Molecular cloning of human chondromodulin-I, a cartilage-derived growth modulating factor, and its expression in Chinese hamster ovary cells

Evolution of parent-of-origin effects on placental gene expression in house mice

The mammalian placenta is a hotspot for the evolution of genomic imprinting, a form of gene regulation that involves the parent-specific epigenetic silencing of one allele. Imprinted genes are central to placental development and are thought to contribute to the evolution of reproductive barriers between species. However, it is unclear how rapidly imprinting evolves or how functional specialization among placental tissues influences the evolution of imprinted expression. We compared parent-of-origin expression bias across functionally distinct placental layers sampled from reciprocal crosses within three closely related lineages of mice ( Mus ). Using genome-wide gene expression and DNA methylation data from fetal and maternal tissues, we developed an analytical strategy to minimize pervasive bias introduced by maternal contamination of placenta samples. We corroborated imprinted expression at 42 known imprinted genes and identified five candidate imprinted genes showing parent-of-origin specific expression and DNA methylation. Paternally-biased expression was enriched in the labyrinth zone, a layer specialized in nutrient transfer, and maternally-biased genes were enriched in the junctional zone, which specializes in modulation of maternal physiology. Differentially methylated regions were predominantly determined through epigenetic modification of the maternal genome and were associated with both maternally- and paternally-biased gene expression. Lastly, comparisons between lineages revealed a small set of co-regulated genes showing rapid divergence in expression levels and imprinted status in the M. m. domesticus lineage. Together, our results reveal important links between core functional elements of placental biology and the evolution of imprinted gene expression among closely related rodent species.

The essential anti-angiogenic strategies in cartilage engineering and osteoarthritic cartilage repair

In the cartilage matrix, complex interactions occur between angiogenic and anti-angiogenic components, growth factors, and environmental stressors to maintain a proper cartilage phenotype that allows for effective load bearing and force distribution. However, as seen in both degenerative disease and tissue engineering, cartilage can lose its vascular resistance. This vascularization then leads to matrix breakdown, chondrocyte apoptosis, and ossification. Research has shown that articular cartilage inflammation leads to compromised joint function and decreased clinical potential for regeneration. Unfortunately, few articles comprehensively summarize what we have learned from previous investigations. In this review, we summarize our current understanding of the factors that stabilize chondrocytes to prevent terminal differentiation and applications of these factors to rescue the cartilage phenotype during cartilage engineering and osteoarthritis treatment. Inhibiting vascularization will allow for enhanced phenotypic stability so that we are able to develop more stable implants for cartilage repair and regeneration.

Review and comparative analysis of machine learning-based predictors for predicting and analyzing of anti-angiogenic peptides

Cancer is one of the leading causes of death worldwide and underlying this is angiogenesis that represents one of the hallmarks of cancer. Ongoing effort is already under way in the discovery of anti-angiogenic peptides (AAPs) as a promising therapeutic route by tackling the formation of new blood vessels. As such, the identification of AAPs constitutes a viable path for understanding their mechanistic properties pertinent for the discovery of new anti-cancer drugs. In spite of the abundance of peptide sequences in public databases, experimental efforts in the identification of anti-angiogenic peptides have progressed very slowly owing to its high expenditures and laborious nature. Owing to its inherent ability to make sense of large volumes of data, machine learning (ML) represents a lucrative technique that can be harnessed for peptide-based drug discovery. In this review, we conducted a comprehensive and comparative analysis of ML-based AAP predictors in terms of their employed feature descriptors, ML algorithms, cross-validation methods and prediction performance. Moreover, the common framework of these AAP predictors and their inherent weaknesses are also discussed. Particularly, we explore future perspectives for improving the prediction accuracy and model interpretability, which represents an interesting avenue for overcoming some of the inherent weaknesses of existing AAP predictors. We anticipate that this review would assist researchers in the rapid screening and identification of promising AAPs for clinical use.

RNA-seq reveals downregulated osteochondral genes potentially related to tibia bacterial chondronecrosis with osteomyelitis in broilers

Background

Bacterial chondronecrosis with osteomyelitis (BCO) develops in the growth plate (GP) of the proximal femur and tibia and is initiated by damage to the less mineralized chondrocytes followed by colonization of opportunistic bacteria. This condition affects approximately 1% of all birds housed, being considered one of the major causes of lameness in fast growing broilers. Although several studies have been previously performed aiming to understand its pathogenesis, the molecular mechanisms involved with BCO remains to be elucidated. Therefore, this study aimed to generate a profile of global differential gene expression involved with BCO in the tibia of commercial broilers, through RNA sequencing analysis to identity genes and molecular pathways involved with BCO in chickens.

Results

Our data showed 192 differentially expressed (DE) genes: 63 upregulated and 129 downregulated in the GP of the tibia proximal epiphysis of BCO-affected broilers. Using all DE genes, six Biological Processes (BP) were associated with bone development (connective tissue development, cartilage development, skeletal system development, organ morphogenesis, system development and skeletal system morphogenesis). The analyses of the upregulated genes did not indicate any significant BP (FDR < 0.05). However, with the downregulated genes, the same BP were identified when using all DE genes in the analysis, with a total of 26 coding genes explaining BCO in the tibia: ACAN, ALDH1A2, CDH7, CHAD, CHADL, COL11A1, COMP, CSGALNACT1, CYR61, FRZB, GAL3ST1, HAPLN1, IHH, KIF26B, LECT1, LPPR1, PDE6B, RBP4A, SERINC5, SFRP1, SOX8, SOX9, TENM2, THBS1, UCHL1 and WFIKKN2. In addition, seven transcription factors were also associated to BCO: NFATC2, MAFB, HIF1A-ARNT, EWSR1-FLI1, NFIC, TCF3 and NF-KAPPAB.

Conclusions

Our data show that osteochondral downregulated genes are potential molecular causes of BCO in broilers, and the bacterial process seems to be, in fact, a secondary condition. Sixteen genes responsible for bone and cartilage formation were downregulated in BCO-affected broilers being strong candidate genes to trigger this disorder.

Chondromodulin-1 in health, osteoarthritis, cancer, and heart disease

The human chondromodulin-1 (Chm-1, Chm-I, CNMD, or Lect1) gene encodes a 334 amino acid type II transmembrane glycoprotein protein with characteristics of a furin cleavage site and a putative glycosylation site. Chm-1 is expressed most predominantly in healthy and developing avascular cartilage, and healthy cardiac valves. Chm-1 plays a vital role during endochondral ossification by the regulation of angiogenesis. The anti-angiogenic and chondrogenic properties of Chm-1 are attributed to its role in tissue development, homeostasis, repair and regeneration, and disease prevention. Chm-1 promotes chondrocyte differentiation, and is regulated by versatile transcription factors, such as Sox9, Sp3, YY1, p300, Pax1, and Nkx3.2. Decreased expression of Chm-1 is implicated in the onset and progression of osteoarthritis and infective endocarditis. Chm-1 appears to attenuate osteoarthritis progression by inhibiting catabolic activity, and to mediate anti-inflammatory effects. In this review, we present the molecular structure and expression profiling of Chm-1. In addition, we bring a summary to the potential role of Chm-1 in cartilage development and homeostasis, osteoarthritis onset and progression, and to the pathogenic role of Chm-1 in infective endocarditis and cancers. To date, knowledge of the Chm-1 receptor, cellular signalling, and the molecular mechanisms of Chm-1 is rudimentary. Advancing our understanding the role of Chm-1 and its mechanisms of action will pave the way for the development of Chm-1 as a therapeutic target for the treatment of diseases, such as osteoarthritis, infective endocarditis, and cancer, and for potential tissue regenerative bioengineering applications.

TargetAntiAngio: A Sequence-Based Tool for the Prediction and Analysis of Anti-Angiogenic Peptides

Cancer remains one of the major causes of death worldwide. Angiogenesis is crucial for the pathogenesis of various human diseases, especially solid tumors. The discovery of anti-angiogenic peptides is a promising therapeutic route for cancer treatment. Thus, reliably identifying anti-angiogenic peptides is extremely important for understanding their biophysical and biochemical properties that serve as the basis for the discovery of new anti-cancer drugs. This study aims to develop an efficient and interpretable computational model called TargetAntiAngio for predicting and characterizing anti-angiogenic peptides. TargetAntiAngio was developed using the random forest classifier in conjunction with various classes of peptide features. It was observed via an independent validation test that TargetAntiAngio can identify anti-angiogenic peptides with an average accuracy of 77.50% on an objective benchmark dataset. Comparisons demonstrated that TargetAntiAngio is superior to other existing methods. In addition, results revealed the following important characteristics of anti-angiogenic peptides: (i) disulfide bond forming Cys residues play an important role for inhibiting blood vessel proliferation; (ii) Cys located at the C-terminal domain can decrease endothelial formatting activity and suppress tumor growth; and (iii) Cyclic disulfide-rich peptides contribute to the inhibition of angiogenesis and cell migration, selectivity and stability. Finally, for the convenience of experimental scientists, the TargetAntiAngio web server was established and made freely available online.

Angiogenic approaches to meniscal healing

Meniscal injuries commonly result in osteoarthritis causing long term morbidity, lifelong treatment, joint replacement and significant financial burden to the Canadian healthcare system. Injuries to the outer third of the meniscus often heal well due to adequate blood supply. Healing of injuries in the inner two thirds of the meniscus are often critically retarded due to a lack of blood flow necessitating partial meniscectomy in many instances. Localized angiogenesis in the inner meniscus has yet to be achieved despite a belief that vascularization of these lesions corresponds with meniscal healing. This review briefly summarizes the growth factors that have been assessed for a role in meniscal healing and points to a significant knowledge gap in our understanding of meniscal healing.

Dual Roles of Ascidian Chondromodulin-1: Promoting Cell Proliferation Whilst Suppressing the Growth of Tumor Cells

Chondromodulin-1 (ChM-1) is an extracellular matrix protein that plays crucial roles in tumor cell growth and angiogenesis in vertebrates and humans. ChM-1 is highly expressed in the invertebrate Ciona savignyi, a marine ascidian chosen as a model. The effect of the recombinant Ciona mature ChM-1 peptide (Cs-mChM-1) on cell proliferation, migration and angiogenesis was evaluated on cultured cells. The results revealed that low concentrations of Cs-mChM-1 (12.5 nM) promoted osteoblastic cell (MC3T3-E1) growth and protected cells from H₂O₂-induced damage. However, a higher concentration of Cs-mChM-1 (i.e., 500 nM) not only suppressed both growth and migration of tumor cells, including human cervical cancer (HeLa) cells and human neuroblastoma (SH-SY5Y) cells, but also significantly inhibited proliferation and angiogenesis of human umbilical vein endothelial cells (HUVECs). The expression levels of cyclinD1 and mitogen-activated protein kinase 1 (MAPK1) were slightly increased in Cs-mChM-1 treated MC3T3-E1 cells, whereas these genes decreased in treated HeLa cells, SH-SY5Y cells and HUVECs. This result indicates that Cs-mChM-1 modifies cell behavior by regulating cell cycle and cell adhesion. Thus, the present results reveal that recombinant peptides of ChM-1 from invertebrates can play a dual role in cell proliferation and migration of different cell types. The inhibition effects on tumor cell growth and angiogenesis indicate potential pharmaceutical applications for recombinant Cs-mChM-1.

Hydrogels derived from cartilage matrices promote induction of human mesenchymal stem cell chondrogenic differentiation

Limited supplies of healthy autologous or allogeneic cartilage sources have inspired a growing interest in xenogeneic cartilage matrices as biological scaffolds for cartilage tissue engineering. The objectives of this study were to determine if shark and pig cartilage extracellular matrix (ECM) hydrogels can stimulate chondrocytic differentiation of mesenchymal stem cells (MSCs) without exogenous growth factors and to determine if the soluble factors retained by these ECM hydrogels are responsible. Human MSCs cultured on hydrogels from shark skull cartilage, pig articular cartilage, and pig auricular cartilage ECM had increased expression of chondrocyte markers and decreased secretion of angiogenic factors VEGF-A and FGF2 in comparison to MSCs cultured on tissue culture polystyrene (TCPS) at one week. MSCs grown on shark ECM gels had decreased type-1 collagen mRNA as compared to all other groups. Degradation products of the cartilage ECM gels and soluble factors released by the matrices increased chondrogenic and decreased angiogenic mRNA levels, indicating that the processed ECM retains biochemically active proteins that can stimulate chondrogenic differentiation. In conclusion, this work supports the use of cartilage matrix-derived hydrogels for chondrogenic differentiation of MSCs and cartilage tissue engineering. Longer-term studies and positive controls will be needed to support these results to definitively demonstrate stimulation of chondrocyte differentiation, and particularly to verify that calcification without endochondral ossification does not occur as it does in shark cartilage.

STATEMENT OF SIGNIFICANCE

The objectives of this study were to determine if shark and pig cartilage extracellular matrix (ECM) hydrogels can stimulate chondrocytic differentiation of mesenchymal stem cells (MSCs) without exogenous growth factors and to determine if the soluble factors retained by these ECM hydrogels are responsible for this induction. Sharks are an especially interesting model for cartilage regeneration because their entire skeleton is composed of cartilage and they do not undergo endochondral ossification. Culturing human MSCs on porcine and shark cartilage ECM gels directly, with ECM gel conditioned media, or degradation products increased mRNA levels of chondrogenic factors while decreasing angiogenic factors. These studies indicate that xenogeneic cartilage ECMs have potential as biodegradable scaffolds capable of stimulating chondrogenesis while preventing angiogenesis for regenerative medicine applications and that ECM species selection can yield differential effects.

Chm-1 gene-modified bone marrow mesenchymal stem cells maintain the chondrogenic phenotype of tissue-engineered cartilage

BACKGROUND

Marrow mesenchymal stem cells (MSCs) can differentiate into specific phenotypes, including chondrocytes, and have been widely used for cartilage tissue engineering. However, cartilage grafts from MSCs exhibit phenotypic alternations after implantation, including matrix calcification and vascular ingrowth.

METHODS

We compared chondromodulin-1 (Chm-1) expression between chondrocytes and MSCs. We found that chondrocytes expressed a high level of Chm-1. We then adenovirally transduced MSCs with Chm-1 and applied modified cells to engineer cartilage in vivo.

RESULTS

A gross inspection and histological observation indicated that the chondrogenic phenotype of the tissue-engineered cartilage graft was well maintained, and the stable expression of Chm-1 was detected by immunohistological staining in the cartilage graft derived from the Chm-1 gene-modified MSCs.

CONCLUSIONS

Our findings defined an essential role for Chm-1 in maintaining chondrogenic phenotype and demonstrated that Chm-1 gene-modified MSCs may be used in cartilage tissue engineering.

The N-terminal cleavage of chondromodulin-I in growth-plate cartilage at the hypertrophic and calcified zones during bone development

Chondromodulin-I (ChM-I) is a 20-25 kDa anti-angiogenic glycoprotein in cartilage matrix. In the present study, we identified a novel 14-kDa species of ChM-I by immunoblotting, and purified it by immunoprecipitation with a newly raised monoclonal antibody against ChM-I. The N-terminal amino acid sequencing indicated that it was an N-terminal truncated form of ChM-I generated by the proteolytic cleavage at Asp37-Asp38. This 14-kDa ChM-I was shown by the modified Boyden chamber assay to have very little inhibitory activity on the VEGF-A-induced migration of vascular endothelial cells in contrast to the intact 20-25 kDa form of ChM-I (ID50 = 8 nM). Immunohistochemistry suggested that 20-25 kDa ChM-I was exclusively localized in the avascular zones, i.e. the resting, proliferating, and prehypertrophic zones, of the cartilaginous molds of developing long bone, whereas the 14-kDa form of ChM-I was found in hypertrophic and calcified zones. Immunoblotting demonstrated that mature growth-plate chondrocytes isolated from rat costal cartilage actively secrete ChM-I almost exclusively as the intact 20-25 kDa form into the medium in primary culture. Taken together, our results suggest that intact 20-25 kDa ChM-I is stored as a component of extracellular matrix in the avascular cartilage zones, but it is inactivated by a single N-terminal proteolytic cleavage in the hypertrophic zone of growth-plate cartilage.

CCN family member 2/connective tissue growth factor (CCN2/CTGF) has anti-aging effects that protect articular cartilage from age-related degenerative changes

To examine the role of connective tissue growth factor CCN2/CTGF (CCN2) in the maintenance of the articular cartilaginous phenotype, we analyzed knee joints from aging transgenic mice (TG) overexpressing CCN2 driven by the Col2a1 promoter. Knee joints from 3-, 14-, 40-, and 60-day-old and 5-, 12-, 18-, 21-, and 24-month-old littermates were analyzed. Ccn2-LacZ transgene expression in articular cartilage was followed by X-gal staining until 5 months of age. Overexpression of CCN2 protein was confirmed through all ages in TG articular cartilage and in growth plates. Radiographic analysis of knee joints showed a narrowing joint space and other features of osteoarthritis in 50% of WT, but not in any of the TG mice. Transgenic articular cartilage showed enhanced toluidine blue and safranin-O staining as well as chondrocyte proliferation but reduced staining for type X and I collagen and MMP-13 as compared with those parameters for WT cartilage. Staining for aggrecan neoepitope, a marker of aggrecan degradation in WT articular cartilage, increased at 5 and 12 months, but disappeared at 24 months due to loss of cartilage; whereas it was reduced in TG articular cartilage after 12 months. Expression of cartilage genes and MMPs under cyclic tension stress (CTS) was measured by using primary cultures of chondrocytes obtained from wild-type (WT) rib cartilage and TG or WT epiphyseal cartilage. CTS applied to primary cultures of mock-transfected rib chondrocytes from WT cartilage and WT epiphyseal cartilage induced expression of Col1a1, ColXa1, Mmp-13, and Mmp-9 mRNAs; however, their levels were not affected in CCN2-overexpressing chondrocytes and TG epiphyseal cartilage. In conclusion, cartilage-specific overexpression of CCN2 during the developmental and growth periods reduced age-related changes in articular cartilage. Thus CCN2 may play a role as an anti-aging factor by stabilizing articular cartilage.

Chondromodulin-I derived from the inner meniscus prevents endothelial cell proliferation

The meniscus is a fibrocartilaginous tissue that plays an important role in controlling complex biomechanics of the knee. A perimeniscal capillary plexus supplies the outer meniscus, whereas the inner meniscus is composed of avascular tissue. Anti-angiogenic molecules, such as chondromodulin-I (ChM-I) and endostatin, have pivotal roles in preserving the avascularity of cartilage. However, the anti-angiogenic role of ChM-I is unclear in the meniscus. We hypothesized that the inner meniscus might maintain its avascular feature by expressing ChM-I. Immunohistochemical analyses revealed that ChM-I was mainly detected in the inner and superficial zones of the meniscus. On the other hand, endostatin distribution was similar between the inner and outer meniscus. In Western blot, ChM-I was detected only in the inner meniscus, whereas endostatin was equally observed in both inner and outer menisci. In addition, ChM-I concentration of the inner meniscus-derived conditioned medium was higher than that of the outer meniscus-derived medium. ChM-I removal from the inner meniscus-derived medium and functional blocking of ChM-I significantly increased endothelial cell proliferation. In this study, we demonstrated that the inner meniscus contained larger amounts of ChM-I, and that the inner meniscus-derived ChM-I inhibited endothelial cell proliferation. Our results suggest that ChM-I may be a key anti-angiogenic factor for maintaining the avascularity of the inner meniscus.

Synthetic disulfide-bridged cyclic peptides mimic the anti-angiogenic actions of chondromodulin-I

Chondromodulin-I (ChM-I) is a 25-kDa glycoprotein in cartilage matrix that inhibits angiogenesis. It contains two distinctive structural domains: the N-terminal third of the molecule is a hydrophilic domain that contains O-linked and N-linked oligosaccharide chains, and the C-terminal two-thirds is a hydrophobic domain that contains all of the cysteine residues. In the present study, we have attempted to further uncover the structural requirements for ChM-I to exert anti-angiogenic activity by monitoring its inhibition of the vascular endothelial growth factor (VEGF)-A-induced migration of HUVEC in vitro. Site-directed mutagenesis experiments revealed that the cyclic structure formed by the disulfide bridge between Cys⁸³ and Cys⁹⁹ in human ChM-I is indispensable for its anti-angiogenic function. Moreover, the C-terminal hydrophobic tail (from Trp¹¹¹ to Val¹²⁰) was found to play an important role in ensuring the effectiveness of ChM-I activity on HUVEC. A synthetic cyclic peptide corresponding to the ChM-I region between Ile⁸² to Arg¹⁰⁰ also inhibited the migration of HUVEC, while replacing the Cys⁸³ and Cys⁹⁹ residues in this peptide with Ser completely negated this inhibitory activity. An additional synthetic cyclic peptide harboring the hydrophobic C-terminal tail of ChM-I clearly mimicked the inhibitory action of this protein on the migration of HUVEC and successfully inhibited tumor angiogenesis and growth in a xenograft mouse model of human chondrosarcoma.

Localization of chondromodulin-I at the feto-maternal interface and its inhibitory actions on trophoblast invasion in vitro

Background

Chondromodulin-I (ChM-I) is an anti-angiogenic glycoprotein that is specifically localized at the extracellular matrix of the avascular mesenchyme including cartilage and cardiac valves. In this study, we characterized the expression pattern of ChM-I during early pregnancy in mice in vivo and its effect on invasion of trophoblastic cells into Matrigel in vitro.

Results

Northern blot analysis clearly indicated that ChM-I transcripts were expressed in the pregnant mouse uterus at 6.5-9.5 days post coitum. In situ hybridization and immunohistochemistry revealed that ChM-I was localized to the mature decidua surrounding the matrix metalloproteinase-9 (MMP-9)-expressing trophoblasts. Consistent with this observation, the expression of ChM-I mRNA was induced in decidualizing endometrial stromal cells in vitro, in response to estradiol and progesterone. Recombinant human ChM-I (rhChM-I) markedly inhibited the invasion through Matrigel as well as the chemotactic migration of rat Rcho-1 trophoblast cells in a manner independent of MMP activation.

Conclusions

This study demonstrates the inhibitory action of ChM-I on trophoblast migration and invasion, implying the potential role of the ChM-I expression in decidual cells for the regulated tissue remodeling and angiogenesis at feto-maternal interface.

Specific recognition and inhibition of Ewing tumour growth by antigen-specific allo-restricted cytotoxic T cells

Background:

The development of a successful immunotherapy is hampered by an ineffective T-cell repertoire against tumour antigens and the inability of the patient's immune system to overcome tolerance-inducing mechanisms. Here, we test the specific recognition and lytical potential of allo-restricted CD8⁺ T cells against Ewing tumour (ET) associated antigens Enhancer of Zeste, Drosophila Homolog 2 (EZH2), and Chondromodulin-I (CHM1) identified through previous microarray analysis.

Methods:

Following repetitive CHM1³¹⁹ (VIMPCSWWV) and EZH2⁶⁶⁶ (YMCSFLFNL) peptide-driven stimulations with HLA-A^*0201⁺ dendritic cells (DC), allo-restricted HLA-A^*0201⁻ CD8⁺ T cells were stained with HLA-A^*0201/peptide multimers, sorted and expanded by limiting dilution.

Results:

Expanded T cells specifically recognised peptide-pulsed target cells or antigen-transfected cells in the context of HLA-A^*0201 and killed HLA-A^*0201⁺ ET lines expressing the antigen while HLA-A^*0201^– ET lines were not affected. Furthermore, adoptively transferred T cells caused significant ET growth delay in Rag2^−/−γ_C^−/− mice. Within this context, we identified the CHM1³¹⁹ peptide as a new candidate target antigen for ET immunotherapy.

Conclusion:

These results clearly identify the ET-derived antigens, EZH2⁶⁶⁶ and CHM1³¹⁹, as suitable targets for protective allo-restricted human CD8⁺ T-cell responses against non-immunogenic ET and may benefit new therapeutic strategies in ET patients treated with allogeneic stem cell transplantation.

A functional role of the glycosylated N-terminal domain of chondromodulin-I

Chondromodulin-I (ChM-I) is a 25-kDa glycoprotein that specifically localizes in the extracellular matrix of cartilage and negatively regulates angiogenesis. ChM-I comprises two domains: an N-terminal hydrophilic domain (domain 1) containing an N-linked glycosylation site and a C-terminal hydrophobic domain (domain 2) with all four disulfide bonds that are present in this protein. We generated a nonglycosylated recombinant human ChM-I (NG-hChM-I) and compared its bioactivity with that of the glycosylated form of human ChM-I (G-hChM-I) expressed in Chinese hamster ovary cells in vitro. NG-hChM-I exhibited the growth factor/inhibitor activity in the cultures of chondrocytes and vascular endothelial cells but required markedly higher doses. Although domain 1 is predicted to be hydrophilic per se on the basis of its amino acid sequence, NG-hChM-I remains insoluble in aqueous solution as much as ΔN-hChM-I that lacks the N-terminal 37 amino acids containing an N-glycosylation site. Circular dichroism measurements revealed that the content of α-helix was calculated to be 34% in G-hChM-I, whereas the content of the characteristic secondary structures in NG-hChM-I was distinctly lower than those in G-hChM-I. These results indicate that glycosylation in domain 1 is critical for the structural integrity for biological functions of ChM-I in vitro.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Transplanted chondrocytes inhibit endochondral ossification within cartilage repair tissue

The aim of this study was to investigate the effect of transplanted chondrocytes on endochondral bone formation in cartilage repair tissue. In the knee joint of miniature pigs, cartilage lesions were treated by microfracturing and were then either left empty, covered with a collagen membrane, or treated by matrix-associated autologous chondrocyte transplantation. In control lesions, the subchondral bone plate was left intact (partial-thickness lesion). The repair tissues were analyzed after 12 weeks by histological methods focusing on bone formation and vascularization. The effect of chondrocytes on angiogenesis was assessed by in vitro assays. The presence of antiangiogenic proteins in cartilage repair tissue, including thrombospondin-1 (TSP-1) and chondromodulin-I (ChM-I), was detected immunohistochemically and their expression in chondrocytes and bone marrow stromal cells was measured by quantitative RT-PCR. Significant outgrowths of subchondral bone and excessive endochondral ossification within the repair tissue were regularly observed in lesions with an exposed or microfractured subchondral bone plate. In contrast, such excessive bone formation was significantly inhibited by the additional transplantation of chondrocytes. Cartilaginous repair tissue that resisted ossification was strongly positive for the antiangiogenic proteins, TSP-1 and ChM-I, which were, however, not detectable in vascularized osseous outgrowths. Chondrocytes were identified to be the major source of TSP-1- and ChM-I expression and were shown to counteract the angiogenic activity of endothelial cells. These data suggest that the resistance of cartilaginous repair tissue against endochondral ossification following the transplantation of chondrocytes is associated with the presence of antiangiogenic proteins whose individual relevance has yet to be further explored.

Benzene metabolite hydroquinone up-regulates chondromodulin-I and inhibits tube formation in human bone marrow endothelial cells

Bone marrow is a major target of benzene toxicity, and NAD-(P)H:quinone oxidoreductase (NQO1), an enzyme protective against benzene toxicity, is present in human bone marrow endothelial cells, which form the hematopoietic stem cell vascular niche. In this study, we have employed a transformed human bone marrow endothelial cell (TrHBMEC) line to study the adverse effects induced by the benzene metabolite hydroquinone. Hydroquinone inhibited TrHBMEC tube formation at concentrations that were not overtly toxic, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or sulforhodamine B analysis. Hydroquinone was found to up-regulate chondromodulin-I (ChM-I), a protein that promotes chondrocyte growth and inhibits endothelial cell growth and tube formation. Recombinant human ChM-I protein inhibited tube formation in TrHBMECs, suggesting that up-regulation of ChM-I may explain the ability of hydroquinone to inhibit TrHB-MEC tube formation. To explore this possibility further, anti-ChM-I small interfering RNA (siRNA) was used to deplete ChM-I mRNA and protein. Pretreatment with anti-ChM-I siRNA markedly abrogated hydroquinone-induced inhibition of tube formation in TrHBMECs. Overexpression of the protective enzyme NQO1 in TrHBMECs inhibited the up-regulation of ChM-I and abrogated the inhibition of tube formation induced by hydroquinone. In summary, hydroquinone treatment up-regulated ChM-I and inhibited tube formation in TrHBMECs; NQO1 inhibited hydroquinone-induced up-regulation of ChM-I in TrHB-MECs and protected cells from hydroquinone-induced inhibition of tube formation. This study demonstrates that ChM-I up-regulation is one of the underlying mechanisms of inhibition of tube formation and provides a mechanism that may contribute to benzene-induced toxicity at the level of bone marrow endothelium.

Chondromodulin-1 directly suppresses growth of human cancer cells

Background

Chondromodulin-1 (ChM1), an endogenous anti-angiogenic factor expressed in cartilage, has been suggested to inhibit invasion of endothelial cells into cartilage. In addition, the ectopic administration of ChM1 has been reported to suppress tumorigenesis in vivo. However, it is unclear whether the anti-tumor effect is due to not only the anti-vascularization effect of ChM1, but also its direct action against oncocytes. In the present study, we sought to determine whether ChM1 has a direct action on tumor cells.

Methods

BrdU incorporation assay was performed on human umbilical vein endothelial cells (HUVECs), normal human dermal fibroblasts (NHDFs), HepG2 cells and HeLa cells in the presence or absence of recombinant human ChM1 (rhChM1). An adenovirus that expresses ChM1, Ad-ChM1, was established and applied to the tumor xenografted in vivo, and to in vitro tumor cells cultured on plates or in soft agar. Cell cycle-related proteins and the phosphorylation of Erk, Akt, and GSK3β, the downstream molecules of the extracellular matrix-integrin signaling pathways, in HepG2 cells treated with or without Ad-ChM1 were detected by western blot analysis. Luciferase reporter assays of STAT, GAS, and ISRE, which participate in another cytokine signaling pathway, ware performed in HepG2, HeLa, and HUVEC cells.

Results

ChM1 suppressed BrdU incorporation in HUVECs and in HepG2 cells dose-dependently, but did not suppress BrdU incorporation in NHDFs and HeLa cells cultured on plates. In soft agar, however, ChM1 suppressed the growth of HeLa cells, as well as HepG2 cells. Western blot analyses demonstrated that ChM1 decreased the levels of cyclin D1, cyclin D3, and cdk6 and increased those of p21^cip1 without affecting the phosphorylation levels of Erk, Akt, and GSK3β in HepG2 cells. The luciferase reporter assay demonstrated that ChM1 suppressed the transcriptional activities of STAT and GAS but not of ISRE.

Conclusion

ChM1 directly suppressed the proliferation of tumor cells in an anchorage-independent manner. However, ChM1 did not alter the phosphorylation of downstream molecules, at which the signaling pathways through growth factor and cytokine receptors converge with the anchorage-dependent pathway. Our results show that ChM1 has a direct anti-tumor effect; moreover, this effect occurs by inhibiting the STAT signaling pathway.

Altered fracture callus formation in chondromodulin-I deficient mice

Chondromodulin-I (Chm-I) is a glycoprotein that stimulates the growth of chondrocytes and inhibits angiogenesis in vitro. Mice lacking the Chm1 gene show abnormal bone metabolism and pathological angiogenesis in cardiac valves in the mature stage although they develop normally without aberrations in endochondral bone formation during embryogenesis or in cartilage development during growth. These findings indicate that Chm-I is critical under conditions of stress such as bone repair through endochondral ossification of a fracture callus. We carried out the present study to examine the expression and role of Chm-I in bone repair using a stabilized tibial fracture model, and compared fracture healing in Chm1 knockout (Chm1(-/-)) mice with that in wild-type mice. Chm-I mRNA and protein localized in the external cartilaginous callus in the reparative phase of fracture healing. Radiological examination showed a delayed union in Chm1(-/-) mice although the fracture site was covered with both external and internal calluses. Chm1 null mutation reduced external cartilaginous callus formation as judged by marked decrease of type X collagen alpha 1 (Col10a1) expression and the total amount of cartilage matrix. Interestingly, the majority of chondrocytes in the periosteal callus failed to differentiate into mature chondrocytes in Chm1(-/-) mice, while the hypertrophic maturation of chondrocytes between the cortices was not affected. These results suggest that Chm-I is involved in hypertrophic maturation of periosteal chondrocytes. Although a direct effect of Chm-I on bones is still unclear, bony callus formation was increased while external cartilaginous callus decreased in Chm1(-/-) mice. We conclude that in the absence of Chm1, predominant primary bone healing occurs due to an indirect effect induced by reduction of cartilaginous callus rather than to a direct effect on osteogenic function, resulting in a delayed union.

Cartilaginous features in matrix-producing carcinoma of the breast: four cases report with histochemical and immunohistochemical analysis of matrix molecules

Matrix-producing carcinoma of the breast is a well-established entity in the group of metaplastic carcinoma, which is histologically characterized by myxochondroid matrix formation and is extremely rare. We describe here four additional cases of matrix-producing carcinoma of the breast. All cases of matrix-producing carcinoma show nest-like, sheet-like, and cord-like growth of tumor cells with cellular atypia, in addition to scattered cancer cells within myxoid or myxohyalinous stroma. Three of four cases showed an acellular or oligocellular matrix-rich zone in the center of the tumor. Immunohistochemically, cancer cells of all cases were positive for cytokeratins and epithelial membrane antigens and partially positive for sox9 and p63. Aggrecan and type II collagen, which are cartilage-specific matrix molecules, were deposited in the stroma of all cases. Type I and type IV collagens were also deposited on the stroma of all cases. These findings suggest that, although cancer cells of matrix-producing carcinoma of the breast are epithelial, they transdifferentiate to chondrocyte-like cells and produce cartilage-specific matrix molecules, which are useful markers for diagnosing matrix-producing carcinoma.

Chondromodulin-I maintains cardiac valvular function by preventing angiogenesis

The avascularity of cardiac valves is abrogated in several valvular heart diseases (VHDs). This study investigated the molecular mechanisms underlying valvular avascularity and its correlation with VHD. Chondromodulin-I, an antiangiogenic factor isolated from cartilage, is abundantly expressed in cardiac valves. Gene targeting of chondromodulin-I resulted in enhanced Vegf-A expression, angiogenesis, lipid deposition and calcification in the cardiac valves of aged mice. Echocardiography showed aortic valve thickening, calcification and turbulent flow, indicative of early changes in aortic stenosis. Conditioned medium obtained from cultured valvular interstitial cells strongly inhibited tube formation and mobilization of endothelial cells and induced their apoptosis; these effects were partially inhibited by chondromodulin-I small interfering RNA. In human VHD, including cases associated with infective endocarditis, rheumatic heart disease and atherosclerosis, VEGF-A expression, neovascularization and calcification were observed in areas of chondromodulin-I downregulation. These findings provide evidence that chondromodulin-I has a pivotal role in maintaining valvular normal function by preventing angiogenesis that may lead to VHD.

Co-localization of chondromodulin-I (ChM-I) and bone morphogenetic protein-6 (BMP-6) in myoepithelial cells of canine mammary tumors

To compare the roles of chondromodulin-I (ChM-I) and bone morphogenetic protein-6 (BMP-6) in ectopic mesenchymal tissue formation in canine mammary gland tumors, 33 tumors and 2 normal mammary glands were examined. Immunohistochemical analysis revealed co-expression of ChM-I and BMP-6 in canine mammary tumors. In mixed tumors, newly formed woven bone with ossified cartilage matrix was observed in 4/9 cases. The osteoblasts lining the woven bone showed moderate immunoreactivity to ChM-I and BMP-6. Almost all chondrocytes and proliferative myoepithelial cells within the basement membrane showed intense immunoreactivity to both, and the myoepithelial cells adjacent to the mature cartilage showed the most intense immunoreactivity. The immunoreactivity to ChM-I and BMP-6 of the interstitial myoepithelial cells in the myxomatous stroma varied in each focus of mixed tumors. Similar findings were found in complex adenomas. In simple adenomas, hyperplasic myoepithelial cells within the basement membrane showed moderate immunoreactivity to both markers. Western blot analysis detected a 25 kDa band of ChM-I in fresh tissue samples from three mixed tumors. Our results support the hypothesis that proliferating myoepithelial cells with ChM-I and BMP-6 expression play important roles in mesenchymal metaplasia in canine mammary tumors.

Recent advances in the basic science of chondrosarcoma

Chondrosarcoma are a heterogeneous group of tumors whose treatment is limited to surgical removal. Molecular genetic analysis of these tumors has revealed some of the abnormalities responsible for the traits of the malignant phenotype.

Chondromodulin-I and tenomodulin: a new class of tissue-specific angiogenesis inhibitors found in hypovascular connective tissues

In tissues and/or organs of mesenchymal origin, the vasculature is usually well developed. However, there are certain hypovascular tissues that exhibit powerful anti-angiogenic resistance, implying the presence of tissue-type specific inhibitors of angiogenesis. Hyaline cartilage is one example, and several anti-angiogenic factors have been purified from cartilage. We previously identified chondromodulin-I (ChM-I) as a tissue-specific inhibitor of angiogenesis in fetal bovine cartilage. ChM-I is specifically expressed in the avascular regions of the growth-plate and cartilaginous bone rudiments in embryos. Recently, we cloned a novel type II transmembrane protein, tenomodulin (TeM), having a domain homologous to ChM-I at its C-terminus. TeM turned out to be expressed specifically in other hypovascular structures in the mesenchyme, such as the epimysium, tendon, and ligaments. In this overview, we discuss the structural characteristics of this class of anti-angiogenic molecules and their pathophysiological role in the control of vascularity.

Angiogenesis inhibitors localized in hypovascular mesenchymal tissues: chondromodulin-I and tenomodulin

The majority of mesenchymal tissues obtain their nutrients via a well-developed network of capillaries. Cartilage, however, is normally devoid of capillary networks and, with the exception of endochondral bone formation, is resistant to vascular invasion from surrounding tissues. However, because of its avascular nature, cartilage is widely regarded as an enriched source of endogenous angiogenesis inhibitors, and many previous attempts have been made to identify these factors. We have identified chondromodulin-I (ChM-I) as an angiogenesis inhibitor derived from extracts of fetal epiphyseal cartilage, based upon its growth inhibitory activity in vascular endothelial cells in vitro. In the musculoskeletal system, ChM-I is specifically expressed in the avascular zones of cartilage. Upon functional expression of human ChM-I precursor cDNA, the purified recombinant protein was found to block the growth of solid tumors by inhibiting angiogenesis. Recently, we also cloned a cDNA that encodes a novel type II transmembrane glycoprotein containing a cysteine rich C-terminal domain homologous to ChM-I. We termed this glycoprotein "tenomodulin" (TeM) after tendons that were found to be the predominant expression sites in addition to other dense connective tissues including ligaments and cornea. Subsequently, by employing an adenovirus-mediated expression system, we demonstrated that the ChM-I-like domain of TeM is both antiangiogenic and antitumorigenic. In this article, we summarize the structural characteristics and biological activities of these two antiangiogenic molecules.

Localization and expression of chondromodulin-I in the rat cornea

The localization and expression in the rat cornea of chondromodulin-I (ChM-I), an inhibitory angiogenesis factor, were examined by immunohistochemistry, Western blot analysis, ribonuclease protection assay, and real-time PCR assay. We found immunoreactivity for ChM-I in the epithelial layer but not the stromal layer or endothelial layer in the cornea, in addition to the positive ChM-I immunoreactivity in other sites in the eye such as the sclera, retina, and ciliary body. The ChM-I immunoreactivity was most intense at the outside of the basal cells and in their cytoplasm while the intensity of the immunoreactivity decreased gradually from the wing cells to the superficial cells in the corneal epithelial layer. No reactivity however, was detected in the Bowman's membrane or conjunctival epithelial cells which had continuity with the corneal epithelial cells. The expression of ChM-I mRNA was demonstrated in the cornea at one-third less intensity than that in the sclera with choroids and retinal pigment epithelium by ribonuclease protection assay and real-time PCR. ChM-I in the corneal epithelial layer may prevent neovascularization and maintain avascularity in the cornea.

Expression and localization of cartilage-specific matrix protein chondromodulin-I mRNA in salivary pleomorphic adenomas

Pleomorphic adenoma is the most common epithelial tumor in the salivary glands. This tumor frequently exhibits "mesenchyme"-like components, including myxoid or chondroid areas. Recently, using immunohistochemical techniques, we reported that cartilage-specific matrix protein, chondromodulin-I (ChM-I), was deposited on the inter-territorial matrix of the chondroid area in salivary pleomorphic adenomas and that ChM-I, which is also a strong angio-inhibitory factor, plays an important role in the avascular nature of the chondroid area and the chondroid formation in this type of tumor. To elucidate which cells express ChM-I mRNA in pleomorphic adenomas, we examined the expression and localization of ChM-I mRNA in this type of tumor using an in situ hybridization technique. Immunoreactivity for ChM-I was observed in the inter-territorial matrix of the chondroid area, especially around the lacunae, and in the cytoplasm of neoplastic myoepithelial cells of the myxoid element of pleomorphic adenomas. On in situ hybridization analysis, strong signals for ChM-I mRNA were detected in the cytoplasm of the lacuna cells of the chondroid element, and moderate to marked signals were observed in the cytoplasm of the neoplastic myoepithelial cells of the myxoid element. Signals for ChM-I mRNA were also seen in the cytoplasm of the spindle-shaped neoplastic myoepithelial cells in the transitional areas between the myxoid and chondroid elements of this tumor. Signals for ChM-I mRNA were not seen in the inner ductal cells or the fibrous element. These findings indicate that lacuna cells and neoplastic myoepithelial cells express ChM-I mRNA and that mature ChM-I, which lacuna cells and neoplastic myoepithelial cells translate, is deposited in the chondroid matrix of pleomorphic adenomas. In conclusion, lacuna cells and neoplastic myoepithelial cells express ChM-I mRNA ectopically in pleomorphic adenoma, and this plays an important role in chondroid formation and hypovascularity in this type of tumor.

Hypoxia induces HIF-1alpha and VEGF expression in chondrosarcoma cells and chondrocytes

Like other tumors, chondrosarcoma must induce neovascularity as they grow. Recent studies have demonstrated that chondrosarcoma are vascular. Since normal cartilage is a hypoxic, yet avascular tissue and since chondrosarcoma bears some phenotypic relation to cartilage, it is not clear if hypoxic pathways remain intact in these tissues. Hypoxia-inducible factor 1alpha (HIF-1alpha) is the inducible subunit of the HIF-1 transcription factor that regulates genes involved in the response to hypoxia, some of which promote neovascularity. Vascular endothelial growth factor (VEGF) is one of the genes upregulated by HIF-1 and is the primary cytokine related to angiogenesis. In this study we examined the response of chondrocytes and chondrosarcoma cell lines to hypoxia. We found that both normal and malignant chondrocytes increased HIF-1alpha protein expression in an oxygen concentration dependent manner and also increased VEGF mRNA expression in response to hypoxia. HIF-1alpha protein and VEGF mRNA decreased when chondrosarcoma cells were transfected with siRNA targeting HIF-1alpha prior to hypoxia exposure, suggesting that HIF-1alpha expression resulted in increased VEGF expression. The role of the HIF-1alpha/VEGF pathway in angiogenesis in chondrosarcoma in vivo and its usefulness as a target for antiangiogenic treatment strategies for this tumor requires further investigation.

The combination of SOX5, SOX6, and SOX9 (the SOX trio) provides signals sufficient for induction of permanent cartilage

OBJECTIVE

To regenerate permanent cartilage, it is crucial to know not only the necessary conditions for chondrogenesis, but also the sufficient conditions. The objective of this study was to determine the signal sufficient for chondrogenesis.

METHODS

Embryonic stem cells that had been engineered to fluoresce upon chondrocyte differentiation were treated with combinations of factors necessary for chondrogenesis, and chondrocyte differentiation was detected as fluorescence. We screened for the combination that could induce fluorescence within 3 days. Then, primary mesenchymal stem cells, nonchondrogenic immortalized cell lines, and primary dermal fibroblasts were treated with the combination, and the induction of chondrocyte differentiation was assessed by detecting the expression of the cartilage marker genes and the accumulation of proteoglycan-rich matrix. The effects of monolayer, spheroid, and 3-dimensional culture systems on induction by combinations of transcription factors were compared. The effects of the combination on hypertrophic and osteoblastic differentiation were evaluated by detecting the expression of the characteristic marker genes.

RESULTS

No single factor induced fluorescence. Among various combinations examined, only the SOX5, SOX6, and SOX9 combination (the SOX trio) induced fluorescence within 3 days. The SOX trio successfully induced chondrocyte differentiation in all cell types tested, including nonchondrogenic types, and the induction occurred regardless of the culture system used. Contrary to the conventional chondrogenic techniques, the SOX trio suppressed hypertrophic and osteogenic differentiation at the same time.

CONCLUSION

These data strongly suggest that the SOX trio provides signals sufficient for the induction of permanent cartilage.

Chondromodulin-I expression in the growth plate of young uremic rats

BACKGROUND

Growth retardation of chronic renal failure is associated with alterations in the growth plate suggestive of a disturbed chondrocyte maturation process and abnormal vascular invasion at the chondro-osseous interphase. Chondromodulin I (ChM-I) is a potent cartilage-specific angiostatic factor. Its pattern of expression in the uremic rat growth plate is unknown. Persistence of ChM-I synthesis and/or imbalance between ChM-I and vascular endothelial growth factor (VEGF) expressions might play a role in the alterations of uremic growth plate.

METHODS

Growth cartilage ChM-I expression was investigated by immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) in growth-retarded young uremic rats (UREM), control rats, fed ad libitum (SAL) or pair-fed with the UREM group (SPF), and uremic rats treated with growth hormone (UREM-GH). VEGF expression was analyzed by immunohistochemistry.

RESULTS

ChM-I and ChM-I mRNA were confined to the proliferative and early hypertrophic zones of growth cartilage. A similar number of chondrocytes per column was positive for ChM-I in the 4 groups. In accordance with the elongation of the hypertrophic stratum in uremia, the distance (X+/-SEM, microm) between the extracellular ChM-I signal and the metaphyseal end of growth cartilage was higher (P < 0.003) in UREM (236 +/- 40) and UREM-GH (297 +/- 17) than in SAL (92 +/- 7) and SPF (113 +/- 6). No differences in ChM-I expression were appreciated by RT-PCR. Similar VEGF positivity was observed in the hypertrophic chondrocytes of all groups.

CONCLUSION

In experimental uremia, expansion of growth cartilage does not result from increased or persistent expression of ChM-I or from reduced VEGF expression at the cartilage-metaphyseal bone interphase. GH treatment does not modify ChM-I and VEGF expressions.

Expression Profiles Provide Insights into Early Malignant Potential and Skeletal Abnormalities in Multiple Endocrine Neoplasia Type 2B Syndrome Tumors

Identifying the molecular basis for genotype-phenotype correlations in human diseases has direct implications for understanding the disease process and hence for the identification of potential therapeutic targets. To this end, we performed microarray expression analysis on benign (pheochromocytomas) and malignant (medullary thyroid carcinomas, MTCs) tumors from patients with multiple endocrine neoplasia (MEN) type 2A or 2B, related syndromes that result from distinctive mutations in the RET receptor tyrosine kinase. Comparisons of MEN 2B and MEN 2A MTCs revealed that genes involved in the process of epithelial to mesenchymal transition, many associated with the tumor growth factor beta pathway, were up-regulated in MEN 2B MTCs. This MEN 2B MTC profile may explain the early onset of malignancy in MEN 2B compared with MEN 2A patients. Furthermore, chondromodulin-1, a known regulator of cartilage and bone growth, was expressed at high levels specifically in MEN 2B MTCs. Chondromodulin-1 mRNA and protein expression was localized to the malignant C cells, and its high expression was directly associated with the presence of skeletal abnormalities in MEN 2B patients. These findings provide molecular evidence that associate the previously unexplained skeletal abnormalities and early malignancy in MEN 2B compared with MEN 2A syndrome.

Anti-angiogenic action of the C-terminal domain of tenomodulin that shares homology with chondromodulin-I

Tenomodulin (TeM) is a type II transmembrane glycoprotein that contains a C-terminal domain with homology to the mature, secreted form of chondromodulin-I (ChM-I), a cartilage-derived angiogenesis inhibitor. TeM transcripts have been found in hypovascular tissues such as tendons and ligaments but the biological activity of TeM has not yet been fully explored. Using an adenovirus expression system, we utilized the forced expression and subsequent secretion of the human TeM C-terminal 116 amino acids (Ad-shTeM) in human umbilical vein endothelial cells (HUVECs) to assess the anti-angiogenic properties of TeM. The C-terminal 120 amino acids of the human ChM-I precursor (Ad-shChM-I) was similarly expressed in HUVECs as a comparison study. Transduction of both Ad-shTeM and Ad-shChM-I resulted in significant impairment of the tube-forming activity of HUVECs, when cultured in Matrigel. Similarly, conditioned medium from COS7 cells, transfected with plasmid DNA encoding shTeM or shChM-I, inhibited tube formation of HUVECs when compared to medium derived from either COS7 cells transfected with control vector or from non-transfected cells. Upon infection of HUVECs with Ad-shTeM or Ad-shChM-I, DNA synthesis stimulated by vascular endothelial growth factor (VEGF) was reduced to 40-50% of normal levels. Additionally, in a modified Boyden chamber assay, migration of HUVECs in response to VEGF was significantly affected following transduction of either Ad-shTeM or Ad-shChM-I and these transduced HUVECs were found to spread well on type I collagen or fibronectin, but not on vitronectin. Furthermore, the transduction of either Ad-shTeM or Ad-shChM-I in human melanoma cells resulted in suppression of tumor growth in association with decreased vessel density in vivo. Hence, we have demonstrated that, similarly to ChM-1, the C-terminal domain of TeM exhibits both anti-angiogenic and anti-tumor activities when expressed in a secreted form.

Expression of the chondromodulin-I gene in chondrosarcomas

We investigated the expression of the Chondromodulin-I (ChM-I) gene, a putative tumor suppressor gene in cartilaginous tumors, by quantitative RT-PCR in 15 chondrosarcomas (CSs). Eight CSs expressed the ChM-I gene at the level higher than those in articular cartilage (positive cases), whereas the expression of the ChM-I gene in the remaining seven CSs was lower than those in articular cartilage (negative cases). All of five peripheral CS were positive, and the ChM-I positive tumors shared expression profiles of cartilage-related genes with articular cartilage cells. On the other hand, all of four central CSs without extramedullary lesions were negative, and the ChM-I negative tumors expressed the parathyroid hormone-related peptide gene at the lower level and the COL10A1 genes at the higher level than articular cartilage cells. Neither the histological grade nor the rate of recurrence showed clear association with the level of ChM-I gene expression. These results suggested that the expression of ChM-I gene in CS has no direct role in tumorigenesis but rather reflects the site of tumor development and therefore precursor of tumor cells.

Suppression of T cell responses by chondromodulin I, a cartilage-derived angiogenesis inhibitory factor: Therapeutic potential in rheumatoid arthritis

OBJECTIVE

Chondromodulin I (ChM-I), a cartilage matrix protein, promotes the growth and proteoglycan synthesis of chondrocytes. However, it also inhibits angiogenesis. Since ChM-I is expressed not only in cartilage, but also in the thymus, we investigated the modulation of T cell function by ChM-I to assess its therapeutic potential in rheumatoid arthritis (RA).

METHODS

The localization of ChM-I expression in mouse thymus tissue was examined by in situ hybridization. The proliferative response of peripheral blood T cells and synovial cells obtained from patients with RA was evaluated by (3)H-thymidine incorporation assay. The effects of ChM-I were examined using recombinant human ChM-I (rHuChM-I). Modulation of the antigen-specific immune response was evaluated by the recall response of splenic T cells and the delayed-type hypersensitivity response induced in the ear of mice primed with ovalbumin (OVA). Antigen-induced arthritis (AIA) was induced in mice by injecting methylated bovine serum albumin into the ankle joints 2 weeks after the priming.

RESULTS

ChM-I was expressed in the cortex of the thymus. Recombinant human ChM-I suppressed the proliferative response of mouse splenic T cells and human peripheral blood T cells stimulated with anti-CD3/CD28 antibodies, in a dose-dependent manner. Production of interleukin-2 was decreased in rHuChM-I-treated mouse CD4 T cells. Ten micrograms of rHuChM-I injected intraperitoneally into OVA-primed mice suppressed the induction of the antigen-specific immune response. Finally, rHuChM-I suppressed the development of AIA, and also suppressed the proliferation of synovial cells prepared from the joints of patients with RA.

CONCLUSION

These results suggest that ChM-I suppresses T cell responses and synovial cell proliferation, implying that this cartilage matrix protein has a therapeutic potential in RA.

Immunohistochemical evaluation of cartilage-derived morphogenic protein-1 and -2 in normal human salivary glands and pleomorphic adenomas

Cartilage-derived morphogenic protein (CDMP)-1 and -2 belong to the bone morphogenetic protein (BMP) family in the transforming growth factor (TGF)-beta superfamily. CDMP-1 and CDMP-2 were reported to play essential roles in limb cartilage and limb-joint formation in developing mice. Although pleomorphic adenoma of the salivary glands is an epithelial tumor, it frequently shows ectopic cartilaginous formation. These findings suggested that CDMP-1 and -2 may play essential roles in chondroid formation in salivary pleomorphic adenoma. To evaluate this hypothesis, we examined the expression and localization of CDMP-1 and -2 immunohistochemically in 20 normal human salivary glands and 35 pleomorphic adenomas. CDMP-1 was immunolocalized in the striated ducts and the intercalated ducts in the normal salivary glands. CDMP-1 was immunolocalized in the cuboidal neoplastic myoepithelial cells around the chondroid areas of the pleomorphic adenomas, whereas these molecules were not localized in the spindle-shaped neoplastic myoepithelial cells of the myxoid element or the lacuna cells of the chondroid element in these tumors. CDMP-2 was expressed neither in normal salivary glands nor any of the elements of the pleomorphic adenomas. Type-II collagen and aggrecan were immunolocalized throughout the matrix around the lacuna cells of the chondroid element, whereas type-X collagen was not immunolocalized in any epithelial or stromal elements, including the chondroid elements. Aggrecan was deposited not only on the chondroid matrix, but also on the myxoid stroma and intercellular spaces of the tubulo-glandular structures, whereas chondromodulin-I was deposited on the chondroid matrix. These results indicated that the cuboidal neoplastic myoepithelial cells around the chondroid areas expressed CDMP-1 and suggested that this molecule may play a role in the differentiation of neoplastic myoepithelial cells in pleomorphic adenoma. The phenotype of the lacuna cells was similar to that of mature to upper hypertrophic chondrocytes of the authentic cartilage. In conclusion, pleomorphic adenoma expressed CDMP-1 but not CDMP-2.

Chondromodulin-I expression in rat articular cartilage

The localization and expression of chondromodulin-I (ChM-I), an angiogenesis inhibitor, in the rat articular cartilage during maturation from 2 to 10 weeks of age were examined by immunohistochemistry, Western blot analysis and ribonuclease protection assay, and the results were compared with those in the epiphyseal cartilage. ChM-I was found to be diffusely immunostained in the inter-territorial space of the cartilage matrix from the intermediate to the deep layers at the immature stage. As the articular cartilage matured, the immunoreactivity was localized around the hypertrophic chondrocytes in the deep layer and the immunoreactivity became weak after maturation. In contrast, the ChM-I immunoreactivity was intense in the epiphyseal cartilage at all ages examined. ChM-I was detected by Western blotting as a broad band or occasionally as a cluster of multiple bands (approximately 25 kDa) in both the articular and the epiphyseal cartilage. The intensity of the bands decreased gradually with age in the articular cartilage, but was unchanged in the epiphyseal cartilage at all ages. Ribonuclease protection assay revealed that ChM-I mRNA also decreased gradually with age in the articular cartilage in parallel with the maturation of the articular cartilage, while no decrease in ChM-I mRNA was found in the epiphyseal cartilage. The expression of ChM-I mRNA in the articular cartilage was less than that in the epiphyseal cartilage at all ages. The decrease in amount of ChM-I in the mature articular cartilage suggests that ChM-I plays a more important role in the maintenance of avascularity in the immature articular cartilage than in the mature one. The avascular condition may be preserved by angiogenic inhibitors or mechanisms other than ChM-I in the mature articular cartilage.

Cartilage-specific matrix protein, chondromodulin-I (ChM-I), is a strong angio-inhibitor in endochondral ossification of human neonatal vertebral tissues in vivo: relationship with angiogenic factors in the cartilage

Although cartilage contains many angiogenic factors during endochondral ossification, it is an avascular tissue. The cartilage-specific non-collagenous matrix protein chondromodulin-I (ChM-I) has been shown to be a strong angio-inhibitor. To elucidate whether ChM-I plays an essential role in angio-inhibition during endochondral ossification in man, we investigated the expression and localization of ChM-I in comparison with those of angiogenic factors and the endothelial cell marker CD34 in human neonatal vertebral tissues. Although invasion of CD34-positive endothelial cells was observed in primary subchondral spongiosa, expression of the marker of endothelial cells, CD34, was not found in neonatal vertebral cartilage matrix. Type II collagen was deposited in all matrices during endochondral ossification, whereas aggrecan was deposited in the matrix of hypertrophic cartilage, especially around lacunae. Vascular endothelial growth factor (VEGF), which is known to be a strong angiogenic factor, was localized in chondrocytes in mature to hypertrophic cartilage and also in bone marrow. Fibroblast growth factor-2 (FGF-2; basic fibroblast growth factor), which is also known to be a strong angiogenic factor, was localized in the cytoplasm of chondrocytes of mature cartilage in human vertebral cartilage tissues. Transforming growth factor (TGF)-beta has been reported to have many functions including angiogenesis, and TGF-beta1 was also localized in mature chondrocytes in endochondral tissues undergoing ossification. On the other hand, the novel cartilage-specific matrix protein ChM-I was localized in interterritorial regions of the matrix in mature to hypertrophic cartilage, especially around lacunae. In conclusion, these observations indicate that ChM-I may serve as a barrier against the angiogenic properties of VEGF, FGF-2 and TGF-beta1 during endochondral ossification, and this matrix molecule may play an essential role in determining the avascular nature of cartilage in vivo.

Role of cartilage-derived anti-angiogenic factor, chondromodulin-I, during endochondral bone formation

OBJECTIVE

Cartilage is a typical avasclar tissue that exhibits powerful resistance to angiogenesis or vascular invasion. We previously identified a cartilage-specific 25 kDa glycosylated protein, chondromodulin-I (ChM-I), as anti-angiogenic factor. Taking advantage of ectopic bone formation and xenograft tumour model by human chondrosarcoma cell line OUMS-27, we examined how ChM-I is involved in switching of angiogenesis in cartilage.

DESIGN

Gene expression pattern of ChM-I was examined in 4-week-old mice and mouse embryos by northern blot analysis and in situ hybridization. To evaluate the effect of ChM-I on ectopic bone formation, guanidine extracts of demineralized bone matrix were mixed with the ChM-I-bound heparin-Sepharose beads and were implanted onto the fasciae of back muscle of 6-week old nude mice. To analyse the effect of ChM-I on tumour angiogenesis, the level of ChM-I mRNA in cartilaginous tumours was assessed by competitive PCR, and compared with that of articular cartilage. Then, human chondrosarcoma OUMS-27 cells were inoculated into the back of nude mice to form a tumour about 45 mm3 in size. Recombinant ChM-I protein was administrated into OUMS-27 xenograft tumours for the initial 5 days to study its effect against tumour-angiogenesis.

RESULTS

ChM-I gene was specifically expressed in cartilage of 4-week-old mice. Eye and thymus were also identified as minor expression sites. However, during endochondral bone development, cartilage changes its character from anti-angiogenic into angiogenic prior to the replacement of calcified cartilage by bone. In embryos, ChM-I mRNA was expressed in proliferative and upper hypertrophic cartilage zones in the developing cartilaginous bone rudiments, but completely abolished in lower hypertrophic and calcified cartilage zones. Purified ChM-I protein apparently inhibited vascular invasion into cartilage induced by the implantation of demineralized bone matrix in nude mice, leading to the inhibition of replacement of cartilage. The level of ChM-I transcripts in the lower-grade chondrosarcomas was substantially reduced to several hundreds or less in the lower-grade chondrosarcomas, compared with that of articular cartilage or other benign cartilage tumours. The local administration of recombinant human ChM-I almost completely blocked tumour angiogenesis and growth in the human chondrosarcoma xenografts in mice.

CONCLUSIONS

ChM-I is involved in the anti-angiogenic property of cartilage and its absence creates a permissive microenvironment for vascular invasion into cartilage under physiological and pathological conditions.

Bizarre parosteal osteochondromatous proliferation (Nora's lesion) of the foot

A 22-year-old man presented with a growing lump on the fifth metatarsal of the right foot. Radiographically, the lesion was a calcified mass stuck on to the bone. The T2-weighted magnetic resonance images showed heterogeneity in intensity. A tumor was suspected and an excisional biopsy was done. The lesion was composed of a cartilaginous cap and bone tissue. Histological examination revealed characteristic features of bizarre parosteal osteochondromatous proliferation (BPOP), such as hypercellularity, a blue tinctorial quality in the osteocartilaginous interfaces, and a scattering of binucleated or bizarre enlarged chondrocytes. Immunohistochemically, basic fibroblast growth factor was expressed in nearly all chondrocytes within the cartilaginous cap, while vascular endothelial growth factor was expressed only in enlarged chondrocytes near the osteocartilaginous interfaces. Reverse transcription-polymerase chain reaction detected chondromodulin-I transcripts in the tissue of the cartilaginous cap. These findings indicate that the processes occurring in BPOP are similar to those occurring in endochondral ossification in the growth plate, and they support the concept that BPOP is a reparative process. BPOP is a rare tumorous lesion of the bone and is occasionally confused with other benign or malignant conditions. Thus, it is important to consider the clinical, radiographical and the gross histological features of the lesion when making a diagnosis.

Sequence analysis of zebrafish chondromodulin-1 and expression profile in the notochord and chondrogenic regions during cartilage morphogenesis

Chondromodulin-I (ChM-I) is suggested in higher vertebrate systems to function as a key regulatory protein for cartilage development. To further understand the process of chondrogenesis and the function of ChM-I, we have cloned the zebrafish cDNA for chondromodulin-1 (chm1) and have mapped the chm1 gene locus. The expression profile of chm1 was determined during zebrafish embryonic development and compared to that of type II collagen (col2a1). Maternal chm1 transcripts were detected before midblastula transition and zygotic expression of chm1 was first observed in the notochord at the 10-somite stage. At later developmental stages, chm1 expression was detected in areas surrounding the otic vesicles, in the developing craniofacial cartilage elements, and in the chondrogenic region of the pectoral fins.

Post-translational processing of bovine chondromodulin-I

Chondromodulin-I (ChM-I) is a small glycoprotein that is abundant in fetal cartilage. Mature chondromodulin-I is processed from a larger precursor form, presumably at a proteolytic site RERR-ELVR. The precursor, mature chondromodulin-I and two processed products, the remnant left after removal of mature chondromodulin-I and a smaller, unglycosylated form, were identified using antipeptide antisera. The products of chondromodulin-I precursor processing were seen in cultured chondrocytes, a stable long-term culture chondrosarcoma cell line, as well as Chinese hamster ovary (CHO) cells transfected with an expression plasmid that contained cDNA coding for the chondromodulin-I precursor. Pulse-chase analysis allowed a processing pathway to be analyzed for chondromodulin-I. To further dissect the processing events, three constructs that express recombinant wild-type or mutant chondromodulin-I were transfected into CHO cells. We showed that chondromodulin-I is cleaved intracellularly at the predicted cleavage site, and that the mature glycopeptide is rapidly secreted immediately after processing. The chondromodulin-1 precursor has a short half-life and is not readily apparent in tissue samples, suggesting that chondromodulin is not a member of the juxtacrine family of growth factors, despite some similarities. The smaller unglycosylated form of chondromodulin-I was only observed in cartilage and not in short-term cultures or transfected cells, suggesting an extracellular processing event. No processing occurred when the precursor cleavage site was mutated to RERQ-SLVR or when precursor chondromodulin-I was expressed in the furin-deficient CHO cell line, suggesting the involvement of furin in processing.

Cartilage-specific matrix protein chondromodulin-I is associated with chondroid formation in salivary pleomorphic adenomas: immunohistochemical analysis

Chondromodulin-I (ChM-I) is a novel cartilage-specific matrix protein. In the growth plates of the long bones, ChM-I was shown to be expressed in mature to upper hypertrophic chondrocytes, and to be deposited in the cartilage matrix. As ChM-I strongly inhibits angiogenesis, cartilage is avascular. Also, ChM-I has bifunctional activity against chondrocyte proliferation. On the other hand, pleomorphic adenomas of the salivary glands frequently have chondroid elements. To elucidate the relationship between chondroid formation and hypovascularity in salivary pleomorphic adenomas, we immunohistochemically examined the expression and localization of ChM-I in 35 cases of this tumor. ChM-I was immunolocalized to the lacunae in the chondroid elements of pleomorphic adenomas (100%). Type II collagen and aggrecan were immunolocalized throughout the matrix around lacuna cells of the chondroid element (100%, 91.7%), and ChM-I was infrequently immunolocalized to the spindle-shaped myoepithelial cells in the myxoid element (37.5%). Fibroblast growth factor-2 was strongly immunolocalized to the lacuna cells in the chondroid element (100%), among the neoplastic myoepithelial cells in the myxoid elements (96.9%), and on the basement membranes around the solid nests of neoplastic myoepithelial cells (71.4%). Although CD34 is a marker of endothelial cells, CD34 was expressed in the endothelial cells in only a few areas around the epithelial elements and in the fibrous element of pleomorphic adenomas. No signals for CD34 were observed in chondroid elements in pleomorphic adenomas (P < 0.001), but a few signals were seen in the myxoid elements (P < 0.05). These findings suggested that lacuna cells and neoplastic myoepithelial cells expressed ChM-I, and that this molecule may play an important role in hypovascularity and chondroid differentiation in pleomorphic adenoma. In conclusion, pleomorphic adenoma expressed ChM-I, which is involved in hypovascularity and chondroid formation in this type of tumor.