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Biomedical subjects

Yuji Hiraki

Publications and source records attributed to Yuji Hiraki.

At least 19 recordsLinked to original sources
PubMed2007

Nondestructive micro-patterning of proteinous occlusion bodies in water by femtosecond laser-induced mechanical force.

Some insect virus produces proteinous occlusion bodies named polyhedra, on which it is possible to immobilize functional proteins, such as green fluorescent proteins, antibodies, and growth factors, with keeping their biological activity. In this work, several kinds of polyhedra were micro-patterned by applying a mechanical force induced by femtosecond laser irradiation of a water buffer. In the printing process, since the laser is not directly irradiated on polyhedra, damages of polyhedra due to dryness and photothermal and photochemical reactions will be suppressed. The ability of the pattering was demonstrated by micro-sized checkerboard pattern, on which polyhedra with and without occluding enhanced green fluorescent protein were sorted. Furthermore, it was indicated that polyhedra are available as a scaffold of animal cell. This patterning method will be a promising technique to realize a microdevice in which functions of cell are artistically activated.

Animals↗
PubMed2006

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.

Aged↗
PubMed2006

Scleraxis positively regulates the expression of tenomodulin, a differentiation marker of tenocytes.

Tenomodulin (TeM) is a type II transmembrane glycoprotein containing a C-terminal anti-angiogenic domain and is predominantly expressed in tendons and ligaments. Here we report that TeM expression is closely associated with the appearance of tenocytes during chick development and is positively regulated by Scleraxis (Scx). At stage 23, when Scx expression in the syndetome has extended to the tail region, TeM was detectable in the anterior eight somites. At stage 25, TeM and Scx were both detectable in the regions adjacent to the myotome. Double positive domains for these genes were flanked by a dorsal TeM single positive and a ventral Scx single positive domain. At stage 28, the expression profile of TeM in the axial tendons displayed more distinct morphological features at different levels of the vertebrae. At stage 32 and later, Scx and TeM showed similar expression profiles in developing tendons. Retroviral expression of Scx resulted in the significant upregulation of TeM in cultured tenocytes, but not in chondrocytes. In addition, the misexpression of RCAS-cScx by electroporation into the hindlimb could not induce the generation of additional tendons, but did result in the upregulation of TeM expression in the tendons at stage 33 and later. These findings suggest that TeM is a late marker of tendon formation and that Scx positively regulates TeM expression in a tendon cell lineage-dependent manner.

Amino Acid Sequence↗
PubMed2005

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↗
PubMed2005

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.

Angiogenesis Inhibitors↗
PubMed2004

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.

Adenoma, Pleomorphic↗
PubMed2004

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.

Gene Expression Profiling↗
PubMed2004

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.

Adenoviridae↗
PubMed2004

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.

Adjuvants, Immunologic↗
PubMed2004

Active proliferation of mesenchymal cells prior to the chondrogenic repair response in rabbit full-thickness defects of articular cartilage.

OBJECTIVES: In full-thickness articular defects, fibroblast growth factor-2 (FGF-2) participates in the chondrogenic repair response which occurs in a defect-size dependent manner. Here we demonstrate that FGF-2 plays a critical role in the proliferation of pre-chondrogenic mesenchymal cells during chondrogenic induction. METHODS: Three-millimeter- or 5-mm-diameter cylindrical defects were created in the femoral trochlea of the rabbit knee. The defects received sterile saline or FGF-2 (50 pg/h) via an osmotic pump for the initial 2 weeks. We assessed the proliferative capacity of undifferentiated mesenchymal cells in the reparative tissue with the anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody. Using a total of 180 rabbits, we performed three sets of experiments. RESULTS: In the 3-mm-diameter defects, undifferentiated mesenchymal cells spontaneously initiated chondrogenic differentiation within 2 weeks, resulting in the regeneration of surfacing articular cartilage concomitantly with the repair of subchondral bone. No evidence of chondrogenesis was seen in the 5-mm-diameter defects, whereas application of FGF-2 promoted successful regeneration of articular cartilage. In the 3-mm-diameter defects and in the FGF-2-treated 5-mm defects, PCNA immunoreactivity was widely detected in undifferentiated cells in the reparative tissue at 1 and 2 weeks after creation of the defects. In contrast, in the 5-mm-diameter defects without FGF-2 treatment, the PCNA-positive cells were found at a significantly lower incidence. CONCLUSIONS: Active expansion of undifferentiated cell population mediated by FGF-2 is required to initiate and support a chondrogenic repair response in full-thickness defects of articular cartilage. Endogenous FGF-2 could not meet the requirements of growth signaling in the center of larger sized defects.

Alkaline Phosphatase↗
PubMed2004

Transcriptome analysis of early chondrogenesis in ATDC5 cells induced by bone morphogenetic protein 4.

We performed serial analysis of gene expression (SAGE) profiling in mouse chondrogenic ATDC5 cells before and 6 h after the onset of chondrogenesis induced by BMP4. A total of 43,656 SAGE tags (21,875 and 21,781 tags from the uninduced and induced libraries, respectively) were analyzed. Our analysis predicted that 139 transcripts were differentially represented in the two libraries (p < 0.05), including 72 downregulated and 67 upregulated transcripts. Ninety-five of them matched single UniGene entries (77 known genes and 18 ESTs), while 12 tags corresponded to potentially novel genes. Surprisingly, many of these known genes have never been implicated in chondrogenic differentiation. Interestingly, we found that a significant fraction of these genes formed physical linkage groups. This suggests that the transcriptional control by BMP signaling is in part targeted to genes in certain chromosomal domains. Together, our results provide novel insights into molecular events regulated by BMP signaling in chondrogenesis.

Animals↗
PubMed2003

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.

Adenoma, Pleomorphic↗
PubMed2003

Suppression of differentiation and proliferation of early chondrogenic cells by Notch.

Notch is a transmembrane protein involved in cell fate determination. In the present study, we observed temporally and spatially restricted expression of Notch1 in developing cartilage. Notch1 was localized starting from the mesenchymal condensation stage of embryonic mouse forelimbs. Interestingly, although localization could not be detected in the proliferating chondrocytes, obvious immunoreactivity indicating its expression was retained in the perichondrial region. Next, we investigated the expression of Notch1 and related molecules in a chondrogenic cell line, ATDC5 cells. Notch1, Delta-like (Dll)1, Deltex2, and Deltex3 were coexpressed after 6-day insulin treatment. Expression of Hairy and Enhancer of split homologue (HES)-1 followed thereafter. These results suggest that Notch may have a role in the early stage of chondrogenesis. To assess the effect of Notch activation, we cultured ATDC5 cells with a myeloma clone constitutively expressing Dll1, a ligand of Notch. We also used an adenovirus vector to express the constitutively active Notch1 intracellular domain (NIC). Activating either the endogenous or exogenous Notch receptor dramatically inhibited chondrogenic cell differentiation of ATDC5 cells, as assessed by Alcian blue staining of the cells and chondrocyte differentiation markers. Last, we investigated the effect of NIC on the proliferation of the ATDC5 cells. Expression of NIC by the adenovirus strongly suppressed thymidine incorporation. These results indicate that Notch is expressed in the initial stage of chondrogenic cell differentiation and has a strong inhibitory effect on both differentiation and proliferation of the cells when activated. The expression of Notch decreases as chondrogenic differentiation proceeds; however, a population of the cells with sustained expression of Notch1 become perichondrial cells. Considering that the perichondrium acts as a stem cell source of osteoblasts and chondrocytes, Notch1 may have a role in the formation of these cells by suppressing both differentiation and proliferation.

Adenoviridae↗
PubMed2003

Chondromodulin I is a bone remodeling factor.

Chondromodulin I (ChM-I) was supposed from its limited expression in cartilage and its functions in cultured chondrocytes as a major regulator in cartilage development. Here, we generated mice deficient in ChM-I by targeted disruption of the ChM-I gene. No overt abnormality was detected in endochondral bone formation during embryogenesis and cartilage development during growth stages of ChM-I(-/-) mice. However, a significant increase in bone mineral density with lowered bone resorption with respect to formation was unexpectedly found in adult ChM-I(-/-) mice. Thus, the present study established that ChM-I is a bone remodeling factor.

Alleles↗
PubMed2003

Expression and localization of tenomodulin, a transmembrane type chondromodulin-I-related angiogenesis inhibitor, in mouse eyes.

PURPOSE: To explore the role in the eye of tenomodulin (TeM), a chondromodulin (ChM)-I-related glycoprotein, the expression, localization, and antiangiogenic potential of TeM were investigated. METHODS: Gene expression and protein localization of TeM in mouse eyes were examined by Northern blot analysis, in situ hybridization, and immunohistochemical analysis. Antiangiogenic function included in the C terminus of TeM and ChM-I was examined in vascular endothelial cells through adenoviral gene transduction. RESULTS: TeM expression was detectable from day 15 of the embryonic stage and was clearly present in the eye and skin. In situ hybridization of the eye tissues revealed TeM mRNA in the tendon of the extraocular muscle, the sclerocornea, the lens fiber cells, and the ganglion cell layer, inner nuclear layer cells, and pigment epithelium of the retina. Corresponding immunoreactivity of TeM was present in most of these cells. Western blot detected 40- and 45-kDa immunoreactive bands of TeM in the eye as differently glycosylated forms of the transmembrane protein. Production of a secreted form of TeM and ChM-I through adenoviral gene transfer caused effective autocrine suppression of cell proliferation and capillary-like morphogenesis of retina vascular endothelial cells. The condition media from soluble TeM- and ChM-I-overexpressing cells also showed a marked inhibitory effect on in vitro angiogenesis. CONCLUSIONS: These results indicate a potential role for TeM in prevention of vascular invasion in the mouse eye and the possibility of both TeM and ChM-I as candidates for use in gene therapy approaches to treatment of ocular angiogenesis.

Adenoviridae↗
PubMed2003

Expression of the cartilage derived anti-angiogenic factor chondromodulin-I decreases in the early stage of experimental osteoarthritis.

OBJECTIVE: Chondromodulin-I (ChM-I), a cartilage derived anti-angiogenic factor, has been shown to regulate the vascular invasion during endochondral bone formation. We evaluated the expression and localization of ChM-I in articular cartilage during the progression of osteoarthritis (OA) in the rat, and correlated ChM-I expression with the increase in vascular invasion into OA articular cartilage. METHODS: Expression of ChM-I, type II collagen, basic fibroblast growth factor, vascular endothelial growth factor (VEGF), and matrix metalloproteinases MMP-9 and MMP-13 were examined in articular cartilage of intact growing and adult rats and in the surgically induced OA model using in situ hybridization, Western blot analysis, and immunohistochemistry. Co-immunostaining for ChM-I and CD-31 was performed to localize ChM-I and neovascularization in articular cartilage at advanced stage of OA. RESULTS: Abundant expression of ChM-I protein was detected in avascular regions of the developing and adult healthy articular cartilage. In early OA, ChM-I expression decreased in the superficial zone of articular cartilage, while levels of proteoglycan and type II collagen were comparable to control. In advanced OA, ChM-I expression was reduced in all zones of articular cartilage, and the number of VEGF-expressing cells was increased. Immunohistochemical studies showed that vascular invasion occurred in proximity to chondrocytes with high expression of pro-angiogenic markers, and decreased expression of ChM-I. CONCLUSION: High expression of ChM-I was detected in articular cartilage of growing and normal adult joints, implicating its role in the maintenance of avascularity of intact articular cartilage. Expression of ChM-I decreased, while expression of VEGF and other pro-angiogenic factors increased, in OA cartilage. These findings suggest the loss of ChM-I from articular cartilage might be responsible in part for promoting blood vessel invasion into the cartilage during progression of OA.

Angiogenesis Inhibitors↗
PubMed2002

Phenotypic switching of in vitro mandibular condylar cartilage during matrix mineralization.

In order to analyze the phenotypic conversion of chondrocytes, mandibular condyles of mice and rabbits were cultured under cell and organ culture systems, and then examined by a combination of morphological and biochemical procedures. In organ culture, mandibular condylar cartilage (MCC) obtained from newborn mice began to mineralize from the central zone and then progressively widened towards the peripheral zone. Electron microscopic observations showed that with the increasing duration of the organ culture, chondrocytes at the central zone converted into spindle-shaped osteoblastic cells accompanying the formation of the bone type of thick-banded collagen fibrils. To obtain a better understanding of the chondrocytic conversion, immunolocalizations for type I and type X collagens and osteocalcin (OC) were examined in mouse MCC cells in cell culture. Type X collagen and OC were expressed almost simultaneously at the late stage of culture, and type I collagen was detected along the calcified nodules after the production of these proteins. Northern blot analysis in cell cultures of rabbit MCC indicated that type II collagen and alkaline phosphatase (ALPase) messenger ribonucleic acids (mRNAs) were highly expressed at day 7, but subsequently decreased. In contrast, mRNA for type I collagen was expressed at a low level on day 7 and peaked on day 12. The present results suggest that, morphologically and biochemically, cellular modification in MCC cells under culture conditions occurs at a cellular morphological level and also at marker-gene-expression level.

Aging↗