Related Experiment Videos
Characterization of link protein(s) from human intervertebral-disc tissues
P J Donohue1, M R Jahnke, J D Blaha
1Department of Biochemistry, West Virginia University Medical Center, Morgantown 26506.
Insights
Young adult human intervertebral discs show early signs of proteoglycan aggregate degradation, with altered link proteins and proteoglycan fragments accumulating by age 20-30. This degradation may impact disc biomechanics.
Area of Science:
- Biochemistry
- Biomaterials Science
- Orthopedics
Background:
- Proteoglycan aggregates are crucial for intervertebral disc (IVD) structure and function.
- Age-related changes in IVD composition can lead to altered biomechanical properties.
- Understanding proteoglycan aggregate changes in young adults is key to early detection of disc degeneration.
Purpose of the Study:
- To compare proteoglycan aggregate composition in postnatal and young adult human IVDs.
- To identify age-dependent alterations in link proteins and proteoglycans within the IVD.
- To investigate the potential impact of these changes on IVD biomechanics.
Main Methods:
- Preparation and fractionation of proteoglycan aggregates (A1) from human IVD tissues.
- CsCl-density-gradient centrifugation to separate proteoglycan components.
- SDS-PAGE and immunolocation using monoclonal antibodies for link protein and proteoglycan analysis.
- Chromatographic techniques (Sepharose CL-6B, Sephacryl S-300) for component separation.
Main Results:
- Young adult IVDs exhibited a higher proportion of non-aggregating proteoglycans and lower-buoyant-density proteoglycans compared to postnatal tissues.
- All three link proteins (1, 2, and 3) were detected in young adults, with link protein 3 predominating, while postnatal tissues primarily showed link protein 1.
- Degraded link proteins and proteoglycan fragments were identified in young adult tissues, but not in postnatal samples.
Conclusions:
- Degraded link protein and proteoglycan fragments accumulate in young adult human IVD tissues at an early age.
- These partially degraded components may significantly alter the biomechanical properties of the intervertebral discs.
- Early accumulation of degraded proteoglycan aggregates suggests a predisposition to disc degeneration in young adulthood.
Abstract:
Proteoglycan aggregates (A1) were prepared from the anulus fibrosus, nucleus pulposus and cartilage-endplate tissues of postnatal (0-6-month-old)-and young-adult (20-30-year-old)-human intervertebral discs. The A1 fractions from young-adult disc contained a greater proportion of non-aggregating proteoglycans than did postnatal tissues. After dissociative CsCl-density-gradient fractionation of the A1, more than 90% of the uronic acid was found in the postnatal A1D1, whereas only 60-80% of the hexuronate was present in the A1D1 isolated from young-adult disc tissues. These results indicated that more lower-buoyant-density proteoglycans occur in the young-adult disc. Link-protein-rich fractions (A1D3) were subjected to SDS/polyacrylamide-gel electrophoresis and immunolocation analyses using monoclonal antibodies specific for epitopes on link protein or proteoglycan. Under non-reducing conditions, the major link protein present in postnatal disc tissues was link protein 1. By contrast, all three link proteins (1, 2 and 3) were detected in young-adult tissues, with the smaller link protein 3 predominating. Analyses of the A1D3 fractions under reducing conditions also indicated the presence of link-protein-degradation peptides (Mr approx. 26,000) from young-adult disc tissues, but not from postnatal tissues. Sequential Sepharose CL-6B and Sephacryl S-300 chromatography in 4 M-guanidinium chloride was employed to separate the link proteins of the A1D3 fraction from protein-rich proteoglycan. Immunolocation analyses indicated that postnatal samples contained no detectable contaminating proteoglycan fragments. However, young-adult link-protein preparations could not be separated from hyaluronic acid-binding region and other proteoglycan fragments by means of these chromatographic procedures. The studies indicate that, compared with hyaline articular cartilage, degraded link protein and proteoglycan accumulate at an early age in young-adult disc tissues. These partially degraded proteoglycan aggregate components may significantly alter the biomechanical properties of disc tissues.