Figure 2.

Morphological changes from P0 (PDL 8) to P8 (PDL 45) cells of human epiphyseal chondrocytes (#1) during expansion. (a) Cytology of the culture cells with Papanicolaou's stain (Pap stain). Cell morphology changed from small polygonal cells with mitosis (P0) to short or long spindle cells (P1), to long spindle cells (P2–P4) with occasional large spindle or polygonal cells (P4-P5), and to large, polygonal cells with long cytoplasmic processes and vacuolation and nuclei with indistinct chromatin structures (P6–P8). (b) Macroscopic views of the tissues by implantation of P0 to P8 cells for two weeks. The nodules of P0 to P2 cells are the same in size, in weight, and in degree of transparency with whitish color on surface. The nodules of P3 and P4 cells, however, decreased in size along with the increase of passages and were accompanied with central vascular invasion. The nodules of P5 to P8 cells became flattened and brownish-white in color. Bars: 3 mm. (c) Microscopic views with hematoxylin and eosin stain. P0 and P1 cells generated two distinct portions, that is, cartilage and perichondrium at the implanted sites. As the passage number increased, the boundary of two portions became ill-defined. P4 to P8 cells exhibited spindle-shaped dedifferentiated chondrocytes, accompanied with reactions of inflammatory cells, macrophages, and foreign-body giant cells.