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PubMed2005

In vitro cartilage tissue engineering with 3D porous aqueous-derived silk scaffolds and mesenchymal stem cells.

Adult cartilage tissue has limited self-repair capacity, especially in the case of severe damages caused by developmental abnormalities, trauma, or aging-related degeneration like osteoarthritis. Adult mesenchymal stem cells (MSCs) have the potential to differentiate into cells of different lineages including bone, cartilage, and fat. In vitro cartilage tissue engineering using autologous MSCs and three-dimensional (3-D) porous scaffolds has the potential for the successful repair of severe cartilage damage. Ideally, scaffolds designed for cartilage tissue engineering should have optimal structural and mechanical properties, excellent biocompatibility, controlled degradation rate, and good handling characteristics. In the present work, a novel, highly porous silk scaffold was developed by an aqueous process according to these criteria and subsequently combined with MSCs for in vitro cartilage tissue engineering. Chondrogenesis of MSCs in the silk scaffold was evident by real-time RT-PCR analysis for cartilage-specific ECM gene markers, histological and immunohistochemical evaluations of cartilage-specific ECM components. Dexamethasone and TGF-beta3 were essential for the survival, proliferation and chondrogenesis of MSCs in the silk scaffolds. The attachment, proliferation, and differentiation of MSCs in the silk scaffold showed unique characteristics. After 3 weeks of cultivation, the spatial cell arrangement and the collagen type-II distribution in the MSCs-silk scaffold constructs resembles those in native articular cartilage tissue, suggesting promise for these novel 3-D degradable silk-based scaffolds in MSC-based cartilage repair. Further in vivo evaluation is necessary to fully recognize the clinical relevance of these observations.

Adult↗
PubMed2005

Repair of cartilage defects with periosteal grafts.

Alternative sources for repair of cartilage defects are limited and donor sites are associated with morbidity. It is known that cartilage development from periosteal grafts is possible. Various factors have been found positively to affect this process in experimental settings. However, all of these studies were limited to joint cartilage. We conducted an experimental study in rabbits for the investigation of the elastic cartilage regeneration from perichondrial and periosteal grafts together with the effects of hyaluronan on this process. 1 x 1 cm(2) cartilage defects were created on the elastic ear cartilage of rabbits. Four experimental groups with 18 ears in each group were created: Group 1 (repair with perichondrium graft), group 2 (repair with periosteum graft), group 3 (repair with periosteum graft+hyaluronan), group 4 (defect-only control group). Macroscopic and microscopic evaluations were done on the 4th, 8th and 12th weeks. Cellular morphology of the regenerated cartilage and its integration and similarity with adjacent cartilage were evaluated. Cartilage regeneration groups 1, 2 and 3 were found to be statistically different from the control group. There was not a significant difference between groups 1 and 2 or 2 and 3. There is no significant difference between perichondrial and periosteal grafts in cartilage regeneration, and hyaluronan has no beneficial effect on this process.

Adjuvants, Immunologic↗
PubMed2003

Propagation of surface fissures in articular cartilage in response to cyclic loading in vitro.

BACKGROUND: Mechanical overloading of synovial joints can damage the articular cartilage surface and may lead to osteoarthritis. However, causal links between mechanical and biological events in cartilage are poorly understood. OBJECTIVES: To test the hypothesis that surface fissures in cartilage can propagate mechanically if the joint surface is subjected to vigorous cyclic loading. METHODS: Thirty-five cartilage-on-bone specimens, 15-mm square, were removed from mature bovine knee and shoulder joints. Specimens were loaded by means of a 9-mm-diameter flat indenter with a beveled edge, and their compressive strength determined. Failure occurred in the cartilage surface at an average stress of 36 MPa. Cartilage fissures were marked with Indian ink, photographed, and their length and width measured using image analysis software. Each damaged specimen was subjected to cyclic loading at 40% of its compressive strength, at 0.5 Hz, for up to 5 h. Fissure length and width were measured at regular intervals. After testing, fissure depth was measured from histological sections, and compared with measurements from damaged cartilage which was not cyclically loaded. RESULTS: Cyclic loading caused cartilage fissures to increase in length (mean 353%, P<0.01) and width (360%, P<0.01) but not depth. Propagation was rapid at first, but approached equilibrium after several hundred cycles. Rehydration in saline had no effect on fissure length, but width returned to pre-cyclic loading values. CONCLUSION: Cartilage fissures can propagate mechanically when a joint surface is subjected to cyclic compressive loading in vitro. The transient opening-up of fissures to form wide surface "wounds" during cyclic loading could be of biological significance if it occurred in living people. RELEVANCE: In living joints, wide open fissures in the cartilage surface could promote degenerative changes in the tissue.

Animals↗
PubMed2006

Age and gender related changes in biomechanical properties of healthy human costal cartilage.

BACKGROUND AND AIMS: For repairing the ear malformation, it is recommended in China to use the over than 10-years-old rib cartilage. However, according to our clinical experience, a better post-operation effect can be found using about the 7-years-old cartilage for the operation. To shape a harvested costal cartilage and to perform it on the transplant site depend on the mechanical properties of the costal cartilage. Hence, the aim of this study is to investigate the age and gender-related biomechanical properties of the human costal cartilage. METHODS: Human costal cartilages were harvested from 25 female and 45 male donors of 5-25 years old after auricular reconstructive surgery. The specimens were divided into six groups: children (5-10 years), adolescent (11-17 years) and adult (18-25 years), respectively, in males and females. Tensile strength, stress-strain relationship, stress relaxation and creep were tested by using a material testing machine. FINDINGS: The biomechanical properties of costal cartilage are donor age and gender related. The children group has the highest tensile strengths (P<0.01) in both male and female groups. The male group relaxed and crept more than that of the female group in all three age groups (P<0.01). INTERPRETATION: These findings provide a further support for the potential age acting on the human costal cartilage. The adolescent has the lowest strength, this could be a reason that compared to using the children costal cartilage, the bigger distortion happened after using the adolescent costal cartilage in the auricular reconstruction operation.

Adolescent↗
PubMed2005

Cultivation of three-dimensional cartilage-carrier-constructs under reduced oxygen tension.

Three-dimensional cartilage-carrier-constructs were produced according to a standard protocol from chondrocytes of an adult mini-pig. Experiments with different oxygen concentrations (21, 10 and 5%, v/v O(2)) were performed and the constructs were compared qualitatively and quantitatively. The appearance of the cartilage obtained under reduced oxygen tension seemed to be closer to native cartilage with respect to shape of the cells, distribution of the cells within the matrix, smoothness of the surface, etc. The thickness of the cartilage formed by free swelling was always in the same range as for native cartilage (approximately 1mm). Qualitatively the most stable attachment of the cartilage on top of the carrier was found for 10% O(2) (v/v). Especially at 5% O(2) (v/v) the attachment between cartilage and carrier was not sufficient. The constructs generated at lower oxygen tensions had a significantly higher amount of glycosaminoglycan per DNA, but still significantly less when compared to native cartilage. Furthermore, the cultivated cartilage contained a large amount of collagen type II. The experiments proved the applied concept for generation of cartilage-carrier-constructs and the usefulness of cultivation under reduced oxygen tension.

Animals↗
PubMed2004

Effects of long-term estrogen replacement therapy on articular cartilage IGFBP-2, IGFBP-3, collagen and proteoglycan levels in ovariectomized cynomolgus monkeys.

OBJECTIVE: The purpose of this study was to determine the effects of long-term estrogen replacement therapy (ERT) on insulin-like growth factor binding protein (IGFBP)-2, IGFBP-3, collagen and proteoglycan levels in the articular cartilage of the knee joint in a well-characterized monkey model of naturally occurring osteoarthritis (OA). A secondary aim was to evaluate the effect of soy phytoestrogen treatment on these articular cartilage components. DESIGN: Monkeys were ovariectomized and given ERT, soy phytoestrogen treatment or no treatment (control) for 3 years. Ten animals were randomly selected from each of the three groups and the cartilage was dissected from the proximal tibia and distal femur of the knee. Levels of IGFBP-2, IGFBP-3, and total protein were measured in cartilage desorptions, and proteoglycan levels and collagen levels were measured in the cartilage tissue. Sections from the tibial plateau of the opposite knee were immunostained using antibodies directed against IGFBPs and evaluated subjectively. RESULTS: IGFBP-3 levels were significantly higher, and total protein levels were significantly lower in the cartilage desorption samples from the estrogen-treated animals compared to the control animals. There were no significant differences in IGFBP-2, collagen or proteoglycan levels between the estrogen-treated and control groups. Soy phytoestrogen treatment had no significant effect on the levels of any of the cartilage components that were measured. The staining patterns observed by immunohistochemistry suggested local production of IGFBP-2 and IGFBP-3 by articular cartilage chondrocytes. CONCLUSIONS: Long-term estrogen treatment results in increased IGFBP-3 levels in articular cartilage without a significant change in IGFBP-2, collagen or proteoglycan content, and IGFBP-3 appears to be synthesized by articular cartilage chondrocytes. Long-term soy phytoestrogen treatment did not have a statistically significant effect on the levels of IGFBP-2, IGFBP-3, collagen or proteoglycan.

Animals↗
PubMed2004

Detection of aggrecanase- and MMP-generated catabolic neoepitopes in the rat iodoacetate model of cartilage degeneration.

OBJECTIVE: To characterize the time course of aggrecan and type II collagen degradation in the rat iodoacetate model of cartilage degeneration in relationship to the temporal sequence that has been described in human osteoarthritis (OA). DESIGN: Rats were injected intra-articularly in one knee joint with iodoacetate and damage to the tibial plateau was assessed from digitized images captured using an image analyzer. The articular cartilage from the tibial plateau was harvested, extracted and glycosaminoglycan (GAG) content was measured using the dimethylmethylene blue (DMMB) assay. Cartilage aggrecan neoepitopes were detected in cartilage extracts by Western blotting using antibodies recognizing the aggrecanase-generated C-terminal neoepitope NITEGE (BC-13) and the MMP-generated C-terminal neoepitope DIPEN (BC-4). A type II collagen collagenase-generated neoepitope was detected in cartilage extracts by ELISA using the Col2-3/4Cshort antibody; denatured collagen was detected using the Col2-3/4m antibody. RESULTS: Degenerative joint changes and proteoglycan (GAG) loss progressed with time after iodoacetate injection. Western blotting of cartilage extracts of iodoacetate treated rats demonstrated an increase in both aggrecanase- and MMP-generated epitopes with the NITEGE aggrecanase neoepitope being significantly elevated on days 7, 14 and 21 while DIPEN the MMP neoepitope was significantly elevated on days 7 and 14. The type II collagen neoepitope recognized by Col2-3/4Cshort was significantly increased in cartilage extracts of rats at days 14 and 21 after iodoacetate injection. CONCLUSION: The proteoglycan fragments extracted from the knee cartilage of rats after the intra-articular injection of iodoacetate appeared to result from cleavage at both aggrecanase and MMP sites. Cleavage of type II collagen by collagenase was also detected after iodoacetate injection and occurred subsequent to the initiation of aggrecan loss. These observations serve to demonstrate similarities in the mechanisms of cartilage degeneration induced by iodoacetate to those seen in articular cartilage in OA.

Aggrecans↗
PubMed2004

A pilot, two-year longitudinal study of the interrelationship between trabecular bone and articular cartilage in the osteoarthritic knee.

OBJECTIVE: To examine the relationship between structural changes of trabecular bone and cartilage, in patients with varying degrees of osteoarthritis (OA) over 2 years, using magnetic resonance imaging. METHODS: High-resolution, axial images were acquired for assessing trabecular bone structure, using a 3-D fast gradient-echo sequence. High-resolution, fat-suppressed, sagittal images were acquired for assessing cartilage structure, using a 3-D spoiled gradient-echo sequence. In a subset of the patients, sagittal images were acquired for measuring T(2) relaxation time, using a 2-D dual-echo spin echo sequence. RESULTS: A large variation in bone and cartilage parameters is evident among individual subjects in each group, however, group-specific means demonstrate decreasing trends (in bone and cartilage parameters) in osteoarthritic subjects (especially in mild OA subjects). The mean T(2) increased significantly (P<0.05) between the baseline and follow-up exams for all cartilage compartments except the lateral tibia. A positive relationship was established between cartilage changes and localized bone changes closest to the joint line, while a negative relationship was established between cartilage changes and global bone changes farthest from the joint line. CONCLUSION: This study quantifies the changes in bone and cartilage structural parameters over time, and demonstrates a longitudinal relationship between the morphological changes in bone and cartilage structure in patients with varying degrees of OA. Although a large variation of bone and cartilage changes is apparent among subjects, significant trends are evident in a relatively small sample size, with a short follow-up duration.

Adult↗
PubMed2005

Considerations in measuring cartilage thickness using MRI: factors influencing reproducibility and accuracy.

OBJECTIVE: The primary goal of this study was to describe and evaluate conditions that could influence the precision and accuracy of measuring in vivo cartilage thickness in the weight bearing regions of the knee from magnetic resonance imaging (MRI). DESIGN: Three-dimensional (3D) models of the femoral cartilage were created from segmented MR images. The weight bearing regions on femoral cartilage were selected for the portion of the tibiofemoral joint that sustains contact during walking. Six regions of interest (three on each condyle) were located on the femur. Average cartilage thickness was calculated over each region. The sensitivity of the precision of the measurements to observer variability was evaluated using intra- and inter-observer reproducibility tests of cartilage thickness measurements from the MRI-derived 3D models. In addition, the quantitative influence of a rule-based protocol for segmentation was evaluated using the inter-observer reproducibility protocol. Accuracy tests were conducted on porcine knees by comparing 3D models from MR images and laser scans across weight bearing and non-weight bearing regions. RESULTS: The precision was substantially better for the intra-observer tests (Coefficient of variation (CV) = 1-3%) than the inter-observer tests. Adding a rule-based protocol reduced variability in inter-observer tests substantially (CV = 6.6% vs 8.3%). Accuracy tests showed that the central and weight bearing regions on each condyle were more accurate than boundary and non-weight bearing regions. In addition, these results indicate that care should be taken when determining cartilage thickness of weight bearing regions with cartilage degenerations, since the thickness of thinner cartilage can be systematically overestimated in MR images. CONCLUSIONS: A rule-based approach can substantially increase inter-observer reproducibility when measuring cartilage thickness from multiple observers. This improvement in inter-observer reproducibility could be an important consideration for longitudinal studies of disease progression. In quantifying cartilage thickness, central and weight bearing regions on each condyle can provide more accurate measurement than boundary and non-weight bearing regions with average accuracy of +/-0.2-0.3 mm. An important finding of this study was that the weight bearing regions, which are usually of the greatest clinical interest, were measured most accurately by sagittal plane imaging.

Cartilage, Articular↗
PubMed2006

Is cartilage thickness different in young subjects with and without patellofemoral pain?

OBJECTIVE: To determine the differences in load-bearing patellofemoral joint cartilage thickness between genders. To determine the differences in load-bearing cartilage thickness between pain-free controls and individuals with patellofemoral pain. METHODS: The articular cartilage thickness of the patella and anterior femur was estimated from magnetic resonance images in 16 young, pain-free control subjects (eight males, eight females) and 34 young individuals with patellofemoral pain (12 males, 22 females). The average age of all subjects was 28+/-4 years. The cartilage surfaces were divided into regions approximating the location of patellofemoral joint contact during knee flexion. The mean and peak cartilage thicknesses of each region were computed and compared using a repeated-measures Analysis of Variance. RESULTS: On average, males had 22% and 23% thicker cartilage than females in the patella (P < 0.01) and femur (P < 0.05), respectively. Male control subjects had 18% greater peak patellar cartilage thickness than males with patellofemoral pain (P < 0.05); however, we did not detect differences in patellar cartilage thickness between female control subjects and females with patellofemoral pain (P = 0.45). We detected no significant differences in femoral cartilage thickness between the control and pain groups. CONCLUSIONS: Thin cartilage at the patella may be one mechanism of patellofemoral pain in male subjects, but is unlikely to be a dominant factor in the development of pain in the female population.

Adult↗
PubMed2006

Determination of in-vivo articular cartilage contact areas of human talocrural joint under weightbearing conditions.

OBJECTIVE: The knowledge of in-vivo cartilage contact biomechanics is important to the understanding of the pathogenesis of joint diseases such as osteoarthritis. This study investigated the in-vivo contact areas of human talocrural joint under weightbearing conditions that simulated the stance phase of walking using a combined magnetic resonance (MR) and dual-orthogonal fluoroscopic imaging technique. DESIGN: Nine healthy ankles of living subjects were recruited for this study. The in-vivo talocrural joint positions were recorded using the dual-orthogonal fluoroscopic images at three ankle positions that simulated those occurring during the stance phase of walking: heel strike, mid-stance, and toe off. Three-dimensional (3D) models of the talocrural joints were created from MR images and used to reproduce the in-vivo ankle positions recorded on the fluoroscopic images. The talocrural cartilage contact area was defined as the overlap area of the distal tibial and the proximal talar cartilage surfaces. The method was validated using an in-vitro experimental setup to evaluate its accuracy in determination of cartilage contact area. RESULTS: The validation study demonstrated that the articular cartilage contact area of the talocrural joint determined using the imaging technique was approximately 4% lower than that of the experimental measurement. In the nine living ankles, the average cartilage coverage area was 964.9+/-156.1 mm(2) on the distal tibia and 1304.8+/-208.4 mm(2) on the proximal talus. The average talocrural cartilage contact areas were 272.7+/-61.1 mm(2) at heel strike, 416.8+/-51.7 mm(2) at mid-stance, and 335.7+/-64.5 mm(2) at toe off. The contact area at mid-stance was significantly larger than those at heel strike and toe off, while the contact area at toe off was significantly larger than that at heel strike. CONCLUSION: The combined dual fluoroscopic and MR imaging technique was shown to be capable of determining in-vivo talocrural cartilage contact areas. During the simulated stance phase of walking, the contact areas were less than 44% and 31% of the cartilage coverage areas of the distal tibia and the proximal talus, respectively. These data may be useful for understanding in-vivo biomechanical function of the cartilage as well as the etiology of osteoarthritis.

Adult↗
PubMed2006

Osteoporosis increases the severity of cartilage damage in an experimental model of osteoarthritis in rabbits.

OBJECTIVE: To evaluate the effect of osteoporosis (OP) in cartilage damage developed in an experimental model of osteoarthritis (OA) in mature female rabbits in order to investigate the relationship between OP and OA. METHODS: OA was experimentally induced by anterior cruciate section and partial medial meniscectomy in the left knee of 12 rabbits. OP was experimentally induced prior to OA in six rabbits by bilateral ovariectomy (OVX) and systemic corticosteroid administration during 4 weeks. Knees were evaluated with high resolution magnetic resonance imaging (MRI) before knee surgery to rule out any detrimental effect of corticosteroids on cartilage. Gross and microscopic cartilage changes were assessed 16 weeks after surgery in bilateral knees. Left knees were considered osteoarthritic or osteoarthritic plus osteoporotic. Right knees were used as osteoporotic and healthy controls, respectively. Bone mineral density (BMD) was measured with dual energy X-ray absorptiometry (DXA) at the lumbar spine, global knee and subchondral knee bone, and its variations correlated with cartilage abnormalities. RESULTS: MRI before knee surgery disclosed no cartilage or bone abnormalities in any of the studied groups. OP increased the severity of cartilage abnormalities in experimental knee OA significantly (P<0.05). Cartilage damage was inversely correlated with BMD variations measured at the lumbar spine (r=-0.74; P=0.015). BMD changes in global and subchondral knee bone also showed a trend to correlate inversely with cartilage damage. CONCLUSIONS: Prior induction of OP increases the severity of cartilage damage in experimental OA. Increase in cartilage damage correlates with bone loss. These findings suggest a direct relationship between OP and OA.

Absorptiometry, Photon↗
PubMed2004

Experimental ischemia of porcine growth cartilage produces lesions of osteochondrosis.

Osteochondrosis is a disorder of growth cartilage in which a focal failure of blood supply has been proposed as an important initiating factor. In the present study we investigated the effect on epiphyseal growth cartilage of experimentally interrupting the blood supply to a limited area of the distal femur of growing pigs. In 12 pigs, a thin full-thickness cartilage slab was removed from the abaxial margin of the medial condyle, thereby transecting a limited number of cartilage canals. The pigs were culled 1, 2, 3, 7, 14, 21 and 29 days post-surgery. The condylar cartilage was studied histologically, immunohistologically and by use of the TUNEL method. The transection induced cellular death of cartilage canal elements followed by cellular death of chondrocytes within the deep layers of the resting zone of the epiphyseal growth cartilage. However, in the superficial layers of the resting zone, chondrocytes appeared to proliferate into and subsequently chondrify some of the necrotic cartilage canals. The dying and dead cells were TUNEL-positive, but active caspase 3-negative. The loss of vascular supply induced increased VEGF-immunostaining in chondrocytes surrounding the affected area. We conclude that transection of cartilage canals produces chondronecrosis in the deep resting zone of the epiphyseal growth cartilage similar to that observed in spontaneously occurring osteochondrosis.

Animals↗
PubMed2004

How do cartilage and other material overlay over a prosthesis affect its vibration transmission properties in ossiculoplasty?

OBJECTIVE: The prosthesis/eardrum interface is often deliberately modified by cartilage overlay, or by soft tissue in-growth. We examined the effects of vibration transmission to the footplate of inserting cartilage of varying sizes, and materials of varying rigidities. STUDY DESIGN AND SETTING: Using fresh human cadaveric temporal bones, stapes vibrations were measured. A partial ossicular reconstruction prosthesis was covered with differing materials and cartilage sizes. Materials used included glass (rigid), cartilage (intermediate), and Merocel (soft). Cartilage sizes varied in size relative to the prosthesis head. RESULTS: Rigidity of material had little impact. Cartilage size had an impact, with smaller cartilage covers performing best. CONCLUSION: Larger cartilage sizes performed worse. This could be a result of increased tension on the eardrum from larger cartilage size. There is little impact stiffness of interposed material stiffness. SIGNIFICANCE: Cartilage of the size used clinically has little impact on vibration transmission to the footplate. A wide range of materials could clinically be interposed over the prosthesis.

Cartilage↗
PubMed2001

Tracheal allotransplantation maintaining cartilage viability with long-term cryopreserved allografts.

BACKGROUND: Cartilage viability of a cryopreserved tracheal allograft seems to affect graft function and durability. We previously reported the influence of warm ischemia and cryopreservation on cartilage viability of tracheal allografts. For the clinical application of tracheal allotransplantation, it is essential to preserve grafts for a long time. In this study, we assessed cartilage viability of tracheal allografts after long-term cryopreservation in transplantation models. METHODS: The tracheas were harvested from Lewis rats. The grafts were frozen to -80 degrees C in a programmable freezer immediately after being harvested and were then stored in liquid nitrogen (-196 degrees C) for different lengths of preservation (1, 2, 6, 9, 12, 18, and 24 months; n for each group = 8). Cartilage viability was evaluated by estimating proteoglycan synthesis. After harvest or thawing of the tracheas, the cartilage was labeled with 4 muCi/mL of Na2 35SO4. Specimens were then hydrolyzed in 0.5 mol/L NaOH, and a solution of the extracts was then counted by a liquid scintillation counter. 35Sulfur incorporation before and after cryopreservation was examined in each group. Tracheal allotransplantation was performed using Lewis rats as donors and Brown Norway rats as recipients. RESULTS: The average 35S incorporation in the cartilage before cryopreservation was 224 +/- 17 disintegrations per minute per milligram of tissue protein. The average 35S incorporation in the cartilage after cryopreservation decreased to 67% to 76% compared with that before cryopreservation. There were no significant differences among the groups in 35S incorporations after cryopreservation. Histologic examination after transplantation revealed normal tracheal cartilage in all groups. CONCLUSIONS: The viability of tracheal cartilage after cryopreservation decreased to 67% to 76%. There were no significant differences in viability of cartilage among the tracheas after different lengths of cryopreservation. Tracheal allotransplantation after long-term cryopreservation can be safely performed in the rat model.

Animals↗
PubMed2001

Estimation of the Young's modulus of articular cartilage using an arthroscopic indentation instrument and ultrasonic measurement of tissue thickness.

We evaluated whether the use of cartilage thickness measurement would improve the ability of the arthroscopic indentation technique to estimate the intrinsic stiffness of articular cartilage. First, cartilage thickness and ultrasound reflection from the surface of bovine humeral head were registered in situ using a high-frequency ultrasound probe. Subsequently, cartilage was indented in situ at the sites of the ultrasound measurements using arthroscopic instruments with plane-ended and spherical-ended indenters. Finally, full-thickness cartilage disks (n=30) were extracted from the indented sites (thickness=799-1654microm) and the equilibrium Young's modulus was determined with a material testing device in unconfined compression geometry. We applied analytical and numerical indentation models for the theoretical correction of experimental indentation measurements. An aspect-ratio (the ratio of indenter radius to cartilage thickness) correction improved the correlation of the indenter force with the equilibrium Young's modulus from r(2)=0.488 to r(2)=0.642-0.648 (n=30) for the plane-ended indenter (diameter=1.000mm, height=0.300mm) and from r(2)=0.654 to r(2)=0.684-0.692 (n=30) for the spherical-ended indenter (diameter=0.500mm, height=0.100mm), depending on the indentation model used for the correction. The linear correlation between the ultrasound reflection and the Young's modulus was r(2)=0.400 (n=30). These results suggest that with large indenters, knowledge of the cartilage thickness improves the reliability of the indentation measurements, especially in pathological situations where cartilage thickness may be significantly lower than normal. Ultrasound measurements also provide diagnostically important information about cartilage thickness as well as knowledge of the integrity of the superficial zone of cartilage.

Animals↗
PubMed1998

Ultrastructure and tensile properties of human tracheal cartilage.

The cartilage of the walls of the trachea and bronchi acts to keep these airways open despite intrathoracic pressure differences during breathing that would otherwise collapse them and limit air flow. Changes in biomechanical properties and composition of airway cartilage may contribute to altered lung function in obstructive lung diseases. To investigate the relationship between collagen organization and equilibrium tensile modulus within the structure of airway cartilage, we used scanning electron microscopy (SEM), histochemistry and equilibrium tensile testing to analyze tracheal cartilage from 10 humans aged 17-81 yr. We show that the surfaces of tracheal cartilage matrix are collagen-rich and surround a proteoglycan-rich core. Collagen fibrils in the superficial zones are oriented in the plane of the cartilage surface. In deeper layers of the cartilage, collagen fibrils are oriented less regularly. Equilibrium tensile modulus of 100 microm thick strips of cartilage was measured and was found to decrease with depth; from 13.6 +/- 1.5 MPa for the ablumenal superficial zone to 4.6 +/- 1.7 MPa in the middle zone (means +/- S.D., n = 10, p < 0.001). Stress-strain curves were linear for strains up to 10% with minimal residual strain. This is consistent with a model in which collagen fibres in the outer layers of the cartilage resist tensile forces, and hydrated proteoglycans in the central zone resist compression forces as the cartilage crescent bends.

Adolescent↗
PubMed2000

Storing live embryonic and adult human cartilage grafts for transplantation using a joint simulating device.

OBJECTIVES: Cartilage transplantation as a means to replace damaged articular surfaces is of interest. A major obstacle is the long-term preservation of cartilage grafts. The commonly used technique of freezing the grafts inevitably leads to cellular death. The current study compares the technique to an innovative approach using a pulsed-pressure perfusion system termed a joint simulating device (JSD), intended to simulate intra-articular mechanical forces. METHODS: Human articular cartilage explants were harvested from both embryonic epiphyseal tissue and femoral heads of elderly women (over 70 years of age) undergoing a partial joint replacement (hemi-arthroplasty) and were divided in two groups: half of the samples were incubated in the JSD while the remaining half were grown in static culture within tissue culture plates. After 10 days all samples were evaluated for: (a) cell vitality as assessed by image analysis and XTT assay; (b) biosynthetic activity as expressed by radioactive sulfate incorporation into glycosaminoglycans (GAG's); and (c) proteoglycan content as assessed by alcian blue staining intensity. RESULTS: A 10-fold increase in sulfate incorporation in samples held in the JSD compared to the static culture group was observed in embryonic cartilage. In adult cartilage culture in the JSD elevated sulfate incorporation by threefold as compared to static culture. Central necrosis was observed in specimens grown in the static culture plates, while it did not occur in the samples held in the JSD. Cell vitality as assessed by XTT assay was significantly better in the JSD group as compared to static culture. The difference was more pronounced in the embryonic specimens as compared to adult cartilage. The specimens cultured within the JSD retained proteoglycans significantly better than those cultured in static culture. CONCLUSIONS: Maintenance of cartilage specimens in a JSD was highly effective in keeping the vitality of cartilage explants in vitro over a 10-day period. A possible future application may be a long-term preservation of chondral grafts, without freezing. Avoidance of freezing of cartilage grafts, might prevent the cartilage degeneration often observed in frozen osteochondral grafts.

Aged↗