Figure 4

TEM of hMSC mixture beads. (A) Structure in TEM of fibrin, thrombin, and atelocollagen without cells. (a) It is a mixture of fibrin and thrombin. Fibrin was observed in the form of fiber (orange arrowhead) and thrombin in the form of a clot (orange arrow). (b) The structure of only atelocollagen and the fibers are observed (orange arrowhead). (B) TEM image of fibrin, thrombin, and atelocollagen with cells. The control I group (mixture of fibrin, hMSCs, and thrombin cultured in basal medium) (a, d, g, j), the control II group (mixture of fibrin, hMSCs, and thrombin cultured in chondrogenic differentiation medium) (b, e, h, k), and the atelocollagen group (mixture of fibrin, atelocollagen, hMSCs, and thrombin cultured in chondrogenic differentiation medium) (c, f, i, l) were investigated after days 0, 3, 7, and 21 of culture. Control I and control II groups changed from a round shape (a and b) to an elongated morphology at 3 days after culture (d and e). Cells tried to touch the matrix such as fibrin and thrombin by stretching foot-like projections (e, black arrow). However, the atelocollagen group maintained the round shape from days 0 to 7 after culture (c, f, and i, * yellow indication). The round shape remained unchanged until 21 days after culture (l), and cells extended to form contacts with the surrounding matrix (l, black arrowhead), but not other groups (j and k, black arrowhead; elongated cells). At 21 days, the matrix was enriched with collagen fiber bundles in the atelocollagen group (m and n, ** yellow indication in the purple box). The purple box of image m and n is an enlargement of the small purple box of image l. Representative TEM images are shown. Scale bar: 1,000 nm (A (a and b), B (m and n)). 2000 nm (B (a–l)).