Transdifferentiation of hypertrophic chondrocytes into osteoblasts in murine fetal metatarsal bones, induced by co-cultured cerebrum

Thesingh, C. W.; Groot, C. G.; Wassenaar, A. M.

doi:10.1016/0169-6009(91)90119-k

Cited by 63 publications

(40 citation statements)

References 25 publications

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“…In contrast to theinitial primary chondrocytes, immortalized cells also contained type I collagen and BGP mRNAs. These two mRNAs were shown by others to be present in hypertrophic chondrocyte cultures after the cells had reached a further stage of differentiation corresponding to an osteoblast-like phenotype (3,8,24,29,37,41,42). Expression of the MGP and OP genes is also characteristic of the osteoblastic phenotype.…”

Section: Discussionmentioning

confidence: 97%

“…Bone Gla protein (BGP, also called osteocalcin), another osteoblast marker (35), is present at low levels in the calcified cartilage matrix surrounding hypertrophic chondrocytes in vivo (4,28,29). Studies with chondrocytes in culture have shown that after the cells became hypertrophic they produced type I collagen and BGP (3,8,24,37,41,42), which led to the suggestion that these cells could acquire osteoblastic properties.…”

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confidence: 99%

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Type X collagen gene expression in mouse chondrocytes immortalized by a temperature-sensitive simian virus 40 large tumor antigen.

Lefebvre

Garofalo

Crombrugghe

1995

The Journal of Cell Biology

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Abstract. Mouse endochondral chondrocytes were immortalized with a temperature-sensitive simian virus 40 large tumor antigen. Several clonal isolates as well as pools of immortalized cells were characterized. In monolayer cultures at the temperature permissive for the activity of the large tumor antigen (32°C), the cells grew continuously with a doubling time of ,~2 d, whereas they stopped growing at nonpermissive temperatures (37°C-39°C). The cells from all pools and from most clones expressed the genes for several markers of hypertrophic chondrocytes, such as type X collagen, matrix Gla protein, and osteopontin, but had lost expression of type lI collagen mRNA and failed to be stained by alcian blue which detects cartilagespecific proteoglycans. The cells also contained mRNAs for type I collagen and bone Gla protein, consistent with acquisition of osteoblastic-like properties. Higher levels of mRNAs for type X collagen, bone Gla protein, and osteopontin were found at nonpermissive temperatures, suggesting that the expression of these genes was upregulated upon growth arrest, as is the case in vivo during chondrocyte hypertrophy. Cells also retained their ability to respond to retinoic acid, as indicated by retinoic acid dose-dependent and timedependent increases in type X collagen mRNA levels. These cell lines, the first to express characteristic features of hypertrophic chondrocytes, should be very useful to study the regulation of the type X collagen gene and other genes activated during the last stages of chondrocyte differentiation. C HONDROCYTES are highly specialized cells that are derived from mesenchymal cells during embryonic development to form the various cartilages of vertebrates. Chondrocytes are characterized by the production of cartHage-specific extracellular macromolecules including the collagen types H, IX, and XI, and the proteoglycan aggrecan (16). In permanent cartilages, the phenotype of chondrocytes is stably maintained, whereas in endochondral cartilages, chondrocytes undergo a further differentiation process (16,34). During this process, chondrocytes mature into hypertrophic ceils around which the cartilage matrix becomes calcified, and subsequently undergo apoptosis, making way for invading osteoblasts. Hypertrophic chondrocytes still contain type II collagen and aggrecan RNAs, although at reduced levels (21, 38), they are characterized by the synthesis of type X collagen, which is uniquely expressed by these cells (10,21,39), and by the expression of markers typically associated with osteoblasts. Both hypertrophic chondrocytes and osteoblasts have the ability to induce mineralization of the extracellular matrix and to produce alka-

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Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 99%

Type X collagen gene expression in mouse chondrocytes immortalized by a temperature-sensitive simian virus 40 large tumor antigen.

Lefebvre

Garofalo

Crombrugghe

1995

The Journal of Cell Biology

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“…vascular invasion. In perichondrium-stripped developing metatarsals, hypertrophic chondrocytes de-differentiated into stromal cells (Thesingh et al, 1991); a study of the fate of chondrocytes in antlers showed that while osteoblasts and chondrocytes occupied the same lacunae, there was no evidence of transdifferentiation (Szuwart et al, 1998).…”

Section: Views Concerning Chondrocyte-to-osteoblast Conversion In Thementioning

confidence: 99%

The Fate of the Terminally Differentiated Chondrocyte: Evidence for Microenvironmental Regulation of Chondrocyte Apoptosis

Adams¹,

Shapiro²

2002

Critical Reviews in Oral Biology & Medicine

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Chondrocytes contained within the epiphyseal growth plate promote rapid bone growth. To achieve growth, cells activate a maturation program that results in an increase in chondrocyte number and volume and elaboration of a mineralized matrix; subsequently, the matrix is resorbed and the terminally differentiated cells are deleted from the bone. The major objective of this review is to examine the fate of the epiphyseal chondrocytes in the growing bone. Current studies strongly suggest that the terminally differentiated epiphyseal cells are deleted from the cartilage by apoptosis. Indeed, morphological, biochemical, and end-labeling techniques confirm that death is through the apoptotic pathway. Since the induction of apoptosis is spatially and temporally linked to the removal of the cartilage matrix, current studies have examined the apoptogenic activity of Ca 2+ -, Pi-, and RGD-containing peptides of extracellular matrix proteins. It is observed that all of these molecules are powerful apoptogens. With respect to the molecular mechanism of apoptosis, studies of cell death with Pi as an apoptogen indicate that the anion is transported into the cytosol via a Na +/ Pi transporter. Subsequently, there is activation of caspases, generation of NO, and a decrease in the thiol reserve. Finally, we examine the notion that chondrocytes transdifferentiate into osteoblasts, and briefly review evidence for, and the rationale of, the transdifferentiation process. It is concluded that specific microenvironments exist in cartilage that can serve to direct chondrocyte apoptosis.

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“…The skeletal phenotype and the expression pattern of Egr2/Krox20 are consistent with a role for this transcription factor in terminally differentiating osteoblasts and in late hypertrophic chondrocytes acquiring an osteoblast-like phenotype (52). OC is a late differentiation marker in both of these cell types (13,53), and, interestingly, OC was also demonstrated in dorsal root ganglia and trigeminal neurons (54), cells that express Egr2/Krox20 (55).…”

mentioning

confidence: 99%

Glucocorticoids inhibit osteocalcin transcription in osteoblasts by suppressing Egr2/Krox20‐binding enhancer

Leclerc¹,

Noh²,

Khokhar³

et al. 2005

Arthritis & Rheumatism

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Objective. Glucocorticoids are widely used for the management of rheumatoid arthritis. Osteoporosis is a major side effect of glucocorticoid therapy and is attributable to inhibition of bone formation. We developed an osteoblast culture system in which glucocorticoids strongly inhibit development of the osteoblast phenotype, including expression of the bone-specific osteocalcin (OC) gene. Using this gene as a model, the goal of this study was to discover glucocorticoid-sensitive transcriptional mechanisms in osteoblasts.Methods. Dexamethasone (DEX; 1 M) was administered to murine MC3T3-E1 osteoblastic cultures under conditions that inhibit mineralized extracellular matrix formation and OC messenger RNA levels by >10-fold. Because standard (short-term) transient transfection assays with OC promoter-reporter constructs did not recapitulate the strong DEX-mediated repression, mapping of OC negative glucocorticoid response elements (GREs) was performed initially by stable transfection and then with long-term transient transfection assays. Transcription factor binding to the OC negative GRE was studied by electrophoretic mobility shift assays.Results. Several-fold repression of OC-luciferase constructs was recapitulated in stable and long-term transient transfection assays, in which the transfected cells were allowed to progress to a sufficiently advanced developmental stage. Analysis of a 5 promoter deletion series mapped an OC negative GRE to a 15-bp G/C-rich motif (؊161/؊147) located just upstream of the binding site for the osteoblast master transcription factor Runx2. Oligonucleotides encompassing this element and MC3T3-E1 cell extracts formed a protein-DNA complex that contained an Egr/Krox family member(s). Complex formation was competed by either an oligonucleotide containing 2 consensus Egr motifs or by anti-Egr2/Krox20 antibodies. Three copies of this Kroxbinding element conferred 20-fold transcriptional activation on the 147-bp basal OC promoter in osteoblasts, and the enhancer activity was inhibited by DEX. Enhancer activity was not observed in 10T1/2 fibroblasts unless these cells were cotransfected with Runx2.Conclusion. An Egr2/Krox20-binding site located immediately upstream of the Runx2 site of the mouse OC promoter was identified as an enhancer in osteoblasts, whose activity is repressed by glucocorticoids. Sequence similarity suggests that such a mechanism is likely operative in both murine and human cells. Because glucocorticoids inhibit Egr2/Krox20 expression in osteoblasts, and because trabecular bone formation is arrested in Egr2/Krox20-knockout mice, the inhibition of Egr2/Krox20 activity likely contributes to glucocorticoid-induced osteoporosis.Since the 1950 Nobel laureates E. Kendall, T. Reichstein, and P. Hench introduced glucocorticoids for the treatment of rheumatoid arthritis, these drugs have been widely used for the treatment of autoimmune and inflammatory diseases. The enthusiasm with which glucocorticoids were initially accepted was quickly dampened upon realization of their deleter...

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Transdifferentiation of hypertrophic chondrocytes into osteoblasts in murine fetal metatarsal bones, induced by co-cultured cerebrum

Cited by 63 publications

References 25 publications

Type X collagen gene expression in mouse chondrocytes immortalized by a temperature-sensitive simian virus 40 large tumor antigen.

Type X collagen gene expression in mouse chondrocytes immortalized by a temperature-sensitive simian virus 40 large tumor antigen.

The Fate of the Terminally Differentiated Chondrocyte: Evidence for Microenvironmental Regulation of Chondrocyte Apoptosis

Glucocorticoids inhibit osteocalcin transcription in osteoblasts by suppressing Egr2/Krox20‐binding enhancer

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