Effect of mechanical loading on mRNA levels of common endogenous controls in articular chondrocytes and intervertebral disk.
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Animals↗
Biomedical subjects
Sibylle Grad
Publications and source records attributed to Sibylle Grad.
Vascular endothelial growth factor serum level is strongly enhanced after burn injury and correlated with local and general tissue edema.
BACKGROUND: Burn associated local and general tissue edema is induced by local cell destruction and capillary leak syndrome. Vascular endothelial growth factor (VEGF) strongly enhances vascular permeability as well as angiogenesis. The principal aim of this study was to investigate the systemic release of VEGF and its kinetics after severe burn injury in humans. METHODS: Thirty-six burn patients and 42 healthy volunteers were enrolled in this study. Circulating VEGF serum levels were measured by enzyme-linked immunosorbent assay at days 1, 3, 7, 14, 21, 28 and 35. Burn surface, tissue edema, complications and outcome were evaluated. RESULTS: VEGF serum levels were significantly increased after burn injuries immediately after injury until wound closure. VEGF levels reached their maximum at day 14 and were 22-fold increased compared to VEGF levels of healthy controls. After wound closure VEGF levels normalized. Local and general tissue edema disappeared after VEGF serum level normalization. CONCLUSIONS: VEGF serum levels are immediately enhanced after burn trauma until wound closure. At the same time, a local and general tissue edema was detected. We may speculate, that specific blockers of VEGF may have beneficial effects on edema and edema-related complications in severe burn patients.
Adolescent↗
Chondrocytes seeded onto poly (L/DL-lactide) 80%/20% porous scaffolds: a biochemical evaluation.
Repair of articular cartilage remains a clinical and scientific challenge. The use of implantable chondrocyte-seeded constructs offers a promising treatment option. The present study is focused on the culture of chondrocytes onto 3-D poly (L-/DL-lactide) 80%/20% porous scaffolds. Scaffolds were seeded with bovine articular chondrocytes and cultured for up to 42 days. After an initial decrease, although not significant, the DNA content of the constructs remained constant over the culture time. A progressive increase in glycosaminoglycans and collagen was observed in the constructs during the culture period. However, a significant release of matrix molecules into the culture medium also was noticeable. On the transcriptional level, aggrecan mRNA expression was highest on day 14 and gradually decreased thereafter. Procollagen I mRNA expression constantly increased whereas procollagen II mRNA expression decreased after day 14, indicating that cells were dedifferentiating. Histologic analysis of the constructs demonstrated the deposition of a proteoglycan-rich extracellular matrix by day 42 of culture. The present data demonstrate that poly (L-/DL-lactide) 80%/20% porous scaffolds support the development of a cartilage-like extracellular matrix. The limitations of the system are the diffusion of large amounts of matrix molecules into the culture medium and the dedifferentiation of the chondrocytes with prolonged time in culture.
Animals↗
Effects of immobilization and dynamic compression on intervertebral disc cell gene expression in vivo.
STUDY DESIGN: An in vivo analysis of the intervertebral disc's cellular response to dynamic compression and immobilization was performed using a rat-tail model. OBJECTIVE: To assess the effects of immobilization and short-term dynamic compression on intervertebral disc cell expression of anabolic and catabolic genes. SUMMARY OF BACKGROUND DATA: Static compressive loads applied in vivo alter the composition of the disc matrix and cell viability in a dose-dependent manner. The effects of in vivo dynamic compression, which is a more physiologic load, and reported risk factor for low back pain have not been investigated. METHODS: An Ilizarov-type device was implanted on the rat tail and used to determine the effects from 72 hours of immobilization (n = 6), 2 hours of dynamic compression (1 MPa/0.2 Hz) (n = 8), and the coupled effect of immobilization followed by compression (n = 8). Real-time reverse transcription-polymerase chain reaction was used to measure changes in anabolic and catabolic gene levels relative to both internal control subjects and a sham-operated group (n = 7). RESULTS: Immobilization and dynamic compression affect anabolic and catabolic genes, with an overall downregulation of types 1 and 2 collagen and upregulation of aggrecanase, collagenase, and stromelysin in the anulus. The effects of immobilization and compression appear to be additive for collagen types 1 and 2 in the anulus, but not in the nucleus, and not for catabolic genes. CONCLUSIONS: Short-duration dynamic compression and immobilization alter gene expression in the rat disc. In studying the response of the disc to loading, it is necessary to look at both anabolic and catabolic pathways, and to consider strain history.
Aggrecans↗
The use of biodegradable polyurethane scaffolds for cartilage tissue engineering: potential and limitations.
The aim of the present study was to evaluate the capability of novel biodegradable polyurethane scaffolds to support attachment, growth and maintenance of differentiated chondrocytes in vitro for up to 42 days. After an initial decrease, although not significant, the DNA content of the constructs remained constant over the culture time. A progressive increase in glycosaminoglycans and collagen was observed during the culture period. However, a significant release of matrix molecules into the culture medium was also noticeable. At the transcriptional level, a decrease in aggrecan and procollagen II mRNA expression was noticeable, whereas procollagen I expression was increased. To conclude, the present data demonstrate that biodegradable polyurethane porous scaffolds seeded with articular chondrocytes support cell attachment and the production of extracellular matrix proteins. The limitations of the system are the diffusion of large amounts of matrix molecules into the culture medium and the dedifferentiation of the chondrocytes with prolonged time in culture. However, due to the favourable mechanical properties of the polyurethane scaffold, stimulation of chondrocytes by mechanical loading can be considered in order to improve the formation of a functional cartilage-like extracellular matrix.
Absorbable Implants↗
Tribology approach to the engineering and study of articular cartilage.
This study has been based on the assumption that articular motion is an important aspect of mechanotransduction in synovial joints. For this reason a new bioreactor concept, able to reproduce joint kinematics more closely, has been designed. The prototype consists of a rotating scaffold and/or cartilage pin, which is pressed onto an orthogonally rotating ball. By oscillating pin and ball in phase difference, elliptical displacement trajectories are generated that are similar to the motion paths occurring in vivo. Simultaneously, dynamic compression may be applied with a linear actuator, while two-step-motors generate the rotation of pin and ball. The whole apparatus is placed in an incubator. The control station is located outside. Preliminary investigations at the gene expression level demonstrated promising results. Compared with free-swelling control and/or simply compression-loaded samples, chondrocyte-seeded scaffolds as well as nasal cartilage explants exposed to interface motion both showed elevated levels of cartilage oligomeric matrix protein mRNA. The final design of the bioreactor will include four individual stations in line, which will facilitate the investigation of motion-initiated effects at the contacting surfaces in more detail.
Animals↗
Fibrin-polyurethane composites for articular cartilage tissue engineering: a preliminary analysis.
In this study we investigated the use of a fibrin hydrogel to improve the potential of a polyurethane (PU) scaffold-based system for articular cartilage tissue engineering. PU-only ("no-fibrin") and PU-fibrin ("fibrin") composites were cultured for up to 28 days and analyzed for DNA content, glycosaminoglycan (GAG) content, type II collagen content, GAG release, and gene expression of aggrecan, collagen I, and collagen II. The use of fibrin allowed for higher viable cell-seeding efficiency (10% higher DNA content on day 2 in fibrin versus no-fibrin composites) and more even cell distribution on seeding, a more than 3-fold increase in the percentage of newly synthesized GAG retained in the constructs, and 2- to 6-fold higher levels of type II collagen and aggrecan gene expression through day 14. Addition of aprotinin to the medium inhibited fibrin degradation, most noticeably in the center of the constructs, but had little effect on biochemical composition or gene expression. Short-term mechanical compression (0-10% sinusoidal strain at 0.1 Hz for 1 h, applied twice daily for 3 days) doubled the rate of GAG release from the constructs, but had little effect on gene expression, regardless of the presence of fibrin. Although further work is needed to optimize this system, the addition of fibrin hydrogel to encapsulate cells in the stiff, macroporous PU scaffold is a step forward in our approach to articular cartilage tissue engineering.
Aggrecans↗
Surface motion upregulates superficial zone protein and hyaluronan production in chondrocyte-seeded three-dimensional scaffolds.
A cartilage engineering bioreactor has been developed that provides joint-specific kinematics. This study investigated the effect of articular motion on the gene expression of superficial zone protein (SZP) and hyaluronan synthases (HASs) and on the release of SZP and hyaluronan of chondrocytes seeded onto biodegradable scaffolds. Cylindrical (8 x 4 mm) porous polyurethane scaffolds were seeded with bovine articular chondrocytes and subjected to static or dynamic compression, with and without articulation against a ceramic hip ball. After loading, the mRNA expression of SZP and HASs was analyzed, and SZP immunoreactivity and hyaluronan concentration of conditioned media were determined. Surface motion significantly upregulated the mRNA expression of SZP and HASs. Axial compression alone had no effect on SZP and increased HAS mRNA only at high strain amplitude. SZP was immunodetected only in the media of constructs exposed to surface motion. The release of hyaluronan into the culture medium was significantly enhanced by surface motion. These results indicate that specific stimuli that mimic the kinematics of natural joints, such as articular motion, may promote the development of a functional articular surface-synovial interface.
Animals↗
Chondrocyte gene expression under applied surface motion.
A cartilage bioreactor has been designed that is intended to approximate the kinematics of natural joints and allows for functional cartilage tissue engineering studies. In particular, interface motion can be generated by oscillation of a ball over the surface of a construct. The present study investigated the specific effect of applied articular motion on the gene expression of chondrocytes cultured in 3D scaffolds, with a particular emphasis on different superficial zone protein (SZP)/lubricin transcripts. Cylindrical porous polyurethane scaffolds were seeded with bovine articular chondrocytes and subjected to dynamic compression, with or without articulation against a ceramic hip ball. Articular motion markedly up-regulated the mRNA expression of the four previously described and two newly identified SZP/lubricin isoforms and of cartilage oligomeric matrix protein (COMP), and, to a lesser extent, aggrecan, type II collagen and TIMPs, while axial compression alone had no effect on the chondrocytes' gene expression levels. These results demonstrate the beneficial effect of articular motion not only for stimulation of important lubricating molecules, but also for the preservation of the chondrocytic phenotype.
Animals↗