Molecular analysis of chondrocytes cultured in agarose in response to dynamic compression.

Authors:
Bougault C, Paumier A, Aubert-Foucher E, Mallein-Gerin F.
In:
Source: BMC Biotechnol
Publication Date: (2008)
Issue: 15;8:71: 1-10
Research Area:
Cancer Research/Cell Biology
Dermatology/Tissue Engineering
Cells used in publication:
Chondrocytes, mouse
Species: mouse
Tissue Origin: cartilage
Platform:
Nucleofector® I/II/2b
Experiment
Transfection Prior to transfection, chondrocytes were amplified in monolayer culture for one week. After trypsinization, 3 × 106 cells were suspended in 100 ?L of electroporation buffer and mixed with 4 ?g plasmid of interest and 1 ?g plasmid encoding ?-galactosidase. The plasmids were transfected by using the Human Chondrocyte Nucleofector kit (Amaxa) according to the manufacturer\\\'s protocol (Program U-24). Although nucleofection leads to about 60% cell mortality, this method provides high transfection efficiency (around 80%) for the viable cells. This transfection efficiency was assessed by monitoring synthesis of green fluorescent protein in chondrocytes observed under a fluorescence microscope, after transfection of the corresponding expression vector (data not shown).
Abstract
BACKGROUND: Articular cartilage is exposed to high mechanical loads under normal physiological conditions and articular chondrocytes regulate the composition of cartilaginous matrix, in response to mechanical signals. However, the intracellular pathways involved in mechanotransduction are still being defined. Using the well-characterized chondrocyte/agarose model system and dynamic compression, we report protocols for preparing and characterizing constructs of murine chondrocytes and agarose, and analyzing the effect of compression on steady-state level of mRNA by RT-PCR, gene transcription by gene reporter assay, and phosphorylation state of signalling molecules by Western-blotting. The mouse model is of particular interest because of the availability of a large choice of bio-molecular tools suitable to study it, as well as genetically modified mice. RESULTS: Chondrocytes cultured in agarose for one week were surrounded by a newly synthesized pericellular matrix, as revealed by immunohistochemistry prior to compression experiments. This observation indicates that this model system is suitable to study the role of matrix molecules and trans-membrane receptors in cellular responsiveness to mechanical stress. The chondrocyte/agarose constructs were then submitted to dynamic compression with FX-4000C Flexercell Compression Plus System (Flexcell). After clearing proteins off agarose, Western-blotting analysis showed transient activation of Mitogen-activated protein kinases (MAPK) in response to dynamic compression. After assessment by capillary electrophoresis of the quality of RNA extracted from agarose, steady-state levels of mRNA expression was measured by real time PCR. We observed an up-regulation of cFos and cJun mRNA levels as a response to compression, in accordance with the mechanosensitive character observed for these two genes in other studies using cartilage explants submitted to compression. To explore further the biological response of mouse chondrocytes to the dynamic compression at the transcriptional level, we also developed an approach for monitoring changes in gene transcription in agarose culture by using reporter promoter constructs. A decrease in promoter activity of the gene coding for type II procollagen, the most abundant protein in cartilage, was observed in response to dynamic loading. CONCLUSION: The protocols developed here offer the possibility to perform an integrated analysis of the molecular mechanisms of mechanotransduction in chondrocytes, at the gene and protein level.