Making artificial organs: the "Lego" principle
It is believed that in the future, tissue engineering will allow the creation of new organs for transplantation instead of those affected by various diseases and injuries. However, as a rule, cells grown in laboratory conditions are spread out on the cultivation surface, and the creation of three-dimensional cellular structures from them is fraught with considerable difficulties.
Researchers at the Massachusetts Institute of Technology have proposed a fundamentally new solution to this problem. They have developed a method of "microlaying", the material for which is living cells encapsulated in polymer cubes, from which, as in a children's designer, three-dimensional structures are assembled. The proposed method is described in detail in the article "Micro-Masonry: Construction of 3D Structures by Microscale Self-Assembly", published on May 3 in the preliminary on-line version of the journal Advanced Materials.
Obtaining individual cells for subsequent use in tissue engineering involves the preliminary cleavage of tissue with the help of enzymes that destroy the extracellular matrix that ensures the integrity of the tissue. However, the reverse process – the creation of structures from individual cells that repeat the microarchitecture of living tissues – is an extremely difficult task.
Researchers have already learned how to use biodegradable scaffolds to create simple tissues and organs such as skin, cartilage and bladder. However, according to one of the authors of the work Ali Khademhosseini, such methods often do not provide a complex microarchitecture characteristic of living tissues.
The authors have developed a method for encapsulating living cells in polyethylene glycol (PEG), a polymer widely used in medical practice. The liquid version of polyethylene glycol used in this case turns into a gel under the action of light, and the cells covered with it are enclosed inside cubes of 100-500 microns in size.
To create structures of the required shape (for example, such a hemisphere), the resulting cubes are placed on a matrix of polydimethylsiloxane, a silicon–based polymer also widely used for medical purposes. The resulting structure is again coated with polyethylene glycol, this time acting as an adhesive that holds tightly packed cubes with cells on the surface of the matrix. After careful distribution of the cubes over the matrix, the entire structure is illuminated again, which leads to solidification of the surface polymer layer. After that, the matrix is removed and a ready-made structure is obtained.
The authors used the described method to create tubes suitable for use as capillaries. Such capillaries can solve one of the main problems associated with artificial organ transplantation – the lack of blood supply to the transplanted organ immediately after the operation. They also hope that in the future their proposed approach will form the basis for the creation of an artificial liver and heart.
They also note that, unlike the previously developed "three-dimensional printing" of organs, the proposed "Lego" method does not require any special equipment and is so simple that it can be reproduced in almost any laboratory.
Currently, the authors are testing the possibility of using various polymers, as well as the possibility of creating and viability of various types of tissues.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on MIT materials: Building organs block by block.
17.05.2010