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Biomedical subjects

A Hanssen

Publications and source records attributed to A Hanssen.

7 recordsLinked to original sources
PubMed2004

A rabbit model to tissue engineer the bladder.

A rabbit model was used for the evaluation of a collagen-based biomatrix of small intestinal submucosa (SIS, COOK) in comparison to a biochemically reconstructed biomatrix for bladder tissue regeneration. Rabbits underwent partial cystectomy and cystoplasty with SIS patch graft or with a biochemically defined collagen biomatrix. The grafts of the regenerated bladder wall were harvested at different intervals and tissue regeneration was evaluated. The results of the SIS and biochemically defined biomatrix grafts were comparable. At harvesting, we found five bladder stones and encrustation of the biomatrix in 21/56 animals. No stone formation was observed in the control group. The results of the molecularly defined biomatrix are thus far comparable to SIS. Both matrices show good epithelialization and ingrowth of smooth muscle cells. Both biomatrices show considerable encrustation, which appears to disappear in time. The rabbit model is suitable for bladder tissue engineering studies as it is an easy model to use. In this model, besides tissue regeneration, also some of the clinical problems are seen such as encrustation of foreign body material in the bladder. These aspects are subject for further pre-clinical studies in this animal model.

Absorbable Implants↗
PubMed2003

Rabbit urethra replacement with a defined biomatrix or small intestinal submucosa.

OBJECTIVE: The evaluation of collagen-based biomatrix (SIS COOK((R))) in comparison to a biochemically reconstructed biomatrix for replacement of the urethra in a rabbit model as a preclinical model. MATERIAL AND METHODS: Rabbits underwent partial urethra replacement (resection of 0.5 to 1.0 cm segment of the urethra), which was replaced with 1 or 4 layers Small Intestinal Submucosa (SIS COOK) patch grafts or with a biochemically defined collagen biomatrix, partly sutured with unresolvable sutures for future reference. Six animals underwent a sham control operation. The grafts of regenerated urethras were harvested at 1, 3 and 9 months after implantation. Urethrography was performed pre-operatively and before sacrificing. The animals were evaluated macroscopically and by routine histology and immunohistochemistry. RESULTS: At 1 month after implantation, the biomatrices (1 layer, 4 layers and our biochemically defined biomatrix) were well distinguishable from the normal surrounding tissues and showed blood vessels at the periphery. Macroscopically, the unresolvable reference sutures were easy to find at all time points. At 3 months the graft was still distinguishable in the 4 layers SIS group. In the 1 layer and the defined biomatrix group a good regeneration of the urethra within the graft was seen with some central fibrosis. Histological and immunohistochemical evaluation showed urothelium regeneration on the 1 layer and on biochemically defined biomatrix with decreasing number of inflammatory cells from 1 month on. In the group treated with 4 layers SIS the urothelium was completely regenerated at 3 months. Histologically, the regeneration of muscle cells in the three biomatrices was comparable. The smooth muscle cells regenerated very slowly as 1 month after implantation no muscle cells were detectable within the grafts. At 3 months a few muscle cells were present in the graft, but cell density did not increase in the following 6 months. Strictures were not observed on control urethrography pre-operatively in the animals. In one case slight narrowing of the urethra on urethrography was seen, but apparently without causing voiding problems. One rabbit developed a fistula near the operation site. CONCLUSION: The biomatrices investigated are feasible scaffolds to repair urethral lesions. The results with our biochemically defined biomatrix are comparable to one layer Small Intestinal Submucosa. Almost no smooth muscle cells population was observed after nine months for the three biomatrices. We conclude that an improved molecularly defined biomatrix focussed on stimulation of smooth muscle cell growth may be necessary to obtain optimal cellular grafting results.

Animals↗
PubMed1993

Metrical information load of lines and angles in line patterns.

Acute angles and long lines are more complex than obtuse angles and short lines. This source of complexity is called metrical information, for which a measure was proposed by Leeuwenberg (1982). According to this measure, the metrical information of a static pattern is specified as the sum of the mechanical impulses necessary to move an object according to this pattern. The perceptual relevance of this metrical load was tested in an experiment in which judged complexities were gathered for a number of simple line patterns.

Adult↗
PubMedDate not supplied

In utero repair of an experimental neural tube defect in a chronic sheep model using biomatrices.

OBJECTIVE: Persistent exposure of the unprotected spinal cord to amniotic fluid and the uterine wall can lead to progressive damage of neural tissue in case of a myelomeningocele (two-hit hypothesis). The aim of this study was to evaluate whether in utero repair of an experimental neural tube defect in a fetal lamb could protect neural tissue from secondary injury and save neurologic functions after birth. METHODS: In 19 fetal lambs, a neural tube defect was created at 79 days' gestation. In 12 lambs the defect was covered either with a novel, molecular defined collagen-based biocompatible and biodegradable matrix (UMC) or with a small intestinal submucosa (SIS) biomatrix (Cook) or by closing the skin over the defect. RESULTS: All lambs with the defect covered showed no or minor neurologic morbidity in contrast to the lambs with the defect uncovered in which major neurologic morbidity was seen. CONCLUSIONS: These results demonstrate that long-term exposure of the open spinal cord to the intrauterine environment can lead to damage of neural tissue and, consequently loss of neurologic functions and that coverage of the defect can lead to a better neurologic outcome. Furthermore, we could show that a UMC biomatrix and an SIS biomatrix are useful for in utero coverage of a surgically created neural tube defect in our model.

Animals↗