Brain diseases such as Huntington's and Alzheimer's have presented some of the most complex challenges in medicine for researchers and clinicians alike.
As neurodegenerative diseases, their complexity arises not only from the fact that the gradual shrinkage and loss of healthy brain tissue ultimately results in cognitive impairment that at present cannot be reversed, but also in that there is still considerable difficulty in even slowing the progress of the disease with pharmaceutical (drug) interventions. Furthermore, the potential for development of more advanced drug interventions is limited by the fact that it is difficult for many pharmaceutical compounds to cross the blood-brain barrier: what most likely evolved as a defense against infection is now one of the more vexing problems in pharmaceutical science.
As a result, therapies involving the regeneration of lost neuronal tissue have emerged as some of the most promising avenues for treatment of these diseases. Induced pluripotent stem cells have been successfully used to produce new neuronal tissue in laboratory conditions, which could then be used to replace lost neurons; this tissue regeneration approach has been used successfully in animal models of both Alzheimer's disease and Huntington's disease, and although research on brain tissue regeneration in humans is only just beginning, it nevertheless holds the potential to dramatically improve outcomes for patients with these diseases.
Induced pluripotent stem cells have also proven enormously useful in shortening and refining the process of decision-making in selecting the most optimal drug or combination of drugs to treat and/or slow the onset of these diseases in patients. Because induced pluripotent stem cells can be turned into any type of cell, neurons that exactly match the patient's DNA can be cultivated outside the body, and this in turn offers the opportunity for physicians to observe the effects of the widest-possible selection of suitable drugs on cultivated brain tissue from patients outside the body in order to observe the effects at an incredibly precise level of detail. This, in turn, will eliminate the need to wait for often-difficult to observe changes in cognitive function to manifest themselves in a patient's day-to-day behavior, and will rapidly accelerate the process of selecting the right drugs with which to treat a patient at the outset, thereby slowing or halting altogether the progress of a disease which ordinarily would drastically reduce a patient's healthy lifespan.