Caroline N. Demers

Value and limitations of using the bovine tail as a model for the human lumbar spine.

Study Design. The contents of DNA, proteoglycan, type II collagen, and denatured type II collagen in the bovine coccygeal intervertebral discs were examined in situ in relation to disc level, age, and tissue region. Objective. To determine whether bovine coccygeal discs are a suitable model to study human lumbar discs. Summary of Background Data. Bovine coccygeal discs have been suggested as a suitable alternative model because they are readily available, in contrast to human discs, and represent a common source of tissue in the disc field. However, it is not known whether the changes in matrix contents in bovine coccygeal discs are similar to those found in the human lumbar spine. Methods. Intervertebral discs from bovine tails were dissected into the nucleus pulposus (NP) and anulus fibrosus (AF). Tissues were weighed and analyzed for matrix contents using specific assays. Results. Similar to water content, the proteoglycan content was higher in the NP than in the AF. Water content of the bovine NP did not change with age, unlike the proteoglycan content, which decreased. type II collagen content was higher in the NP than in the AF, and both did not change overall significantly with age. The percent of denatured type II collagen decreased with age only in the NP. The DNA content did not vary with age in the AF and in the NP. Conclusion. Differences in matrix contents exist between the bovine coccygeal discs and the human lumbar spine. Thus, caution must be exercised when using the bovine tail as a model for the human lumbar spine in biochemical studies.

A synthetic peptide of link protein stimulates the biosynthesis of collagens II, IX and proteoglycan by cells of the intervertebral disc

To date, there have been no reports on the effect on disc cells of the intervertebral disc (IVD) of the amino terminal peptide of link protein (DHLSDNYTLDHDRAIH) (link N) which is generated by the cleavage of human link protein by stromelysins 1 and 2, gelatinase A and B, and collagenase between His16 and Ile17. However, link N has been shown to act as a growth factor and stimulate synthesis of proteoglycans and collagen by chondrocytes of human articular cartilage. There are also no studies on the effect of link N on type IX collagen in any tissue. In the studies reported here, a serum‐free pellet culture system has been used to examine whether link N can play a role in maintaining the integrity of disc matrix, specifically at the level of matrix assembly by cells of the IVD. Using this culture system, we determined the capacity of link N to stimulate accumulation of these matrix proteins in the annulus fibrosus (AF) and nucleus pulposus (NP). Gross inspection of separate AF and NP pellet cultures in the absence of link N revealed a progressive increase in size and a transition from “spherical” to “polygonal” pellets after centrifugation. Addition of 10 ng/ml link N resulted in increased pellet sizes for both AF and NP pellet cultures. Link N increased proteoglycan, type II and type IX collagen contents with an increase in DNA content over time. This study demonstrates that link N can act directly on disc cells to stimulate matrix production, which involves increased accumulation of proteoglycan, and types II and IX collagens. This study also identifies the value of pellet cultures for studies of the IVD cells in a serum‐free chemically defined medium, in which pellets can continue growing in size in response to growth factors with minimal cell loss. Link N may have value in stimulating the growth and regeneration of the damaged IVD. J. Cell. Biochem. 88: 1202–1213, 2003.

Quantitative magnetic resonance imaging of enzymatically induced degradation of the nucleus pulposus of intervertebral discs

Study Design. The structural integrity of the nucleus pulposus (NP) of intervertebral discs was targeted by enzyme-specific degradations to correlate their effects to the magnetic resonance (MR) signal. Objective. To develop quantitative MR imaging as an accurate and noninvasive diagnostic tool to better understand and treat disc degeneration. Summary of Background Data. Quantitative MR analysis has been previously shown to reflect not only the disc matrix composition, but also the structural integrity of the disc matrix. Further work is required to identify the contribution of the structural integrity versus the matrix composition to the MR signal. Methods. The bovine coccygeal NPs were injected with either enzyme or buffer, incubated at 37°C as static, unloaded and closed 3-disc segments, and analyzed by a 1.5-Tesla MR scanner to measure MR parameters. Results. Collagenase degradation of the NP significantly decreased the relaxation times, slightly decreased the magnetization transfer ratio, and slightly increased the apparent diffusion coefficient. Targeting the proteoglycan and/or hyaluronan integrity by trypsin and hyaluronidase did not significantly affect the MR parameters, except for an increase in the apparent diffusion coefficient of the disc after trypsin treatment. Conclusions. Our results demonstrate that changes in the structural integrity of matrix proteins can be assessed by quantitative MR.

Evaluation of quantitative magnetic resonance imaging, biochemical and mechanical properties of trypsin‐treated intervertebral discs under physiological compression loading

To investigate the influence of targeted trypsin digestion and 16 hours compression loading on MR parameters and the mechanical and biochemical properties of bovine disc segments.