In contrast to hair cloning, where germinative cells are multiplied outside the body, hair multiplication involves donor hair being implanted directly into the scalp in the hope that they will regenerate. It is important to recognise that hair cloning and hair multiplication are not the same, as the two techniques are often confused.
The Model for Hair Cloning
When it comes to hair cloning, follicles are in a tough spot. They are too complex to be simply cultured (growing hair follicles in a test tube would be like trying to grow a set of teeth) and follicles are not whole organisms (like Dolly the sheep) and therefore cannot be outright cloned. Fortunately, a pair of clever scientists, Drs. Amanda Reynolds and Colin Jahoda (now working with Dr. Christiano), seem to have made great headway in solving the dilemma.
In their paper Trans-Gender Induction of Hair Follicles, the researchers have shown that dermal sheath cells, found in the lower part of the human follicle, can be isolated from one person and then injected into the skin of another to promote the formation of new intact hair. The implanted cells interacted locally to stimulate the creation of full terminal (i.e. normal) hair follicles. Although this is not actually cloning (see the definition above), the dermal sheath cells can potentially be multiplied in a Petri dish and then injected in great numbers to produce a full head of hair. The word potentially is highlighted, as this multiplication has not yet been accomplished. It seems, however, that this hair “induction” processes is the model most likely to work.
Another interesting aspect of their experiment is that the donor cells came from a male but the recipient, who actually grew the hair, was a female. The importance of this is that donor cells can be transferred from one person to another without being rejected. Since repeat implantations did not provoke the typical rejection responses, even though the donor was of the opposite sex and had a significantly different genetic profile, this indicates that the dermal sheath cells have a special immune status and that the lower hair follicle is one of the bodies “immune privileged” sites.
In addition, there is some evidence that the recipient skin can influence the look of the hair. Thus, the final appearance of the patient may more closely resemble the bald person’s original hair, than the hair of the person donating the inducer cells. The person-to-person transfer of cells would be important in situations where there was a total absence of hair. Fortunately, in androgenetic alopecia (genetic hair loss) there is a supply of hair on the back and sides of the scalp that would serve as the source of dermal sheath cells, so the transfer between people would rarely be necessary.
Probably the most important aspect of this experiment is the fact that these “inducer” dermal sheath cells are fibroblasts. Fibroblasts, as it turns out, are among the easiest of all cells to culture, so that the donor area could potentially serve as an unlimited supply of hair.
Why is hair cloning not yet widely available?
There are a number of problems that still confront us in cloning hair. First, there is the need to determine the most appropriate follicular components to use (dermal sheath cells, the ones used in the Collin/Jahoda experiment, are hard to isolate and may not actually produce the best hair). Next, these extracted cells must be successfully cultured outside the body. Third, a cell matrix might be needed to keep them properly aligned while they are growing. Finally, the cells must be successfully injected into the recipient scalp in a way that they will consistently induce hair to grow.
Unlike, Follicular Unit Transplantation (FUT), in which an intact follicular units are planted into the scalp in the exact direction the surgeon wants the hair to grow, with cell implantation there is no guarantee that the induced hair will grow in the right direction or have the colour, hair thickness or texture to look natural. To circumvent this problem, one might use the induced hair in the central part of the scalp for volume and then use traditional FUT for refinement and to create a natural appearance. However, it is not even certain that the induced follicles will actually grow long enough to produce cosmetically significant hair. And once that hair is shed in the normal hair cycle, there are no assurances that it will grow and cycle again. (Normal hair grows in cycles that last 2-6 years. The hair is then shed and the follicle lies dormant for about three months before it produces a new hair and starts the cycle over again.)
A major technical problem to cloning hair is that cells in culture begin to de-differentiate as they multiply and revert to acting like fibroblasts again, rather than hair. Finding the proper environment in which the cells can grow, so that they will be maintained in a differentiated (hair-like) state, is a major challenge to the researchers and appears to be the single greatest obstacle to this form of therapy coming to fruition. This is not unlike the problems in cloning entire organisms where the environment that the embryonic cells grow in is the key to their proper differentiation and survival.
Finally, although remote, there may be safety concerns that cells that induce hair may also induce tumors, or exhibit malignant growth themselves. Once these obstacles have been overcome, there are still the requirements of FDA approval (in the United States) which further guarantees safety as well as effectiveness. This is a process that involves three, very formalized stages of clinical testing and generally takes years.
On the status of hair cloning – it is still a work in progress. Although there has been much recent success, and we finally have a working model for how hair cloning might eventually be accomplished, much work still needs to be done.