Introduction - Microsurgery: Advances, Simulations, and Applications - page 36

As cell sheet manipulation, two techniques have been performed
according to cell types and objects. One is to manipulate cell
sheets directly with forceps or pipetting after the sheets are
completely harvested resulting in proportionally shrunk and thicker
constructs due to active cytoskeletal reorganization. As indicated by
synchronized beating of shrunk cardiomyocyte sheets, cell-to-cell
connections are preserved after this procedure [114]. The other is
to use support membranes, including a hydrophilically modiied
poly(vinylidene diluoride) (PVDF) membrane, for preserving cell
sheet morphology without any shrinkage. Before cell sheets release,
support membranes are placed over the conluent cells. Then the cell
sheets physically attached to the support membranes are harvested
from PIPA Amgrafted surfaces below 32 ° C and transferred onto
other surfaces. Incubation at 37 ° C causes reattachment of the cell
sheets to new surfaces via remaining adhesive proteins. Finally,
only the support membranes are removed. The latter technique has
realized the cell sheet manipulation preserving their structure and
function.
These cell sheet manipulation techniques without using any
biodegradable scaffolds have been applied to tissue engineering
in three types of contexts. First is transplanting single-cell sheet
for skin and cornea reconstruction. Advantages of skin epithelial
cell sheets harvested by using PIPAAm-grafted surfaces have
been conirmed in comparison with those harvested by dispase
treatments. E-cadherin, which is an essential protein for skin cell-
to-cell junctions, and laminin 5, which is a major component of
epithelial basement membranes, were retained in skin cell sheets
released from PIPAAm-grafted surfaces [109]. It should attenuate
the risk of infection after artiicial skin transplantation. Second is
to layer same cell sheets for reconstructing homogeneous tissues
including myocardium. Third is to layer several types of cell sheets
for fabricating laminar structures including liver, kidney and vascular.
Layered co-culture comprising a hepatocyte sheet and an endothelial
cell sheet has revealed the differentiated cell shape and extensive
albumin expression of hepatocytes, which have never been seen in
hepatocyte mono-culture [114]. Cell sheet engineering technology
described above has been applied into regeneration of myocardium
[113], cornea [115] and hepatic tissue [116].