Engineered full-organ 3D intervertebral disc as standardized model for studying disc degeneration and disease – INDEED

Background: Intervertebral disc (IVD) degeneration is a major source of human suffering and disability. The study of IVD disorders is hampered by the intrinsic complexity of this organ, and the absence of standardized models harnessing IVD structure, composition and properties is a severe limitation towards better understanding the mechanisms causing degeneration, pain and disability. The overall aim of the project is using biofabrication for creating a tissue-engineered 3-dimensional (3D) IVD model as standardized and adaptable model outperforming current options for studying IVD disorders; the know-how generated will also be a step towards biofabrication of IVD tissue replacements. Specific objectives. 1) Material development. We will study new collagen-hyaluronic acid (COL-HA) composites to develop bio-inks for 3D printing the IVD model. Such composites will be prepared from a tyramine-derivative of HA and unmodified COL, cross-linked via enzymatic oxidation or visible-light irradiation with preservation of COL fibrillogenesis. The gradient of tissue composition and matrix organisation from the annulus fibrosus (AF) to the nucleus pulposus (NP) will be engineered using additive manufacturing. 2) 3D printing and mechanical characterization. We will develop an ad-hoc path for printing within the same construct both AF and NP – like tissues, creating a stable interface between them to harness both composition and mechanical properties gradients. 3) Biological characterization. The bio-inks will be loaded with bovine AF/NP cells or with human stem cells to characterize their viability, proliferation and phenotype, as well as the matrix deposition and organization; the impact of the printing process on these properties will be studied and bio-ink + 3D printing process will be adapted for optimal biofabrication and biological performance. 4) Final prototype validation. The IVD model will be produced and its mechanical and biological properties tested against those of bovine discs. Then the human IVD model developed with stem cells will be tested and its properties compared to those of human disc (from the literature).
Expected results and impact: We will produce a 3D IVD model allowing the assessment of biomaterials and biological therapies in a controlled environment as the model will be (i) standardized, (ii) customizable in its biochemical composition, cells type and density, to allow targeting precise research questions (iii), more representative of the IVD compared to standard ex vivo bioreactor models and overcoming limitations of using IVDs from animals, which have different composition, structure and load compared to human ones and (iv) independent of availability, donor variability, comorbidities and degeneration state typical of models from human tissue. Besides, such model will constitute a step towards using tissue engineering and 3D printing for fabricating tissue replacements for regenerative medicine. The results from the specific objectives above will be disseminated as conference communications and scientific publications in specialized and high-impact journals, as well as in mainstream media. In the long term, advancement in the 3D printing process and bio-ink development will impact research laboratories and pharmaceutical companies dedicated to innovative regenerative biotherapies.