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Antisense inhibition of CD44 tailless splice variant in human articular chondrocytes promotes hyaluronan
H Jiang1, C B Knudson, W Knudson
1Rush University Graduate School, Chicago, IL, USA.
Objective:
To determine whether alternatively spliced variants of CD44, in particular a short, intracellular tail CD44 isoform, are used by articular chondrocytes to modulate the functions of this matrix receptor.
Methods:
Normal human articular chondrocytes were cultured with or without interleukin-1alpha (IL-1alpha), and the relative expression of CD44 exon 19 and CD44 exon 20, hyaluronan synthase 2, aggrecan, and GAPDH messenger RNA (mRNA) was determined using reverse transcriptase-polymerase chain reaction. Next, CD44 exon 19 mRNA was selectively inhibited by the use of antisense oligonucleotides. The effects of exon 19 loss were analyzed by matrix assembly and hyaluronan internalization assays.
Results:
Human articular chondrocytes express varying levels of exon 19 (short tail)- and exon 20 (long tail)-containing CD44 mRNA. Both CD44 mRNA are up-regulated by IL-1alpha. Selective inhibition of CD44 exon 19 results in enhanced hyaluronan internalization and smaller cell-associated matrices.
Conclusion:
The expression of a natural CD44 decoy-like receptor by articular chondrocytes modulates the function of this matrix receptor.
Insights
Articular chondrocytes use a short CD44 variant to control matrix receptor function. This finding reveals how CD44 isoforms regulate chondrocyte behavior and matrix interactions.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Articular chondrocytes are key cells in cartilage maintenance.
- CD44 is a matrix receptor involved in cell-matrix interactions.
- Alternative splicing of CD44 generates isoforms with potentially different functions.
Purpose of the Study:
- To investigate if articular chondrocytes utilize alternatively spliced CD44 variants.
- To determine the role of a short intracellular tail CD44 isoform in modulating matrix receptor function.
Main Methods:
- Cultured human articular chondrocytes with and without interleukin-1alpha (IL-1alpha).
- Quantified CD44 exon 19 and 20 mRNA levels using RT-PCR.
- Inhibited CD44 exon 19 mRNA with antisense oligonucleotides.
- Assessed matrix assembly and hyaluronan internalization.
Main Results:
- Human articular chondrocytes express CD44 mRNA variants with short (exon 19) and long (exon 20) intracellular tails.
- IL-1alpha up-regulated both CD44 mRNA variants.
- Inhibiting CD44 exon 19 enhanced hyaluronan internalization and reduced cell-associated matrices.
Conclusions:
- Articular chondrocytes express a CD44 variant acting as a decoy receptor.
- This CD44 isoform modulates the function of the primary matrix receptor.
- Alternative splicing of CD44 plays a role in chondrocyte matrix regulation.