The disc nucleus is commonly thought of as a largely unstructured gel. However, exactly how the nucleus integrates structurally with the endplates remains somewhat ambiguous. The purpose of this study was to investigate whether a substantial level of structural/mechanical cohesion does, in fact, exist across the nucleus-endplate junction. Vertebra-nucleus-vertebra samples were obtained from mature ovine lumbar motion segments and subjected to a novel technique involving circumferential transverse severing (i.e. ring-severing) of the annulus fibrosus designed to eliminate its strain-limiting influence. These samples were loaded in tension and then chemically fixed in order to preserve the stretched nucleus material. Structural continuity across the nucleus-endplate junctions was sufficient for the samples to support, on average, 20 N before tensile failure occurred. Microscopic examination revealed nucleus fibres inserting into the endplates and the significant level of load carried by the nucleus material indicates that there is some form of structural continuity from vertebra to vertebra in the central nucleus region.
A simple
and environmentally friendly approach toward the thermoplastic
processing of rapidly degradable plastic-enzyme composites using three-dimensional
(3D) printing techniques is described. Polycaprolactone/Amano lipase
(PCL/AL) composite films (10 mm × 10 mm; height [h] = ∼400 μm) with an AL loading of 0.1, 1.0, and 5.0%
were prepared via 3D printing techniques that entail direct mixing
in the solid state and thermal layer-by-layer extrusion. It was found
that AL can tolerate in situ processing temperatures
up to 130 °C in the solid-state for 60 min without loss of enzymatic
activity. The composites were degraded in phosphate buffer (8 mg/mL,
composite to buffer) for 7 days at 37 °C and the resulting average
percent total weight loss (WLavg %) was found to
be 5.2, 92.9, and 100%, for the 0.1, 1.0, and 5.0% films, respectively.
The degradation rates of PCL/AL composites were found to be faster
than AL applied externally in the buffer. Thicker PCL/AL 1.0% films
(10 mm × 10 mm; h = ∼500 μm) were
also degraded over a 7 day period to examine how the weight loss occurs
over time with 3.0, 18.1, 36.4, 46.4, and 70.2% weight loss for days
1, 2, 3, 4, and 7, respectively. Differential scanning calorimetry
(DSC) analysis shows that the film’s percent crystallinity
(D
xtal%) increases over time with D
xtal% = 46.5 for day 0 and 53.1% for day 7.
Scanning electron microscopy (SEM) analysis found that film erosion
begins at the surface and that water can penetrate the interior via
surface pores activating the enzymes embedded in the film. Controlled
release experiments utilizing dye-loaded PCL/AL/dye (AL = 1.0%; dye
= 0.1%) composites were degraded over a 7 day period with the bulk
of the dye released by the fourth day. The PCL/AL multimaterial objects
containing AL-resistant polylactic acid (PLA) were also printed and
degraded to demonstrate the application of this material on more complex
structures.
Objective The nucleus pulposus of the human intervertebral disc contains 2 cell types: notochordal (NC) and mature nucleus pulposus (MNP) cells. NC cell loss is associated with disc degeneration and this process may be initiated by mechanical stress and/or nutrient deprivation. This study aimed to investigate the functional responses of NC and MNP cells to hydrostatic pressures and glucose restriction. Design Bovine MNP and NC cells were cultured in 3-dimensional alginate beads under low (0.4-0.8 MPa) and high (1.6-2.4 MPa) dynamic pressure for 24 hours. Cells were cultured in either physiological (5.5 mM) glucose media or glucose-restriction (0.55 mM) media. Finally, the combined effect of glucose restriction and high pressure was examined. Results Cell viability and notochordal phenotypic markers were not significantly altered in response to pressure or glucose restriction. MNP cells responded to low pressure with an increase in glycosaminoglycan (GAG) production while high pressure significantly decreased ACAN gene expression compared with atmospheric controls. NC cells showed no response in matrix gene expression or GAG production with either loading regime. Glucose restriction decreased NC cell TIMP-1 expression but had no effect on MNP cells. The combination of glucose restriction and high pressure only affected MNP cell gene expression, with decreased ACAN, Col2α1, and ADAMTS-5 expression. Conclusion This study shows that NC cells are more resistant to acute mechanical stresses than MNP cells and provides a strong rationale for future studies to further our understanding the role of NC cells within the disc, and the effects of long-term exposure to physical stresses.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.