Carotid Body Transplants as a Therapy for Parkinson’s Disease

Intrastriatal grafts of CB cells can produce important recovery in different preclinical models of Parkinson’s disease (PD). The carotid body (CB) is a bilateral neural crest‐derived chemoreceptor organ that is composed of a cluster of highly dopaminergic glomus cells. Although anti‐Parkinsonian CB cell therapy was originally thought to be a dopamine‐replacement approach, different studies have demonstrated that the beneficial action exerted by the CB implant is mainly due to a trophic action on the nigrostriatal pathway rather than to the mere release of dopamine. Accordingly, it has been shown that CB implants produce high levels of glial cell line neurotrophic factor (GDNF). In addition, the trophic action induced by the graft shows a dose‐dependent relation with respect to the size and GDNF expression of the implant. Thus, dopaminergic CB glomus cells appear to be ideally suited for the endogenous release of GDNF, and probably other trophic factors, in PD. In parallel with the preclinical studies, two Phase I/II clinical trials have shown that CB autotransplantation can improve motor symptoms in PD patients although with less efficiency than in experimental models. In this chapter, we review the different preclinical and clinical studies performed on CB transplantation in PD, paying special attention to the mechanisms underlying the grafts’ actions.