There are 3 major types of stem cells scientists use today – embryonic, ‘somatic’ or ‘adult’ stem cells, and induced pluripotent stem cells (iPSC’s). The uniqueness of stem cells and their self-renewal and regenerative abilities provide incredible potential for advancements in the field of regenerative medicine. However, a lot of work still remains to be performed and studied in order to fully understand these unique cells and reach the full potential of their use. Researchers hope that one day stem cells can be used to treat various diseases such as diabetes and heart disease.
Self-Renewal of Stem Cells- A stem cell must be able to renew itself indefinitely, and also produce cell progeny which mature into organ specific cells with a specific function. In order to do this, the stem cell needs to divide continuously. To ensure that a stem cell population is maintained, two mechanisms exist. The first is obligatory asymmetric replication, in which a stem cell divides into one ‘father’ cell that is identical to the original stem cell, in addition to another daughter cell that is differentiated. Stochastic differentiation also occurs, which means that when one stem cell develops into two differentiated daughter cells, another stem cell undergoes mitosis and produces two stem cells identical to the original.
Scientists are still a long way from understanding this mechanism. For example, researchers have tried to grow human hematopoietic stem cells in culture without much success, as the cells fail to maintain stem cell characteristics, even when the numbers of cells are increased dramatically. Embryonic stem cells are currently the only stem cells that can be propagated and amplified in culture without losing their stem cell characteristics, and are therefore a primary subject of stem cell research. Research is ongoing to understand everything there is to know behind the asymmetric divisions of stem cells, to unravel the molecular pathway behind self-renewal, and analyzing global gene expression patterns in various types of stem cells. A great understanding of these pathways is vital to scientists as they try to grow the very small number of stem cells they obtain from patients for therapeutic purposes.
As we have discussed stem cells can give way to several different types of specialized cells. The process through which non-specialized cells acquires functional characteristics to form highly specific cells such as, muscle cells, heart cells etc. is called as differentiation.
Differentiation is affected and partly controlled by interaction of physical and chemical condition prevalent outside the cell with genes within a cell. These interactions usually take place through internal and external signaling through proteins embedded on the cell surface. These signals control changes in cell structures and functions, which could be chemical or physical in nature. Cells undergo through various step in order to become very specifically specialized when they undergo differentiation.
Differentiation is a really important aspect of stem cells that allow us to potentially generate large no of cells with specific characteristics. Directed differentiation is a process where stem culture conditions are manipulated in order to induce differentiation for specific characteristics.
Modeling of Stem Cells- Stem cells when modeled towards our need for a specific type of cell through controlled differentiation, opens possibilities for variety of cell therapies that could help replacement of tissues in the body, generate a lost limb and could possibly treat variety of diseases such as heart diseases, Parkinson’s disease, Alzheimer’s disease, diabetes etc.
The heterogeneity of stem cells is extremely unique, separating stem cells as one of the most fascinating areas of biology. Scientific questions regarding stem cell self-renewal and differentiation continue to be explored and answered. However, with nearly every new discovery, new questions arise. Some of these questions may be answered through the use of computer modeling, with the hope of speeding up the scientific discovery process so we many someday fully understand every aspect of stem cell properties and capabilities.
- Graf, T., and M. Stadtfield. "Heterogeneity of Embryonic and Adult Stem Cells." ScienceDirect.com. Cell Stem Cell, Nov. 2008. Web. Feb. 2012. <http://www.cell.com/cell-stem-cell/retrieve/pii/S1934590908005304>.
- Kaderei, S. "Stem Cells and Self-Renewal." International Society for Stem Cell Research. Web. Feb. 2012. <http://www.isscr.org/public/SC_self-renewal.pdf>.
- "Stem Cell Properties." THE MEDICAL NEWS. Web. Feb. 2012. <http://www.news-medical.net/health/Stem-Cell-Properties.aspx>.