Biomedical subjects

J D de Bruijn

Publications and source records attributed to J D de Bruijn.

At least 19 recordsLinked to original sources

PubMed2006

A comparison of bone formation in biphasic calcium phosphate (BCP) and hydroxyapatite (HA) implanted in muscle and bone of dogs at different time periods.

Physicochemical modification could implement synthetic materials into osteoinductive materials, which induce bone formation in nonosseous tissues. We hereby studied the relevance between the osteogenic capacities of osteoinductive materials in nonosseous tissues and in osseous sites. Biphasic calcium phosphate ceramic (BCP) and hydroxyapatite ceramic (HA) were implanted in femoral muscles and femoral cortical bone of dogs for 7, 14, 21, 30, 45, 60, 90, 180, and 360 days, respectively. Two dogs were used in each time point. In each dog, four cylinders (phi5x6 mm) per material were implanted in femoral muscles and 2 cylinders (phi5x6 mm) per material in femoral cortical bone. The harvested samples were processed for both histological and histomorphometric analyses. Bone was observed in BCP implanted in femoral muscles since day 30, while in HA since day 45. Quantitatively, more bone was formed in BCP than in HA at each time point after day 30 (p<0.05). The earlier and more bone formed in BCP than in HA suggests BCP a higher osteoinductive potential than HA in muscle. In femoral cortical bone defects, a bridge of bone in the defect with BCP was observed at day 21, while with HA at day 30. At days 14, 21, and 30, significantly more bone was formed in BCP than in HA (p<0.05). The results herein show that osteogenic capacities of osteoinductive materials in nonosseous tissues and osseous sites are correlated: the higher the osteoinductive potential of the material, the faster the bone repair.

Animals↗

PubMed2005

Parallel high-resolution confocal Raman SEM analysis of inorganic and organic bone matrix constituents.

In many multi-disciplinary fields of science, such as tissue engineering, where material and biological sciences are combined, there is a need for a tool that combines ultrastructural and chemical data analysis in a non-destructive manner at high resolution. We show that a combination of confocal Raman spectroscopy (CRS) and scanning electron microscopy (SEM) can be used for such analysis. Studies of atomic composition can be done by X-ray microanalysis in SEM, but this is only possible for atomic numbers greater than five and does not reveal molecular identity. Raman spectroscopy, however, can provide information on molecular composition and identity by detection of wavelength shifts caused by molecular vibrations. In this study, CRS-SEM revealed that early in vitro-formed bone extracellular matrix (ECM) produced by rat osteoprogenitor cells resembles mature bone chemically. We gained insight into the structure and chemical composition of the ECM, which was composed of mainly mineralized collagen type I fibres and areas of dense carbonated calcium phosphate related to the collagen fibre density, as revealed by Raman imaging of SEM samples. We found that CRS-SEM allows the study of specimens in a non-destructive manner and provides high-resolution structural and chemical information about inorganic and organic constituents by parallel measurements on the same sample.

Animals↗

PubMed2004

Design and fabrication of standardized hydroxyapatite scaffolds with a defined macro-architecture by rapid prototyping for bone-tissue-engineering research.

This investigation describes the production and characterization of calcium phosphate scaffolds with defined and reproducible porous macro-architectures and their preliminary in vitro and in vivo bone-tissue-engineered response. Fugitive wax molds were designed and produced using a rapid prototyping technique. An aqueous hydroxyapatite slurry was cast in these molds. After sintering at 1250 degrees C and then cleaning, dimensional and material characterizations of the scaffolds were performed. The resulting scaffolds represented the design, and their dimensions were remarkably consistent. A texture inherent to the layer-by-layer production of the mold was impressed onto the vertical surfaces of the scaffolds. The surface roughness (R(a)) of the textured surfaces was significantly greater than that of the nontextured surfaces. Material analyses revealed a beta-TCP phase in addition to hydroxyapatite for the molded ceramics. Non-molded control ceramics exhibited only hydroxyapatite. Thirty scaffolds were seeded with culture-expanded goat bone-marrow stromal cells (BMSCs) and implanted subcutaneously in nude mice for 4 or 6 weeks. Histology revealed mineralized bone formation in all the scaffolds for both implantation periods. After 4 weeks, bone was present primarily as a layer on scaffold surfaces. After 6 weeks, the surface bone formation was accompanied by bone budding from the surface and occasional bridging of pores. This budding and bridging bone formation almost always was associated with textured scaffold surfaces. However, the area percentage of bone in pores was similar for the 4- and 6-week implantation periods.

Animals↗

PubMed2004

Bone tissue engineering and spinal fusion: the potential of hybrid constructs by combining osteoprogenitor cells and scaffolds.

In this paper, we discuss the current knowledge and achievements on bone tissue engineering with regard to spinal fusion and highlight the technique that employs hybrid constructs of porous scaffolds with bone marrow stromal cells. These hybrid constructs potentially function in a way comparable to the present golden standard, the autologous bone graft, which comprises besides many other factors, a construct of an optimal biological scaffold with osteoprogenitor cells. However, little is known about the role of the cells in autologous grafts, and especially survival of these cells is questionable. Therefore, more research will be needed to establish a level of functioning of hybrid constructs to equal the autologous bone graft. Spinal fusion models are relevant because of the increasing demand for graft material related to this procedure. Furthermore, they offer a very challenging environment to further investigate the technique. Anterior and posterolateral animal models of spinal fusion are discussed together with recommendations on design and assessment of outcome parameters.

Animals↗

PubMed2004

In vivo and in vitro degradation of poly(ether ester) block copolymers based on poly(ethylene glycol) and poly(butylene terephthalate).

Two in vivo degradation studies were performed on segmented poly(ether ester)s based on polyethylene glycol (PEG) and poly(butylene terephthalate) (PBT) (PEOT/PBT). In a first series of experiments, the in vivo degradation of melt-pressed discs of different copolymer compositions were followed up for 24 weeks after subcutaneous implantation in rats. The second series of experiments aimed to simulate long-term in vivo degradation. For this, PEOT/PBT samples were pre-degraded in phosphate buffer saline (PBS) at 100 degrees C and subsequently implanted. In both series, explanted materials were characterized by intrinsic viscosity measurements, mass loss, proton nuclear magnetic resonance spectroscopy (1H-NMR) and differential scanning calorimetry (DSC). In both studies the copolymer with the higher PEO content degraded the fastest, although all materials degraded relatively slowly. To determine the nature of the degradation products formed during hydrolysis of the copolymers, 1000 PEOT71PBT29 (a copolymer based on PEG with a molecular weight of 1000 g/mol and 71 wt% of PEO-containing soft segments) was degraded in vitro at 100 degrees C in phosphate buffer saline (PBS) during 14 days. The degradation products present in PBS were analyzed by 1H-NMR and high performance liquid chromatography/mass spectroscopy (HPLC/MS). These degradation products consisted of a fraction with high contents of PEO that was soluble in PBS and a PEOT/PBT fraction that was insoluble at room temperature. From the different in vitro and in vivo degradation experiments performed, it can be concluded that PEOT/PBT degradation is a slow process and generates insoluble polymeric residues with high PBT contents.

Animals↗

PubMed2004

Relation between in vitro and in vivo osteogenic potential of cultured human bone marrow stromal cells.

The use of cell therapies in bone reconstruction has been the subject of extensive research. It is known that human bone marrow stromal cell (HBMSC) cultures contain a population of progenitor cells capable of differentiation towards the osteogenic lineage. In the present study, the correlation between the in vitro osteogenic potential of HBMSC cultures and their capacity to form bone in vivo was investigated. HBMSC cultures were established from 14 different donors. Fourth passage cells were examined for the expression of alkaline phosphatase (ALP), procollagen I (PCI) and osteopontin (OP), through flow cytometry and the effect of the osteogenic differentiation factor dexamethasone (Dex) on this expression was evaluated. In addition, the capacity of the cultures to induce in vivo bone formation was analysed by culturing the cells on porous hydroxyapatite (HA) scaffolds followed by subcutaneous implantation of these constructs in nude mice. Results showed expression of PCI, OP and ALP in all cultures, irrespective of the presence of Dex in the culture medium. Dex failed to have a significant effect on the expression of PCI and OP but it induced a consistent increase in the relative amount of cells expressing ALP. Nevertheless, although in vitro testing clearly indicated osteogenic potential in all cultures, HBMSC from six of the 14 tested donors did not form bone in vivo. The results, therefore, demonstrate that neither the expression of PCI, OP and ALP nor the absolute increase in Dex-stimulated ALP expression can as yet be used as predictive markers for in vivo bone formation by HBMSC. However, preliminary data indicate that not the absolute, but the relative increase in the percentage of ALP expressing cells caused by Dex stimulation may be related to the ability of the HBMSC to form bone.

Adult↗

PubMed2003

Studying the effect of different macrostructures on in vitro cell behaviour and in vivo bone formation using a tissue engineering approach.

In the present study, we tested the in vitro process of differentiation and mineralization as well as the process of in vivo bone formation on substrates with different macrostructures. We used carbonated apatite-coated titanium discs that were respectively smooth, plasma spayed with titanium or had a porous structure. Subcultured rat bone marrow cells were seeded on the substrates and after 7 days of culture, the tissue-coated substrates were subcutaneously implanted in nude mice for 4 weeks. After 1 week of culture in the presence of the osteogenic differentiation promoter dexamethasone, the cells had formed a continuous layer of mineralized tissue on the smooth and titanium plasma-sprayed discs. In the case of the porous titanium discs, the bone-like tissue coverage was restricted to the outer surface and the peripheral pores. The influence of the macrostructure on the process of differentiation of the cultured cells depended on the presence of dexamethasone. When dexamethasone was present, the highest ALP/DNA ratios were obtained with the smooth surfaces. In the absence of dexamethasone, the highest ALP/DNA values were obtained with the rough macrostructured discs. We postulate that these different patterns were due to the shielding of cells in pits or pores of rough structured substrates by dense overlying cell layers. These cell layers are suggested to increase the exposure of excreted osteoinductive proteins and decrease the exposure of dexamethasone to underlying cells. Four weeks post-implantation, abundant bone formation could be observed on all in vitro tissue-coated substrates. The percentage of direct bone contact on the porous discs (42.3 +/- 22.3) was significantly lower compared to the non-porous discs. This was related to the process of bone infiltration into the central oriented pores that predominantly occurred in a centrifugal manner. The percentage of direct bone contact on the smooth discs (96.3 +/- 2.3) was significantly higher compared to the titanium plasma-sprayed discs (81.5 +/- 10.7). This was not due to fibrous tissue infiltration, but due to the extensive formation of bone marrow. Nevertheless, for practical reasons regarding protection of the layer of cultured cells during the implantation procedure, the use of rough or porous surface structures is suspected to be advantageous in revision surgery.

Alkaline Phosphatase↗

PubMed2003

Poly(ether ester amide)s for tissue engineering.

Poly(ether ester amide) (PEEA) copolymers based on poly(ethylene glycol) (PEG), 1,4-butanediol and dimethyl-7,12-diaza-6,13-dione-1,18-octadecanedioate were evaluated as scaffold materials for tissue engineering. A PEEA copolymer based on PEG with a molecular weight of 300 g/mol and 25wt% of soft segments (300 PEEA 25/75) and the parent PEA polymer (0/100) sustain the adhesion and growth of endothelial cells. The in vivo degradation of melt-pressed PEEA and PEA discs subcutaneously implanted in the back of male Wistar rats was followed up to 14 weeks. Depending on the copolymer composition, a decrease in intrinsic viscosity of about 20-30% and mass loss up to 12% were measured. During the degradation process, erosion of the surface was observed by scanning electron microscopy and light microscopy. The thermal properties of the polymers during degradation were measured by differential scanning calorimetry. During the first 2 weeks, a broadening of the melting endotherm was observed, as well as an increase in the heat of fusion. Porous matrices of PEEAs and PEA could be prepared by molding mixtures of polymer and salt particles followed by leaching of the salt.

Amides↗

PubMed2003

Evaluation of two biodegradable polymeric systems as substrates for bone tissue engineering.

The aim of this study was to evaluate two biodegradable polymeric systems as scaffolds for bone tissue engineering. Rat bone marrow cells were seeded and cultured for 1 week on two biodegradable porous polymeric systems, one composed of poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) and the other composed of cornstarch blended with poly(epsilon-caprolactone) (SPCL). Porous hydroxyapatite granules were used as controls. The ability of cells to proliferate and form extracellular matrix on these scaffolds was assessed by a DNA quantification assay and by scanning electron microscopy examination; their osteogenic differentiation was screened by the expression of alkaline phosphatase. In addition, the in vivo osteogenic potential of the engineered constructs was evaluated through ectopic implantation in a nude mouse model. Results revealed that cells were able to proliferate, differentiate, and form extracellular matrix on all materials tested. Moreover, all constructs induced abundant formation of bone and bone marrow after 4 weeks of implantation. The extent of osteogenesis (approximately 30% of void volume) was similar in all types of implants. However, the amount of bone marrow and the degree of bone contact were higher on HA scaffolds, indicating that the polymers still need to be modulated for higher osteoconductive capacity. Nevertheless, the findings suggest that both PEGT/PBT and SPCL systems are excellent candidates to be used as scaffolds for a cell therapy approach in the treatment of bone defects.

Alkaline Phosphatase↗

PubMed2003

Viable osteogenic cells are obligatory for tissue-engineered ectopic bone formation in goats.

In this study we investigated the bone-forming capacity of tissue-engineered (TE) constructs implanted ectopically in goats. As cell survival is questionable in large animal models, we investigated the significance of vitality, and thus whether living cells instead of only the potentially osteoinductive extracellular matrix are required to achieve bone formation. Vital TE constructs of porous hydroxyapatite (HA) covered with differentiated bone marrow stromal cells (BMSCs) within an extracellular matrix (ECM) were compared with identical constructs that were devitalized before implantation. The devitalized implants did contain the potentially osteoinductive ECM. Furthermore, we evaluated HA impregnated with fresh bone marrow and HA only. Two different types of HA granules with a volume of approximately 40 microm were investigated: HA70/800, a microporous HA with 70% interconnected macroporosity and an average pore size of 800 microm, and HA60/400, a smooth HA with 60% interconnected macropores and an average size of 400 microm. Two granules of each type were combined and then treated as a single unit for cell seeding, implantation, and histology. The tissue-engineered samples were obtained by seeding culture-expanded goat BMSCs on the HA and subsequently culturing these constructs for 6 days to allow cell differentiation and ECM formation. To devitalize, TE constructs were frozen in liquid nitrogen according to a validated protocol. Fresh bone marrow impregnation was performed perioperatively (4 mL per implant unit). All study groups were implanted in bilateral paraspinal muscles. Fluorochromes were administered at three time points to monitor bone mineralization. After 12 weeks the units were explanted and analyzed by histology of nondecalcified sections. Bone formation was present in all vital tissue-engineered implants. None of the other groups showed any bone formation. Histomorphometry indicated that microporous HA70/800 yielded more bone than did HA60/400. Within the newly formed bone, the fluorescent labels showed that mineralization had occurred before 5 weeks of implantation and was directed from the HA surface toward the center of the pores. In conclusion, tissue-engineered bone formation in goats can be achieved only with viable constructs of an appropriate scaffold and sufficient BMSCs.

Animals↗

PubMed2002

Bone tissue-engineered implants using human bone marrow stromal cells: effect of culture conditions and donor age.

At present, it is well known that populations of human bone marrow stromal cells (HBMSCs) can differentiate into osteoblasts and produce bone. However, the amount of cells with osteogenic potential that is ultimately obtained will still be dependent on both patient physiological status and culture system. In addition, to use a cell therapy approach in orthopedics, large cell numbers will be required and, as a result, knowledge of the factors affecting the growth kinetics of these cells is needed. In the present study we investigated the effect of dexamethasone stimulation on the in vivo osteogenic potential of HBMSCs. After a proliferation step, the cells were seeded and cultured on porous calcium phosphate scaffolds for 1 week, and then subcutaneously implanted in nude mice for 6 weeks, in order to evaluate their in vivo bone-forming ability. Furthermore, the effect of donor age on the proliferation rate of the cultures and their ability to induce in vivo bone formation was studied. In 67% of the assayed patients (8 of 12), the presence of dexamethasone in culture was not required to obtain in vivo bone tissue formation. However, in cultures without bone-forming ability or with a low degree of osteogenesis, dexamethasone increased the bone-forming capacity of the cells. During cellular proliferation, a significant age-related decrease was observed in the growth rate of cells from donors older than 50 years as compared with younger donors. With regard to the effect of donor age on in vivo bone formation, HBMSCs from several donors in all age groups proved to possess in vivo osteogenic potential, indicating that the use of cell therapy in the repair of bone defects can be applicable irrespective of patient age. However, the increase in donor age significantly decreased the frequency of cases in which bone formation was observed.

Age Factors↗

PubMed2002

Exploiting the natural diversity in adenovirus tropism for therapy and prevention of disease.

Since targeting of recombinant adenovirus vectors to defined cell types in vivo is a major challenge in gene therapy and vaccinology, we explored the natural diversity in human adenovirus tissue tropism. Hereto, we constructed a library of Ad5 vectors carrying fibers from other human serotypes. From this library, we identified vectors that efficiently infect human cells that are important for diverse gene therapy approaches and for induction of immunity. For several medical applications (prenatal diagnosis, artificial bone, vaccination, and cardiovascular disease), we demonstrate the applicability of these novel vectors. In addition, screening cell types derived from different species revealed that cellular receptors for human subgroup B adenoviruses are not conserved between rodents and primates. These results provide a rationale for utilizing elements of human adenovirus serotypes to generate chimeric vectors that improve our knowledge concerning adenovirus biology and widen the therapeutic window for vaccination and many different gene transfer applications.

Adenoviruses, Human↗

PubMed2001

Bone induction by porous glass ceramic made from Bioglass (45S5).

Porous glass ceramic, which was prepared from Bioglass powder (45S5, U.S. Biomaterials) by foaming with diluted H(2)O(2) solution and sintering at 1000 degrees C for 2 h, was implanted as cylinders (5 mm in diameter and 6 mm in length) in thigh muscles of dogs for 3 months. Histological observation was made on thin un-decalcified sections. Bone formation was histologically found in pores of all implants (X16) retrieved from 16 dogs. The bone tissue was also identified with backscattered scanning electron microscopy observation (BSE) and energy dispersive X-ray microanalysis (EDX). This is the first report of bone induction in soft tissues of animals by glass ceramic that has long been recognized as a bioactive (osteoconductive) biomaterial. The present results justify the impetus to investigate the osteoinductivity of calcium phosphate-based biomaterials, to study the mechanism of bone induction (osteoinduction) by calcium phosphate-based biomaterials, to develop osteoinductive calcium phosphate-based biomaterials, and to examine the relation between osteoinduction and osteoconduction.

Animals↗

PubMed2001

Cytocompatibility and response of osteoblastic-like cells to starch-based polymers: effect of several additives and processing conditions.

This work reports on the biocompatibility evaluation of new biodegradable starch-based polymers that are under consideration for use in orthopaedic temporary applications and as tissue engineering scaffolds. It has been shown in previous works that by using these polymers it is both possible to produce polymer/hydroxyapatite (HA) composites (with or without the use of coupling agents) with mechanical properties matching those of the human bone, and to obtain 3D structures generated by solid blowing agents, that are suitable for tissue engineering applications. This study was focused on establishing the influence of several additives (ceramic fillers, blowing agents and coupling agents) and processing methods/conditions on the biocompatibility of the materials described above. The cytotoxicity of the materials was evaluated using cell culture methods, according to ISO/EN 109935 guidelines. A cell suspension of human osteosarcoma cells (HOS) was also seeded on a blend of corn starch with ethylene vinyl alcohol (SEVA-C) and on SEVA-C/HA composites, in order to have a preliminary indication on cell adhesion and proliferation on the materials surface. In general, the obtained results show that all the different materials based on SEVA-C, (which are being investigated for use in several biomedical applications), as well as all the additives (including the novel coupling agents) and different processing methods required to obtain the different properties/products, can be used without inducing a cytotoxic behaviour to the developed biomaterials.

Animals↗

PubMed2001

Biocompatibility testing of novel starch-based materials with potential application in orthopaedic surgery: a preliminary study.

This paper describes an extensive biocompatibility evaluation of biodegradable starch-based materials aimed at orthopaedic applications as temporary bone replacement/fixation implants. For that purpose, a polymer (starch/ethylene vinyl alcohol blend, SEVA-C) and a composite of SEVA-C reinforced with hydroxyapatite (HA) particles, were evaluated in both in vitro and in vivo assays. For the in vitro analysis cell culture methods were used. The in vivo tissue reactions were evaluated in an intramuscular and intracortical bone implantation model on goats, using light and scanning electron microscopy. A computerized image analysis system was used to obtain histomorphometric data regarding bone contact and remodelling after 6 and 12 weeks of implantation. In both in vitro and in vivo models, the SEVA-C-based materials did not induce adverse reactions, which in addition to their bone-matching mechanical properties makes them promising materials for bone replacement fixation.

Animals↗

PubMed2000

Tissue responses of calcium phosphate cement: a study in dogs.

The in vivo properties of a new kind of calcium phosphate cement were investigated in this study. Calcium phosphate cement was implanted as paste into femoral bone and dorsal muscle of dogs for 3 and 6 months, and as prehardened form into thigh muscles of dogs for 1, 2 and 6 months. Histology was performed on thin un-decalcified sections. No foreign body reaction, no inflammation and no necrosis were found both in bony site and in muscles. There was no connective tissue layer between the cement and bone when cement paste was implanted in the bone. A creeping substitution of cement by bone, in which osteoclast-like cells resorbed the cement as if the cement is a part of bone and new bone was formed directly on the resorption line of calcium phosphate cement, was found. Bone formation was found histomorphologically in pores and deep rugged surface of cement samples (both paste and prehardened form) implanted in muscles of dogs. The induced bone was also identified with backscattered scanning electron microscopy (BSE) and by energy-dispersive X-ray micro-analysis (EDX). The results suggest that the calcium phosphate cement used in this study is biocompatible, resorbable in a manner of creeping substitution, osteoconductive and osteoinductive. It seems that an ideal bone substitute can be developed by using this type of calcium phosphate cement.

Absorbable Implants↗

PubMed1999

A preliminary study on osteoinduction of two kinds of calcium phosphate ceramics.

With respect to the effect of material factors on calcium phosphate biomaterial-induced osteogenesis, the osteoinductive property of two kinds of porous hydroxyapatite ceramics, which were made by different producers, was investigated in dorsal muscles of dogs. One hydroxyapatite ceramic (S-HA), macroporous implants with rough pore walls containing abundant micropores, was made by Sichuan Union University (Chengdu, China); the other hydroxyapatite ceramic (J-HA), porous implants with smooth macropore walls composed of regularly aligned crystal grains, was provided by Mitsubishi Ceramic Int. (Japan). Different tissue response was detected histologically and microradiographically after the ceramic samples had been implanted in dorsal muscles of dogs for 3 and 6 months. Bone formation was found in S-HA at 3 months, which increased at 6 months. In contrast, no bone formation was detected in J-HA at both 3 and 6 months. These results indicate that with the special architecture, calcium phosphate ceramic can induce bone formation in soft tissue. As both materials were very similar in their chemical and crystallographic structures, but varied in their microstructures, the latter seem to be an important factor affecting the osteoinductive capacity of calcium phosphate ceramics. These data suggest that, by controlling the preparation of calcium phosphate ceramic, bone substitutes with intrinsic osteoinductive property can be developed from calcium phosphates.

Animals↗

PubMed1999

Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a metabolic rate more comparable with that of humans than small animals. The critical size defect, located in the goat's iliac wing, is easily reproducible and allows qualitative and quantitative evaluation of bone grafts and bone graft substitutes. After 3 months of healing, the unfilled defects showed 13.5% bone in the defect, the autografted defects 36.3%, and the allografted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in contrast to previous reports. The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.

Animals↗