Bioartifizielles autologes Urothel etabliert aus Spülungen der Harnblase

Reconstructive surgery of lower urinary tract disorders can be limited by a shortage of adequate autologous tissue. Tissue engineering is an option for surgical reconstruction with evolved biological substitutes. Urethral repair with bioartificial urothelial implants can be an innovative method for sustained urothelial regeneration in situ. The needed urothelial cells are commonly isolated from native urothelium requiring surgery.The aim of this study was to establish primary human urothelial cell cultures from bladder washings in serum-free media and to generate urothelial tissue without seeding of matrices in a feeder cell-free system. It could be demonstrated that under these conditions bioartificial urothelium can be developed successfully from bladder washings. Its multilayered cellular structure and the initial differentiation in vitro, similar to native-grown urothelial tissue, are promising with regard to intended clinical application. Current work focuses on establishing cell culture techniques according to legal regulations, terminal differentiation of the urothelial constructs in vitro, and techniques to surgically implant lab-grown bioartificial urothelium.     

Transmyocardial laser revascularization: current status.

Transmyocardial laser revascularization (TMLR) has been widely evaluated for treatment of the ischemic myocardium either in conjunction with coronary artery bypass grafting or as sole therapy. Clinically, it has shown significant improvement for angina symptoms, but the mechanism by which this modality works is unknown at this time. The original premise on which transmyocardial revascularization was established depended on its ability to essentially generate channels that would directly carry blood from the ventricle into the ischemic myocardium. This theory, however, has not been substantiated, so other mechanisms have been postulated. This article gives a historical perspective on the advent of transmyocardial revascularization and the many animal and human studies that have paved the way for its clinical use. Current controversies are examined, along with the new advances in laser technology and where the future of TMLR is headed.     

Perfluorocarbon for organ preservation before transplantation

Perfluorocarbons (PFC) are hydrocarbons in which all or most of the hydrogen atoms have been replaced with fluorine. PFC have a very high capacity for dissolving oxygen (O2 ), and a negligible oxygen-binding constant allows them to release O2 more effectively than hemoglobin into the surrounding tissue. As a result of this unique property, PFC-based solutions have been examined as oxygen carriers. PFC was first used for organ preservation as a component of the two-layer method (TLM) (University of Wisconsin [UW] solution-perfluorochemical plus oxygen) of pancreas preservation. Pancreata preserved in the TLM are oxygenated through the PFC and substrates are supplied by the UW solution. This allows pancreata stored in the TLM to generate adenosine triphosphate during storage and prolong the preservation period. In the canine model, TLM has been shown to repair and resuscitate warm ischemically injured pancreata during preservation, improve pancreas graft survival after transplantation, and improve islet yields after isolation. Current clinical trials using the TLM of pancreas preservation before whole-pancreas transplantation and islet isolation show promising results. The TLM has also been shown to be beneficial for preserving other difficult organs, such as heart and small bowel.     

Bioactive-Coated Implants in Trauma Surgery

Abstract Complications still occur in musculoskeletal surgery despite improvements in operating techniques and optimization of implants. Problems include delayed fracture healing, non-unions and extensive osseous infections. Growth factors for local application are in clinical use, but have not become widely accepted. Reasons may be that these proteins are expensive and of limited availability and considerable quantities have to be implanted locally. Coated implants incorporating active ingredients could release drugs locally and thereby generate a high concentration directly in the area of interest without systemic side effects. Compounds that could be used in this way include growth factors for the improvement of fracture healing and antibiotics for prophylaxis of implant-related infections. The biodegradable poly(D,L-lactide) coating of implants can facilitate the local controlled release of incorporated growth factors directly into the fracture and thus serves both as a fracture stabilization device and as a carrier for active components. This review presents different models (fracture healing; intervertebral fusion; infection model) demonstrating the efficiency of the coating technology. These findings seem to justify the transfer of this technology into clinical settings. In a preliminary study, gentamicin-coated intramedullary tibial nails were implanted in patients exhibiting fractures with severe soft tissue damage. The preliminary findings do not allow conclusions to be drawn in respect of therapy of fractures with severe soft tissue damage or revision surgery. However, the coating seems to be suitable as a “key technology” for the incorporation of active ingredients and might be helpful in revision arthroplasty.     

Hyperspectral imaging in wound care: A systematic review

Multispectral and hyperspectral imaging (HSI) are emerging imaging techniques with the potential to transform the way patients with wounds are cared for, but it is not clear whether current systems are capable of delivering real‐time tissue characterisation and treatment guidance. We conducted a systematic review of HSI systems that have been assessed in patients, published over the past 32 years. We analysed 140 studies, including 10 different HSI systems. Current in vivo HSI systems generate a tissue oxygenation map. Tissue oxygenation measurements may help to predict those patients at risk of wound formation or delayed healing. No safety concerns were reported in any studies. A small number of studies have demonstrated the capabilities of in vivo label‐free HSI, but further work is needed to fully integrate it into the current clinical workflow for different wound aetiologies. As an emerging imaging modality for medical applications, HSI offers great potential for non‐invasive disease diagnosis and guidance when treating patients with both acute and chronic wounds.     

The general case for redox control of wound repair

The orthodox view has been that reactive oxygen species are primarily damaging to cells. There is general agreement that while high (3%) doses of H(2)O(2) may serve as a clinical disinfectant, its overall effect on healing is not positive. Current work shows that at very low concentrations, reactive oxygen species may regulate cellular signaling pathways by redox-dependent mechanisms. Recent discoveries show that almost all cells of the wound microenvironment contain specialized enzymes that utilize O(2) to generate reactive oxygen species. Numerous aspects of wound healing are subject to redox control. An understanding of how endogenous reactive oxygen species are generated in wound-related cells may influence the healing process and could result in new redox-based therapeutic strategies. Current results with growth factor therapy of wounds have not met clinical expectations. Many of these growth factors, such as platelet-derived growth factor, rely on reactive oxygen species for functioning. Redox-based strategies may serve as effective adjuncts to jump-start healing of chronic wounds. The understanding of wound-site redox biology is also likely to provide novel insights into the fundamental mechanisms that would help to optimize conditions for oxygen therapy. While a window of therapeutic opportunity seems to exist under conditions of low concentrations of reactive oxygen species, high levels may complicate regeneration and remodeling of nascent tissue.     

Three-dimensional reconstruction of the scoliotic spine and pelvis from uncalibrated biplanar x-ray images

Current three-dimensional (3D) reconstruction methods based on explicit or implicit calibration procedure require a calibration object to generate calibrated x-rays for the 3D reconstruction of the human spine and the pelvis. However, to conduct retrospective studies where no 3D technology is available, 3D reconstruction must be performed from x-ray images where no calibration object was used. The current state of the art offers a variety of methods to obtain a personalized 3D model of a patient's spine, however, none have presented a clinically proven method which allows a 3D reconstruction using uncalibrated x-rays. The main objective of this study was to propose a self-calibration method using only the anatomic content of the x-ray images and evaluate its clinical feasibility on uncalibrated x-ray images for the 3D reconstruction of the scoliotic spine and pelvis. The rationale for proposing a 3D reconstruction method from uncalibrated x-rays is to allow access to 3D evaluation of spinal deformities in any standard clinical setup and to enable the conduct of retrospective studies of any kind. To assess the validity of the 3D reconstructions yielded by the proposed algorithm, a clinical study using 60 pairs of digitized x-rays of children was conducted. The mean age for this group of 60 patients was of 14+/-3 (range 8 to 18) years old. All the children in the study group had scoliosis, with an average Cobb angle on the frontal plane of 25 degrees (range 3 to 70 degrees). For each case, a 3D reconstruction of the spine and pelvis was obtained using both explicit and self-calibration methods, from calibrated and uncalibrated x-rays, respectively. Results show that 3D reconstructions obtained with the proposed method from uncalibrated x-ray images yield- geometrical models that exhibit insignificant differences for 2D and 3D clinical indices commonly used in the evaluation of spinal deformities. This allows a 3D clinical assessment of scoliotic deformities from standard x-rays without the need for calibration, and providing access to this technology in any clinical setup and allowing to perform retrospective studies, which were previously impossible.     

Möglichkeiten und Grenzen des „tissue engineering“ des vorderen Kreuzbandes

Although current concepts of cruciate ligament reconstruction using tendon transplants provide midterm knee joint stabilization, a single-bundle or double-bundle tendon cannot adequately restore the complex three-dimensional structure of the anterior cruciate ligament. Therefore, researchers are attempting to develop alternatives using tissue engineering technology. The basic principle includes seeding of suitable cells on a resorbable carrier construct, in vitro biological and mechanical stimulation to generate a ligament-like extracellular matrix, and subsequent implantation as a cruciate ligament bioprosthesis. Several natural and synthetic materials have proven to be suitable as cell carriers; however, most of these exhibit inadequate tensile strength as well as minor fatigue properties, making an additional load carrier necessary. In principle, research has shown that tissue engineering technology is capable of generating a construct with a ligament-like extracellular matrix. However, the step from basic research to clinical application has not yet been taken.     

Tissue-engineered vascularized bone grafts: basic science and clinical relevance to trauma and reconstructive microsurgery

Bone grafts are an important part of orthopaedic surgeon's armamentarium. Despite well-established bone-grafting techniques, large bone defects still represent a challenge. Efforts have therefore been made to develop osteoconductive, osteoinductive, and osteogenic bone-replacement systems. The long-term clinical goal in bone tissue engineering is to reconstruct bony tissue in an anatomically functional three-dimensional morphology. Current bone tissue engineering strategies take into account that bone is known for its ability to regenerate following injury, and for its intrinsic capability to re-establish a complex hierarchical structure during regeneration. Although the tissue engineering of bone for the reconstruction of small to moderate sized bone defects technically feasible, the reconstruction of large defects remains a daunting challenge. The essential steps towards optimized clinical application of tissue-engineered bone are dependent upon recent advances in the area of neovascularization of the engineered construct. Despite these recent advances, however, a gap from bench to bedside remains; this may ultimately be bridged by a closer collaboration between basic scientists and reconstructive surgeons. The aim of this review is to introduce the basic principles of tissue engineering of bone, outline the relevant bone physiology, and discuss the recent concepts for the induction of vascularization in engineered bone tissue.     

Mesenchymal stem cell sheets revitalize nonviable dense grafts: implications for repair of large-bone and tendon defects

BACKGROUND: Large musculoskeletal defects are commonly reconstructed with allogeneic grafts. As cryopreserved allogeneic grafts lack viable cells, this often results in poorer clinical outcome. Current technology can not incorporate large number of cells to the dense grafts. This study aimed to investigate the feasibility of fabricating sheets of mesenchymal stem cells (MSCs) to revitalize cryopreserved grafts. METHODS: Human MSCs were isolated, characterized, and cultured to form a cell sheet in the presence of ascorbic acid. Once a sheet of MSCs was obtained, it was assembled onto the demineralized bone grafts or frozen tendon grafts by a wrapping technique. Then the assembled structure was cultured for 3 weeks. The macro morphology, histology, and immunohistochemistry of the grafts were evaluated. RESULTS: It was found that MSCs were able to form coherent cellular sheets within 3 weeks. When assembled with demineralized bone matrix, MSC sheets were similar to in situ periosteum and were able to differentiate into the osteochondral lineage. When assembled with frozen tendon graft, MSCs sheets were well-incorporated within the tissue sheath (peritenon) around the tendon, and adopted the characteristic spindle-shaped morphology of tenocyte-like cells. CONCLUSIONS: The results therefore demonstrated that MSCs sheets are easily fabricated and can maintain their differentiation potential within particular scaffolds, which would suggest a novel and convenient strategy for revitalizing large tissue grafts to improve clinical outcome.     

Metabolic activity of a new atrophic nonunion model in rabbits.

The aetiology of atrophic nonunions is not well understood: they are often thought to be nonreactive and metabolically inactive. Investigation of their biological processes is hampered by the lack of a useful animal model. Current models involve either wide segmental excision of the diaphysis or interposition of Silastic to impede the normal healing processes. neither of which resembles the clinical situation. We therefore aimed to establish a model of atrophic nonunion that more closely resembles the clinical situation and to use this model to evaluate the metabolic activity of the gap tissue of the nonunion. A simple and reliable model of atrophic nonunion has been developed in rabbits. It more closely represents the clinical situation by avoiding large segmental excisions and the interposition of foreign materials. Clinical, radiological, and histological data support the diagnosis of atrophic nonunion in the model. The concentration of adenosine triphosphate in the gap tissue of the nonunion served as a marker of metabolic activity. The gap tissue of established atrophic nonunions had a significantly higher concentration of adenosine triphosphate than did the control specimens. In this model, the gap tissue is metabolically active; therefore, under certain conditions, it may be possible to induce union if the correct stimulus is provided.     

Factors affecting size and configuration of neodymium:YAG (Nd:YAG) laser lesions in the prostate

Laser surgery for benign prostatic hypertrophy is a clinical reality and a promising alternative to traditional transurethral electroresection of the prostatic adenoma (TURP). Current methods of laser prostatectomy involve coagulation of prostate tissue using a quartz side-firing fiber that redirects a Nd:YAG laser beam at 70–90° most commonly by means of a metal reflector. In this communication we describe a method of tissue evaporation using a side-firing fiber that avoids use of a metal reflector by means of internal reflection. It is relatively resistant to damage when coming in contact with tissue. By placing the fiber tip in direct contact with tissue, much larger lesions are created because of more efficient energy transfer resulting in rapid evaporation of tissue under water. In prostate surgery, this phenomenon of accelerated evaporation can be used to bloodlessly evaporate adenomatous tissue creating a defect that resembles that of a traditional TURP. © 1994 Wiley-Liss, Inc.     

Tissue engineering in urology

Tissue engineering encompasses a multidisciplinary approach geared toward the development of biological substitutes designed to restore and maintain normal function in diseased or injured tissues. This article reviews the basic technology that is used to generate implantable tissue-engineered grafts in vitro that will exhibit characteristics in vivo consistent with the physiology and function of the equivalent healthy tissue. We also examine the current trends in tissue engineering designed to tailor scaffold construction, promote angiogenesis and identify an optimal seeded cell source. Finally, we describe several currently applied therapeutic modalities that use a tissue-engineered construct. While notable progress has clearly been demonstrated in this emerging field, these efforts have not yet translated into widespread clinical applicability. With continued development and innovation, there is optimism that the tremendous potential of this field will be realized.     

Intravenous polymethyl methacrylate after cemented hemiarthroplasty of the hip

Current cementing techniques used during hip arthroplasty aim to maximize the bond at the bone-cement interface in an effort to increase the longevity of the prosthesis. To accomplish this, one must generate high intramedullary pressures, which are known to be associated with complications such as cement implantation syndrome. We record a rare complication following cement pressurization of a hip hemiarthroplasty that resulted in intravenous polymethyl methacrylate (PMMA). This complication however, is not associated with a significant morbidity or mortality, but it is important to identify and distinguish from a femoral cortical defect, which can be created during surgery.     

Nucleoplasty

Nucleoplasty is a novel technique of percutaneous disc decompression gaining popularity among interventional pain physicians. Nucleoplasty has evolved through the historical learning of the successes and failures from previous percutaneous disc decompression approaches and in hopes of developing a safe and effective therapy for disc disease. The concept of nucleoplasty involves the use of radiofrequency energy to ablate nucleus pulposus tissue in a controlled approach leading to a reduction of pressure on the nerve roots. A patented coblation technology is applied through a PERC-D wand. By creating channels within the disc, portions of the nucleus pulposus are removed. This leads to a decompression of the disc. Current success of nucleoplasty is determined on the selection of patients based on clinical examination, imaging studies, and positive concordant discography. Basic and clinical studies show that percutaneous nucleoplasty can lead to a safe controlled decompression of the disc.     

Electromagnetic fields for bone healing

Electrical stimulation has been applied in a number of different ways to influence tissue healing. Most of the early work was carried out by orthopedic surgeons looking for new ways of enhancing fracture healing, particularly those fractures that had developed into nonunions. Electrical energy can be supplied to a fracture by direct application of electrodes or inducing current by use of pulsed electromagnetic field or capacitive coupling. Many of these techniques have not been standardized, so interpretation of the literature can be difficult and misleading. Despite this, there have been a few good laboratory and clinical studies to investigate the effect of electrical stimulation on fracture healing, which are reviewed. These do not permit recommendation or rejection of the technique per se; however, there is some room for optimism. The authors present some of the guidelines for using this treatment modality but suggest that all treatment should be carried out as part of a clinical trial in order to generate reliable data.     

Tissue Engineering von Gef??prothesen

Vascular tissue engineering represents a new but rapidly growing field due to the need for better vascular prostheses for coronary or peripheral revascularization procedures. Current synthetic prostheses have a high incidence of failure due to thrombosis and/or intimal hyperplasia especially in small caliber artificial vascular prostheses. New approaches such as decellularized, natural or synthetic, 3-D stable/degradable scaffolds are being developed for acellular or cell-based vascular replacements. The drawbacks of cellular bioreactor matured prostheses are delayed availability and that they are, labor and cost-intensive. However, some research groups have shown limited clinical applications. The acellular approach is based on a biodegradable, electrospun, porous 3-D structure made of nano- and micro-sized polycaprolactone fibers. Animal studies in rats and pigs have shown good short and long-term results after arterial replacement with autologous cellular and matrix ingrowth, angiogenesis, confluent endothelialization and absence of occlusions or aneurysm formation. Therefore, the in vivo vascular tissue engineering approach produces shelf-ready biodegradable vascular prostheses which might be an option for future clinical applications.     

Magnetic resonance imaging of the genitourinary tract

MRI is in its infancy as a clinical imaging tool. It is undergoing intensive investigation in various areas of the body. Evaluation of the brain and spine is superb, and in some areas of the brain, like the posterior fossa, it is thought to be superior to CT. Evolving indications for body scanning include staging of pelvic malignancies, evaluation of liver malignancy, evaluation and staging of musculoskeletal problems, and, to a lesser degree, staging of renal malignancies and evaluation of vascular disease. The main problem in body imaging stems from image degradation because of respiratory motion that is transmitted to upper abdominal organs. Respiratory gating of image acquisition or utilization of short heavily T1-weighted pulse sequences will likely overcome this problem in due time. Minimizing motion artifact will make MR images comparable to, if not better than, CT images with regard to transverse anatomic display, and MR images have the added advantage of multiplanar scanning, which can be done directly, without need of additional computer reconstruction time and without having to move the patient. The second major problem in MRI is the lack of understanding of equipment potential. Unlike conventional radiography and CT, in which the behavior of the X-ray beam is understood with regard to image formation, in MRI new parameters are used to generate images. As stated earlier, MR signal intensity is due to hydrogen concentration, T1 and T2 relaxation times of the tissue, and flow of protons through the imaged volume. How these factors are weighted depends on pulse sequence selection, and thus image contrast and information content of the scans change. On the surface, these images display anatomic information as do other imaging modalities, but manipulation of pulse sequences may ultimately lead to the ability to demonstrate physiologic and chemical parameters previously unavailable in imaging. Current research is geared to help extract this data by testing new pulse sequences, using different types of receiver RF coils, and using MR-specific contrast materials. Minor MRI problems such as long scan times are being dealt with to decrease time to an acceptable length. The nonvisualization of soft tissue calcifications will probably remain a problem that may have to be weighed against other known advantages. At this time further research and clinical experience are the key to what is needed in MRI, to gain further knowledge with regard to imaging physiologic phenomena, such as flow and spectroscopy, and possibly to monitor the chemical basis of disease.(ABSTRACT TRUNCATED AT 400 WORDS)     

Optimizing leg length and cup position: A surgical navigation tool

Inaccurate component placement during total hip arthroplasty (THA) can have significant and costly consequences. Malpositioning of the acetabular cup components can lead to dislocation and revision surgery, while postoperative discrepancies in leg length – the primary driver for litigation against orthopaedic surgeons – can lead to biomechanical imbalances, causing chronic low back pain. Current methods for monitoring these parameters intraoperatively rely on manual methods such as tissue tensioning or on the surgeon's experience, both of which are subject to inaccuracies. Computer-assisted navigation, while currently used in only a small percentage of THA procedures, is an emerging technology that has the potential to improve the accuracy with which surgeons place components during THA by providing real-time, intraoperative data. One innovative navigation system – Intellijoint HIP® (Intellijoint Surgical, Waterloo, ON) – has demonstrated its accuracy, time-neutrality, safety and effectiveness in several clinical studies and has the potential to improve outcomes and reduce re-admissions and revision during both primary and revision THA.     

Stem cells, tissue engineering and organogenesis in transplantation

Tissue engineering is an attempt to generate living tissues for surgical transplantation. In vitro and in vivo approaches have led to the production of vascular and cardiovascular components, bones, cartilages and gastrointestinal tissues. Organogenesis has a different aim, which is to create transplantable organs from embryonic tissue implanted into the recipient's omentum. This approach has been successful in creating kidneys and pancreases in animals. The use of stem cells in organogenesis and in tissue engineering has vastly enlarged the potential for clinical applications. The technique of nuclear transfer offers the possibility of creating cells, which are genetically identical to the host. Tissue engineering and organogenesis represent the future of transplantation in medicine. The progress in this field is of tremendous importance because it can produce a new generation of morphologically complex tissues and organs. In this review, the most relevant experiences in this area are summarized, including its perspectives for therapeutical applications.