From root to tip: new test systems for the hair research
Until recently, there were no meaningful test systems with which substances and mixtures that have an active impact on hair biology could be rapidly analyzed to demonstrate their effectiveness in the cells of the hair root in an exact and cost-effective manner. Henkel therefore developed a three-dimensional in-vitro model of the human hair follicle as a test system. The team of scientists cultivates the model from cells that are also present in human hair follicles. The hair researchers isolate these cells from, for example, individually plucked hairs and multiply them in a test tube.
In the reconstructed hair follicle model, the individual cell types communicate with each other as they do in nature and, for example, secrete growth factors. Because the Henkel hair follicle model is readily available and yields reliable results, the hair researchers can now test the effectiveness of a large number of substances each year and study the biological processes in the hair root in every detail. This is a breakthrough in the search for active ingredients for hair cosmetics.
The growth cycle of a hair consists of three phases:
1) The anagen (growth) phase, which lasts two to six years. 2–3) The two- to four-week catagen (transitional) phase: During this time, hair growth ceases and the hair follicle becomes shorter. 4) The three- to four-month telogen (rest) phase: No hair growth occurs during this time. 5) Start of a new anagen phase: A new hair bulb forms and a new hair begins to grow. The old hair is gradually pushed up and out. Over the course of a person’s life, a single hair root can thus produce ten to twelve hairs in succession.
The speeded-up life of a hair
Alongside biological ‘internal’ factors, many external influences can age the hair: sunshine, wind and weather, as well as daily blow-drying and styling all damage hair, and especially its surface. The tip of a 12-centimeter hair, for example, which has grown an average of one centimeter per month, has probably been washed and blow-dried about 200 times. Researchers previously had no way of reproducibly simulating the daily life of a hair and measuring how the chemical composition and biophysical properties of hair change over the years.
Henkel scientists therefore designed a complex automated test procedure. In the life cycle simulator, hairs are reproducibly shampooed, rinsed, dried and exposed to defined amounts of light. This is all done automatically with the help of a small laboratory robot. The Henkel researchers can therefore track four months in the life of a hair in just five days.
