NGF and Alzheimer disease: Most recently, attempts to apply NGF therapeutically in the context of AD have employed gene therapy to overexpress the NGF gene (Tuszynski et al., 2005, 2015; Rafii et al., 2014) or the implantation of microencapsulated patient-derived fibroblasts, genetically engineered to overproduce NGF (Eriksdotter-Jönhagen et al., 2012; Eyjolfsdottir et al., 2016).