The human hair, for centuries, has been a symbol of beauty, pride and glamour. Composed mainly of a protein called keratin that also makes up nails, claws, hooves and horns, hair grows from the follicles present on the skin at a steady rate of around 0.5 inches a month, forcing us to visit the barber once every few months!
All warm-blooded animals, including humans, have fur or hair on their skin whose main function is regulating the body temperature - keeping the blood at a constant temperature in spite of the external conditions. In some animals, fur or hair help to camouflage, protecting them from predators or dangers, or act as a means of communicative display during a mating ritual.
Unlike other parts of our body, hair is not easily biodegradable and can remain intact for several years due to its slow rate of decomposition and inert chemical properties. Hence, discarded hair has found a range of uses throughout history. Human hair has been used since antiquity to make wigs, eyelashes and other cosmetic products, with the oldest known wigs coming from Egypt and dating back to 1400 BC. The early man used animal fur to keep himself warm. With the dawn of the industrial revolution, hair has found applications in fertilizers, pest control, reinforcement of construction materials, building furniture, oil-water separation and even as composites in superconducting systems.
Keratin in Bioengineering
A recent innovative application of hair has been in the field of medical science. Keratin, the protein derived from hair, is now being extensively used in many bioengineering products like protein based thin films used in tissue engineering. In 2002, scientists developed methods to easily extract keratin from hair, thus opening up possibilities for using this protein in new materials including protein scaffolds and hydrogels used in tissue regeneration.
“A cell needs something to attach to, on which it can grow. Apart from a few cells in the blood, most cells are stationary and attached to some type of a scaffold which helps the cells grow. As material engineers, we look for materials which can be used as scaffolds, where the cell can attach itself and grow”, explains Prof. Kaushik Chatterjee, Associate Professor at the Department of Materials Engineering at IISc, on the need for a substrate in tissue engineering. In a recent study, his group has explored the idea of using keratin as the basis of regenerative medicine or tissue repair, and also as a substrate for stem cell research.
What makes hair suitable for this? “Ideally, a substrate needs to enable cell growth or tissue regeneration, and should not be toxic to the body. And, once the tissue regeneration is complete, the scaffold has to decompose and be metabolized by the body. Keratin satisfies all these conditions”, says Prof. Chatterjee.
Until now, substrates used in tissue engineering have been developed using different types of polymers or metals. “Synthetic polymers or metals may be structurally strong and chemically non-toxic, but ultimately the cells that grow on these structures have to secrete proteins to be happy on such materials”, remarks Dr. Lopamudra Ghosh, a research scientist working with Prof. Chatterjee. “The best thing about using proteins derived from the human body - be it collagen from the skin or keratin from the hair, is that cells seem to grow better on these surfaces”, she adds emphasizing the need for the substrate to be compatible with our body.
The novelty of using keratin for tissue engineering applications is that human hair is easily available and inexpensive. “What’s exciting about keratin is that it is human derived and it is extracted from hair - a discarded and non controversial material. This not only reduces the difficulty of acquiring the substance, but also makes medical research using keratin much cheaper”, says Ms. Aditi Jain, a Ph.D. student from the Centre for Biosystems Science and Engineering in IISc, who is involved in this work.
Keratin in Cardiac and Stem Cell Research
Related research with researchers from the Department of Microbiology and Cell Biology at IISc, has demonstrated the use of keratin coated surfaces to grow cardiomyocytes - the cells that makes up the muscles in the heart. “Heart diseases are one of the leading causes of death in the world. It is primarily due to the inability of the heart to repair itself upon damage. This compromises the function of the heart, making it increasingly susceptible to failure. We were therefore interested in developing engineered biomaterials that can support the growth of heart cells outside the milieu of the body”, explains Prof. Ravi Sundaresan from the Department of Microbiology and Cell Biology, IISc.
Prof. Ravi’s group has been successful in growing live heart cells in a lab dish using nanoscale keratin extracted from human hair. “We have also shown it to be a cost effective and an efficient model to study and understand the mechanisms underlying heart failure”, says Prof. Sundaresan, explaining how this work provides a suitable laboratory substitute to conduct research on cardiac cells for developing better therapies to treat heart diseases.
Researchers from the above two labs collaborated to use keratin coated surfaces to grow stem cells derived from adult bone marrow. The stem cells were efficiently converted to heart-like cells that could one day find use for regenerating damaged tissue in the heart, giving us a glimpse of what the treatment of damaged cardiac tissue would look like in the future.
What do these innovative researchers have in future for the lumps of hair that go down the drain? “We have just shown that a keratin coated surface is much better for cell growth than just growing them on a polymer surface. Now, as a next step, we would like to make a scaffold out of keratin, or a polymer with keratin coated surface, which would enable much more efficient method to grow cells”, remarks Dr. Chatterjee.
With such novel uses of our hair, perhaps the glitz and glamour in the advertisements of shampoos and hair care products may be justified after all!