Joined: 16 Oct 2005
|Posted: Sat Feb 22, 2014 12:21 pm Post subject: Gene Therapy
Feasibility of Gene Therapy for Hereditary Hair Loss Established
A team of investigators from the University of Pennsylvania Medical Center has demonstrated for the first time that it is possible to introduce DNA into human hair follicles. By delivering marker genes encapsulated in liposomes -- lipid-based, non-viral vectors -- the researchers showed that human hair follicles are particularly susceptible to taking up DNA at the onset of their growth phase. In fact, half of all early-growth-phase follicles incorporated the DNA.
"These early results in our ongoing research to find treatments suggest that certain types of hair loss might be suitable for gene therapy," says George Cotsarelis, MD, assistant professor of dermatology and director of Penn's Hair and Scalp Clinic. The researchers presented their findings at the 2nd annual meeting of the American Society of Gene Therapy meeting in Washington, DC, in June.
"We're interested in many different types of hair loss, especially a disease called alopecia areata, an autoimmune disorder that can result in hair loss over the entire scalp or body," notes Cotsarelis. "It often occurs in children and can be psychologically devastating."
The team used liposomes to topically introduce DNA to human scalp that was grafted to immunodeficient mice. Liposomes are non-living microscopic capsules made from lipids, or fat, and have been used for years to deliver DNA to cells in culture. The reseachers used plasmid DNA, a simple, circular form of the genetic material. Specifically, they transfected a reporter gene that codes for an enzyme called beta galactosidase, which showed up as a blue color in follicles to which it was successfully introduced.
"When we apply the preparation to the follicles, the liposomes bind to the cell membrane and the DNA is released into the cell, quickly finding its way to the nucleus," says Cotsarelis.
In order to perform the transfection, the researchers had to alter the cycle of hair growth on the grafted scalp. Individual hair follicles go through resting and growing stages, which can each last for several years. The team introduced DNA into follicles as they entered a new growth phase, a critical time when the lower portion of the follicle regenerates. On a bald scalp, the majority of the hair follicles that produce hair are in a resting state. To stimulate the onset of the growth phase, the researchers plucked hair from the grafted scalp and applied retinoic acid. They reasoned that at the onset of the growing phase, follicles are anatomically more accessible to the topical application of the liposomes.
The combination of the specific timing of the lipsosome application and the preparation of the scalp increased the efficiency of the transfection: Half of the follicles entering the growth phase were successfully transduced with the plasmid DNA. Overall, 6 percent of all follicles - resting and growing - expressed the DNA.
In hereditary hair loss, the problem is that the follicle becomes smaller and smaller during each regeneration, and eventually becomes so miniscule that the hair it produces is microscopic. "This miniaturization occurs at the onset of the growing phase so that's theoretically the best time to block miniaturization and alter the appearance of the new hair," says Cotsarelis. "We have discovered that we can introduce genes into follicles during this critical time." He is quick to point out, however, that definitive genes that cause common types of hair loss have yet to be discovered, but there are some candidate genes that the lab will be trying to transfect in the near future.
Using gene therapy to study the follicle will also be important to understanding wound healing, regeneration, and skin cancer. The follicle is one of the only tissues in the body that regenerates on a regular basis. "If we begin to understand how the follicle regenerates -- and how to manipulate its regeneration and growth -- then we may be able to impact the treatment of skin cancer and chronic wounds, in addition to hair loss," says Cotsarelis.