Morphologic observation of induced pluripotent stem cells induced by corneal endothelium cells with atomic force microscopy

Background Induced pluripotent stem cells (iPSCs)can differentiate into various types of somatic cells without causing ethical controversy and immune rejection in clinical activity,which is similar to differentiation ability of embryonic stem cells.So,iPSCs may be used as seed cells for tissue engineering corneal endothelial reconstruction.Objective The present study was to survey the morphologic change of iPSCs after coculture with corneal endothelium cells(CECs) under the atomic force microscopy(AFM).Methods Rabbit CECs and human MMC-iPSCs were isolated and cultured respectively.The iPSCs were identified with the marker by immunochemistry.iPSCs passaged for 7 days were then cultured with 60％ confluent CECs to establish the co-culture model.The surface morphology and cellular membrane ultrastructure of differentiated iPSCs after induced by CECs were examined by AFM combination with inverted microscope,and compared with CECs and undifferentiated iPSCs.Results Thelengthand width were(66.93±10.48)μm and (44.85 ± 8.14) μm in CECs,(12.51±1.40)μm and (10.93 ±1.69) μm in uninduced iPSCs,and(36.12±10.29) μm and(31.53±9.65)μm in CECs-induced iPSCs.Both the length and width values of CECs-induced iPSCs were statistically bigger than those uninduced iPSCs,with significant differences between them (P＜0.05),but no significant difference was seen in the width valne of CECs-induced iPSCs in comparison with CECs(P＞0.05).The convex structure of CECs cytomembrane surface showed the digitation in shape with the size and height(2.11 ± 1.03) μm and (115.68±92.08) nm respectively,and the concave structure of cytomembrane surface of CECs was fenestrae-like depression and the size was (1.49 ± 0.65) μm.The numerical valuc of mean square root roughness (Rq)and average roughness (Ra)of cytomembrane surface of CECs were(39.20±7.82)nm and (30.37±5.32)nm respectively.The convex surface of cytomembrane of iPSCs was granular-like in shape with size and height(0.39±0.22)μm and(13.11±9.18)nm respectively.The concave surface of cytomembrane of iPSCs was worm-eaten-like concave with the size(0.34±0.18)μm.The numerical value of Rq and Ra of geometrical parameters of cytomembrane surface of iPSCs were (26.60 ± 4.93)nm and (9.97 ± 3.78) nm respectively.The convex surface of cytomembrane of induced iPSCs was digital-like in shape with the size and height (1.91±0.76) μm and(106.55±77.27) nm respectively.The concave surface of cytomembrane of induced iPSCs was fenestrae-like depression and the size of concave was(1.6l±1.25) μm.The numerical value of Rq and Ra on surface of cytomembrane of induced iPSCs was (57.33± 12.80) nm and (43.63± 11.17) nm respectively.The numerical values of the size and height of convex,the size of concave,Rq and Ra on surface of cytomembrane in induced iPSCs were statistically bigger than in iPSCs(P＜0.05)and were not significant differences in comparison with CECs (P＞0.05).Conclusions Morphology of iPSCs translate toward the CECs after induce for 7 days under the AFM.This outcome lays the foundation for further study on iPSCs. Key words: Induced pluripotent stem cell;  Corneal endothelium cell;  Mix co-culture;  Differentiation; Atomic force microscopy