Meniscal regeneration using tissue engineering with a scaffold derived from a rat meniscus and mesenchymal stromal cells derived from rat bone marrow

The purpose of this study was to regenerate a meniscus using a scaffold from a normal meniscus and mesenchymal stromal cells derived from bone marrow (BM-MSCs). Thirty Sprague-Dawley rat menisci were excised and freeze-thawed three times with liquid nitrogen to kill the original meniscal cells. Bone marrow was aspirated from enhanced green fluorescent protein transgenic Sprague-Dawley rats. BM-MSCs were isolated, cultured for 2 weeks, and 2 x 10(5) cells were then seeded onto the meniscal scaffolds. Using a fluorescent microscope and immunohistochemical staining, repopulation of enhanced green fluorescent protein positive cells was observed in the superficial zone of the scaffold after 1 week of culture, and then in the deep zone after 2 weeks. At 4 weeks, expression of extracellular matrices was detected histologically and expression of mRNA for aggrecan and type X collagen was detected. Stiffness of the cultured tissue, assessed by the indentation stiffness test, had increased significantly after 2 weeks in culture, and approximated the stiffness of a normal meniscus. From this study, we conclude that a scaffold derived from a normal meniscus seeded with BM-MSCs can form a meniscus approximating a normal meniscus.