Cell distribution and regenerative activity following meniscus replacement.

PURPOSE: Meniscus replacement is of clinical benefit, but universal efficacy remains elusive. A greater understanding of the biological activity within implanted allografts or synthetic scaffolds may assist the development of improved surgical strategies. MATERIALS: Biopsies of fresh-frozen allograft (n=20), viable allograft (n=18) and polyurethane scaffolds (n=20) were obtained at second-look arthroscopy. Histological evaluation of tissue morphology and cell density/distribution was performed using haematoxylin-eosin (H&E) staining. Immunohistochemistry was used to detect the presence of CD34 (on progenitor cells and blood vessels) and smooth muscle actin (SMA)-positive structures and aggrecan. Collagen presence was investigated using picrosirius red staining.
RESULTS: Cell density in the deep zone of the meniscus replacement was significantly higher in polyurethane scaffolds versus allograft transplants (p<0.01) and also significantly higher in viable allograft compared with deep-frozen allograft (p<0.01). CD34 staining was significantly higher in polyurethane and viable allografts versus deep-frozen allograft (progenitor cells p<0.05; blood vessels p<0.01). There were no significant differences in SMA or aggrecan staining across groups. All three specimen types demonstrated strong presence of collagen type I.
CONCLUSIONS: Both viable allograft and a polyurethane meniscal scaffold show enhanced morphological, cell-distribution and regenerative patterns over deep-frozen allograft following surgical implantation. Given the limitations in viable allograft availability, these findings support the continued development of synthetic scaffolds for meniscus replacement surgery.