The reason for the maintenance of the stem cell markers in the cultured cells under the influence of feeder layer is not clearly understood, but could be multifactorial such as the possible release of diffusible factors or cytokines released by the 3T3 fibroblast system, presence of antiapoptotic survival factor in 3T3 fibroblast conditioned medium, (15) and the similarity of the 3T3 feeder layer in mimicking the numerous signal transduction pathways between the limbus and the limbal epithelial cells in maintaining the stemness of the cells.
3T3 feeder layer has also been used for the in vitro propagation of human ocular epithelial transplantation.
The limbal corneal epithelial cells cultured over denuded AM under the influence of feeder layer were able to retain the expression of the putative stem cell makers, ABCG2 and p63 in contrast to cells cultured over denuded AM minus feeder layer.
Liu et al (25) observed that the cells co-cultured with 3T3 feeder layer shows the expression of p63 and faint expression of K3 and 12.
Similarly the expression of connexin -43 and keratin 3 and 12 was comparatively more on the cells cultured over the denuded AM without 3T3 feeder layer (Fig.
1 shows the growth of the cells on the denuded AM and with 3T3 feeder layer.
16-19) Grueterich et al (14) have studied the modulation of connexin 43 (Cnx43) and keratin 3/12 (K3/K12) expression on the cells cultured over the intact and denuded membrane with and without the presence of 3T3 feeder layer.
Other than increasing the potential to guide stem cells to create desired materials for research and clinical applications, using nanoscale topographies could eliminate (or alternatively enhance) steps including those involving feeder layers
and synthetic induction supplements currently used in stem cell culture.