Evaluation of Engineered Meniscal Cartilage Constructs Based on Different Scaffold Geometries Using Magnetic Resonance Imaging and Spectroscopy

Magnetic resonance imaging (MRI) and spectroscopy (MRS) were used to evaluate the properties of different scaffold geometries for the production of bioartificial meniscal cartilage constructs. Engineered constructs were generated in perfusion bioreactors from mature sheep meniscal fibrochondrocytes, using scaffolds cut from a knitted polyethylene therephtalate (PET) fabric, with a chaotic distribution of fibers, 50 µm pores and a density of 45 mg/cm³ (NF scaffolds), and from two modified versions of this fabric, which included larger pore sizes (1500 × 500 µm²) and densities of 48 (sIV scaffolds) and 83 mg/cm³ (sV scaffolds). MRI methods were used to determine the permeability of the constructs to a low molecular weight MR contrast agent and to measure the macroscopic flow of medium through and around the constructs. These parameters were correlated with MRS measurements of cell growth and cellular energetics. Cell-free sIV scaffolds were 2- and 5- fold more porous to flow than the empty sV and NF scaffolds, respectively. These scaffolds, after 14 days of cell growth, were also more permeable to an MR contrast agent. sIV scaffolds yielded constructs (n = 9) with higher cellularities (41 ± 1%) compared with NF (32 ± 1%, p < 0.0001) and sV (30 ± 1%, p < 0.0001) and, when normalized to cell numbers, demonstrated proportionally higher levels of nucleoside triphosphates (NTP), indicating increased cell viability. Scaffold geometry had a marked effect on the properties of engineered meniscal cartilage. MRI and MRS are powerful noninvasive techniques that can be used to optimize the design of engineered meniscal cartilage tissue and that could be used subsequently to evaluate clinical outcome postimplantation.