Dedifferentiation-associated changes in morphology and gene expression in primary human articular chondrocytes in cell culture.
OBJECTIVE
The aim of the present study was the investigation of differential gene expression in primary human articular chondrocytes (HACs) and in cultivated cells derived from HACs.


METHODS
Primary human articular chondrocytes (HACs) isolated from non-arthritic human articular cartilage and monolayer cultures of HACs were investigated by immunohistochemistry, Northern analysis, RT-PCR and cDNA arrays.


RESULTS
By immunohistochemistry we detected expression of collagen II, protein S-100, chondroitin-4-sulphate and vimentin in freshly isolated HACs. Cultivated HACs, however, showed only collagen I and vimentin expression. These data were corroborated by the results of Northern analysis using specifc cDNA probes for collagens I, II and III and chondromodulin, respectively, demonstrating collagen II and chondromodulin expression in primary HACs but not in cultivated cells. Hybridization of mRNA from primary HACs and cultivated cells to cDNA arrays revealed additional transcriptional changes associated with dedifferentiation during propagation of chondrocytes in vitro. We found a more complex hybridization pattern for primary HACs than for cultivated cells. Of the genes expressed in primary HACs the early growth response (EGR1) transcription factor showed the strongest expression whereas D-type cyclin was expressed in proliferating cells. Other factors associated with differentiated HACs were the adhesion molecules ICAM-1 and VCAM-1, VEGF, TGFbeta2, and the monocyte chemotactic protein receptor.


CONCLUSIONS
Our data support the hypothesis that HACs dedifferentiate when grown in monolayer cultures. Moreover, the expression patterns also show that proliferation and differentiation are exclusive features of human chondrocytes.
Schnabel
M
M
Department of Traumatology, Philipps-University of Marburg, Germany.
Marlovits
S
S
Eckhoff
G
G
Fichtel
I
I
Gotzen
L
L
Vécsei
V
V
Schlegel
J
J
D000368:Aged; D000369:Aged, 80 and over; D015152:Blotting, Northern; D002358:Cartilage, Articular / Q000166:cytology* / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000502:physiology; D002809:Chondroitin Sulfates / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D051766:Early Growth Response Protein 1; D005260:Female; D015870:Gene Expression; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009418:S100 Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D014746:Vimentin / Q000378:metabolism
D024042:Collagen Type I; D024043:Collagen Type II; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D006133:Growth Substances; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009418:S100 Proteins; D014157:Transcription Factors; D014746:Vimentin; C068675:CNMD protein, human; D002809:Chondroitin Sulfates