Objective: To evaluate the use of hypothermically stored human amniotic membrane for cartilage repair in adult sheep. Studies show that human amniotic membrane contains pluripotent mesenchymal stem cells that can be influenced to produce chondrocytes. It is unknown if human amniotic cells can produce hyaline-like cartilage. This study evaluates the use of hypothermically stored amniotic membrane (HSAM) to fill chondral defects in a sheep model. We hypothesized HSAM would fill defects with hyaline-like cartilage with chondrocytes populating the matrix. One sheep was used as a control, and four sheep received amniotic membrane. Two of these sheep were used as a normal control comparison. A 1 cm2 defect was created on the trochlear grove in all specimens. Each membrane was sized and laid over with the stromal layer facing the subchondral bone and covered with Fibrin sealant. The knees were harvested at five months and underwent morphological, histological, and immunohistological evaluation based on the original validated scoring system by O’Driscoll. The control defect didn’t fill in with hyaline cartilage or fibrocartilage. The defects that successfully retained the graft had evidence of diffuse chondrocyte cell proliferation and showed a stromal matrix similar to hyaline cartilage. The graft samples showed a near 100% morphological fill in the HSAM defect contrasting to <10% fill in the control defect. The retained HSAM grafts scored 2.5 on a 0 - 3 cartilage appearance scale compared with 0.5 for the control defects. HSAM is a potential source of pluripotent cells that can influence chondrogenesis in a sheep model. The implications for application in a human model are promising and warrant further study.
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