Back pain is one of the leading causes of disability worldwide. Degeneration of the intervertebral discs (IVDs) has been implicated in 40% of cases; however, treatments are ineffective and regenerative therapies are becoming essential. Bioprinting is a powerful tool enabling the creation of biomimetic tissue analogues with properties closely matched to complex tissues. This study therefore optimised and used shear-thinning alginate-collagen hydrogels and suspended layer additive manufacturing (SLAM) to bioprint a range of multi-cellular, multi-material, biphasic IVD models containing immortalised and patient-derived primary human nucleus pulposus (NP) and annulus fibrosus (AF) cells. Immunofluorescent staining was used to quantitatively assess the impact of matrix stiffness, laminin concentration, and oxygen tension on the area, intensity, and integrated density of regional matrix production, in isolation and synchronously. All three conditions were shown to regulate matrix production. The influence of stiffness on cell phenotype was not as substantial as expected; however, increased tissue stiffness was shown to upregulate collagen type VI production in NP cells but downregulate it in AF cells. The data also hinted at differences in stiffness-mediated regulation of collagen and glycosaminoglycan production in AF cells. There was clear evidence that oxygen tension affected protein expression in almost all instances, while hypoxia in particular was shown to increase aggrecan production in both cell types. To the authorâs knowledge, this is the first presentation of a whole IVD co-culture model created solely using bioprinting, and, through the use of multi-material SLAM, furthers the state of the art in suspension bioprinted tissue models for regenerative research using regionally specific matrix cues. The findings provide insight into the importance of microenvironmental factors known to drive irreversible tissue degeneration.
3D Bioprinting Whole Intervertebral Discs to Understand Degeneration & Inform Regenerative Therapies
Kibble, M. (Author). 31 Dec 2023
Student thesis: Phd