79 Flexible Support Materials Maintain Disc Height and Support the Formation of Hydrated Tissue Engineered Intervertebral Discs in Vivo

Abstract

OBJECTIVES/GOALS: We evaluated the long-term success of tissue engineered intervertebral discs (TE-IVDs) cultured in flexible (FPLA) or stiff (PLA) support materials, hypothesizing that FPLA would maintain disc height and tissue hydration in the minipig spine. METHODS/STUDY POPULATION: TE-IVD: NP cells were encapsulated in alginate and NP plugs were placed in the center of FPLA cages. AF cells were encapsulated in type I collagen and pipetted around NP plugs. Implantation: Empty FPLA cages (n=4), and TE-IVDs cultured in FPLA (n=4) were implanted at C3-4 or C5-6 following complete discectomy (DX) in skeletally mature minipigs (n=4). Imaging and Quantification: Terminal disc height indices (DHI) were calculated from weekly x-rays using a previously described method, and results were compared to the PLA pilot study. T2 MRI scans were taken of levels treated with TE-IVDs to quantify disc hydration as previously described. RESULTS/ANTICIPATED RESULTS: FPLA cages restored DHIs to native levels until endpoint. In contrast, PLA cages fractured, and terminal DHIs were statistically similar to DX levels. Of the four levels treated with TE-IVDs, 2 were displaced from the disc space. Stabilized levels yielded DHIs which were statistically similar to native IVD and greater than displaced and DX levels. Displaced levels yielded DHIs which were significantly lower than native and stabilized levels, but greater than DX levels (P<0.05). T2 MRIs of stabilized TEIVDs revealed that levels treated with a construct maintained tissue hydration which was significantly greater than levels treated with an empty cage or DX levels (P<0.0001), but which was about half the hydration of native disc tissue. DISCUSSION/SIGNIFICANCE: Implanting TE-IVDs with FPLA support cages leads to disc height maintenance and the stabilization of hydrated tissues in the spine, enhancing the long term success of TE-IVD implants and providing a basis for clinical translation.