Collagen Network Of Cartilage Research Articles

Cellular solids and prestressed affine networks as models of the elastic behavior of soft biological structures.

We reviewed two microstructural models, cellular solid models and prestressed affine network models, that have been used previously in studies of elastic behavior of soft biological materials. These models provide simple and mathematically transparent equations that can be used to interpret experimental data and to obtain quantitative predictions of the elastic properties of biological structures. In both models, volumetric density and elastic properties of the microstructure are key determinants of the macroscopic elastic properties. In the prestressed network model, geometrical rearrangement of the microstructure (kinematic stiffness) is also important. As examples of application of these models, we considered the shear behavior of the cytoskeleton of adherent cells, of the collagen network of articular cartilage, and of the lung parenchymal network since their ability to resist shear is important for their normal biological and physiological functions. All three networks carry a pre-existing stress (prestress). We predicted their shear moduli using the microstructural models and compared those predictions with existing experimental data. Prestressed network models of the cytoskeleton and of the lung parenchyma provided a better correspondence to experimental data than cellular solid models. Both cellular solid and prestressed network models of the cartilage collagen network provided reasonable agreements with experimental values. These findings suggested that the kinematic stiffness and material stiffness of microstructural elements were both important determinants of the shear modulus of the cytoskeleton and of the lung parenchyma, whereas elasticity of collagen fibrils had a predominant role in the cartilage shear behavior.

Micro-computed Tomography-Based Collagen Orientation and Anisotropy Analysis of Rabbit Articular Cartilage

The collagen network is the highly organized backbone of articular cartilage providing tissue tensile stiffness and restricting proteoglycan bleaching out of the tissue. Osteoarthritis (OA) diminishes proper collagen network adaptation. Our aim was to provide quantitative three-dimensional (3D) information of the cartilage collagen network adaptation in early osteoarthritis using high resolution micro-computed tomography (µCT)-imaging. Osteochondral samples from the femoral condyles were collected from healthy (N = 8, both legs) and experimental OA rabbit model with anterior cruciate ligament transection (N = 14, single leg). Samples were processed for cartilage µCT-imaging and histological evaluation with polarized light microscopy (PLM). Structure tensor analysis was used to analyse the collagen fibre orientation and anisotropy of the µCT-images, and PLM was used as a validation for structural changes. Depth-wise comparison of collagen fibre orientation acquired with µCT-imaging and PLM correlated well, but the values obtained with PLM were systematically greater than those measured with µCT-imaging. Structure tensor analysis allowed for 3D quantification of collagen network anisotropy. Finally, µCT-imaging revealed only minor differences between the control and experimental groups.

Contrast-enhanced x-ray microscopy of articular cartilage

ABSTRACT Osteoarthritis is a common chronic disease of joints characterized by degenerative changes of articular cartilage. An early diagnosis of osteoarthritis may be possible when imaging excised tissue for research in situ at the cellular-molecular scale. Whereas cartilage histopathology is destructive, time-consuming, and limited to 2D views, contrast-enhanced x-ray microscopy (XRM) can image articular cartilage and subchondral bone in 3D. This study evaluates articular cartilage structure ex vivo using both techniques. Osteochondral plugs were excised from non-diseased bovine knees and stained in phosphotungstic acid for 0 to 32 h. XRM imaging revealed an optimal staining time of 16 h and a saturated staining time of 24 h. Histology sections were cut and analyzed by polarized light microscopy (PLM) and second-harmonic-generation dual-photon (SHG-DP) microscopy. Histology photomicrographs were aligned with matching XRM slices and evaluated for features relevant in histopathological scoring of osteoarthritis cartilage, including the tidemark, collagen architecture and chondrocyte morphology. The cartilage collagen network and chondrocytes from the 3D contrast-enhanced XRM were correlated with the 2D histology. This technique has two distinct advantages over routine histopathology: (1) the avoidance of dehydration, demineralization, and deformation of histological sectioning, thereby preserving the intact articular cartilage and subchondral bone plate ex vivo, and (2) the ability to evaluate the entire osteochondral volume in 3D. This work explores several diagnostic features of imaging cartilage, including: visualization of the tidemark in XRM and SHG-DP microscopy, validating the morphology of chondrocytes and nuclei with XRM, SHG-DP and PLM, and correlating collagen birefringence with XRM image intensity.

Rethinking articular cartilage regeneration based on a 250-year-old statement.

Cartilage has a limited healing capacity; however, studies into the basic biological characteristics, formation and structural maintenance of the cartilage collagen network are providing explanations for the failure of current therapeutic approaches, urging us to rethink our approach to the regeneration of articular cartilage.

Proteoglycan degradation mimics static compression by altering the natural gradients in fibrillar organisation in cartilage

Structural and associated biomechanical gradients within biological tissues are important for tissue functionality and preventing damaging interfacial stress concentrations. Articular cartilage possesses an inhomogeneous structure throughout its thickness, driving the associated variation in the biomechanical strain profile within the tissue under physiological compressive loading. However, little is known experimentally about the nanostructural mechanical role of the collagen fibrils and how this varies with depth. Utilising a high-brilliance synchrotron X-ray source, we have measured the depth-wise nanostructural parameters of the collagen network in terms of the periodic fibrillar banding (D-period) and associated parameters. We show that there is a depth dependent variation in D-period reflecting the pre-strain and concurrent with changes in the level of intrafibrillar order. Further, prolonged static compression leads to fibrillar changes mirroring those caused by removal of extrafibrillar proteoglycans (as may occur in aging or disease). We suggest that fibrillar D-period is a sensitive indicator of localised changes to the mechanical environment at the nanoscale in soft connective tissues. Statement of SignificanceCollagen plays a significant role in both the structural and mechanical integrity of articular cartilage, allowing the tissue to withstand highly repetitive loading. However, the fibrillar mechanics of the collagen network in cartilage are not clear. Here we find that cartilage has a spatial gradient in the nanostructural collagen fibril pre-strain, with an increase in the fibrillar pre-strain with depth. Further, the fibrillar gradient changes similarly under compression when compared to an enzymatically degraded tissue which mimics age-related changes. Given that the fibrils potentially have a finite capacity to mechanically respond and alter their configuration, these findings are significant in understanding how collagen may alter in structure and gradient in diseased cartilage, and in informing the design of cartilage replacements.

Arthroscopic Determination of Cartilage Proteoglycan Content and Collagen Network Structure with Near-Infrared Spectroscopy

Conventional arthroscopic evaluation of articular cartilage is subjective and insufficient for assessing early compositional and structural changes during the progression of post-traumatic osteoarthritis. Therefore, in this study, arthroscopic near-infrared (NIR) spectroscopy is introduced, for the first time, for in vivo evaluation of articular cartilage thickness, proteoglycan (PG) content, and collagen orientation angle. NIR spectra were acquired in vivo and in vitro from equine cartilage adjacent to experimental cartilage repair sites. As reference, digital densitometry and polarized light microscopy were used to evaluate superficial and full-thickness PG content and collagen orientation angle. To relate NIR spectra and cartilage properties, ensemble neural networks, each with two different architectures, were trained and evaluated by using Spearman’s correlation analysis (ρ). The ensemble networks enabled accurate predictions for full-thickness reference properties (PG content: ρin vitro, Val= 0.691, ρin vivo= 0.676; collagen orientation angle: ρin vitro, Val= 0.626, ρin vivo= 0.574) from NIR spectral data. In addition, the networks enabled reliable prediction of PG content in superficial (25%) cartilage (ρin vitro, Val= 0.650, ρin vivo= 0.613) and cartilage thickness (ρin vitro, Val= 0.797, ρin vivo= 0.596). To conclude, NIR spectroscopy could enhance the detection of initial cartilage degeneration and thus enable demarcation of the boundary between healthy and compromised cartilage tissue during arthroscopic surgery.

Use of Second Harmonic Imaging and Fourier Transformation to Analyze Cartilage Repair in Mice Injected with a Novel Peptide CK2.1

Second harmonic generation (SHG) imaging is a powerful imaging tool that allows to study the distribution of the collagen network in cartilage. This imaging modality has been successfully utilized for visualizing physiologic and pathological changes in tissues and organs. However only recently the quantification of SHG images by Fourier Transform analysis allowed for successful quantification of the collagen network in cartilage. Here, we demonstrate that systemic injection of CK2.1, a novel mimetic peptide based on the Bone Morphogenetic Protein (BMP) receptor type I sequence, induced cartilage formation in mice and reassembly of collagen fibers. Intra-articular injections of slow release HGPCK2.1 demonstrated a robust regeneration of the damaged cartilage tissue and the collagen network. Collection of the forward (aligned) and backward (non-aligned) SHG allowed us to quantify the fibrillar distribution in peptide induced cartilage formation and repair. Our data show that the Forward SHG obtained by the collagen structures were greater compared to Backward SHG in CK2.1 in the cartilage of CK2.1 injected mice. These data suggest the cartilage elasticity to withstand stresses placed on the tissue is increased. Our data provide us insights into the peptides capabilities as a future therapeutic agent that can regenerate the lost cartilage to its native form.

The development of a mature collagen network in cartilage from human bone marrow stem cells in Transwell culture

Damaged hyaline cartilage shows a limited capacity for innate repair. Potential sources of cells to augment the clinical repair of cartilage defects include autologous chondrocytes and mesenchymal stem cells. We have reported that culture of human bone marrow mesenchymal stem cells with specific growth and differentiation factors as shallow multilayers on Transwell permeable membranes provided ideal conditions for chondrogenesis. Rigid translucent cartilaginous disks formed and expressed cartilage-specific structural proteins aggrecan and type II collagen. We report here the analysis of the collagen network assembled in these cartilage constructs and identify key features of the network as it became mature during 28days of culture. The type II collagen was co-polymerized with types XI and IX collagens in a fibrillar network stabilized by hydroxylysyl pyridinoline cross-links as in epiphyseal and hyaline cartilages. Tandem ion-trap mass-spectrometry identified 3-hydroxylation of Proline 986 and Proline 944 of the α1(II) chains, a post-translational feature of human epiphyseal cartilage type II collagen. The formation of a type II collagen based hydroxy-lysyl pyridinoline cross-linked network typical of cartilage in 28days shows that the Transwell system not only produces, secretes and assembles cartilage collagens, but also provides all the extracellular mechanisms to modify and generate covalent cross-links that determine a robust collagen network. This organized assembly explains the stiff, flexible nature of the cartilage constructs developed from hMSCs in this culture system.

Racial differences in biochemical knee cartilage composition between African-American and Caucasian-American women with 3 T MR-based T2 relaxation time measurements – data from the Osteoarthritis Initiative

To determine whether knee cartilage composition differs between African-American and Caucasian-American women at risk for Osteoarthritis (OA) using in vivo 3 T MRI T2 relaxation time measurements. Right knee MRI studies of 200 subjects (100 African-American women, and 100 closely matched Caucasian-American women) were selected from the Osteoarthritis Initiative (OAI). Knee cartilage was segmented in the patellar (PAT), medial and lateral femoral (MF/LF), and medial and lateral tibial compartments (MT/LT)). Mean T2 relaxation time values per compartment and per whole joint cartilage were generated and analyzed spatially via laminar and grey-level co-occurrence matrix (GLCM) texture methods. Presence and severity of cartilage lesions per compartment were graded using a modified WORMS grading. Statistical analysis employed paired t- and McNemar testing. While African-American women and Caucasian-Americans had similar WORMS cartilage lesion scores (P = 0.970), African-Americans showed significantly lower mean T2 values (∼1 ms difference; ∼0.5SD) than Caucasian-Americans in the whole knee cartilage (P < 0.001), and in the subcompartments (LF: P = 0.001, MF: P < 0.001, LT: P = 0.019, MT: P = 0.001) and particularly in the superficial cartilage layer (whole cartilage: P < 0.001, LF: P < 0.001, MF: P < 0.001, LT: P = 0.003, MT: P < 0.001). T2 texture parameters were also significantly lower in the whole joint cartilage of African-Americans than in Caucasian-Americans (variance: P = 0.001; contrast: P = 0.018). In analyses limited to matched pairs with no cartilage lesions in a given compartment, T2 values remained significantly lower in African-Americans. Using T2 relaxation time as a biomarker for the cartilage collagen network, our findings suggest racial differences in the biochemical knee cartilage composition between African-American and Caucasian-American women.

Helium ion microscopy for high‐resolution visualization of the articular cartilage collagen network

The articular cartilage collagen network is an important research focus because network disruption results in cartilage degeneration and patient disability. The recently introduced helium ion microscope (HIM), with its smaller probe size, longer depth of field and charge neutralization, has the potential to overcome the inherent limitations of electron microscopy for visualization of collagen network features, particularly at the nanoscale. In this study, we evaluated the capabilities of the helium ion microscope for high-resolution visualization of the articular cartilage collagen network. Images of rabbit knee cartilage were acquired with a helium ion microscope; comparison images were acquired with a field emission scanning electron microscope (FE-SEM) and a transmission electron microscope (TEM). Sharpness of example high-resolution helium ion microscope and field emission scanning electron microscope images was quantified using the 25-75% rise distance metric. The helium ion microscope was able to acquire high-resolution images with unprecedented clarity, with greater sharpness and three-dimensional-like detail of nanoscale fibril morphologies and fibril connections, in samples without conductive coatings. These nanoscale features could not be resolved by field emission scanning electron microscopy, and three-dimensional network structure could not be visualized with transmission electron microscopy. The nanoscale three-dimensional-like visualization capabilities of the helium ion microscope will enable new avenues of investigation in cartilage collagen network research.

High Resolution Visualization of the Articular Cartilage Collagen Network by Helium Ion Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Mechanical stimulation to stimulate formation of a physiological collagen architecture in tissue-engineered cartilage: a numerical study

The load-bearing capacity of today's tissue-engineered (TE) cartilage is insufficient. The arcade-like collagen network in native cartilage plays an important role in its load-bearing properties. Inducing the formation of such collagen architecture in engineered cartilage can, therefore, enhance mechanical properties of TE cartilage. Considering the well-defined relationship between tensile strains and collagen alignment in the literature, we assume that cues for inducing this orientation should come from mechanical loading. In this study, strain fields prescribed by loading conditions of unconfined compression, sliding indentation and a novel loading regime of compression–sliding indentation are numerically evaluated to assess the probability that these would trigger a physiological collagen architecture. Results suggest that sliding indentation is likely to stimulate the formation of an appropriate superficial zone with parallel fibres. Adding lateral compression may stimulate the formation of a deep zone with perpendicularly aligned fibres. These insights may be used to improve loading conditions for cartilage tissue engineering.

Alterations in structure and properties of collagen network of osteoarthritic and repaired cartilage modify knee joint stresses

Organization of the collagen network is known to be different in healthy, osteoarthritic and repaired cartilage. The aim of the study was to investigate how the structure and properties of collagen network of cartilage modulate stresses in a knee joint with osteoarthritis or cartilage repair. Magnetic resonance imaging (MRI) at 1.5 T was conducted for a knee joint of a male subject. Articular cartilage and menisci in the knee joint were segmented, and a finite element mesh was constructed based on the two-dimensional section in sagittal projection. Then, the knee joint stresses were simulated under impact loads by implementing the structure and properties of healthy, osteoarthritic and repaired cartilage in the models. During the progression of osteoarthritis, characterized especially by the progressive increase in the collagen fibrillation from the superficial to the deeper layers, the stresses were reduced in the superficial zone of cartilage, while they were increased in and under menisci. Increased fibril network stiffness of repair tissue with randomly organized collagen fibril network reduced the peak stresses in the adjacent tissue and strains at the repair-adjacent cartilage interface. High collagen fibril strains were indicative of stress concentration areas in osteoarthritic and repaired cartilage. The collagen network orientation and stiffness controlled the stress distributions in healthy, osteoarthritic and repaired cartilage. The evaluation of articular cartilage function using clinical MRI and biomechanical modeling could enable noninvasive estimation of osteoarthritis progression and monitoring of cartilage repair. This study presents a step toward those goals.

Changes in collagen fibril network organization and proteoglycan distribution in equine articular cartilage during maturation and growth

The aim of this study was to record growth-related changes in collagen network organization and proteoglycan distribution in intermittently peak-loaded and continuously lower-level-loaded articular cartilage. Cartilage from the proximal phalangeal bone of the equine metacarpophalangeal joint at birth, at 5, 11 and 18 months, and at 6-10 years of age was collected from two sites. Site 1, at the joint margin, is unloaded at slow gaits but is subjected to high-intensity loading during athletic activity; site 2 is a continuously but less intensively loaded site in the centre of the joint. The degree of collagen parallelism was determined with quantitative polarized light microscopy and the parallelism index for collagen fibrils was computed from the cartilage surface to the osteochondral junction. Concurrent changes in the proteoglycan distribution were quantified with digital densitometry. We found that the parallelism index increased significantly with age (up to 90%). At birth, site 2 exhibited a more organized collagen network than site 1. In adult horses this situation was reversed. The superficial and intermediate zones exhibited the greatest reorganization of collagen. Site 1 had a higher proteoglycan content than site 2 at birth but here too the situation was reversed in adult horses. We conclude that large changes in joint loading during growth and maturation in the period from birth to adulthood profoundly affect the architecture of the collagen network in equine cartilage. In addition, the distribution and content of proteoglycans are modified significantly by altered joint use. Intermittent peak-loading with shear seems to induce higher collagen parallelism and a lower proteoglycan content in cartilage than more constant weight-bearing. Therefore, we hypothesize that the formation of mature articular cartilage with a highly parallel collagen network and relatively low proteoglycan content in the peak-loaded area of a joint is needed to withstand intermittent stress and shear, whereas a constantly weight-bearing joint area benefits from lower collagen parallelism and a higher proteoglycan content.

Novel Contrast Mechanisms at High Field 1

This article reviews the technical principles of novel contrast mechanisms for musculoskeletal imaging. Ultrashort echo-time imaging allows the visualization of fast T2 relaxing tissue components that are not directly detectable by standard magnetic resonance imaging. This offers several new applications, especially in musculoskeletal imaging, to visualize these tissue components directly. Magnetization transfer techniques, which have been successfully applied to assess demyelinization processes in white brain matter, for example, can be used to detect the integrity of the collagen network of cartilage, and they may help for the detection of early cartilage degradations. Finally, diffusion-weighted imaging represents a further technique to detect bone marrow pathologies or indicate collagen degradation and water content in cartilage. The technical details and implementation techniques of these dedicated imaging modalities are demonstrated and reviewed in this article, and some clinical examples are presented.

The zonal architecture of human articular cartilage described by T2 relaxation time in the presence of Gd-DTPA2−

The depth-wise variation of T(2) relaxation time is known to reflect the collagen network architecture in cartilage, while the delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) technique is sensitive to tissue proteoglycan (PG) concentration. As the cartilage PG content varies along the tissue depth, the depth-dependent accumulation of the contrast agent may affect the inherent T(2) of cartilage in a nonconstant manner. Therefore, T(2) and dGEMRIC are typically measured in separate MRI sessions. In the present in vitro MRI study at 9.4 T, depth-wise T(2) profiles and collagenous zone thicknesses as determined from T(2) maps in the absence and presence of Gd-DTPA(2-) (T(2) and T(2Gd), respectively) were compared in samples of intact human articular cartilage (n=65). These T(2) measures were further correlated with birefringence (BF) of polarized light microscopy (PLM) to quantify the ability of MRI to predict the properties of the collagen fibril network. The reproducibility of the T(2) measurement in the current setup was also studied. Typical tri-laminar collagen network architecture was observed both with and without Gd-DTPA(2-). The inverse of BF (1/BF) correlated significantly with both T(2) and T(2Gd) (r=0.91, slope=0.56 and r=0.90, slope=0.63), respectively. The statistically significant linear correlations between zone thicknesses as determined from T(2) and T(2Gd) were r=0.55 (slope=0.49), r=0.74 (slope=0.71) and r=0.95 (slope=0.94) for superficial, middle and deep tissue zones, respectively. Reproducibility of the T(2) measurement was worst for superficial cartilage. Consistent with PLM, T(2) and T(2Gd) measurements reveal highly similar depth-dependent information on collagen network in intact human cartilage. Thus, dGEMRIC and T(2) measurements in one MRI session are feasible for intact articular cartilage in vitro.

Contribution of collagen network features to functional properties of engineered cartilage

Damage to articular cartilage is one of the features of osteoarthritis (OA). Cartilage damage is characterised by a net loss of collagen and proteoglycans. The collagen network is considered highly important for cartilage function but little is known about processes that control composition and function of the cartilage collagen network in cartilage tissue engineering. Therefore, our aim was to study the contribution of collagen amount and number of crosslinks on the functionality of newly formed matrix during cartilage repair. Bovine articular chondrocytes were cultured in alginate beads. Collagen network formation was modulated using the crosslink inhibitor beta-aminopropionitrile (BAPN; 0.25mM). Constructs were cultured for 10 weeks with/without BAPN or for 5 weeks with BAPN followed by 5 weeks without. Collagen deposition, number of crosslinks and susceptibility to degradation by matrix metalloproteinase-1 (MMP-1) were examined. Mechanical properties of the constructs were determined by unconfined compression. BAPN for 5 weeks increased collagen deposition accompanied by increased construct stiffness, despite the absence of crosslinks. BAPN for 10 weeks further increased collagen amounts. Absence of collagen crosslinks did not affect stiffness but ability to hold water was lower and susceptibility to MMP-mediated degradation was increased. Removal of BAPN after 5 weeks increased collagen amounts, allowed crosslink formation and increased stiffness. This study demonstrates that both collagen amounts and its proper crosslinking are important for a functional cartilage matrix. Even in conditions with elevated collagen deposition, crosslinks are needed to provide matrix stiffness. Crosslinks also contribute to the ability to hold water and to the resistance against degradation by MMP-1.

Biochemical and functional modulation of the cartilage collagen network by IGF1, TGFβ2 and FGF2

Examine effects of insulin-like growth factor 1 (IGF1), transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 2 (FGF2) on proteoglycan and collagen network and biomechanical properties of the newly formed cartilage matrix. Bovine articular chondrocytes were cultured in alginate beads for 3 weeks with or without FGF2, TGFbeta2 or IGF1 in the presence of 10% FCS. Proteoglycan content, collagen content, hydroxylysylpyridinoline cross-links and overall matrix metalloproteinase (MMP) activity in the culture medium were measured. Alginate disks cultured for 5 weeks were used to evaluate the effect of growth factors on mechanical properties of the construct by determining the equilibrium aggregate modulus and secant modulus. IGF1 increased collagen and proteoglycan deposition. FGF2 mainly decreased collagen deposition and TGFbeta2 proteoglycan deposition. A decrease in cross-links was observed in matrix produced by chondrocytes cultured in the presence of TGFbeta2. IGF1 and FGF2 had no influence on the number of cross-links per collagen molecule. Overall MMP activity was significantly higher in culture medium of cells cultured with FGF2. TGFbeta2 and IGF1 had no effect on MMP activity. After 35 days of culture, the matrix produced under influence of IGF1 had a lower permeability and a trend to increase stiffness. FGF2 showed a trend to lower both properties. TGFbeta2 had no effect on these parameters. IGF1, TGFbeta2 and FGF2 had differential effects on collagen network formation. Of the three growth factors tested, IGF1 seems to be best in promoting the formation of a functional collagen network since it increased proteoglycan and collagen deposition and improved the mechanical properties.

Collagene order of articular cartilage by clinical magnetic resonance images and its age dependency

The present papers describes a novel method to obtain information on the degree of order of the collagen network of the knee meniscal cartilage by means of a single clinical MRI. Images were obtained from 34 healthy volunteers aged between 6 and 76 years as well as from one patient with clinically-diagnosed arthrosis at the age of 32 and 37 years. A Siemens Vision (1.5 T) MRT with TR = 750 ms, TE = 50 ms, FoV = 160 mm, and Matrix 512×512 was used for this purpose.The MR signal intensities of the cartilage were read out along slices with constant height above the subchondral bone and plotted versus the actual angle to the external magnetic field. The obtained intensity curves were fitted by a model distribution, and the degree of order of the collagen fibers was calculated. For the knee meniscal cartilage, there was an age-dependency of the degree of order and a significant deviation of the volunteer with arthrosis from the normal curve.The results are discussed in view of the arcade model and of a possible use of non-invasive clinical MRT for the detection of early arthrotic changes of cartilage.

A human COL2A1 gene with an Arg519Cys mutation causes osteochondrodysplasia in transgenic mice.

An arginine-to-cysteine substitution at position 519 of the COL2A1 gene causes early generalized osteoarthritis with mild chondrodysplasia in humans. In this study, a human COL2A1 gene with the same mutation was introduced into a murine genome having 1 or no alleles of the murine Col2a1 gene, and the skeletal phenotypes of the transgenic mice were compared with those of control mice. Mice with 1 allele of the normal murine Col2a1 gene and 1 allele of the mutated human COL2A1 gene (n = 10), those with no murine Col2a1 gene and 2 alleles of the mutated human COL2A1 gene (n = 13), those with no murine Col2a1 gene and only 1 allele of the mutated COL2A1 gene (n = 9), and normal control mice (n = 11) were studied for skeletal abnormalities, using radiographic imaging and light microscopic analyses of histologic sections. The collagen network of cartilage was also investigated with transmission electron microscopy. At 2 months of age, all transgenic mice had dysplastic changes in their long bones, flattened vertebral bodies, and osteoarthritic changes in their joints. The intervertebral discs of the transgenic animals were degenerated, and their histologic structure was disturbed. The changes were more severe in mice with no murine Col2a1 allele. The human COL2A1 gene with the Arg519Cys mutation causes osteochondrodysplasia in mice, as it does in humans.