Biomedical subjects

J A Jansen

Publications and source records attributed to J A Jansen.

At least 55 records · Page 3Linked to original sources

PubMed2004

The influence of bone formation on anchoring percutaneous devices with titanium fibre mesh flanges.

For man-made percutaneous devices (PD), it is known that anchoring will improve the clinical success. Previously, our Department has designed PDs that use a sheet of titanium (Ti) fibre mesh for anchoring. In nature, a very successful natural PD occurs, namely the tooth. Teeth are anchored in the alveolar bone. In the current study, we evaluated whether a sheet of (ectopic) bone can be made, and be used to anchor a skin-penetrating device. Using available tissue engineering techniques, sheets of Ti fibre mesh were loaded with osteoblast-like cells. These sheets, and non-loaded controls, were placed subcutaneously in 20 syngeneic rats. After four weeks 10 rats were sacrificed, and tissues were prepared for histology. On the other 10 rats, a percutaneous Ti bar was screwed. These rats were evaluated clinically up to eight weeks. Finally, also their tissues were prepared for histology. The results showed, that bone formation was only established in one cell-loaded implant, of the four-week group. Clinical evaluation, and the histomorphometrical data, showed no differences between cell-loaded and unloaded samples. We concluded that the combination of Ti mesh with rat bone marrow cells was not able to generate bone formation after subcutaneous implantation predictably. Thus, our original aim could not be met. On the other hand, our results did confirm the biocompatible behaviour of a PD equipped with a Ti fibre mesh anchoring flange.

Animals↗

PubMed2004

Mandibular reconstruction: a histological and histomorphometric study on the use of autogenous scaffolds, particulate cortico-cancellous bone grafts and platelet rich plasma in goats.

Twenty-eight goats underwent a continuity resection of the mandibular angle. In all goats primary reconstruction was carried out using specially designed pre-shaped osteosynthesis plates and monocortical screws. The original cortical scaffold was used to bridge the defect, filled with an autogenous particulate bone graft in 14 goats, whereas platelet-rich-plasma (PRP) was added in another 14 goats. Both groups were divided in three subgroups that were sacrificed after 3, 6 and 12 weeks. Histological and histomorphometric evaluation revealed that the use of PRP enhanced the bone healing considerably. This effect was statistically significant and particularly visible in the 6 and 12 weeks' groups

Animals↗

PubMed2004

[Laboratory animal models for the manufacture of tissue substitutes].

Currently, a lot of interest exists in tissue substitution by so-called tissue engineering methods. However, before the newly developed products can be applied in humans, their efficacy has to be proven in experimental animal research. The article provides an overview of the various animal models which are currently used for the analysis of tissue engineered bone, cartilage, skin, nerve and muscle tissue.

Animals↗

PubMed2003

Intermittent versus continuous stretching effects on osteoblast-like cells in vitro.

The objective of this study was to quantify and compare stretch-mediated responses of primary rat osteoblast-like cells to uniform cyclic strain applied intermittently or continuously. Primary rat osteoblast-like cells were seeded and cultured in silicone rubber dishes for 2 days. They were then subjected to 1000 microstrains at 1 Hz for periods of 60 consecutive minutes or to a series of 15-min stretch followed by 15-min rest, until a total stretch of 60 min. After stretching, cells were incubated and assayed on days 4, 8, 16, and 24 for DNA content, alkaline phosphatase (ALP) activity, and calcium (Ca) content. Additionally, qualitative information was obtained via scanning electron and confocal laser scanning micrographs. Significant increases in DNA were observed for cells stretched intermittently versus cells stretched continuously and versus controls. Results showed significant decreases (p < 0.05) in ALP for cells between stretched groups and between both stretched groups versus controls. Additionally, Ca content was greater in cells stretched intermittently versus controls on days 4 and 8 and versus cells stretched continuously on day 24. In conclusion, intermittently strained cells demonstrated significant decreases in ALP and increases in DNA and Ca versus cells strained continuously. This supports the theory that cells respond to mechanical loading in a "trigger-like" response.

Alkaline Phosphatase↗

PubMed2003

Use of injectable calcium-phosphate cement for the fixation of titanium implants: an experimental study in goats.

This in vivo study evaluated the fixation of two types of titanium implants with the use of an injectable calcium-phosphate (CaP) cement. The cement was either used to create a cement mantle (Type A implant) or as an additive to press-fit placed titanium plasma sprayed implants (Type B implant). The implants were placed in trabecular bone of the medial femoral condyle of goats and left in place for 2 and 10 weeks. Mechanical evaluation of the implant fixation was done by torque testing. This showed that for the Type A implants the calcium-phosphate cement's performance was significantly inferior (P < 0.05) to that of polymethylmethacrylate cement fixation. For the two-week Type B implants a significant increase (P < 0.05) in failure load was found for calcium-phosphate cemented implants compared with just press-fitted Type B implants. Histological evaluation revealed that for Type A implants, failure during torque testing occurred at the implant-cement interface. In contrast, for Type B implants, failure occurred in the bone-implant interface for press-fit-placed devices and in the cement layer for CaP-cemented devices. Further, the CaP cement was found to be overgrown with new formed bone already after 2 weeks of implantation. The cement showed resorption due to regular bone remodeling. On the basis of these observations, it was concluded that the use of injectable CaP cement might facilitate earlier loading of press-fit inserted titanium implants. Nevertheless, the results have to be confirmed in dynamical mechanical as well as loaded in vivo studies.

Animals↗

PubMed2003

In vivo bone response to porous calcium phosphate cement.

We conducted an in vivo experiment to evaluate the resorption rate of a calcium phosphate cement (CPC) with macropores larger than 100 microm, using the CPC called Biocement D (Merck Biomaterial, Darmstadt, Germany), which after setting only shows pores smaller than 1 microm. The gas bubble method used during the setting process created macroporosity. Preset nonporous and porous cement implants were inserted into the trabecular bone of the tibial metaphysis of goats. The size of the preset implants was 6 mm and the diameter of the drill hole was 6.3 mm, leaving a gap of 0.3 mm between implant surface and drill wall. After 2 and 10 weeks, the animals were euthanized and cement implants with surrounding bone were retrieved for histologic evaluation. Light microscopy at 2 weeks revealed that the nonporous implants were surrounded by connective tissue. On the cement surface, we observed a monolayer of multinucleated cells. Ten weeks after implantation, the nonporous implants were still surrounded by connective tissue. However, a thin layer of bone now covered the implant surface. No sign of cement resorption was observed. In contrast, the porous cement evoked a completely different bone response. At 2 weeks, bone formation had already occurred inside the implant porosity. Bone formation even appeared to occur as a result of osteoinduction. Also, at their outer surface, the porous implants were completely surrounded by bone. At 2 weeks, about 31% of the initial cement was resorbed. After 10 weeks, 81% of the initial phosphate cement was resorbed and new bone was deposited. On the basis of these observations, we conclude that the creation of macropores can significantly improve the resorption rate of CPC. This increased degradation is associated with almost complete bone replacement.

Animals↗

PubMed2003

Bone formation in CaP-coated and noncoated titanium fiber mesh.

The osteogenic activity of calcium phosphate (CaP)-coated and noncoated porous titanium (Ti) fiber mesh loaded with cultured syngeneic osteogenic cells after prolonged in situ culturing was compared in a syngeneic rat ectopic assay model. Rat bone marrow (RBM) cells were loaded onto the CaP-coated and noncoated Ti scaffolds using either a droplet or a suspension loading method. After loading, the RBM cells were cultured for 8 days in vitro. Thereafter, implants were subcutaneously placed in 39 syngeneic rats. The rats were euthanized and the implants retrieved at 2, 4, and 8 weeks postoperatively. Further, in the 8 week group fluorochrome bone markers were injected at 2, 4, and 6 weeks. Histological analysis demonstrated that only the CaP-coated meshes supported bone formation. The amount of newly formed bone varied between single and multiple spheres to filling a significant part of the mesh porosity. In the newly formed bone, osteocytes embedded in a mineralized matrix could be observed clearly. On the other hand, in the noncoated titanium implants, abundant deposition of calcium-containing material was seen. This deposit lacked a bonelike tissue organization. Further analysis revealed that the cell-loading method did not influence the final amount of bone formation. In CaP-coated implants the accumulation sequence of the fluorochrome markers showed that bone formation started on the mesh fibers. In conclusion, our results prove that the combination of a thin CaP coating, Ti-mesh, and RBM cells can indeed generate ectopic bone formation after prolonged in vitro culturing. No effect of the loading method was observed on the final amount of bone.

Animals↗

PubMed2003

Soft-tissue response to injectable calcium phosphate cements.

In this study, the soft tissue reaction to two newly developed injectable calcium phosphate bone cements (cement D and W) was evaluated after implantation in the back of goats. For one of the cements (cement D) the tissue reaction was also investigated after varying the concentration of accelerator Na(2)HPO(4) in the cement liquid (resulting in cement D1 and D2). Eight healthy mature female Saanen goats were used. The cement was applied 10min after mixing while it was still moldable and plastic. The material was given a standardized cylindrical shape. Thirty-two implants of each cement formulation were inserted and left in place for 1, 2, 4, and 8weeks. At the end of the study, eight specimens of each material and healing period were available for further analysis. Two specimens were used for X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) and six specimens were used for light microscopical evaluation. XRD and FTIR showed that the cements did set as microcrystalline carbonate apatite with the disappearance of monetite from the cements during implantation. Histological analysis showed that after 8weeks of implantation around all materials a thin soft-tissue capsule was formed (thickness ranging from 5 to 15 cell layers) with almost complete absence of inflammatory cells. Only in some specimens a slightly higher inflammatory reaction was observed. This was due to cement surface defects and a zone of dispersed particles near the cement-soft tissue interface. There was almost no resorption of the material after 8 weeks of implantation. In a few 4 and 8weeks samples, small areas of calcification were found in the fibrous capsule surrounding the implants. On the basis of our observations, we conclude that the tested cements were biocompatible and can be used next to soft tissue.

Animals↗

PubMed2003

Histological evaluation of the bone response to calcium phosphate cement implanted in cortical bone.

The aim of this study was to investigate the physicochemical and biological properties of a newly developed calcium phosphate cement (CaP cement) implanted in cortical bone. CaP cement was injected as a paste into tibia cortical bone defects in goats. Polymethylmethacrylate (PMMA) bone cement was used as a control. The animals were killed after 3 days, 2, 8, 16 and 24 weeks. X-ray diffraction and Fourier transform infrared spectroscopy performed at retrieved samples showed that the CaP cement had set as a carbonate apatite and remained stable over time. Light microscopic evaluation showed that after 2 weeks the cement was in tight contact with the bone without any inflammatory reaction or fibrous encapsulation. At later time points, the CaP cement implants were totally covered by a thin layer of bone and osteoclasts, present at the interface, which were clearly resorbing the cement. At locations where CaP cement was resorbed, new bone was deposited. Transmission electron microscopy revealed that indeed a seamless contact existed between CaP cement and bone, as characterized by the occurrence of an electron dense line of 50-60 nm thick that covered the CaP cement. Osteoblasts, in contact with the cement, were depositing new bone. Although the bulk of the material was still in situ after 24 weeks, the progressive osteoclast resorption of the cement followed by new bone formation suggests that all of the material may be replaced eventually. In contrast to the CaP cement, the PMMA reference cement was always surrounded by a thin fibrous capsule. The results indicate that the investigated CaP cement is biocompatible, osteoconductive as well as osteotransductive and is a candidate material for use as a bone substitute.

Animals↗

PubMed2003

In vivo dissolution behavior of various RF magnetron-sputtered Ca-P coatings on roughened titanium implants.

RF magnetron sputter deposition was used to produce 0.1, 1.0 and 4.0 microm thick Ca-P coatings on TiO(2)-blasted titanium discs. Half of the as-sputtered coated specimens were subjected to an additional infrared heat treatment for 30s at 425-475 degrees C. X-ray diffraction demonstrated that infrared radiation changed the amorphous 4 microm sputtered coatings into an amorphous-crystalline structure, while the amorphous 0.1 and 1 microm changed in a crystalline apatite structure with the presents of tetracalciumphosphate as a second phase. Scanning electron microscopically examination of the sputtered coatings revealed that annealing of the 4 microm thick coatings resulted in the appearance of small cracks. Subsequently, the discs were implanted subcutaneous into the back of rabbits. After 1, 4, 8 and 12 weeks of implantation, the implants were retrieved and prepared for histological and physicochemical evaluation. Histological evaluation revealed that the tissue response to all coated implants was very uniform. A very thin connective tissue capsule surrounded all implants. The capsule was usually free of inflammatory cells. At the interface, there was a close contact between the capsule and implant surface and no inflammatory cells were seen. Physicochemical evaluation showed that the 0.1 and 1 microm thick amorphous coatings had disappeared within 1 week of implantation. On the other hand, the 4 microm thick amorphous phase disappeared during the implantation periods, which was followed by the precipitation of a crystalline carbonate apatite. Further, at all implantation periods the heat-treated 1 and 4 microm thick coatings could be detected. Occasionally, a granular precipitate was deposited on the heat-treated 4 microm thick coating. Fourier transform infrared spectroscopy showed the formation of carbonate apatite (CO(3)-AP) on the 4 microm thick amorphous coating and on the heat-treated specimens. On basis of our findings, we conclude that 1 microm thick heat-treated Ca-P sputter coating on roughened titanium implants appear to be of sufficient thickness to show bioactive properties, under in vivo conditions.

Animals↗

PubMed2003

Soft tissue reaction to microgrooved poly-L-lactic acid implants loaded with transforming growth factor beta(3).

In both normal and disturbed wound healing, the generation of large, contracting scars can raise serious functional and cosmetic problems. A possible strategy to minimize or avoid the generation of scar tissue surrounding an implant is to apply transforming growth factor-beta(3) (TGF-beta(3)) to the implant. TGF-beta(3) (0, 1, or 2.5 microg) was freeze-dried onto poly-L-lactic acid (PLA) microgrooved substrates (width, 10 microm; depth, 1 microm) and implanted subcutaneously on the backs of rats for 2 and 8 weeks. After sacrifice, implants and surrounding tissue were histologically processed. Light microscopic and histomorphometric evaluation of capsule thickness, capsule quality, and implant-tissue interface was performed. In addition, we stained for alpha-smooth muscle actin (SMA), collagen, and ED-1 (a monocyte-macrophage marker). All implants were surrounded by a fibrous capsule. Capsules of the implants loaded with 1 or 2.5 microg of TGF-beta(3) showed significantly higher capsule quality. This meant that capsules were more mature compared with implants without TGF-beta(3). However, no significant differences were found in terms of thickness of the capsules or quality of the interface. Finally, apparently significant differences were also found in the expression of alpha-SMA, when comparing the various growth factor concentrations at both implantation points. In conclusion, the use of microgrooved PLA substrates with TGF-beta(3) did not lead to an overall improvement of periimplant tissue healing.

Actins↗

PubMed2002

Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates.

From previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed alpha2, alpha3, alpha5, alpha6, alphav, and beta1 subunits. Expression of alpha1, alpha4, alphavbeta3, beta3, beta4, and beta7 was extremely low or was not found. The beta1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of alpha2, alpha5, alpha6, and alphav expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material.

Calcium Phosphates↗

PubMed2002

Histological characterization of the early stages of bone morphogenetic protein-induced osteogenesis.

On the basis of currently available knowledge, we hypothesize that the initial bone formation, as induced by bone morphogenetic protein (BMP), is influenced by the chemical composition and three-dimensional spatial configuration of the used carrier material. Therefore, in the current study, the osteoinductive properties of porous titanium (Ti) fiber mesh with a calcium phosphate (Ca-P) coating (Ti-CaP), insoluble bone matrix (IBM), fibrous glass membrane (FGM), and porous particles of hydroxy apatite (PPHAP) loaded with rhBMP-2 were compared in a rat ectopic assay model at short implantation periods. Twelve Ti-CaP, 12 IBM, 12 FGM, and 12 PPHAP implants, loaded with rhBMP-2, were subcutaneously placed in 16 Wistar King rats. The rats were sacrificed at 3, 5, 7, and 9 days post-operative, and the implants were retrieved. Histological analysis demonstrated that IBM and Ti-CaP had induced ectopic cartilage and bone formation by 5 and 7 days, respectively. However, in PPHAP, bone formation and cartilage formation were seen together at 7 days. At 9 days, in Ti-CaP, IBM, and PPHAP, cartilage was seen together with trabecular bone. At 9 days, in FGM, only cartilage was observed. Quantitative rating of the tissue response, using a scoring system, demonstrated that the observed differences were statistically significant (Wilcoxon rank sum test, p < 0.05). We conclude that IBM, CaP-coated Ti mesh, FGM, and PPHAP provided with rhBMP-2 can indeed induce ectopic bone formation with a cartilaginous phase in a rat model at short implantation periods. Considering the different chemical composition and three-dimensional spatial configuration of the carrier materials used, these findings even suggest that endochondral ossification is present in rhBMP-2-induced osteogenesis, even though the amount of cartilage may differ.

Animals↗

PubMed2002

[Subcutaneously implantable glucose sensors in patients with diabetes mellitus; still many problems].

Despite considerable scientific efforts, no clinical method is currently available for the continuous monitoring of glucose in subcutaneous tissue fluid. In general, good results were obtained during in-vitro experiments with various implantable glucose sensors. However, after implantation these devices exhibited a progressive loss of sensor function. It is evident that the tissue reaction to the implanted sensor, especially the interactions at the sensor-tissue interface, plays an important role in this loss of function. Adequate strategies to improve in-vivo sensor performance can only be developed if there is a better understanding of the processes involved in sensor inactivation.

Biosensing Techniques↗

PubMed2002

Transforming growth factor-beta 1, 2, and 3 can inhibit epithelial tissue outgrowth on smooth and microgrooved substrates.

In this study, we describe the influence of parallel surface microgrooves, and of TGF-beta, on the outgrowth of corneal epithelial tissue. Microgrooves (depth 1 microm, width 1-10 microm) were made in polystyrene culturing surfaces. These surfaces were left untreated, or loaded with TGF-beta 1, 2, or 3 (6.0 ng/cm(2)). Subsequently, epithelial explants from bovine corneas were placed on the experimental surfaces. After 9 days of culturing, tissue outgrowth was evaluated. Furthermore, the tissue cultures were analyzed histologically. It was shown that epithelial tissue grew from the explants over all experimental surfaces. On microgrooved surfaces outgrowth proceeded in the direction of the grooves, rather than perpendicular to the grooves. The addition of each type of TGF-beta resulted in a reduction of outgrowth. However, outgrowth remained directed by the grooves. Further, the explants had shrunk after TGF treatment. Histology showed that this shrinkage was not related to alpha-smooth muscle actin expression in the explants. We conclude that microgrooves can direct, and TGF-betas can inhibit the outgrowth of epithelial tissue. This finding could be useful in biomaterial applications where the growth of epithelial tissue needs to be discouraged.

Animals↗

PubMed2002

Trabecular bone response to injectable calcium phosphate (Ca-P) cement.

The aim of this study was to investigate the physicochemical, biological, and handling properties of a new developed calcium phosphate (Ca-P) cement when implanted in trabecular bone. Ca-P cement consisting of a powder and a liquid phase was implanted as a paste into femoral trabecular bone of goats for 3 days and 2, 8, 16, and 24 weeks. The cement was tested using three clinically relevant liquid-to-powder ratios. Polymethylmethacrylate bone cement, routinely used in orthopedics, was used as a control. The Ca-P cement was easy to handle and was fast setting with good cohesion when in contact with body fluids. X-ray diffraction at the different implantation periods showed that the cement had set as an apatite and remained stable over time. Histological evaluation after 2 weeks, performed on 10 microm un-decalcified sections, showed abundant bone apposition on the cement surface without any inflammatory reaction or fibrous encapsulation. At later time points, the Ca-P cement implants were totally covered by a thin layer of bone. Osteoclast-like cells, as present at the interface, had resorbed parts of the cement mass. At locations where Ca-P cement was resorbed, new bone was formed without loss of integrity between the bone bed and the cement. This demonstrated the osteotransductive property of the cement, i.e., resorption of the material by osteoclast-like cells, directly followed by the formation of new bone. Histological and histomorphometrical evaluation did not show any significant differences between the Ca-P cement implanted at the three different liquid/powder ratios. The results indicate that the investigated Ca-P cement is biocompatible, osteoconductive, as well as osteotransductive and is a candidate material for use as a bone substitute.

Animals↗

PubMed2002

Effect of calcium phosphate coating crystallinity and implant surface roughness on differentiation of rat bone marrow cells.

In this study, we examined the effect of calcium phosphate (Ca-P) coating crystallinity and of surface roughness on growth and differentiation of osteogenic cells. Grit-blasted titanium substrates were provided with Ca-P coatings of different crystallinities. Rat bone marrow (RBM) cells were cultured on these substrates and on noncoated rough and smooth titanium substrates. After specific culture times, expression of osteogenic markers by the cells was studied. Cells cultured on crystalline coatings and on titanium substrates proliferate, express alkaline phosphatase, osteocalcin (OC), and show mineralization of the extracellular matrix. Rough titanium substrates only express low OC levels. Significantly higher OC levels were expressed on smooth titanium, and even higher levels on the crystalline Ca-P coating. No difference was found in calcification between smooth and rough titanium. The crystalline coating showed more calcification than the titanium substrates. When substrates without cells were incubated in medium, precipitation of calcium was found. On the titanium substrates, this precipitate disappeared after prolonged incubation. The precipitate on the crystalline coating was stable and increased with longer incubation times. On the amorphous coatings, no proliferation and differentiation of RBM cells were found. After longer culture periods, substrates showed extensive dissolution. Cells on the amorphous coatings did express high levels of prostaglandin E2. In contrast, prostaglandin E2 expression was low for the other substrates. We conclude that crystalline Ca-P coatings stimulate differentiation of RBM cells, to a higher extent than titanium substrates. Surface roughness only has a limited effect on phenotype expression of the cells. In contrast, thin amorphous coatings show negative effects on the growth and differentiation of cultured RBM cells.

Alkaline Phosphatase↗

PubMed2002

Soft-tissue response to silicone and poly-L-lactic acid implants with a periodic or random surface micropattern.

Tissue reaction to biomaterials is dependent on properties such as surface topography. The aim of this study was to evaluate the tissue reaction around implants with different surface topographies. We made coin-shaped silicone and poly-L-lactic acid (PLLA) implants with double-sided parallel microgrooves (depth 1.0 microm; width 10.0 microm) and random roughness on a micrometer scale. The control implants were smooth. These implants were inserted into subcutaneous pockets created on the flanks of goats. After 1, 3, or 12 weeks, the goats were sacrificed and the implants retrieved and histologically processed. Light microscopic evaluation revealed the formation of fibrous tissue capsules around all implant materials. The PLLA did not visibly degrade during the study period. Histomorphometric analyses were performed on capsule thickness, capsule quality, and on the implant-tissue interface quality. Compared with the silicone implants, the capsules around the PLLA implants showed significantly better capsule quality. Compared to the smooth implants, the capsules around the microgrooved implants were thicker, but the capsules around the roughened implants were thinner. However, randomly roughened implant surfaces generally elicited a stronger and more prolonged inflammatory reaction compared to smooth and microgrooved implant surfaces. We conclude that the application of microgrooves or random surface roughness to polymer implants apparently does not have beneficial effects on peri-implant tissue healing.

Animals↗