What are iPSCs?

Induced pluripotent stem cells (iPSCs) are a type of stem cell derived from adult somatic cells, such as skin or blood cells. They are generated by reprogramming the adult cells into an embryonic-like pluripotent state that enables the development of an unlimited source of any type of cell in the human body. iPSCs were first discovered in 2006 by a team of researchers led by Shinya Yamanaka, from Kyoto University in Japan, who won the Nobel Prize for his work on iPSCs in 2012.

How are iPSCs created?

iPSCs are created through a process called reprogramming, which involves introducing specific genes into adult somatic cells using genetic engineering techniques including viral transduction. The four genes that are typically used for reprogramming are Oct4, Sox2, Klf4, and c-Myc. The transfected cells are then incubated on feeder layers under appropriate media conditions and after the expression of the reprogramming factors, the cells reset to an embryonic-like state. The resulting iPSCs can then be cultured and directed to differentiate into specific cell types, such as heart cells or nerve cells.

What are the applications of iPSCs?

iPSCs have a wide range of applications in research and medicine.­ One of the most promising areas of research is disease modelling. As iPSCs are capable of self-renewing, these cells can easily differentiate into all types of cells which can be used for the preparation of disease models to study those diseases. For example, iPSCs can be generated from patients with genetic diseases or complex diseases like Alzheimer’s and Parkinson’s, which allow researchers to better understand the mechanisms of the disease and develop new treatments.

iPSCs are also being used in drug discovery or cytotoxicity studies. They can be used to screen large numbers of compounds for their ability to treat specific diseases, which can speed up the drug development process and reduce the need for animal testing. iPSCs are also used in toxicology testing to identify compounds that are toxic, offering an alternative to animal testing for better chemical safety assessment.  

In cell therapy and regenerative medicine, iPSCs have the potential to treat a wide range of diseases and conditions. They can be used to generate healthy cells to replace damaged or diseased tissue, which could be used to treat conditions like heart disease, diabetes, and spinal cord injuries.

What are the advantages of iPSCs?

iPSCs have several advantages over other types of stem cells. As iPSCs can be generated from a patient’s own cells, this reduces the risk of immune rejection when used in therapeutic applications. This personalised approach could lead to more effective and targeted treatments for individual patients. iPSCs also avoid the ethical concerns associated with the use of embryonic stem cells. Another advantage is the ability of gene targeting, modifying the disease-causing mutations to normal genomic sequence. Due to their versatility, iPSCs can be directed to and differentiated into any type of cell in the body, making them an attractive tool for regenerative medicine and disease modelling.

Extracellular Matrix – an important factor in iPSC culture

MEFs, or mouse embryonic fibroblasts, are commonly used as a feeder layer in culturing iPSCs. MEFs are a type of connective tissue cell that is derived from the embryonic stage of mice and are typically used as a feeder layer to support the growth and differentiation of iPSCs. MEFs serve as a source for essential growth factors and other molecules that iPSCs need to grow and differentiate.

While MEFs are commonly used as a feeder layer for iPSC culture, there are some limitations to this approach. For example, MEFs can be difficult to prepare and maintain, and there is a risk of contamination with pathogens or other unwanted cells. Additionally, the use of animal-derived feeder layers raises ethical concerns and may limit the clinical use of iPSCs in humans.

Matrigel is another commonly used extracellular matrix (ECM) in iPSC cultures. It is a commercially available ECM derived from mouse sarcoma cells and contains a complex mixture of ECM proteins, including laminin, collagen IV, and heparan sulfate proteoglycans. Though Matrigel is highly effective at supporting iPSC growth and differentiation, it has some limitations. As it is derived from mouse sarcoma cells, its composition varies from lot-to-lot and may contain unknown factors that could influence iPSC behaviour and could affect the reproducibility of results. Like MEFs, the use of animal-derived products in iPSC culture raises ethical concerns and could limit the clinical applications of iPSCs.

iMatrix-511 enhances iPSC culture

Laminin-511 is a major component of the ECM and has been found to play an important role in iPSC culture. Despite it being an important ECM for iPSC culture, laminin-511 is not suitable for large-scale production because of its large molecular weight and heterotrimeric nature. As such, Prof. Sekiguchi’s group developed and produced a recombinant fragment of laminin-511 (E8 fragment) that fully retains the integrin binding activity of intact laminin-511.

The recombinant fragment, called ‘iMatrix-511’, has two important advantages over the intact laminin-511. Firstly, due to its smaller size, iMatrix-511 is easier in large-scale production than intact laminin-511. Secondly, iMatrix-511 is more potent than intact laminin-511 to secure the adhesion and expansion of human pluripotent stem cells after single-cell dissociation.

iMatrix-511 can also be used in the “Pre-mix method” where pre-coating is not required before the seeding of cells and it requires only half the iMatrix-511. The new method of using iMatrix-511 supports cell adhesion and long-term expansion as compared with the precoated manner, allowing less costly and time-consuming maintenance of hPSCs.

Apart from iPSCs, iMatrix-511 can be used for hESCs and human primary cells. iMatrix-511 is widely used by many researchers and has been published in many peer-reviewed articles. iMatrix-511 is also available in clinical grade, which meets the Standards of Biological Ingredients by the Pharmaceutical and Medical Devices Agency (PMDA), a government agency in Japan that is similar to the FDA. The regulation is one of the strictest in the world and iMatrix-511MG not only fulfils regulatory requirements but has also been used for a number of high-profile clinical applications in Japan, including transplantation of corneal epithelial cell sheet.  The clinical iMatrix-511 is also GMP compatible which enables a seamless move from basic research using the RUO-grade iMatrix-511to clinical. Overall, iMatrix-511 is a powerful tool to facilitate growth and a high cell survival rate, making the culture of iPSCs simple and reliable!

References

Miyazaki, T., Futaki, S., Suemori, H. et al. Laminin E8 fragments support efficient adhesion and expansion of dissociated human pluripotent stem cells. Nat Commun 3, 1236 (2012). https://doi.org/10.1038/ncomms2231

Miyazaki, T., Isobe, T., Nakatsuji, N. et al. Efficient Adhesion Culture of Human Pluripotent Stem Cells Using Laminin Fragments in an Uncoated Manner. Sci Rep 7, 41165 (2017). https://doi.org/10.1038/srep41165

Moradi, S., Mahdizadeh, H., Šarić, T. et al. Research and therapy with induced pluripotent stem cells (iPSCs): social, legal, and ethical considerations. Stem Cell Res Ther 10, 341 (2019). https://doi.org/10.1186/s13287-019-1455-y