Experimental approaches included, i.e., GDNF encapsulated in microspheres composed of biodegradable polymer materials (Garbayo et al., 2009, 2011), DNA nanoparticle gene transfer to achieve long term GDNF expression (Fletcher et al., 2011), encapsulated fibroblasts transfected to produce GDNF and confer behavioral improvements in the 6-OHDA rat model of Parkinson’s disease (Grandoso et al., 2007). The gene discussed is GDNF; the disease is Parkinson disease.