Surgical treatments available today are limited in effectiveness because no new hair is added. Current surgical methods simply cannot produce a full head of thicker hair. The art of surgical hair restoration is rearranging the patient's existing DHT-resistant hair follicles for an appearance that looks fuller. But no new hair is added. Current surgical methods are very labor intensive and costly, and include the minor discomfort of recovery following surgery. The obvious key to improving surgical treatment is cloning hair follicles. Successfully cloning multiple hair follicles from a donor area follicle that is already programmed to continue to grow new hairs for a lifetime will result in a limitless supply of hair transplant grafts, which translates into limitless hair thickness. The cloned follicles may even be individually injected directly into the scalp, eliminating surgery altogether.
So, if scientists can already clone an entire sheep, why isn't human hair follicle cloning a commercial reality? The answer is somewhat complicated, and requires some explanation of cell biology, genetics, cell replication, and then a review of some of the different types of cloning that may apply in the future to mass duplication of human hair follicles.
Cells are the basic units of all living organisms. Cells in a multi-celled organism have specialized characteristics that enable them to most efficiently do their particular jobs. Individual cells in an organism work together with other similar cells in tissue, or they work together with different types of cells in specialized cell structures called organs. For example, in a hair follicle, which is a miniature organ, there are several different types of cells working together to grow a hair.
Inside of just about every mature cell is a structure called a cell nucleus that contains chromosomes composed of double strands of twisted DNA molecules. DNA molecules contain information about creating particular types of proteins, and the cell uses that information to make the proteins that allow it to perform its particular function. Some proteins are structural, such as keratin protein in hair, while others have the function of sending messages, such as the hormone DHT, and some proteins such as the enzyme 5-alpha-reductase, help convert proteins from one form to another.
Sections of DNA molecules that contain the code for particular types of proteins are called genes. That's all genes are: instructions for making specific proteins. There are no genes for particular body characteristics, such as "pattern baldness" or "green eyes" or "curly hair". Only instructions for making proteins. But the particular types of proteins that genes instruct cells to make, in turn determine characteristics such as inherited hair loss and eye color and hair curling. Usually many different genes, and many different proteins, together determine particular inherited body characteristics.
A remarkable feature of cells in a multi-celled organism is that each one contains in its chromosomes a complete DNA blueprint of all the genes for all the proteins for the entire organism. Individual cells only use the protein-making information that they need to do their particular job, even though they contain the protein-making information for the entire organism. For example, cells in the iris of the eye may make the proteins that express the characteristics for green eyes, but not the proteins that could cause pattern baldness or curly hair, or any of the other thousands of genetic traits of the organism. But the information to make all of those proteins is contained in the iris cells; just as the information for making proteins that result in green eyes is contained in hair follicle cells. Unlocking the DNA information in mature specialized cells is an important aspect of some cloning techniques.
In a rapidly growing embryo, cells replicate by splitting in half and then growing to full size again. This process is called cell mitosis, and each half of a cell that splits containing a complete and exact set of the organism's DNA. As the embryo grows into a more fully functioning organism, its cells begin to take on more specialized characteristics, and begin to divide less. As cells become more specialized, cell replication shifts to special precursor cells called stem cells.
Mature specialized cells do not replicate easily, probably as a defense against cancer, which is characterized by uncontrolled cell division. But all cells wear out over time, and have to be replaced by new cells. Some cells only last for days; others for years, and others for decades, but eventually all cells wear out. The inability of mature cells to replicate themselves limits the body's ability to repair itself, to heal wounds and to replace aging cells. It also makes the process of cloning more difficult.
In mature organisms, undifferentiated cells called stem cells are responsible for replacing old or injured specialized cells. Stem cells are present in all self-repairing tissue, but most stem cells are difficult to detect in a mature living organism. Stem cells in a mature organism are like embryonic cells, in that they can create many different types of specialized cells. When stem cells are not actively making new cells, they divide infrequently, which reduces the risk of undesirable DNA mutations. But when they are signaled to make new cells of a particular type, they produce typically short-lived intermediate cells called transient amplifying cells, which in turn engage in rapid cell mitosis and create the specialized cells that the organism needs.
OK, for a quick review, we've learned that cells make up tissue and organs, which make organisms. The DNA in cells contains genes that are instructions for making proteins, and these proteins determine specialized cell characteristics and functions. Specialized cells in turn, determine characteristics of an organism, including inherited characteristics, such as resistance to the hormone DHT, for example. Specialized cells do not easily replicate themselves. When an organism needs new specialized cells, stem cells are signaled to create transient amplifying cells, which in turn make the needed specialized cells.