Recent Breakthrough in Differentiating Stem Cells into Bone Cells
A recent development has come about at the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering where researchers were better able to control the differentiation of stem cells into bone cells. Stem cells are undifferentiated cells in an organism which could potentially turn into any other type of cell in the organism such as a liver cell or red blood cell. Each cell has its own microenvironment, which includes the proteins and polymers surrounding the cell and the cell’s connections to other cells. Stem cells can be induced to undergo differentiation into certain cells by altering the cell’s microenvironment in specific mechanisms. The issue with this fine-tuning was that it was assumed that the energy used in altering the microenvironment was elastic, or that the cell goes back to its original shape after the stress is removed. However, researchers learned that the cell’s microenvironment does not have elastic properties such as those seen in rubber but rather has viscoelastic properties, which can be exemplified in chewing gum. Viscoelastic materials release their energy over time when a stress is applied instead of all at once as seen in elastic materials, and they do not return to their original shape after the stress has been removed, having some amount of permanent distortion due to the stress. Researchers attempted to replicate the viscoelastic properties seen in the cell’s microenvironment through creating materials called hydrogels. When stem cells were put into these hydrogels, the gels were given stress and relaxed with certain factors, leading to differentiation of stem cells. When the hydrogel was stiff, and stress was applied to it with the stem cells inside. Increasing the rate at which the gel relaxed led to bone cell differentiation. After the added stress was fully removed, the bone cells that were initially formed continued to differentiate and form a tight set of connections, called an interconnected mineralized matrix, of collagen, which is a key property of bones.
It is exciting that researchers have better precision in converting stem cells into bone cells because potential applications of this research include bone regeneration, growth, and healing. This work has several implications in further research which would examine the hydrogels made to initially differentiate the stem cells into bone cells. The hydrogels could be modified so that other types of cells could be created, such as fat cells. The key take-away points from this research are that bone cells “need fast-relaxing environments to grow into bone, which is very stiff and elastic”. This knowledge of having fast-relaxing environments could be used as the healing of fractures, where there is a physical crack in the bone, so that the fractured bone could be placed under conditions similar to those experienced by the hydrogels discussed earlier which had fast-relaxation periods, potentially allowing bones to form and heal faster. The work produced in this study could lead to further analysis of how mechanical properties, such as fast relaxation, can influence cell behavior.
Sources: http://www.eurekalert.org/pub_releases/2015-11/hjap-abw113015.php http://stemcells.nih.gov/info/basics/Pages/Default.aspx https://www.teachengineering.org/view_lesson.php?url=collection/cub_/lessons/cub_surg/cub_s urg_lesson04.xml