Towards clinical translation of the cell sheet engineering: Technological aspects

Cell sheet engineering is a rapidly growing field of tissue engineering and regenerative medicine. The ease of cell sheet obtainment techniques and the resulting unique characteristics and microenvironment of these multicellular structures give rise to the wide range of their in vivo application. At the same time, there are also macroscale cell sheet properties such as thickness, shrinkage after detachment due to cytoskeleton relaxation, and resulting mechanical characteristics. The main topic of this review is the discussion of these properties and how they define the need to use special approaches to manipulating cell sheets during stacking several structures, transferring them to surgical sites, or cryopreserving them. We aimed to systematize the existing techniques of cell sheet transferring, and describe their principles, advantages, and drawbacks regarding cell sheet application during surgical procedures on various tissues and organs. Attention is also paid to such aspects and details as cell sheet positioning in vivo, their ability to spontaneous adhesion, and the requirement for additional fixation at particular surgical sites. Finally, the last section of this review covers the subject of cell sheet cryopreservation – the discussion of freezing and thawing protocols, the variety of cryoprotectants and their mixtures, as well as special requirements such as cryoprotectant loading systems, and cell sheet supporting systems that also stem from their unique macroscale characteristics. Altogether, this systematized review of existing technological approaches related to cell sheet application in vivo can be potentially helpful for the new and expert researchers in this area of tissue engineering.