ABSTRACT
PURPOSE: The role of mesenchymal stem cells (MSC) in supporting the formation of new meniscal tissue in a meniscal scaffold is not well understood. The objective of this study was to assess the quality of the meniscal tissue produced in a fibronectin (FN)-coated polyurethane (PU) meniscal scaffold after a meniscal injury was made in an experimental rabbit model. METHODS: Twelve New Zealand white rabbits were divided in two groups after performing a medial meniscectomy of the anterior horn. In group 1, the meniscal defect was reconstructed with a non-MSC supplemented FN-coated PU scaffold. On the other hand, the same scaffold supplemented with MSCs was used in group 2. The animals were sacrificed at 12 week after index surgery. A modified scoring system was used for histological assessment. This new scoring (ranging from 0 to 15) includes a structural evaluation (meniscal scaffold interface and extracellular matrix production) and tissue quality evaluation (proteoglycan and type I-collagen content). RESULTS: The meniscal scaffold was found loose in the joint in three cases, corresponding to two cases in group 1 and 1 case in group 2. No differences were observed between the groups in terms of the total score (7.0 ± 0.9 vs. 9.4 ± 2.6, p = 0.09). However, differences were observed in group 2 in which 2 out of the 5 scored items, scaffold integration (1 ± 0.0 vs. 1.9 ± 0.6, p = 0.03) and proteoglycan production (1.2 ± 0.3 vs. 2.4 ± 0.2, p = 0.001). A trend to a higher production of Type I-Collagen production was also observed in group 2 (1.1 ± 0.4 vs. 1.4 ± 0.7, p = 0.05). CONCLUSION: In a rabbit model at 12 weeks, the adhesion of MSCs to a FN-coated PU scaffold improves scaffold integration, proteoglycan production and the characteristics of the new meniscal-like tissue obtained when compared to a non-supplemented scaffold. This fact could be a major step toward improving the adhesion of the MSCs to meniscal scaffolds and, consequently, the obtention of better quality meniscal tissue.
ABSTRACT
INTRODUCTION: Partial meniscectomy is one of the most common surgical strategy for a meniscal injury, but sometimes, patients complain of knee pain due to an overload in the ablated compartment. In these cases, implantation of tissue engineering scaffold could be indicated. Currently, two commercial scaffolds, based on collagen or polycaprolactone-polyurethane (PCL-PU), are available for meniscus scaffolding. In short term follow-up assessments, both showed clinical improvement and tissue formation. However, long-term studies carried out in PCL-PU showed that the new tissue decreased in volume and assumed an irregular shape. Moreover, in some cases, the scaffold was totally reabsorbed, without new tissue formation.Mesenchymal stem cells (MSCs) combined with scaffolds could represents a promising approach for treating meniscal defects because of their multipotency and self-renewal. In this work, we aimed to compare the behaviour of MSCs and chondrocytes on a PCL-PU scaffold in vitro. MSCs express integrins that binds to fibronectin (FN), so we also investigate the effect of a FN coating on the bioactivity of the scaffold. METHODS: We isolated rabbit bone marrow MSCs (rBM-MSCs) from two skeletally mature New Zealand white rabbits and stablished the optimum culture condition to expand them. Then, they were seeded over non-coated and FN-coated scaffolds and cultured in chondrogenic conditions. To evaluate cell functionality, we performed an MTS assay to compare cell proliferation between both conditions. Finally, a histologic study was performed to assess extracellular matrix (ECM) production in both samples, and to compare them with the ones obtained with rabbit chondrocytes (rCHs) seeded in a non-coated scaffold. RESULTS: A culture protocol based on low FBS concentration was set as the best for rBM-MSCs expansion. The MTS assay revealed that rBM-MSCs seeded on FN-coated scaffolds have more cells on proliferation (145%; 95% CI: 107%-182%) compared with rBM-MSCs seeded on non-coated scaffolds. Finally, the histologic study demonstrated that rCHs seeded on non-coated scaffolds displayed the highest production of ECM, followed by rBM-MSCs seeded on FN-coated scaffolds. Furthermore, both cell types produced a comparable ECM pattern. CONCLUSION: These results suggest that MSCs have low capacity attachment to PCL-PU scaffolds, but the presence of integrin alpha5beta1 (FN-receptor) in MSCs allows them to interact with the FN-coated scaffolds. These results could be applied in the design of scaffolds, and might have important clinical implications in orthopaedic surgery of meniscal injuries.
