Biomedical subjects

Stefan Neuenschwander

Publications and source records attributed to Stefan Neuenschwander.

9 recordsLinked to original sources

PubMed2006

Living autologous heart valves engineered from human prenatally harvested progenitors.

BACKGROUND: Heart valve tissue engineering is a promising strategy to overcome the lack of autologous growing replacements, particularly for the repair of congenital malformations. Here, we present a novel concept using human prenatal progenitor cells as new and exclusive cell source to generate autologous implants ready for use at birth. METHODS AND RESULTS: Human fetal mesenchymal progenitors were isolated from routinely sampled prenatal chorionic villus specimens and expanded in vitro. A portion was cryopreserved. After phenotyping and genotyping, cells were seeded onto synthetic biodegradable leaflet scaffolds (n=12) and conditioned in a bioreactor. After 21 days, leaflets were endothelialized with umbilical cord blood-derived endothelial progenitor cells and conditioned for additional 7 days. Resulting tissues were analyzed by histology, immunohistochemistry, biochemistry (amounts of extracellular matrix, DNA), mechanical testing, and scanning electron microscopy (SEM) and were compared with native neonatal heart valve leaflets. Fresh and cryopreserved cells showed comparable myofibroblast-like phenotypes. Genotyping confirmed their fetal origin. Neo-tissues exhibited organization, cell phenotypes, extracellular matrix production, and DNA content comparable to their native counterparts. Leaflet surfaces were covered with functional endothelia. SEM showed cellular distribution throughout the polymer and smooth surfaces. Mechanical profiles approximated those of native heart valves. CONCLUSIONS: Prenatal fetal progenitors obtained from routine chorionic villus sampling were successfully used as an exclusive, new cell source for the engineering of living heart valve leaflets. This concept may enable autologous replacements with growth potential ready for use at birth. Combined with the use of cell banking technology, this approach may be applied also for postnatal applications.

Absorbable Implants↗

PubMed2006

Functional growth in tissue-engineered living, vascular grafts: follow-up at 100 weeks in a large animal model.

BACKGROUND: Living autologous vascular grafts with the capacity for regeneration and growth may overcome the limitations of contemporary artificial prostheses. Particularly in congenital cardiovascular surgery, there is an unmet medical need for growing replacement materials. Here we investigate growth capacity of tissue-engineered living pulmonary arteries in a growing lamb model. METHODS AND RESULTS: Vascular grafts fabricated from biodegradable scaffolds (ID 18+/-l mm) were sequentially seeded with vascular cells. The seeded constructs were grown in vitro for 21 days using biomimetic conditions. Thereafter, these tissue-engineered vascular grafts (TEVGs) were surgically implanted as main pulmonary artery replacements in 14 lambs using cardiopulmonary bypass and followed up for < or = 100 weeks. The animals more than doubled their body weight during the 2-year period. The TEVG showed good functional performance demonstrated by regular echocardiography at 20, 50, 80, and 100 weeks and computed tomography-angiography. In particular, there was no evidence of thrombus, calcification, stenosis, suture dehiscence, or aneurysm. There was a significant increase in diameter by 30% and length by 45%. Histology showed tissue formation reminiscent of native artery. Biochemical analysis revealed cellularity and proteoglycans and increased collagen contents in all of the groups, analogous to those of native vessels. The mechanical profiles of the TEVG showed stronger but less elastic tissue properties than native pulmonary arteries. CONCLUSIONS: This study provides evidence of growth in living, functional pulmonary arteries engineered from vascular cells in a full growth animal model.

Absorbable Implants↗

PubMed2005

Fibrin as a cell carrier in cardiovascular tissue engineering applications.

In cardiovascular tissue engineering approaches, efficient seeding methods are essential. To achieve this and to save time, cells can be encapsulated in gels. Combining the advantages of a gel as a cell carrier with the advantages of a fiber-based scaffold, providing structural integrity to the developing tissue, might offer several advantages. In this study, seeding by using fibrin as a cell carrier is compared to the conventional static seeding method with regard to tissue development. Seeding with fibrin resulted in less loss of soluble collagen into the medium and a more mature extracellular matrix in a shorter period of time. The use of fibrin degradation inhibitors was shown to inhibit extracellular matrix formation, although it did not hamper cell proliferation. The use of fibrin as a cell carrier to seed cells into a fiber-based scaffold may represent a promising, timesaving approach in cardiovascular tissue engineering applications.

Biocompatible Materials↗

PubMed2005

Living patches engineered from human umbilical cord derived fibroblasts and endothelial progenitor cells.

OBJECTIVE: A major shortcoming in contemporary congenital heart surgery is the lack of viable replacement materials with the capacity of growth and regeneration. Here we focused on living autologous patches engineered from human umbilical cord derived fibroblasts and endothelial progenitor cells (EPCs) as a ready-to-use cell source for paediatric cardiovascular tissue engineering. METHODS: EPCs were isolated from 20 ml fresh umbilical cord blood by density gradient centrifugation and myofibroblasts were harvested from umbilical cord tissue. Cells were differentiated and expanded in vitro using nutrient media containing growth factors. Before seeding, cell-phenotypes were assessed by immuno-histochemistry. Biodegradable patches fabricated from synthetic polymers (PGA/P4HB) were seeded with myofibroblasts followed by endothelialization with EPCs. All patches were cultured in a perfusion bioreactor. A subgroup of patches was additionally stimulated by cyclic strain. Analysis of the neo-tissues comprised histology, immuno-histochemistry, extracellular matrix (ECM) analysis and biomechanical testing. RESULTS: Endothelial phenotypes of EPCs before seeding were confirmed by Ac-Dil-LDL, CD 31, von-Willebrand-Factor and eNOS staining. Histology of the seeded patches demonstrated layered viable tissue formation in all samples. The cells in the newly formed tissues expressed myofibroblast markers, such as desmin and alpha-SMA. The EPCs derived neo-endothelia showed constant endothelial phenotypes (CD 31, vWF). major constituents of ECM such as collagen and proteoglycans were biochemically detected. Stress-strain properties of the patches showed features of native-analogous tissues. CONCLUSIONS: Living tissue engineered patches can be successfully generated from human umbilical cord derived myofibroblasts and EPCs. This new cell source may enable the tissue engineering of versatile, living, autologous replacement materials for congenital cardiac interventions.

Biocompatible Materials↗

PubMed2004

Intragenic deletion in the gene encoding L-gulonolactone oxidase causes vitamin C deficiency in pigs.

The absence of L-ascorbic acid (L-AA, or AA) synthesis in scurvy-prone organisms, including humans, other primates, guinea pigs, and flying mammals, was traced to the lack of L-gulonolactone oxidase (GULO) activity. GULO is a microsomal enzyme that catalyzes the terminal step in the biosynthesis of L-AA. Clinical cases of scurvy were described in a family of Danish pigs. This trait is controlled by a single autosomal recessive allele designated od (osteogenic disorder). Here we demonstrate that the absence of GULO activity and the associated vitamin C deficiency in od/od pigs is due to the occurrence of a 4.2-kbp deletion in the GULO gene. This deletion includes 77 bp of exon VIII, 398 bp of intron 7 and 3.7 kbp of intron 8, which leads to a frame shift. The mutant protein is truncated to 356 amino acids, but only the first 236 amino acids are identical to the wild-type GULO protein. In addition, the od allele seems to be less expressed in deficient and heterozygous pigs compared with the normal allele in heterozygous and wild-type animals as determined by ribonuclease protection assay. We also developed a DNA-based test for the diagnosis of the deficient allele. However, we failed to identify the mutated allele in other pig populations.

Animals↗

PubMed2004

Arthrogryposis multiplex congenita (AMC), a hereditary disease in swine, maps to chromosome 5 by linkage analysis.

Arthrogryposis multiplex congenita (AMC), defined as permanent joint contractures present at birth, is one of the most common congenital defects in piglets and other mammals. A genetic form of arthrogryposis was recently identified in Swiss Large White (LW) pigs. The disease is controlled by a single autosomal recessive allele designated as amc. At least 14 LW AI (artificial insemination) boars (about 25% of the Swiss population) are known to be carriers of the amc allele. A total of 219 pigs were used for linkage analysis, including seven founders (F1), three F0, 160 F2, and 49 F3 animals. All founder pigs were full or half sibs. Of the 219 pigs, 41 (18.7%) were found to be affected, while the remaining 178 (81.3%) were healthy. A comprehensive genome scan revealed that microsatellite SW1987 located on pig (Sus scrofa) Chromosome 5 (SSC5), was linked with AMC. Sixteen additional SSC5 microsatellites were selected for further genotyping to generate a multipoint map covering the AMC region. Significant pairwise linkage (LOD > 6.00) was found for AMC and eight marker loci. The order that best fit with the data was SW963-SW1987-SW152-AMC-(SW904, SW1094)-SWR1526-(SWR1974, SW310). AMC was mapped by linkage analysis to the position 92 cM, between SW152 and SW904/SW1094, which are located on SSC5 in bands q12-q23.

Animals↗

PubMed2004

Umbilical cord blood derived endothelial progenitor cells for tissue engineering of vascular grafts.

BACKGROUND: A substantial limitation regarding present pediatric cardiac surgery is the lack of appropriate materials for the repair of congenital defects. To address this shortcoming, tissue engineering is a scientific field that aims at in vitro fabrication of living autologous grafts with the capacity of growth, repair, and regeneration. Here we focused on tissue engineered vascular grafts using human umbilical cord blood derived endothelial progenitor cells (EPCs), as a noninvasive cell source for pediatric applications. METHODS: EPCs were isolated from 20 ml fresh human umbilical cord blood by Ficoll gradient centrifugation and cultured in endothelial basal medium containing growth factors. After proliferation and differentiation cells were analyzed by immunohistochemistry and seeded onto three-dimensional (3D) biodegradable vascular scaffolds (porosity > 95%, n = 22). Twenty-four hours after seeding the vascular grafts were positioned into a pulse-duplicator-in vitro system and grown for 48 hours under biomimetic conditions. A second group was grown 6 days statically and an additional 6 days biomimetically. Controls were cultured statically. Analysis of the grafts included immunohistochemistry, histology, and scanning electron microscopy. RESULTS: Preseeding differentiated EPCs indicated constant endothelial phenotypes including acetylated low-density lipoprotein, cluster of differentiation 31, von Willebrand factor, and endothelial nitric oxide synthetase. Seeded EPCs established favorable cell-to-polymer attachment and proliferation into the 3D tubular scaffolds. Both conditioned and static cellular constructs demonstrated positive staining for cluster of differentiation 31, von Willebrand factor, and expression of endothelial nitric oxide synthase. CONCLUSIONS: Human umbilical cord derived EPCs indicated exceptional growth characteristics used for tissue engineering of vascular grafts. These cells demonstrated a constant endothelial phenotype and related functional features. Based on these results EPCs seem to be a promising autologous cell source with regard to cardiovascular tissue engineering, particularly for the repair of congenital defects.

Absorbable Implants↗

PubMed2004

Heart valve tissue engineering.

Valvular heart disease is a significant cause of morbidity and mortality world-wide. Classical replacement surgery involves the implantation of mechanical valves or biological valves (xeno- or homografts). Tissue engineering of heart valves represents a new experimental concept to improve current modes of therapy in valvular heart surgery. Various approaches have been developed differing either in the choice of scaffold (synthetic biodegradable polymers, decellularised xeno- or homografts) or cell source for the production of living tissue (vascular derived cells, bone marrow cells or progenitor cells from the peripheral blood). The use of autologous bone marrow cells in combination with synthetic biodegradable scaffolds bears advantages over other tissue engineering approaches: it is safe, it leads to complete autologous prostheses and the cells are more easily obtained in the clinical routine. Even though we demonstrated the feasibility to construct living functional tissue engineered heart valves from human bone marrow cells, so far their general potential to differentiate into non-hematopoietic cell lineages is not fully exploited for tissue engineering applications.

Absorbable Implants↗

PubMed2003

The GENETPIG database: a tool for comparative mapping in pig (Sus scrofa).

The GENETPIG database has been established for storing and disseminating the results of the European project: 'GENETPIG: identification of genes controlling economic traits in pig'. The partners of this project have mapped about 630 porcine and human ESTs onto the pig genome. The database collects the mapping results and links them to other sources of mapping data; this includes pig maps as well as available comparative mapping information. Functional annotation of the mapped ESTs is also given when a significant similarity to cognate genes was established. The database is accessible for consultation via the Internet at http://www.infobiogen.fr/services/Genetpig/.

Animals↗