The effect of visible light irradiation on the expression of pluripotent genes (Oct-4, Sox2, and Nanog) in amniotic fluid-derived stem cells (AFSCs) and on the osteogenic differentiation ability of AFSCs was investigated using light-emitting diodes (LEDs) at 0-2 mW/cm(2) in various wavelengths: [blue (470 nm), green (525 nm), yellow (600 nm), and red (630 nm)]. Pluripotent gene expression in AFSCs was up-regulated by visible light irradiation from a LED for more than 6 h. Green light irradiation of AFSCs up-regulated the expression of pluripotent genes more significantly than irradiation with other light. The osteogenic differentiation of AFSCs was facilitated by green and blue light irradiation. Facilitated differentiation into osteogenic cells by visible light irradiation was not mediated by reactive oxygen species (ROS); alkaline phosphatase activity (a marker of early osteogenic differentiation) and gene expression of osteopontin (a marker of late osteogenic differentiation) did not change significantly between AFSCs in differentiation medium with or without a ROS scavenger (vitamin C). The mitogen-activated protein kinase/extracellular signal-regulated protein kinase pathway, as well as other unknown signaling pathways, may be responsible for the activation of signaling pathways that facilitate the differentiation of AFSCs into osteogenic cells on light irradiation.

Stem cells from amniotic fluid were cultured on dishes coated or grafted with extracellular matrix (ECM) or Matrigel where gelatin, collagen, fibronectin, laminin, and vitronectin were selected as ECM components (nanosegments). The effects of interactions between amniotic fluid stem cells and nanosegments were investigated on the expression of surface markers of mesenchymal stem cells and on the differentiation abilities of osteoblasts and neural cells. The ECM-coated dishes produced water contact angles from 35 to 65 degrees, whereas ECM-grafted dishes produced water contact angles from 50 to 70 degrees, which was an adequate water contact angle range for our cell culture conditions. Culture on ECM-immobilized dishes enhances amniotic fluid stem cell differentiation into osteoblasts more than culture on polystyrene dishes grafted with amino groups (PS-NH2 dishes). This finding indicates that specific interactions between amniotic fluid cells and the ECM grafted onto the culture dishes promote the differentiation of cells into osteoblasts. Matrigel-immobilized dishes promoted a more extensive differentiation of amniotic fluid stem cells into neural cells than did ECMimmobilized dishes, but they did not promote differentiation into osteoblasts. Immobilization of the optimal nanosegments (ECM or Matrigel) onto culture dishes enhances amniotic fluid stem cell differentiation into osteoblasts and neural cells; the choice of nanosegments depends on the desired differentiated cell type.