Biomedical subjects

Theo G van Kooten

Publications and source records attributed to Theo G van Kooten.

9 recordsLinked to original sources

PubMed2006

Bone marrow-derived myofibroblasts contribute to the renal interstitial myofibroblast population and produce procollagen I after ischemia/reperfusion in rats.

Bone marrow-derived cells (BMDC) have been proposed to exert beneficial effects after renal ischemia/reperfusion injury (IRI) by engraftment in the tubular epithelium. However, BMDC can give rise to myofibroblasts and may contribute to fibrosis. BMDC contribution to the renal interstitial myofibroblast population in relation to fibrotic changes after IRI in rats was investigated. A model of unilateral renal IRI (45 min of ischemia) was used in F344 rats that were reconstituted with R26-human placental alkaline phosphatase transgenic BM to quantify BMDC contribution to the renal interstitial myofibroblast population over time. After IRI, transient increases in collagen III transcription and interstitial protein deposition were observed, peaking on days 7 and 28, respectively. Interstitial infiltrates of BMDC and myofibroblasts reached a maximum on day 7 and gradually decreased afterward. Over time, an average of 32% of all interstitial alpha-smooth muscle actin-positive myofibroblasts coexpressed R26-human placental alkaline phosphatase and, therefore, were derived from the BM. BMD myofibroblasts produced procollagen I protein and therefore were functional. The postischemic kidney environment was profibrotic, as demonstrated by increased transcription of TGF-beta and decreased transcription of bone morphogenic protein-7. TGF-beta protein was present predominantly in interstitial myofibroblasts but not in BMD myofibroblasts. In conclusion, functional BMD myofibroblasts infiltrate in the postischemic renal interstitium and are involved in extracellular matrix production.

Animals↗

PubMed2006

Development of an accommodating intra-ocular lens--in vitro prevention of re-growth of pig and rabbit lens capsule epithelial cells.

Cataract surgery is routinely performed to replace the clouded lens by a rigid polymeric intra-ocular lens unable to accommodate. By implanting a silicone gel into an intact capsular bag the accommodating properties of the natural lens can be maintained or enhanced. The implantation success of accommodating lenses is hampered by the occurrence of capsular opacification (PCO) due to lens epithelial cell (LEC) growth. In order to prevent LEC proliferation, a treatment regime using actinomycin D, cycloheximide and water was developed. The effectiveness of treatment was analyzed using an in vitro, MTT-based cell culture system and an ex vivo pig eye model in which the implanted lens-in-the-bag is cultured as a whole. LEC were exposed to treatment solutions for 5 min, then the cells were allowed to recover and to re-colonize the substratum. MTT conversion by cells was transiently inhibited by cycloheximide dissolved in water and by water alone. Exposure to actinomycin D resulted in a lasting inhibition of MTT conversion and consequently cell proliferation. These in vitro data could not be fully reproduced in the ex vivo pig eye model due to essential differences between both models. Treatment with actinomycin D containing solutions, however, resulted in a nearly complete absence of cells on the capsular wall. The pig eye model is a promising approach to further evaluate the effects of peri-surgical treatment during the accommodating intra-ocular lens implantation.

Animals↗

PubMed2006

Experimental results of the tracheoesophageal tissue connector for improved fixation of shunt valves in laryngectomized patients.

BACKGROUND: After total laryngectomy and voice rehabilitation using a tracheoesophageal shunt valve, patients often have valve-related complications such as leakage. To solve these problems, a tracheoesophageal tissue connector (TE-TC) was devised to serve as an interface between the patient's tissue (trachea and esophagus) and the shunt valve. METHODS: The TE-TC is a permucosal connection constructed from a titanium ring (filled with a silicon rubber plug) combined with polypropylene or titanium mesh. After implantation in adult goats for 12 weeks the implants were submitted to histologic investigation. RESULTS: Firm implant fixation was achieved. In nearly all (18/19), no signs of infection of the implant were seen; 11 of 19 animals died before the end of the experiment owing to complications not related to the implant. CONCLUSIONS: The TE-TC is a new device with potential in the solution for fixation-related problems in tracheoesophageal voice rehabilitation.

Animals↗

PubMed2006

Accommodative lens refilling in rhesus monkeys.

PURPOSE: Accommodation can be restored to presbyopic human eyes by refilling the capsular bag with a soft polymer. This study was conducted to test whether accommodation, measurable as changes in optical refraction, can be restored with a newly developed refilling polymer in a rhesus monkey model. A specific intra- and postoperative treatment protocol was used to minimize postoperative inflammation and to delay capsular opacification. METHODS: Nine adolescent rhesus monkeys underwent refilling of the lens capsular bag with a polymer. In the first four monkeys (group A) the surgical procedure was followed by two weekly subconjunctival injections of corticosteroids. In a second group of five monkeys (group B) a treatment intended to delay the development of capsular opacification was applied during the surgery, and, in the postoperative period, eye drops and two subconjunctival injections of corticosteroids were applied. Accommodation was stimulated with carbachol iontophoresis or pilocarpine and was measured with a Hartinger refractometer at regular times during a follow-up period of 37 weeks in five monkeys. In one monkey, lens thickness changes were measured with A-scan ultrasound. RESULTS: In group A, refraction measurement was possible in one monkey. In the three other animals in group A, postoperative inflammation and capsular opacification prevented refraction measurements. In group B, the maximum accommodative amplitude of the surgically treated eyes was 6.3 D. In three monkeys the accommodative amplitude decreased to almost 0 D after 37 weeks. In the two other monkeys, the accommodative amplitude remained stable at +/-4 D during the follow-up period. In group B, capsular opacification developed in the postoperative period, but refraction measurements could still be performed during the whole follow-up period of 37 weeks. CONCLUSIONS: A certain level of accommodation can be restored after lens refilling in adolescent rhesus monkeys. During the follow-up period refraction measurements were possible in all five monkeys that underwent the treatment designed to prevent inflammation and capsular opacification.

Accommodation, Ocular↗

PubMed2005

Bacterial transmission from contact lenses to porcine corneas: an ex vivo study.

PURPOSE: To quantify the transmission to ex vivo porcine eyes of Staphylococcus aureus 835 and Pseudomonas aeruginosa 3 from three types of contact lenses-one daily wear and two extended wear-differing in hydrophobicity and roughness. METHODS: One daily wear lens (etafilcon) and two extended-wear lenses (one lotrafilcon A and one balafilcon A) were inoculated in a bacterial suspension for 30 minutes and then placed on ex vivo porcine eyes. After 16 hours of contact between lens and eye, confocal laser scanning microscopy was used to determine the number of bacteria on the lens and cornea for the calculation of transmission percentages. RESULTS: Transmission percentages were significantly different for both bacterial strains from an etafilcon A lens and balafilcon A lens (P = 0.006 and 0.04, respectively). Percentages varied from 51% to 68% for the hydrophobic P. aeruginosa and from 54% to 82% for the hydrophilic S. aureus strain, depending on the contact lens involved. Both strains were transferred the least from the most hydrophilic and roughest lens made of lotrafilcon A, although the difference was only statistically significant for S. aureus. CONCLUSIONS: Bacterial transmission to the porcine cornea differed in the various types of contact lenses and was least in the hydrophilic and rough lens type.

Animals↗

PubMed2004

Path-dependency of the interaction between coaggregating and between non-coaggregating oral bacterial pairs--a thermodynamic approach.

Coaggregation, i.e. specific recognition between bacteria from different species, is a well-described phenomenon in the human oral cavity but remains physically poorly understood. With our study we aimed at elucidating some aspects of the mechanism of the coaggregation between the oral bacteria Streptococcus oralis J22 and Actinomyces naeslundii 147, in particular with respect to the driving force for coaggregation and its pathway-dependency. To that end, the macroscopic turbidity of the bacterial suspension, the morphology of the coaggregates, binding isotherms and heats of interaction were compared between the above-mentioned coaggregating bacterial pair and a non-coaggregating pair, Streptococcus sanguis PK1889 and A. naeslundii 147. The coaggregating pair forms large aggregates, which rapidly sediment from the suspension while the non-coaggregating pair forms only very small coaggregates that remain homogeneously suspended. Coaggregation is further characterized by a high affinity between the partner cells that bind to each other in a strong cooperative mode. The interactions between both pairs occur under the release of heat and are thus enthalpically favorable. More heat is released for the coaggregating than for the non-coaggregating pair. Adding the coaggregating bacteria in steps to each other leads to saturation of enthalpically favorable binding sites. This is observed when the streptococcus is added to the actinomyces as well as when the addition is done the other way around. It is concluded that the cooperativity of the coaggregation process is based on an increase of entropy. It is furthermore shown that the density of the coaggregates as well as the heat effect of formation of these coaggregates depend on the number of steps in which the partner cells are added to each other. Adding S. oralis J22 in three steps to A. naeslundii 147 results in the formation of denser coaggregates under the release of less heat, as compared to that of addition in one step. These differences point to a larger entropy increase when in a step-wise mixing the coaggregating bacteria are allowed to form more densely-packed coaggregates.

Actinomyces↗

PubMed2004

Plasma-treated polystyrene surfaces: model surfaces for studying cell-biomaterial interactions.

Biocompatibility of biomaterials relates, amongst others, to the absence of adverse cellular reactions and modulation of cell adhesion and subsequent responses. With respect to tissue-engineering applications, most materials need to evoke cell adhesion and spreading, while potentially displaying differential cell function. Adhesion has frequently been studied in a controlled fashion, using adhesion-supporting and -inhibiting substrata. The aim of this study is to create a panel of related materials with gradually changing surface characteristics in order to sustain similar individual cell adhesion and spreading, yet different cell population behaviour. A series of polystyrene materials was created with increasing oxygen surface incorporation and, concurrently, decreasing water-contact angles. Individual cells adhered and spread on all surfaces whilst showing well-developed focal adhesions and stress fibres. Cell populations demonstrated a decreased growth on surfaces with lower wettability. The biochemical activity of cell populations was not influenced by the surface treatment, but cell proliferation on surfaces increased with increasing oxygen incorporation. Furthermore, surface coverage with assembled fibronectin matrix was higher on the substrata with higher wettability. Finally, the expression of the adhesion-related proteins cadherin-5, focal adhesion kinase and RhoA was increased on surfaces with higher wettability. Further explorations of the cell biological basis of the observed differential behaviour will give more detailed answers on the rules governing cell-material interactions.

Biocompatible Materials↗

PubMed2003

Detection of biomaterial-associated infections in orthopaedic joint implants.

Biomaterial-associated infection of orthopaedic joint replacements is the second most common cause of implant failure. Yet, the microbiologic detection rate of infection is relatively low, probably because routine hospital cultures are made only of swabs or small pieces of excised tissue and not of the surfaces of potentially infected implants. Joint replacements from patients in whom infection was suspected, after clinical, radiologic, and biochemical examinations, were used in this study. The aim of the current study was to compare the detection rate of infection in total joint replacements based on cultures of the excised tissue and scrapings from the biomaterial surface. Joint prostheses were retrieved from 22 patients requiring orthopaedic revision surgery because of suspected infection of their prostheses. Routine hospital culturing of tissue only showed bacterial growth in nine patients (41%). However, after prolonged culturing, bacterial growth was observed in 14 patients (64%), whereas extensive culturing of scrapings from the biomaterial surface indicated bacterial growth in 19 of the 22 patients (86%). In addition, confocal laser scanning microscopy enabled observation of biofilm bacteria on the surfaces of the explanted prostheses. Diagnosis in orthopaedic revision surgery should consider using a microbial or microscopic analysis of the surface of an explanted prosthesis, where the biofilm mode of growth firmly anchors and protects the infecting organisms. Improved detection of infection by analysis of the implant surface is expected to yield ameliorated therapy and a reduced need for revision surgery.

Biocompatible Materials↗

PubMed2002

Surface modifications created by using engineered hydrophobins.

Hydrophobins are small (ca. 100 amino acids) secreted fungal proteins that are characterized by the presence of eight conserved cysteine residues and by a typical hydropathy pattern. Class I hydrophobins self-assemble at hydrophilic-hydrophobic interfaces into highly insoluble amphipathic membranes, thereby changing the nature of surfaces. Hydrophobic surfaces become hydrophilic, while hydrophilic surfaces become hydrophobic. To see whether surface properties of assembled hydrophobins can be changed, 25 N-terminal residues of the mature SC3 hydrophobin were deleted (TrSC3). In addition, the cell-binding domain of fibronectin (RGD) was fused to the N terminus of mature SC3 (RGD-SC3) and TrSC3 (RGD-TrSC3). Self-assembly and surface activity were not affected by these modifications. However, physiochemical properties at the hydrophilic side of the assembled hydrophobin did change. This was demonstrated by a change in wettability and by enhanced growth of fibroblasts on Teflon-coated with RGD-SC3, TrSC3, or RGD-TrSC3 compared to bare Teflon or Teflon coated with SC3. Thus, engineered hydrophobins can be used to functionalize surfaces.

Amino Acid Sequence↗