SPP1 and Parkinson disease: The similar strong upregulation (to 244%, P=0.01) of the immunity regulator osteopontin (SPP1) transcript was assessed, because osteopontin levels were previously identified as a biomarker of PD in blood serum, cerebrospinal fluid, microglia and affected neurons (Iczkiewicz et al., 2006; Maetzler et al., 2007; Shi et al., 2015).