Abstract
Intervertebral disk (IVD) degeneration is commonly described by loss of height and hydration. However, in the first stage of IVD degeneration, this loss has not yet occurred. In the current study, we use an ex vivo degeneration model to analyze the changes in IVDs mechanical behavior in the first phase of degeneration. We characterize these changes by stretched-exponential fitting, and suggest the fitted parameters as markers for early degeneration. Enzymatic degeneration of healthy lumbar caprine IVDs was induced by injecting 100 μL of Chondroïtinase ABC (Cabc) into the nucleus. A no-intervention and phosphate buffered saline (PBS) injected group were used as controls. IVDs were cultured in a bioreactor for 20 days under diurnal, simulated-physiological loading (SPL) conditions. Disk deformation was continuously monitored. Changes in disk height recovery behavior were quantified using stretched-exponential fitting. Disk height, histological sections, and water- and glycosaminoglycan (GAG)-content measurements were used as gold standards for the degenerative state. Cabc injection caused significant GAG loss from the nucleus and had detrimental effects on poro-elastic mechanical properties of the IVDs. These were progressive over time, with a propensity toward more linear recovery behavior. On histological sections, both PBS and Cabc injected IVDs showed moderate degeneration. A small GAG loss yields changes in IVD recovery behavior, which can be quantified with stretched-exponential fitting. Parameters changed significantly compared to control. Studies on disk degeneration and biomaterial engineering for degenerative disk disease (DDD) could benefit from focusing on IVD biomechanical behavior rather than height and water-content, as a marker for early disk degeneration.
| Original language | English |
|---|---|
| Article number | 091008 |
| Pages (from-to) | 1-9 |
| Number of pages | 9 |
| Journal | Journal of Biomechanical Engineering |
| Volume | 140 |
| Issue number | 9 |
| Early online date | 24 May 2018 |
| DOIs | |
| Publication status | Published - Sept 2018 |
Funding
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors thank Dr. Arno Bisschop from the Department of Orthopedic Surgery at the VU University Medical Center in Amsterdam for his technical support and useful discussions on spine biomechanics. We also thank Dr. M. de Graaf from the Department of Orthopedic Surgery, Willem de Jong from the Department of Oral Pathology and Wim Vos from the Department of Neuro-Immunodiagnostics at the VU University Medical Center in Amsterdam for their work on the histological sections and scoring. • Dutch Government ZonMw Program “Alternatives for life animal testing” (Grant No. 11400090). • The development of the LDCS is co-funded by the Dutch Ministry of Economic Affairs, Agriculture and Innovation led Government research program IDiDAS for the develop-ment of Biomedical Materials (BMM project P2.01).
Keywords
- biomechanical
- bioreactor
- caprine
- degeneration
- GAG
- glycosaminoglycans
- intervertebral disk
- IVD
- lumbar
- puncture
- spine
- stretched-exponential fitting
