantly.

Humans↗
PubMed2002

Human recombinant EGF protein delivered by a biodegradable cell transplantation system.

We have previously shown a new approach to expand cultured human keratinocytes and reconstitute the epidermis in full-thickness wounds using a new microsperical transport system. This was a new approach to increase the cell yield for seeding without altering the anchoring proteins by enzymatic steps. That time we used Cytodex 3 which failed to be degraded and induced an inflammatory reaction in a t-cell-deficient organism. Therefore, we have investigated another microcarrier consisting of PLGA, which is a well-known carrier material for cell culture and transplantation. After coating the PLGA carrier with gelatine the seeding time of viable cells reached 4 h and the cell gain after 7 days of spinner culture was 16-fold. At 14 days after transplantation, we could detect a new stratified epithelium in our full-thickness wound healing model. Because cytokines play a major role in wound healing, we loaded this carrier material with different concentrations of rhEGF, showing a dose dependent release of the protein in vitro and in vivo. This result might lead to a different approach in the treatment of wounds.

Absorbable Implants↗
PubMed2001

[Minimally invasive surgical therapy of gynecomastia: liposuction and exeresis technique].

INTRODUCTION: A number of techniques are available for the correction of gynecomastia. Nonscarring sparing methods are preferred, and the minimally invasive technique is to use liposuction for the gland and the fatty tissue exclusively. In this retrospective study we present our experience with a combination of liposuction and subsequent resection of the remaining gland. METHODS: Sixty-two patients (112 breasts) were surgically treated for gynecomastia from January 1996 and September 2000. From 1996 to 1997 all patients suffering from gynecomastia grade Simon I-II were treated by the method described by Rosenberg and Stark, which is exclusively suction of the fatty and glandular tissue. In a retrospective chart study a high recurrence rate was found in these patients. Subsequently we changed our technique to liposuction of the fatty tissue followed by sharp excision of the glandular tissue through the incision made for the liposuction cannula in the submammary fold. RESULTS: Suction alone was not sufficient to remove the glandular tissue; the rate of recurrence after suction was 35%. When sharp resection of the glandular tissue was carried out after the liposuction the recurrence rate dropped to under 10%. In total our complication rate was 50% including minor sequelae. The most frequent complication was unacceptable scarring of the nipple-areola complex. Hypesthesia of the nipple-areola occurred in 13.4% of the patients. CONCLUSION: The combination of liposuction and resection of the glandular tissue is a minimally invasive correction that can be used in all cases of gynecomastia grade Simon I-II.

Adult↗
PubMed2001

Management of hypovascularized wounds not responding to conventional therapy by means of free muscle transplantation.

BACKGROUND: Chronic ulceration as a complication of arteriosclerotic disease, venous congestion or diabetes mellitus is still a serious clinical problem, resulting in immobilization, extended hospitalization and cost-intensive treatment. Other than standard conservative treatment protocols or early amputation, microsurgical free transfer of well vascularized muscle tissue onto chronic wounds can induce angiogenesis and improve wound healing even in the hypovascularized wound. PATIENTS: From 1993-1999 we treated 12 patients (mean age: 46 years) with vascular ulcers of the lower extremity with free muscle or fasciocutaneous tissue transfer. RESULTS: The average hospitalization was 51.4 days. The perioperative mortality was zero. In one patient with factor V deficiency a partial flap necrosis occurred. Two revisions of the micro anastomoses had to be performed. Two seromas occurred at the donor site. No secondary flap loss was observed. Extremity or stump length preservation was achieved in all cases. CONCLUSIONS: Optimal postoperative treatment with physiotherapy and orthopaedic shoe support is important. If all these factors are present and if the patient is highly motivated a reintegration into normal life can be achieved.

Adult↗
PubMed2001

Metastatic malignant acrospiroma of the hand.

We present the case of a 37-year-old man with multiple pulmonary metastases of a primarily unknown primary tumour. Thorough revision of the medical history yielded that he had already passed three resections of a right palmar mass, which had been described as a benign tumour. Clinical examination showed a thickened scar with a suspicious palpable mass in the right hand. Excision of this scar and the tumour mass with histopathological examination now revealed a malignant acrospiroma. Resection of the pulmonary metastases histologically also confirmed a malignant acrospiroma. The following radical resection of the metacarpals II and III with the index and middle finger under the assumption of a wide compartment resection achieved tumour free margins and proved to be efficient with the patient being relapse free for 4 years from this operation. Although the prognosis of this tumour is generally unfavourable this particular case demonstrates the value of a radical surgical resection as the mainstay of treating such highly malignant sweat gland tumours of the hand.

Adult↗
PubMed2001

[Reconstruction of abdominal-wall midline defects--The Abdominal-Wall Components Separation].

AIM OF THE STUDY: The recurrence rate of midline defects like incisional hernias is high. Alloplastic material in sublay or onlay technique is often be used if the suture tension is to high for a primary closure. Free or pedicled musculocutaneous flaps transfer denervated muscle and lack dynamic resistance against the intraabdominal pressure. The separation of the lateral abdominal wall achieves autogenous, dynamic material for a tension free closure in small and moderate midline defects. METHODS: In 1990 Ramirez described a technique, which separates parts of the lateral abdominal wall and advances it towards the midline. The innervation and blood supply of the advanced part is maintained. With this technique it is possible to close defects tension free with dynamic abdominal wall. 9 patients were treated with this technique and followed up. RESULTS: Midline defects up to 16 cm at the waistline could be closed without tension. There were no major complications (one small delayed wound healing). There were no recurrences in a follow up time of 14.2 months. CONCLUSION: The separation of parts of the lateral abdominal wall can achieve tension free closure of e.g. incisional hernias of small and moderate size. The advancement of the medial component provides well innervated muscle for dynamic resistance against the abdominal pressure.

Adult↗
PubMed2001

Fibrin glue as matrix for cultured autologous urothelial cells in urethral reconstruction.

In the present study, we have established a technique to create an artificial urethra in a rat animal model by transplantation of in vitro-expanded urothelial cells onto an in vivo-prefabricated tube formation using tissue engineering methods. Urothelial cells from isogenic rats were harvested for culture. A silicon catheter was used to induce a connective tissue capsule-tube formation underneath the abdominal skin. Two weeks later, the cultivated urothelial cells were seeded onto the lumen of this tube using fibrin glue as delivery matrix. The histomorphological and immunohistochemical studies revealed a viable multilayered urothelium, lining the inner surface of the prior formed connective tissue tube-formation 4 weeks after grafting the cells. We have shown that cultured and in vitro-expanded urothelial cells can be successfully reimplanted onto a prefabricated tube-like structure using fibrin glue as a delivery matrix and native cell expansion vehicle. The results suggest that the creation of an artificial urethra may be achieved in vivo using tissue engineering methods, showing potential for urethral reconstruction and providing autologous urothelium for reconstructive surgery in the genitourinary tract.

Animals↗
PubMed2001

Plasmid gene delivery to human keratinocytes through a fibrin-mediated transfection system.

We have developed a matrix-mediated transfection system to deliver plasmids to human keratinocytes. The matrix is a soluble, self-hardening fibrin matrix (Tissucol), Baxter) that has been used clinically. Recently it has been shown that full thickness burn wounds can be successfully treated with a keratinocyte fibrin glue suspension. Further, it has been demonstrated that hEGF transfected cells accelerate wound healing. In this study, we inoculated the matrix with the hEGF expression plasmid and resuspended the matrix with either cultured or noncultured human keratinocytes. We obtained successful transfection rates of these cells (up to a 100-fold increase compared to controls containing no EGF expression plasmid) in vitro. After transplantation to full thickness wounds on athymic mice we were able to show a 180-fold increase in EGF concentration compared to controls, which persisted over the entire 7-day monitored period, decreasing from 180 to 20 pg/mL at day seven. This unique approach indicates the possible utility to combine a matrix for cell transplantation with a transfection system to release therapeutic proteins in vitro and in vivo.

Animals↗
PubMed2000

[Cell transplantation in surgery--reality and prospects for tissue engineering].

Traditionally surgical repair of tissue defects and loss or failure of function has relied on mechanical means, medical (drug) treatment, autologous and allogenic transplantation, and alloplastic/synthetic devices. Tissue engineering represents a new interdisciplinary field of applied research combining engineering and biosciences together with clinical application (mainly in surgical specialities) to develop living substitutes for tissues and organs. The understanding of cell-cell interactions and chemical signalling (growth factors) and the selection of appropriate matrices (cell-matrix interaction) is the key for success. Gene therapy represents the logical combination with tissue engineering on the molecular biology level. Application of cultivated skin and cartilage has already become reality, engineering of vascularized, more complex organs remains a challenge for this century.

Cells, Cultured↗
PubMed2000

The contralateral bilobed trapezius myocutaneous flap for closure of large defects of the dorsal neck permitting primary donor site closure.

BACKGROUND: Various reliable local flaps can be used to cover soft tissue defects of the posterior neck. Among others, the (either vertical or transverse) trapezius myocutaneous flap is a reliable option in this context. However, for defects with a diameter larger than 15 cm, these flaps require skin grafting of the donor site. METHODS: To prevent this additional morbidity we describe a contralaterally based bilobed trapezius musculocutaneous flap successfully applied in two elderly patients with large tumors of the posterior neck in palliative situations. RESULTS: This novel approach makes use of a standard vertical skin paddle to cover the neck, together with a transverse cervical flap in a bilobed design to primarily close the paravertebral donor site. CONCLUSIONS: The bilobed technique allows the primary closure of massive soft tissue neck wounds. Preservation of the accessory nerve to the superior fibers of the trapezius muscle permitted normal arm elevation in our patients.

Accessory Nerve↗