Pluripotent cell culture techniques
Stem cells have the potential to differentiate into various types of cells. They function as a repair system for the body. There are two types of stem cells present in the body; embryonic stem cells and adult stem cells. They differ from all other types of cells in 3 ways (1):
1) They are able to divide and self renew indefinitely
2) They are non differentiated and therefore consists of unspecialized cells
3) In response to appropriate signals they are able to differentiate and become specialized cells such as, blood cells, brain cells etc.
Multipotent stem cells
Multipotent or adult stem cells can either self renews and aid in repair and regeneration, or differentiate to become tissue specific specialized cells. For instance, hematopoietic stem cells differentiate in to various types of blood cells, and neural stem cells differentiate in to neurons astrocytes and oligodendrocytes (1).
Pluripotent stem cells
Pluripotent stem cells have the potential to differentiate to any cell type. Embryonic stem cells originate from embryos and can divide indefinitely. Perinatal stem cells are derived from umbilical or placental tissues. Induced pluripotent stem cells (iPSCs) are a pluripotent stem cell line that is produced directly from a somatic cell, by the introduction of four specific genes coding for transcription factors (MyC, Oct3/4, Sox2 and Klf4) (2).
Currently the most widely used pluripotent stem cells are the perinatal cells, and iPSCs. iPSCs in particular has great potential in regenerative medicine, due to the its potential to proliferate indefinitely and give rise to every other cell type in the body, thus being a single source of cells that could be used in cell therapies, tissue engineering and drug discovery. Stem cells can also be used in patient specific therapy to minimize the risk of graft rejection. Additionally in conjunction with gene editing tools like CRISPR system, stem cells can be studied to understand the progression and treatment of hard to treat disorders (3).
Stem cell culture techniques
These applications of stem cells require large amount of cells of high quality in an efficient, defined and modifiable platform. Stem cell cultures need high quality media and well-defined, reproducible, reliable culturing techniques, to generate clinically translatable data in laboratory (4). Any defects in either media or culturing techniques, can result in unwanted cell differentiation or cellular senescence.
It is also important to choose the right stem cell line (Multipotent on pluripotent), and the appropriate in-vivo transcription factors that can induce differentiation in an in-vitro cell culture. In recent years advances in 3D cell culture systems (spheroid and organoid) has enabled production of high quality cells in a reliable and reproducible manner.
3D cell cultures of iPSCs mimic both cell-cell and cell-matrix interactions in studying the differentiation of cells. iPSCs can be cultured with or without a supporting scaffold. Spheroid cultures of iPSCs are cultured using cell repellant-coated plates such as BIOFLOATTM 96 well plates, to generate uniform spheroids in a relatively short period of time. These cell cultures remain viable for longer periods with the inclusion of scaffolds such as hydrogels, thus making it possible to create disease models where progressive changes can be observed, such as in neurodegenerative diseases (4).
References
1) Atala A, Lanza R (2012-12-31). Handbook of Stem Cells. Academic Press. p. 452
2) Takahashi K, Yamanaka S (2006). “Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors”. Cell. 126 (4): 663–76.
3) Yuguo Lei, David V. Schaffer (2013). “3D culture system for human pluripotent stem cells” Proceedings of the National Academy of Sciences Dec 2013, 110 (52) E5039-E5048
4) Haishuang Lin, Qiang Li, and Yuguo Lei (2017. “Three-dimensional tissues using human pluripotent stem cell spheroids as biofabrication building blocks”. Biofabrication 9 025007
5) Chan SW, Rizwan M and Yim EKF (2020) Emerging Methods for Enhancing Pluripotent Stem Cell Expansion. Front. Cell Dev. Biol. 8:70.
