Cell-based therapies for Parkinson's disease include various investigational procedures which transplant specific populations of cells into the brains of people with Parkinson's disease. The investigation of cell transplantation therapies followed the discovery that the death of dopaminergic neurons in the substantia nigra pars compacta resulted in the motor symptoms of the disease. Thus, cell transplantation has focused on various dopamine producing cells throughout the body.
The first cell-based therapy investigated for Parkinson's disease utilized the adrenal medulla. The adrenal medulla is the innermost part of the adrenal gland and contains neural crest derived chromaffin cells which secrete norepinephrine, epinephrine and to a far lesser extent dopamine into the blood. Autotransplantation of adrenal medullary tissue into the brains of animal models of Parkinson's disease showed minimal benefits. Despite this, open-label trials were undergone in humans which showed only modest benefits. Following these initial disappointing results however, a trial in Mexico demonstrated significant motor benefits in two patients with Parkinson's disease who had undergone the procedure. This publication incited widespread interest in the field and over the next few years hundreds of patients received adrenal medulla transplants. It was only when a registry was set up to consolidate all the data was it revealed that most patients did not benefit from the procedure to any significant extent. Furthermore, postoperative complications such as psychiatric disturbances were realized. These combined findings eventually led to the abandonment of this transplant procedure, which was largely flawed from the start.
Sympathetic ganglia
Carotid body
The carotid body is a group of chemoreceptor cells located at the bifurcation of the common carotid artery. It includes two populations of cells; glomus cells and sustentacular cells. Glomus cells are derived from the neural crest and secrete dopamine in response to hypoxemia. Based on their ability to secrete dopamine and also glial cell-derived neurotrophic factor, these cells have been investigated as an intrastriatalautograft therapy for patients with Parkinson's disease. A clinical trial exploring this initially demonstrated motor benefits, unfortunately these benefits disappeared after 6–12 months, in correlation with poor survival of the grafted cells.
