Cerebral dopamine neurotrophic factor (CDNF) protects the nigrostriatal dopaminergic (DA) neurons in rodent models of Parkinson’s disease and restores DA circuitry when delivered after these neurons have begun to degenerate. These DA neurons have been suggested to transport striatal CDNF retrogradely to the substantia nigra (SN). However, in cultured cells the binding and internalization of extracellular CDNF has not been reported. The first aim of this study was to examine the cellular localization and pharmacokinetic properties of recombinant human CDNF (rhCDNF) protein after its infusion into rat brain parenchyma. Second, we aimed to study whether the transport of rhCDNF from the striatum to the SN results from its retrograde transport via DA neurons or from its anterograde transport via striatal GABAergic projection neurons. We show that after intrastriatal infusion, rhCDNF diffuses rapidly and broadly, and is cleared with a half-life of 5.5h. Confocal microscopy analysis of brain sections at 2h and 6h after infusion of rhCDNF revealed its widespread unspecific internalization by cortical and striatal neurons, exhibiting different patterns of subcellular rhCDNF distribution. Electron microscopy analysis showed that rhCDNF is present inside the endosomes and multivesicular bodies. In addition, we present data that after intrastriatal infusion, the rhCDNF found in the SN is almost exclusively localized to the DA neurons, thus showing that it is retrogradely transported.
Significance Statement The wide spreading and unspecific uptake of rhCDNF after its delivery into brain parenchyma imply that therapeutically applied CDNF could directly influence a large number of cells in different brain areas. In addition, we show that infused rhCDNF is retrogradely transported from the striatum to the substantia nigra by the dopamine neurons that it rescues in rodent models of Parkinson’s disease. Along with the presented pharmacokinetic characteristics of rhCDNF after intrastriatal delivery, this information on the distribution of infused rhCDNF is important for the design of subsequent preclinical and clinical trials.
Yes (Please explain): MS and MHV are inventors in a CDNF-related patent application that is owned by Herantis Pharma Plc. SB and HJH are employees and shareholders of Herantis Pharma Plc. MS is a shareholder of Herantis Pharma Plc.
This study was financed from the Academy of Finland program 11186236 (Finnish Centre of Excellence Program 2008–2013), The Finnish funding agency for technology and innovation (Tekes; project 1505/31/10), European Union through the European Social Fund (Mobilitas grant MTT84) and Estonian Research Council grant PUT110. M.A. was supported by the Academy of Finland grant number 250275, 256398 and the Sigrid Jusélius foundation. K.M. was supported by the Finnish Graduate School of Neuroscience and the Ella and Georg Ehrnrooth Foundation.