Annales chirurgiae et gynaecologiae. Supplementum最新文献

We developed adequate delivery systems for bone morphogenetic protein (BMP) to express its bone-inducing activity by combining it with biodegradable synthetic polymers, these causing no unfavorable tissue reaction or anti-BMP effect. Their efficacy was tested for ectopic bone formation in mice and reconstruction of large segmental bone defects of the tibiae in rabbits. Composites of semipurified BMP and polylactic acid--polyethylene glycol block copolymer (PLA-PEG), and composites of BMP, PLA-PEG and lactic acid--glycolic acid copolymer (PLGA) were implanted under the fasciae of the dorsal muscles of mice. Three weeks after implantation, both the BMP/PLA-PEG and BMP/PLA-PEG/PLGA composites were completely absorbed and replaced by newly induced bone with hematopoietic marrow. Because the BMP/PLA-PEG composite is a viscous semiliquid and the BMP/PLA-PEG/PLGA composite is a plastic and moldable, the former can be used as an injectable bone-inducing material and the latter as a plastic mold. The BMP/PLA-PEG/PLGA composites were implanted in large segmental bone defects in the tibiae in rabbits. Twelve weeks after implantation, the bone defect was completely restored by a newly formed bone mass of the original thickness and structure.

This review covers advances in current researches on delivery systems for bone morphogenetic protein. In summary, it notes that the diversity of carriers, inorganic, organic and synthetic composite, have possessed physiochemical and biological properties and efficacy of delivery of bone morphogenetic protein promoting bone induction in experimental animals. It also traces a new trend in research on carrier systems for bone morphogenetic protein. A desirable carrier of BMP will bridge basic research with clinical application of bone morphogenetic protein.

A bone morphogenetic protein purification method for minor quantities of bone material was developed based on collagenase splitting of bone connective tissue. Our aim was to remove and characterize the osteoinductive protein preparation in native form without using strongly dissociative agents. We started from 80 g of HCl-demineralized reindeer bone material which was treated with type I collagen splitting collagenase. The solution was dialyzed against 10 mM glycine-HCl buffer, pH 5.2. The formed precipitate was found to be osteoinductive. After fractionation of the material using HPLC gel filtration it was observed that the high-molecular-weight component of the precipitate was biologically active. Isoelectric focusing revealed that the component consisted of at least eight different protein molecules. Lower-molecular-weight components induced no bone formation. These preliminary findings suggest that in native form at least one part of BMP is in a complex form and other extracellular matrix components bound to the osteoinductive protein complex are significant for BMP action and may act synergistically or as carriers for the BMP.

Standardized 11 mm rabbit skull trephine defects were implanted with 9 mm diameter hydroxyapatite (HA) blocks. New bone and connective tissue ingrowth was studied histologically and by X-ray after 8, 12 and 16 weeks. Empty defects without HA served as controls. Increasing amounts of new bone and fibrous connective tissue appeared inside the pores of the HA block with time. The interface area was constituted at 8 weeks predominantly by fibrous connective tissue which changed gradually at 12 weeks and definitely showed a solid bony union between the HA block and the host bone at 16 weeks. Movement of the implant was a possible reason for the prolonged healing time. However, trabecular new bone ingrowth appeared slowly even though a contact between the host bone and the HA block was not primarily provided. Comparison between a calvarial defect inserted with an HA block and an empty defect is not critically valuable, although the amount of new bone increased and that of connective tissue decreased in the empty defect during 16 weeks of observation. At the end of the experiment the HA-filled defect was seen to be totally repaired while the empty control defect was repaired with new bone to about half of its area.

Bone grafts which have been supplemented with a growth factor might incorporate faster. In this study we investigated the effect of basic fibroblast growth factor (bFGF). Titanium bone harvest chambers were implanted bilaterally in the proximal tibia of rabbits. These chambers were pierced by a transverse bone ingrowth canal from which 1 x 1 x 5 mm cancellous bone rods were repeatedly harvested at 5 weeks intervals. The bone rods to be used as allografts were frozen as ordinary bank bone, and then lipid-extracted. This treatment yields a graft which elicits less of an immunologic response than allografts which are only frozen and thawed. Before implantation, the bone rods were soaked in a cellulose gel containing 0.5 microgram/ml recombinant human bFGF or gel without bFGF as a control. The grafts were then implanted pair wise (bFGF and control) in the chambers of recipient rabbits. These chambers were harvested after 2 weeks. Evaluation was made by Tc-MDP scintimetry, histomorphometry and histology. Upon histology new living tissue had filled the grafted chambers entirely and partly replaced the graft. bFGF induced an increased amount of pre-osteoblastic tissue in the bFGF-treated grafts (p < 0.02), but there was no difference in the amount of osteoid or new bone.

In an experimental study in rats hydroxyapatite (HA) ceramics of characteristics and inactive rat bone matrix were investigated comparatively for their suitability as carriers for osteoinductive factors. Bone morphogenetic protein was extracted from long bones of pigs under dissociative conditions and partially purified by gel filtration. The resulting pBMP was combined with the granular hydroxyapatite ceramics Osprovit, Algipore, Frialit and inactive rat bone matrix (IBM) by precipitation of aliquots of this pBMP fraction onto pellets of each carrier material. The osteogenic activity of these composite implants and of corresponding controls was bioassayed by implantation into muscle pouches of immunodeficient rats. All pBMP-HA ceramic implants elicited ectopic bone formation within 25 days after implantation, whereas control implants did not show any osteoinductive ability. Alkaline phosphatase (AP) activity of the explant tissues was determined for quantitation of bone formation. Due to the high incidence of bone formation found in each pBMP group all HA ceramics tested seem to be basically suitable as carriers for osteoinductive factors. Algipore, a highly porous phycogen HA ceramic, was found to be quantitatively superior to all other materials investigated due to its very large surface available for protein binding.

The characterization and molecular cloning of the family of the bone morphogenetic proteins (BMPs) have laid the foundation for the cellular and molecular analysis of bone development and regeneration. A carrier substratum is required, however, to optimize osteogenic activity initiated by BMPs bound to the surface of the carrier. Native and recombinant human (rh) BMPs induce local endochondral bone formation in conjunction with the insoluble collagenous bone matrix, the inactive residue obtained after dissociative extraction of the matrix with chaotropic agents. While the cellular and molecular biology of BMPs and related members is advancing at a furious pace, progress in the formulation and implementation of novel delivery systems has been slow. The creation of inorganic nonimmunogenic carriers with defined geometries capable of delivering BMPs in the absence of the collagenous matrix is a crucial goal for skeletal reconstructionists and molecular biologists alike. Significant advances in skeletal reconstruction may be expected when novel carrier substrata are implemented for delivery of optimal doses of now available recombinant human BMPs.

The cytotoxicity of latex urinary catheters has been earlier documented. During the manufacturing process tens of chemicals are added to the natural rubber base. Several of the accelerators and other chemicals used have carcinogenic and acute toxic effects. Some of the accelerators are zinc compounds. In the present study, the cytotoxicity and zinc concentration of 68 latex catheter extracts were analysed. The siliconized latex catheters were the most toxic, and a correlation was seen between the IC50 values and the zinc concentration. The good manufacturing practice (GMP) has to some extent resolved the cytotoxicity problem of latex urinary catheters. There is, however, still a need to reformulate the manufacturing process and to find new catheter materials to meet the new EN standards concerning the biological safety of urinary catheters.

New bone formation induced by allogeneic demineralized bone matrix (DBM) and bone morphogenetic protein (BMP) combined with bioactive glass (BG) was studied in a rat abdominal muscle pouch model. At four weeks the amount of new bone was not influenced by DBM combined with BMP and/or bioactive glass. The mean proportional areas of new bone varied among different DBM test groups from 8.6% to 13.4%. New bone was induced in inactivated DBM samples containing BG, while no bone formation was seen in DBM samples without BG. The results indicate that bioactive glass favours bone induction in inactivated allogeneic bone matrix.

Although endoscopic optical urethrotomy is the primary treatment for urethral stricture, it is associated with a high recurrence rate, and the essential problem is how to stop the scar from shrinking after cutting. In a controlled study the effect of treatment of recurrent urethral stricture by internal urethrotomy followed by clean intermittent self-catheterization (CIC) for 6 or 12 months was compared in 25 and 24 patients, respectively. Patients learnt easily how to perform CIC: only one patient was not able to do it at home. All patients were evaluated by uroflowmetry before and immediately after urethrotomy, and 3, 6, 9 and 12 months later. Recurrence was defined as the need for further treatment. There was no difference in the recurrence rate between the two groups, but the maximum flow rate was significantly lower at 12 months in the patients who had ceased catheterization at six months. Complications included in two patients asymptomatic bacteriuria and in 10 patients symptomatic urinary infection. CIC is a very satisfactory method of managing patients with recurrent stricture, it is easy to learn, it prevents a decrease in the maximum flow rate and can thus be applied to most patients instead of regular bouginage. On the basis of the present study we could not determine any optimal time for the duration of CIC after urethrotomy, or whether it has any effect on the natural course of the disease.