ARTICLE | hair research |
■ The simplest approach is to implant DP cells by themselves. The DP cells would be placed in or near existing miniaturised follicles. These DP-only approaches are under study in a phase ii clinical trial conducted by intercytex ■ another strategy under investigation is to co-implant cultured keratinocytes together with DP cells. in one version, cells would be implanted as a mixed suspension that contains both cell types. after implantation, hair neogenesis would occur within the implant site. in another form of mixed-cell implants, keratinocytes and DP cells would be cultured together. These culture-grown hairs would then be implanted into the patient. This phase ii clinical trial is being conducted by aderans. ■ an alternative that is under development is to implant cells together with a matrix composed of collagen. a matrix might be used with DP cells alone or in combination with cultured keratinocytes. clinical trials must be performed.
Androgenetic alopecia and hair follicle stem cells aGa is characterised by a marked decrease in hair follicle size, which could be related to the loss of hair follicle stem or progenitor cells (18). These findings support the notion that a defect in conversion of hair follicle stem cells to progenitor cells plays a role in the pathogenesis of aGa. The loss of cD200hiiTGa6hi cells and cD34hi cells in aGa provides insight into possible mechanisms leading to follicular miniaturisation, the hallmark of aGa. Decreased matrix cell numbers would result in
diminutive hair shafts. cD200hi hair follicle stem cells are preserved in chronologic ageing of the scalp.
Hair cloning The success of hair transplantation is sometimes limited by the availability of donor hair. hair cloning is based on the inductive capacity of the dermal papilla cell to form a new hair follicle (19). a few hair follicles are first excised from the occipital scalp by biopsy punch. These follicles are then dissected to isolate the dermal papilla. each DP contains approximately 200–400 cells. These cells can be cultured in the laboratory to make millions of offspring cells. On reinjection into the bald scalp of the same individuals, the cultured DP cells will induce the development of new hair follicles. This process is basically hair multiplication, or follicular neogenesis, rather than true ‘cloning’. although the principle of hair cloning is proven (15),
turning it into a practical technique for clinical use is full of problems, for instance: ■ The new hair follicles induced in studies using rodents are usually disorientated and grow at a variety of different angles ■ hair follicles induced by hair cloning do not have an even distribution over the skin as seen in natural hair follicles. They appear as clumps of growing hair
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