The characterization of versican and its message in human articular cartilage and intervertebral disc

Abstract

Splicing variation of the versican message and size heterogeneity of the versican core protein were analyzed in human articular cartilage and intervertebral disc. Splicing variation of the message was studied by PCR analysis to detect the presence or absence of exons 7 and 8, which encode large chondroitin sulfate attachment regions. At all ages in normal cartilage from the third trimester fetus to the mature adult, the presence of the versican isoform possessing exon 8 but not exon 7 ( V , ) could be readily detected. The message isoforms possessing neither exon 7 nor 8 (V,) or both exons 7 and 8 (V,) were only detectable in the fetus, and the isoform possessing only exon 7 (V,) was never detected. In osteoarthritic cartilage and in adult intervertebral disc the versican message pattern was the same as that observed in the normal adult with only the isoform possessing exon 8 being detected. Core protein heterogeneity was studied by immunoblotting following enzymic removal of the glycosaminoglycan chains from the proteoglycan, using an antibody recognizing the globular GI region of versican. All articular cartilage extracts from the fetus to the mature adult contained multiple core protein sizes of greater than 200 kDa. The adult cartilage extracts tended to have an increased proportion of the smaller sized core proteins and osteoarthritic cartilage possessed similar core protein sizes to the normal adult. In contrast, intervertebral disc at all post-natal ages showed a greater range of size heterogeneity with a prominent component of about 50 kDa. The abundance of this component increased if the samples were treated with keratanase prior to analysis, suggesting that the GI region of versican in disc can be substituted with keratan sulfate. The increased presence of versican in the disc relative to articular cartilage may suggest a more pronounced functional role for this proteoglycan, particularly in the nucleus pulposus.

Identification and Characterization of Versican/PG-M Aggregates in Cartilage

“…Although previous immunohistochemical studies failed to detect versican in human adult cartilage (3), biochemical studies demonstrated the presence of versican in human articular cartilage from the fetal stage to mature adult (13). An age-associated decrease in versican transcription of the human articular cartilage has also been reported (11).…”

Myocardial Extracellular Matrix

“…Hence, glycosylation further increases their molecular weight, as a result of which they are found in the ECM with sizes ranging from 1000 to 2500 kDa. [98][99][100] Further alternative splicing of the versican gene, which encodes the GAG chain-binding sites, generates ≥4 isoforms with different molecular weights, creating even more variation. These large matrix components interact with other matrix proteins, growth factor, and cell surface receptors.…”

Limitations of using aggrecan and type X collagen as markers of chondrogenesis in mesenchymal stem cell differentiation

“…2 A high proteoglycan-to-collagen ratio and low aggrecan-toversican ratio can be used to distinguish NP from cartilage. 2,5 MSCs have been shown to undergo chondrogenesis in vitro using a high cell density pellet culture system, [6][7][8] which mimics the cellular condensation requirements for embryonic mesenchymal chondrogenesis and provides the physical and biochemical environmental factors conducive to cartilage formation. 7 Treatment with transforming growth factor b (TGF-b) superfamily members, TGF-b1 7,[9][10][11][12] or TGF-b3, 6,8 and dexamethasone 7,8,13,14 are key requirements for the in vitro chondrogenic differentiation of MSCs.…”