The basal forebrain cholinergic system as target for cell replacement therapy in Parkinson’s disease

Abstract

In recent years there has been a renewed interest in the basal forebrain (BF) cholinergic system as a target for the treatment of cognitive impairments in patients with Parkinson´s disease (PD), due in part to the need to explore novel approaches to treat the cognitive symptoms of the disease, and in part to the development of more refined imaging tools that have made it possible to monitor the progressive changes in the structure and function of the BF system as they evolve over time. In parallel, emerging technologies allowing the derivation of authentic BF cholinergic neurons from human pluripotent stem cells are providing new powerful tools for the exploration of cholinergic neuron replacement in animal models of PD-like cognitive decline. In this review, we discuss the rationale for cholinergic cell replacement as a potential therapeutic strategy in PD and how this approach can be explored in rodent models of PD-like cognitive decline, building on insights gained from the extensive animal experimental work that was performed in rodent and primate models in the 1980s and 90 s. Although therapies targeting the cholinergic system has so far been focused mainly on patients with Alzheimer´s disease, PD with dementia may be a more relevant condition. In PD with dementia the BF system undergoes progressive degeneration, and the magnitude of cholinergic cell loss has been shown to correlate with the level of cognitive impairment. Thus, cell therapy aimed to replace the lost BF cholinergic neurons represents an interesting strategy to combat some of the major cognitive impairments in patients with PD dementia.