Newly Identified Skin Stem Cells Strikingly Similar to Those Found in Embryos

Recent findings show that a new type of stem cell found in the skin acts similarly to certain stem cells found in embryos.  Like embryos, these stem cells can generate fat, bone, cartilage, and even nerve cells. According to HHMI International Research Scholar, Freda Miller, these newly-identified dermal cells may prove useful for treating persistent wounds or even neurological disorder. These cells were first noticed several years ago in rodents and humans but have only now been confirmed as stem cells. These cells are capable of self-renewal and can even grow into cell types that make up the skin’s dermal layer under the right conditions. This is particularly interesting in our industry because the dermal stem cells also appear to help form the basis for hair growth.  This new work was published in its entirety December 4, 2009, in the journal Cell Stem Cells.

Miller’s team examined the dermal layer of the skin in both mice and people. The dermis is a thick layer of cells in which hair follicles and sweat glands are rooted. In 2001, Miller’s team had a remarkable revelation when they discovered cells that respond to the same growth factors that make brain stem cells differentiate. She named them skin-derived precursors (SKPs, or ‘skips’).  Miller later discovered that these cells acted like neural crest cells from embryo (stem cells that generate part of the nervous system and head.  Despite SKPs resemblance to stem cells in Petri dishes, Miller was initially unsure if they would behave the same way in the body.  A team member, therefore, performed a series of experiments to test whether SKPs did behave similar to stem cells in the body.

Previous work had shown that the SKPs produce a transcription factor called SOX2, one produced in many types of stem cells. The team used genetically engineered mice with SOX2 genes tagged with green fluorescent protein, which allowed them to track where SOX2 was expressed in the animals. They found that about 1% of skin cells from adult mice contained the SOX2-making cells, and they were concentrated in the bulb at the base of hair follicles. Interestingly, when the team cultured these cells, they began behaving like SKPs.

Miller’s team then decided to see if the cells would, rather than just settling at the base of hair follicles, actually grow new hair. Fluorescent cells were mixed with epidermal cells (both of which make up the majority of cells in a hair follicle) and the mixture was transplanted under the skin of hairless mice. The team was intrigued to find that these mice began growing hair. The team also transplanted rat SKP cells under the skin of mice. Finally, the team gave mice small puncture wounds and then transplanted their fluorescent SKPs next to the wound. Within a month, many transplanted cells appeared in the scar, showing they had contributed to wound healing. The SKPs were also found in new hair follicles in the healed skin.

The cells behavior (both in wound healing and hair growth) led Miller’s team to conclude that the SKPs are, in fact, dermal stem cells. Miller said the finding complements work by HHMI investigator Elaine Fuchs, who found epidermal stem cells, which help renew the top layer of skin. Miller believes that combining the evidence from the two labs suggests a possible path to hair loss treatments. However, much about the signaling mechanism remains unknown.

Moving forward, Miller wants to investigate less cosmetic applications for these findings, such as treating nerve and brain diseases. She is searching for signals that could trigger the dermal stem cells to rev up their innate wound-healing ability. If such a signal can be found and copied, Miller can envision one day treating chronic wounds with a topical cream. Another possible application: improving skin grafts, which today consist of only epidermal, not dermal, cells. While skin grafts can dramatically help burn victims, those grafts don’t function like normal skin.

What is the importance of hair characteristics in hair transplant surgery?

These characteristics are significant in that they determine to a great degree how much coverage of the scalp there is, in order to block light. When light is not blocked and penetrates through to the scalp, the appearance is of thinning or balding.

The other big factor here is the density, which is another topic unto itself. The density is the number of hairs or follicular units per unit area (square centimeters or square inches or whatever unit you prefer; the centimeter is the standard for physicians). Although this density usually gets most of the attention when discussing hair loss, hair characteristics are equally, if not more, important.

First let’s look at color. At first, one might think that the darker the hair, the better the coverage. This is generally not correct. Lighter hair usually goes with lighter skin, and the tow together tend to mask thinning very well. Darker hair can cover well, but in the case of poor hair transplant work (pluggy looking, or larger graft on frontal hairline) they may stand out much worse than lighter hair. We will discuss color in more detail when we discuss contrast.

Curl is another very important factor in coverage. Generally speaking, curly hair provides coverage in proportion to the degree of curl (i.e., wavy hair gives better coverage than straight hair, curly hair better than wavy, very curly better than slightly curly, etc.). This has to do with light blockage as well. The curlier the hair is, the more it creates a meshwork of sorts (kind of like a thatched roof) which “stands up” a little bit off the scalp and keeps the light from penetrating to the scalp.

Contrast has to do with the difference between hair color and skin color. The closer to each other the hair and scalp are, the better the coverage. In a way, this “fools” the eye of the observer into not noticing the decrease in density. If a person with blonde hair and light skin loses 50% or his or her density, they may appear much less affected than a person with equally light skin and jet black hair. In this case the dark hairs of the second example are highlighted against the light skin and it shows the sparseness of the hair. The person with the blonde hair reveals very little difference between the hair and scalp, in other words, the observer cannot detect where the hair leaves off and the scalp begins.

Last, let’s consider caliber. Thicker strands of hair provide more “hair mass”, which is a term doctors use to describe the total effect of length times caliber. The more hair mass in a given area, the better the coverage. This makes intuitive sense. Imagine covering a hut with logs. If you place 20 logs as a roof, which will give better coverage, skinny logs or big round ones with large diameters? Of course, the bigger ones, so the thicker hairs do the same over the scalp. And remember, what appears as thinning or balding is simply the appearance of light shining through to the scalp.

I would like to know what is the CIT hair transplant? why is it better then the strip?

CIT or “The Cole Isolation Technique” (former known as FIT) is a hair transplant harvesting technique developed by Dr. John P. Cole in the early years of this century. It is similar, but not identical to, FUE, or follicular unit extraction. CIT uses proprietary technology and instruments to harvest intact follicular groups ranging from 1 to as many as 6 or more individual hairs along with their intact dermal elements. It must be stressed that these dermal elements are essential for the growth of new hairs in the recipient areas (these are the areas of thinning or balding that are being transplanted). Extracting hairs without the dermal elements is easy, but amounts to nothing more than a “pluck”; these hairs will not grow.
As with any other harvesting method, the hair transplant surgeon will first outline the donor areas to be harvested, as well as the areas which will be receiving the harvested grafts later on. Then, local anesthetic is infiltrated into the donor area to render the skin and deeper structures numb and insensitive to pain. Then, just before harvesting begins, the area is injected with a “tumescent” fluid consisting of saline, and often medications to minimize bleeding. This tumescent technique is fairly common in a number of cosmetic procedures. It is beneficial in a number of ways; it helps decrease bleeding with medications and also by virtue of the pressure of the fluid on blood vessels in the tissue; it brings the skin up and away from deeper structures; it provides a taut, firm surface on which to score the skin, and it slightly separates the follicular groups from each other so that they may be more easily isolated from one another.
Then, the skin around the follicular groups is scored with the special instruments; the surrounding tissues are teased away from the follicles and then the entire unit, that is, the hair shafts, the dermal elements surrounding the shafts, the sebaceous glands and a tiny ring of skin at the top is gently pulled out. The graft is perfect, and ready for placement in the recipient area. No trimming or preparation is generally needed. This is one of many benefits of CIT compared with the older style strip harvest method, which requires microscopic dissecting of all grafts prior to placement, necessitating a large team using stereo microscopes.
Healing of the tiny sites from which the grafts are pulled commences almost immediately. Usually by the second or third day, the tissue has grown in to cover the hole and there remains only a pale pink dot at the site. In some individuals, this may eventually appear as a slight “white dotting”, which is not strictly speaking a scar, but rather an area of hypopigmentation. This just means that the cells within the follicles that produce the dark pigment called melanin are gone, and the skin here is a slightly lighter shade than the adjacent skin. This phenomenon is relatively unpredictable; it is most common in darker complexioned people, but may manifest in pale-skinned folks. Likewise, it may occur after CIT with very small instruments, and not at all with larger-sized extractors (or vice versa!)
We feel that, compared to a linear, ear-to-ear strip scar, these tiny white dots have minimal negative cosmetic impact. With the hair only a few millimeters long, these dots are undetectable. A strip scar, on the other hand, may be visible with the hair considerably longer, and it may widen, sometimes for no apparent reason. In addition, the strip scar changes the direction of hair growth below it, relative to the direction above it. Unless a person desires to wet shave their hair down to the skin, these white dots, if they do occur, are invisible to the casual observer.
Now, once the grafts are extracted and ready for implantation, the process is quite similar to strip harvest hair transplant surgery. Tiny jeweler’s forceps are used to very gently grasp the hair-bearing grafts and place them into miniscule recipient sites. These sites are created by the hair transplant surgeon using various blades or needles; each site is made carefully and with a deliberately natural pattern. The angle relative to the axis of the head is extremely important, because the hair normally grows in specific patterns. These patterns have a general similarity in all people, but there are specific ways in which these patterns diverge in individuals. A “cowlick” at the frontal hairline is a good example, as is a unique “whorl” at the vertex or crown. It is often appropriate to closely mimic the existing pattern to obtain the most natural effect.
The so-called angle of emergence is of utmost importance as well. This is the angle at which the hair emerges from the scalp. This angle may be quite acute, that is, the hair may lie down very close to the plane of the scalp. If an inexperienced or minimally gifted surgeon makes these angles too high, then the look will be peculiar and unnatural. We have seen many cases such as this, and it is especially noticeable at the leading edge of the frontal hairline; follicles growing on the hairline at or close to a 90 degree angle are an aesthetic and cosmetic disaster.
Regional placement of various graft sizes is another challenge for inexperienced surgeons. One hair grafts ONLY should be placed at the leading edge of the hairline. Two hair grafts are then placed behind these “singles”; the “full-sized” three, four, or larger grafts are only placed further back behind the soft, feathered hairline. We commonly see repair cases with two, three, and even four hair grafts all over the frontal hairline! Fortunately, we can now remove these unsightly, inappropriately-placed grafts with the CIT technique and redistribute them further back where they rightly belong.
As with all hair transplants, the hair shafts themselves, which are essentially dead protein, will begin to shed at about 2 to 3 weeks. However, the follicular germinal elements are safely lying dormant beneath the skin. Usually at about 3 to 4 months, the first “new” hairs will begin to emerge. There will continue to be further growth for up to a year or more, but usually the full cosmetic effect will be evident at about 12 months.