Acute and subchronic oral toxicity studies in rats of a hydrolyzed chicken sternal cartilage preparation

Two acute and subchronic oral toxicity studies were conducted in rats to evaluate safety of a patented preparation of hydrolyzed chicken sternal cartilage (BioCell Collagen II) containing collagen type II, chondroitin sulfate, and hyaluronic acid. In the acute oral toxicity study, five males and five females of Sprague-Dawley rats were administered a single dose of 5000 mg of the test product per kg body weight and observed for 14 days. All animals survived and exhibited normal body weight gain throughout the study. Macroscopic necropsy examination conducted on day 15 revealed no gross pathological lesions in any of the animals. In the subchronic study, Sprague-Dawley rats (40 males, 40 females) were divided into four same-sex groups (10 animals/group). Animals in each group were administered daily either 0, 30, 300 or 1000 mg of the test product per kg of body weight for over 90 days. All animals survived and showed no significant changes in their body weights and histopathology. Although some differences were observed between the treated and control animals in several parameters, they were generally not dose-related or considered to be of toxicological significance. In conclusion, the results from the two oral toxicity studies with male and female young adult rats indicated that the test preparation from hydrolyzed chicken sternal cartilage collagen (BioCell Collagen II) was well tolerated at all four doses tested.

A biomimetic three-dimensional woven composite scaffold for functional tissue engineering of cartilage

Tissue engineering seeks to repair or regenerate tissues through combinations of implanted cells, biomaterial scaffolds and biologically active molecules. The rapid restoration of tissue biomechanical function remains an important challenge, emphasizing the need to replicate structural and mechanical properties using novel scaffold designs. Here we present a microscale 3D weaving technique to generate anisotropic 3D woven structures as the basis for novel composite scaffolds that are consolidated with a chondrocyte-hydrogel mixture into cartilage tissue constructs. Composite scaffolds show mechanical properties of the same order of magnitude as values for native articular cartilage, as measured by compressive, tensile and shear testing. Moreover, our findings showed that porous composite scaffolds could be engineered with initial properties that reproduce the anisotropy, viscoelasticity and tension-compression nonlinearity of native articular cartilage. Such scaffolds uniquely combine the potential for load-bearing immediately after implantation in vivo with biological support for cell-based tissue regeneration without requiring cultivation in vitro.

Enhanced matrix synthesis in de novo, scaffold free cartilage-like tissue subjected to compression and shear

Production of a de novo cartilage-like tissue construct is a goal for the repair of traumatic chondral defects. We aimed to enhance the matrix synthesis within a scaffold free, de novo cartilage-like tissue construct by way of mechanical load. A novel loading machine that enables the application of shear, as well as compression, was used to subject tissue engineered cartilage-like tissue to mechanical stress. The machine, which applies the load through a roller mechanism, can load up to 20 constructs with four different loading patterns simultaneously. The expression of mRNA encoding matrix products, and subsequent changes in matrix protein content, were analyzed after various loading regimes. The force applied to the immature tissue had a direct bearing on the short-term (first 4 h) response. A load of 0.5 N caused an increase in collagen II and aggrecan mRNA within an hour, with a peak at 2 h. This increased mRNA expression was translated into an increase of up to 60% in the glycosaminoglycan content of the optimally loaded constructs after 4 days of intermittent cyclical loading. Introducing pauses between load cycles reproducibly lead to an increase in GAG/DNA. In contrast, constant cyclical load, with no pause, lead to a decrease in the final glycosaminoglycan content compared with unloaded controls. Our data suggest that a protocol of mechanical stimulation, simulating in vivo conditions and involving shear and compression, may be a useful mechanism to enhance the properties of tissue engineered tissue prior to implantation.

A hierarchy of Runx transcription factors modulate the onset of chondrogenesis in craniofacial endochondral bones in zebrafish

The Runx (runt-related) family of transcription factors are important regulators of cell fate decisions in early embryonic development, and in differentiation of tissues including blood, neurons, and bone. During skeletal development in mammals, while only Runx2 is essential for osteoblast differentiation, all family members seem to be involved in chondrogenesis. Runx2 and Runx3 control chondrocyte maturation. Both Runx1 and Runx2 are expressed early in mesenchymal condensations, but how they contribute to the initial stages of chondrocyte differentiation is unclear. Here we show that a hierarchy of Runx transcriptional regulation promotes the early program of chondrocyte differentiation from pre-cartilage mesenchyme in the zebrafish head skeleton. We have previously characterized the zebrafish orthologs for all Runx genes. Zebrafish runx2 is duplicated, but not runx1 or runx3. In the work presented here, we determined the early expression pattern of the runx genes in the craniofacial region. The earliest expression detected was that of runx3 in the pharyngeal endoderm, then runx2a and b in mesenchymal condensations, and later runx1 in the epithelium. Using antisense morpholino knockdown analysis, we examined their respective activities in early chondrogenesis. Depletion of runx2b (but not runx2a) and runx3 severely compromised craniofacial cartilage formation. Because runx2b expression was abolished in Runx3 morphants, we propose that endodermal Runx3 has a role in influencing signaling activities from the endoderm to promote chondrocyte differentiation. We also show that, in contrast to data from mouse studies, zebrafish Runx1 is not required in the initial steps of chondrogenesis leading to endochondral bone formation.

Amelogenin expression in long bone and cartilage cells and in bone marrow progenitor cells

The amelogenin protein is considered as the major molecular marker of developing ectodermal enamel. Recent data suggest other roles for amelogenin beyond structural regulation of enamel mineral crystal growth. Here we describe our novel discovery of amelogenin expression in long bone cells, in cartilage cells, in cells of the epiphyseal growth plate, and in bone marrow stromal cells.

Identification of the Origin of Chondroitin Sulfate in "Health Foods"

Twelve "health foods" products containing chondroitin sulfate (CS) were purchased from the Japanese market and the origin of the CS was investigated by conducting disaccharide compositional analysis after enzymatic depolymerization and by 1H-NMR spectroscopy. Nine of the 12 products had labels indicating that the origin of the CS was shark cartilage. However, two of them were found to contain mammalian CS. Next, we compared the ratio of the sulfate group to the galactosamine residue after the acid hydrolysis of CS. The results suggest that all of the CS from sharks had a ratio of more than 1.0, while the CS from mammals had a ratio of less than 1.0. Since this comparative analysis does not require expensive purified enzyme, it would be an economical way to identify the origin of CS in "health foods." Being able to determine the origin of the ingredients in natural products is very important for ensuring their quality, safety, and efficacy. Therefore, we think that regulatory requirements for accurately indicating the origin of "health foods" and effective enforcement of these requirements are needed.

[Effect of peptide regulators on the structural and functional status of bone tissue in ageing rats]

The wide spread of osteoporosis in women in the post-menopausal period stipulates the need for new effective means of prevention and correction of pathologic alterations in the bone tissue. Effect of two peptide bioregulators: cartilages preparation based on the cartilaginous tissue extract and T-31 substance on the mineral density of rat bone tissue has been studied in the experimental model of osteoporosis. The study has revealed an osteoprotective effect of both studied substances, with significantly higher efficacy of the preparation based on cartilaginous tissue extract. The substances exerted both prophylactic effect on the status of the cartilaginous tissue, preventing the decrease of mineral density of the bone tissue in rats after ovariectomy, and corrective effect by increasing the bone tissue density, which was reduced as a result of ovariectomy.

Feasibility of noninvasive evaluation of biophysical properties of tissue-engineered cartilage by using quantitative MRI

The application of tissue-engineered cartilage in a clinical setting requires a noninvasive method to assess the biophysical and biochemical properties of the engineered cartilage. Since articular cartilage is composed of 70-80% water and has dense extracellular matrixes (ECM), it is considered that the condition of the water molecules in the tissue is correlated with its biomechanical property. Therefore, magnetic resonance imaging (MRI) represents a potential approach to assess the biophysical property of the engineered cartilage. In this study, we test the hypothesis that quantitative MRI can be used as a noninvasive assessment method to assess the biophysical property of the engineered cartilage. To reconstruct a model of cartilaginous tissue, chondrocytes harvested from the humeral head of calves were embedded in an agarose gel and cultured in vitro up to 4 weeks. Equilibrium Young's moduli were determined from the stress relaxation tests. After mechanical testing, MRI-derived parameters (longitudinal relaxation time T1, transverse relaxation time T2, and water self-diffusion coefficient D) were measured. The equilibrium Young's modulus of the engineered cartilage showed a tendency to increase with an increase in the culture time, whereas T1 and D decreased. Based on a regression analysis, T1 and D showed a strong correlation with the equilibrium Young's modulus. The results showed that T1 and D values derived from the MRI measurements could be used to noninvasively monitor the biophysical properties of the engineered cartilage.

Isolation and bioactivity of an angiogenesis inhibitor extracted from the cartilage of Dasyatis akajei

The aim of this study is to isolate, characterize, and identify the bioactivity of an angiogenesis inhibitor derived from the Dasyatis akajei cartilage. By guanidine hydrochloride extract, refrigerated centrifugation, ultrafiltration, 20%-80% acetone precipitation, dialysis and refrigerated desiccation, the DCGE (Dasyatis akajei cartilage guanidine hydrochloride extract) of molecular weights from 3 kDa to approximately 300 kDa was obtained from the Dasyatis akajei cartilage. DCAI (Dasyatis akajei cartilage angiogenesis inhibitor) from 20%-30% acetone precipitation of DCGE was found to have the strongest angiogenesis inhibitory effect. Protein quantification of DCAI shows the main components were proteins with about 73.5% weight of the total DCAI. The bioactivity of the DCAI was investigated by inhibiting the formation of the blood vessels of the chick embryo chorioallantoic membrane (CAM). The ratio between the vascular area and the non-vascular area (VA/ NVA) in sampling point was used for quantitative analysis of the inhibitory effect of DCAI, which can be obtained by computer image analysis system (CIAS). Compared with the control group, the sampling point of the DCAI group had significantly lower VA/NVA. A large area of blood vessels in sampling point was significantly faded and the vascular structure was blurred with broken branches accompanied by the decreased density of vessels. The inhibitory effect with same dosage of DCAI is about ten times higher than that in the positive control group (chondroitin sulphate group) and the effect increases with the concentration of DCAI. The results from the present study indicates that the DCAI from Dasyatis akajei cartilage has an angiogenesis inhibitory effect, and there is also a positive correlation between the concentration and the inhibitory effect.

Agrin is highly expressed by chondrocytes and is required for normal growth

Agrin is a heparan sulfate proteoglycan that is best known for its crucial involvement in the organization and maintenance of postsynaptic structures at the neuromuscular junction. Consistent with this role, mice deficient of agrin die at birth due to respiratory failure. Here we examined the early postnatal development of agrin-deficient mice in which perinatal death was prevented by transgenic expression of neural agrin in motor neurons. Such transgenic, agrin-deficient mice were born at Mendelian ratio but exhibited severe postnatal growth retardation. Growth plate morpholgy was markedly altered in these mice, with changes being most prominent in the hypertrophic zone. Compression of this zone was not caused by reduced viability of hypertrophic chondrocytes, as no differences in the apoptosis rates could be observed. Furthermore, deposition of the major cartilage matrix components collagen type II and aggrecan was slightly reduced in these mice. Consistent with a role for agrin in skeletal development, we show for the first time that agrin is highly expressed by chondrocytes and localizes to the growth plate in wild-type mice. Our data show that agrin is expressed in cartilage and that it plays a critical role in normal skeletal growth.

FT-IR imaging of native and tissue-engineered bone and cartilage

Fourier transform infrared (FT-IR) imaging and microspectroscopy have been extensively applied to the analyses of tissues in health and disease. Spatially resolved mid-IR data has provided insights into molecular changes that occur in diseases of connective or collagen-based tissues, including, osteoporosis, osteogenesis imperfecta, osteopetrosis and pathologic calcifications. These techniques have also been used to probe chemical changes associated with load, disuse, and micro-damage in bone, and with degradation and repair in cartilage. This review summarizes the applications of FT-IR microscopy and imaging for analyses of bone and cartilage in healthy and diseased tissues, and illustrates the application of these techniques for the characterization of tissue-engineered bone and cartilage.

Salmon cartilage proteoglycan modulates cytokine responses to Escherichia coli in mouse macrophages

Proteoglycans (PGs) are complex glycohydrates, which are composed of core proteins and glycosaminoglycans and widely distributed in connective tissues and on the cell surface of mammalian tissues. We investigated the effect of PG extracted from salmon cartilage on cytokine responses to stimulation with heat-killed Escherichia coli (HKEC) in a mouse macrophage cell line, RAW264.7. PG exhibited the suppression of tumor necrosis factor-alpha production compared with chondroitin 4 sulfate (C4S) and chondroitin 6 sulfate (C6S). PG also revealed the up-regulation of interleukin-10 production. HKEC-induced Toll-like receptor 4 (TLR4) and inducible nitric oxide synthase expression was dose-dependently suppressed by treatment with PG, C4S or C6S, and the PG showed the strongest suppressive effect among 3 compounds. Only PG dramatically up-regulated the expression of signal transducer and activator of transcription 3 (STAT3), and the phosphorylation of STAT3 in mouse macrophages. Our results suggested that the novel interaction might exist between the extracellular matrix and immune system.

The structure and function of cartilage proteoglycans

Cartilage contains a variety of proteoglycans that are essential for its normal function. These include aggrecan, decorin, biglycan, fibromodulin and lumican. Each proteoglycan serves several functions that are determined by both its core protein and its glycosaminoglycan chains. This review discusses the structure/function relationships of the cartilage proteoglycans, and the manner in which perturbations in proteoglycan structure or abundance can adversely affect tissue function.

Analyzing the "correct" endpoint

The choice of QOL endpoints for a study should be based on which score will most likely change if the treatment is favorable. How the QOL change is calculated should be based on the expected amount of missing data, how many time points data will be collected, and whether extreme outliers in the scores impact results. The study should have sufficient power to detect a meaningful difference between arms (typically 10 points on a 0-100 point scale) in the chosen QOL endpoint. At the conclusion of a study, several secondary endpoints can be analyzed which can provide additional information and confirm primary endpoint results.

Solution structure and dynamics of cartilage aggrecan

We studied the structure and dynamics of porcine laryngeal aggrecan in solution using a range of noninvasive techniques: dynamic light scattering (DLS), small-angle neutron scattering (SANS), video particle tracking (VPT) microrheology, and diffusing wave spectroscopy (DWS). The data are analyzed within the framework of a combined static and dynamic scaling model, and evidence is found for reptation of the comb backbones with unentangled side-chain dynamics. Small-angle neutron scattering indicated standard polyelectrolyte scaling of the mesh size (xi) with concentration (c) in semidilute solutions for the whole aggrecan aggregate, xi = Ac(-0.47+/-0.04), with the prefactor (A) implying there is on average 60 nm between the aggrecan subunits along the backbone. VPT demonstrated large exponents for the power law dependence of the intrinsic viscosity (eta) on the polymer concentration in the semidilute concentration regime, eta approximately c(alpha); with alpha equal to 2.04 +/- 0.06 and 1.95 +/- 0.08 for the assembled and disassembled aggrecan aggregates, respectively. DWS at high frequencies (10(4)-10(5) Hz) gave evidence for internal Rouse modes of the aggrecan monomers, independent of the degree of self-assembly of the molecules.

Biomimetic porous scaffolds made from poly(L-lactide)-g-chondroitin sulfate blend with poly(L-lactide) for cartilage tissue engineering

A novel biodegradable graft copolymer chondroitin sulfate-grafted poly(L-lactide) (CS-PLLA) was synthesized. The graft copolymer was blended with PLLA to form biomimetic porous scaffolds. Natural CS was introduced into the polyester matrix to promote the proliferation of cells. Three-dimensional spongelike scaffolds were fabricated by a combination of salt leaching and solvent casting methods. The morphology of the scaffolds was observed with scanning electron microscopy with an average pore size between 50 and 250 microm, and its porosity was high (>85%). Compression analysis indicated that the mechanical properties of the scaffold were adequate to support the proliferation of cells. The hydrophilicity increased with an increase in the copolymer content in the blend, as determined by measuring the contact angle. Hematoxylin and eosin, Masson, and Safranin-O staining showed that cells formed a chondro tissue gradually. Histological results revealed that abundant cartilaginous matrixes surrounded spherical chondrocytes in the center of the explants. Chondrocytes cultured in this extracellular-matrix-like scaffold maintained a round morphology phenotype, characterized by a significant quantity of extracellular matrixes of sulfated glycosaminoglycans and collagens. Additionally, phenotypic gene expression (reverse transcriptase-polymerase chain reaction) indicated that chondrocytes expressed transcripts that encoded type II collagen and aggrecan and generated sulfated glycosaminoglycans.

In vivo contribution of amino acid sulfur to cartilage proteoglycan sulfation

Cytoplasmic sulfate for sulfation reactions may be derived either from extracellular fluids or from catabolism of sulfur-containing amino acids and other thiols. In vitro studies have pointed out the potential relevance of sulfur-containing amino acids as sources for sulfation when extracellular sulfate concentration is low or when its transport is impaired such as in DTDST [DTD (diastrophic dysplasia) sulfate transporter] chondrodysplasias. In the present study, we have considered the contribution of cysteine and cysteine derivatives to in vivo macromolecular sulfation of cartilage by using the mouse model of DTD we have recently generated [Forlino, Piazza, Tiveron, Della Torre, Tatangelo, Bonafe, Gualeni, Romano, Pecora, Superti-Furga et al. (2005) Hum. Mol. Genet. 14, 859-871]. By intraperitoneal injection of [35S]cysteine in wild-type and mutant mice and determination of the specific activity of the chondroitin 4-sulfated disaccharide in cartilage, we demonstrated that the pathway by which sulfate is recruited from the intracellular oxidation of thiols is active in vivo. To check whether cysteine derivatives play a role, sulfation of cartilage proteoglycans was measured after treatment for 1 week of newborn mutant and wild-type mice with hypodermic NAC (N-acetyl-L-cysteine). The relative amount of sulfated disaccharides increased in mutant mice treated with NAC compared with the placebo group, indicating an increase in proteoglycan sulfation due to NAC catabolism, although pharmacokinetic studies demonstrated that the drug was rapidly removed from the bloodstream. In conclusion, cysteine contribution to cartilage proteoglycan sulfation in vivo is minimal under physiological conditions even if extracellular sulfate availability is low; however, the contribution of thiols to sulfation becomes significant by increasing their plasma concentration.

Proteomic analysis of cartilage- and bone-associated samples

The skeleton of the human body is built of cartilage and bone, which are tissues that contain extensive amounts of extracellular matrix (ECM). In bone, inorganic mineral hydroxyapatite forms 50-70% of the whole weight of the tissue. Although the organic matrix of bone consists of numerous proteins, 90% of it is composed of type I collagen. In cartilage, ECM forms a major fraction of the tissue, type II collagen and aggrecans being the most abundant macromolecules. It is obvious that the high content of ECM components causes analytical problems in the proteomic analysis of cartilage and bone, analogous to those in the analysis of low-abundance proteins present in serum. The massive contents of carbohydrates present in cartilage proteoglycans, and hydroxyapatite in bone, further complicate the situation. However, the development of proteomic tools makes them more and more tempting also for research of musculoskeletal tissues. Application of proteomic techniques to the research of chondrocytes, osteoblasts, osteocytes, and osteoclasts in cell cultures can immediately benefit from the present knowledge. Here we make an overview to previous proteomic research of cartilage- and bone-associated samples and evaluate the future prospects of applying proteomic techniques to investigate key events, such as cellular signal transduction, in cartilage- and bone-derived cells.

An essential role for zebrafish Fgfrl1 during gill cartilage development

The vertebrate craniofacial skeleton develops via a complex process involving signaling cascades in all three germ layers. Fibroblast growth factor (FGF) signaling is essential for several steps in pharyngeal arch development. In zebrafish, Fgf3 and Fgf8 in the mesoderm and hindbrain have an early role to pattern the pouch endoderm, influencing craniofacial integrity. Endodermal FGF signaling is required for the differentiation and survival of postmigratory neural crest cells that form the pharyngeal skeleton. We identify a novel role for zebrafish Fgf receptor-like 1a (Fgfrl1a) that is indispensable during gill cartilage development. We show that depletion of Fgfrl1a is sufficient to abolish cartilage derivatives of the ceratobranchials. Using an Fgfrl1a-deficient model, we analyzed expression of genes critical for chondrogenesis in the different compartments of the developing pharyngeal arch. Fgfrl1a-depleted animals demonstrate typical neural crest specification and migration to populate the arch primordia as well as normal pouch segmentation. However, in the absence of Fgfrl1a, larvae fail to express the transcription factor glial cells missing 2 (gcm2), a gene necessary for cartilage and gill filament formation, in the ectodermal lining of the branchial arches. In addition, two transcription factors essential for chondrogenesis, sox9a and runx2b, fail to express within the mesenchymal condensations of the branchial arches. A duplicate zebrafish gene, fgfrl1b, has now been identified. We show that Fgfrl1b is also required for proper formation of all ventral cartilage elements and acts cooperatively with Fgfrl1a during gill cartilage formation.

Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)

Elasmobranchs, particularly sharks, function at speed and size extremes,exerting large forces on their cartilaginous skeletons while swimming. This casts doubt on the generalization that cartilaginous skeletons are mechanically inferior to bony skeletons, a proposition that has never been experimentally verified. We tested mineralized vertebral centra from seven species of elasmobranch fishes: six sharks and one axially undulating electric ray. Species were chosen to represent a variety of morphologies, inferred swimming speeds and ecological niches. We found vertebral cartilage to be as stiff and strong as mammalian trabecular bone. Inferred swimming speed was a good, but not infallible, predictor of stiffness and strength. Collagen content was also a good predictor of material stiffness and strength, although proteoglycan was not. The mineral fraction in vertebral cartilage was similar to that in mammalian trabecular bone and was a significant predictor of material properties.

Optimizing detection of tissue anisotropy by fluorescence recovery after photobleaching

Fluorescence recovery after photobleaching (FRAP) has been widely used to measure fluid flow and diffusion in gels and tissues. It has not been widely used in detection of tissue anisotropy. This may be due to a lack of applicable theory, or due to inherent limitations of the method. We discuss theoretical aspects of the relationship between anisotropy of tissue structure and anisotropy of diffusion coefficients, with special regard to the size of the tracer molecule used. We derive a semi-mechanistic formula relating the fiber volume fraction and ratio of fiber and tracer molecule diameters to the expected anisotropy of the diffusion coefficients. This formula and others are tested on simulated random walks through random simulated and natural media. We determine bounds on the applicability of FRAP for detection of tissue anisotropy, and suggest minimum tracer sizes for detection of anisotropy in tissues of different composition (fiber volume fraction and fiber diameter). We find that it will be easier to detect anisotropy in monodisperse materials than in polydisperse materials. To detect mild anisotropy in a tissue, such as cartilage, which has a low fiber fraction would require a tracer molecule so large that it would be difficult to deliver to the tissue. We conclude that FRAP can be used to detect tissue anisotropy when the tracer molecule is sufficiently large relative to the fiber diameter, volume fraction, and degree of polydispersivity, and when the anisotropy is sufficiently pronounced.

Spatiotemporal distribution of heparan sulfate epitopes during murine cartilage growth plate development

Heparan sulfate proteoglycans (HSPGs) are abundant in the pericellular matrix of both developing and mature cartilage. Increasing evidence suggests the action of numerous chondroregulatory molecules depends on HSPGs. In addition to specific functions attributed to their core protein, the complexity of heparan sulfate (HS) synthesis provides extraordinary structural and functional heterogeneity. Understanding the interactions of chondroregulatory molecules with HSPGs and their subsequent outcomes has been limited by the absence of a detailed analysis of HS species in cartilage. In this study, we characterize the distribution and variety of HS species in developing cartilage of normal mice. Cryo-sections of femur and tibia from normal mouse embryos were evaluated using immunostaining techniques. A panel of unique phage display antibodies specific to particular HS species were employed and visualized with secondary antibodies conjugated to Alexa-fluor dyes. Confocal microscopy demonstrates that HS species are dynamic structures within developing growth plate cartilage and the perichondrium. GlcNS6S-IdoUA2S-GlcNS6S species are down regulated and localization of GlcNS6S-IdoUA-GlcNS6S species within the hypertrophic zone of the growth plate is lost during normal development. Regional differences in HS structures are present within developing growth plates, implying that interactions with and responses to HS-binding proteins also may display regional specialization.

Fetal cartilage engineering from amniotic mesenchymal progenitor cells

We determined whether cartilage could be engineered from mesenchymal progenitor cells (MPCs) normally found in amniotic fluid. Mesenchymal amniocytes were isolated from ovine amniotic fluid samples (n = 5) and had their identity confirmed by immunocytochemistry. Cells were expanded and then cultured as micromass pellets (n = 5) in a chondrogenic medium containing transforming growth factor-beta2 (TGF-beta2) and insulin growth factor-1 (IGF-1) for 6-12 weeks. Pellets derived from fetal dermal fibroblasts (n = 4) were cultured under identical conditions. Additionally, expanded mesenchymal amniocytes were seeded onto biodegradable polyglycolic acid scaffolds (n = 5) and maintained in the same chondrogenic medium within a rotating bioreactor for 10-15 weeks. Engineered specimens were analyzed quantitatively and compared with native fetal hyaline cartilage samples (n = 5). Statistical analysis was by the unpaired Student's t-test (p < 0.05). The isolated cells stained positively for vimentin and cytokeratins-8 and -18, but negatively for CD31. Micromass pellets derived from mesenchymal amniocytes exhibited chondrogenic differentiation by both standard and matrix-specific staining. In contrast, these findings could not be replicated in dermal fibroblast-based pellets. The engineered constructs derived from mesenchymal amniocytes similarly displayed histological evidence of chondrogenic differentiation and maintained their original size and three-dimensional architecture. Quantitative assays of the engineered constructs revealed lower concentrations of collagen type II, but similar amounts of glycosaminoglycans, elastin, and DNA, when compared to native fetal hyaline cartilage. We conclude that mesenchymal amniocytes can be used for the engineering of cartilaginous tissue in vitro. Cartilage engineering from the amniotic fluid may become a practical approach for the surgical treatment of select congenital anomalies.

In vivo association of CReMM/CHD9 with promoters in osteogenic cells

Molecular mechanisms that control cell differentiation involve with chromatin remodeling activities. We recently identified Chromatin Related Mesenchymal Modulator (CReMM), a CHD protein expressed by mesenchymal cells. In this study, we analyzed CReMM expression on RNA and protein levels during embryonic development in mouse skeletal tissues. CReMM appears transiently during mesenchymal cell differentiation, being detected first in osteoprogenitors and declining in mature cells. A novel aspect of the study elaborates on in vivo association of CReMM with promoters in cells obtained by laser capture micro-dissection (LCM) technique from periosteum and endochondreal ossification regions. Using chromatin immunoprecipitation (ChIP), we proved that CReMM binds to skeletal tissue-specific promoters: CBFA1, biglycan, osteocalcin (OC), collagen-II, and myosin in a differential manner. The results imply that CReMM selectively interacts with analyzed promoters activated in the tissue at the appropriate time of development. The identification of CReMM and its tissue distribution and function provides an attractive clue for the study of transcriptional regulation of osteogenic cells' maturation.

The structure and degradation of aggrecan in human intervertebral disc

The ability of the intervertebral disc to resist compression is dependent on its high proteoglycan concentration. The disc proteoglycans are classified as aggregating or non-aggregating depending on their ability to interact with hyaluronan. The majority of the aggregating proteoglycans are derived from aggrecan, though their glycosaminoglycan substitution pattern has not been determined. In contrast, the origin of the non-aggregating proteoglycans is unclear, though it has been postulated that they are derived from aggrecan by proteolysis. The present work demonstrates that keratan sulfate (KS) in the glycosaminoglycan-binding region of disc aggrecan is confined to the KS-rich domain of the core protein and is not present in association with chondroitin sulfate (CS) in the CS1 and CS2 domains. It also shows that the non-aggregating disc proteoglycans are derived from aggrecan, with the large molecules possessing both the KS-rich and CS1 domains and the smaller molecules being generated from either the KS-rich or CS2 domain. The origin and spectrum of disc proteoglycan heterogeneity is the same in both the annulus fibrosus and nucleus pulposus.