Towards an iNPC-proSAAS therapy for Parkinson's disease

University Of California Los Angeles, Los Angeles CA

Investigators

Abstract

SUMMARY Cellular chaperones are promising targets for therapeutic intervention in neurodegenerative disease due to their ability to limit misfolding and promote degradation of pathological proteins. ProSAAS is among the few brain-specific chaperones that are actively secreted and therefore capable of interacting with toxic proteins in both the extra- and intra-cellular environments, making it particularly attractive as a therapeutic candidate. Moreover, ProSAAS has been identified as a potential biomarker for Parkinson’s disease (PD) and is colocalized with Lewy bodies in post-mortem PD tissue. ProSAAS blocks alpha-synuclein (α-Syn) fibrillation and α-Syn toxicity to rat dopamine (DA) neurons in primary culture and its lentivirus-mediated overexpression in rat substantia nigra (SN) protects DA neurons from AAV- α-Syn toxicity in vivo, even when administered several weeks after the onset of motor deficits, portending therapeutic efficacy in post-symptomatic PD. Overexpression within DA neurons themselves may not be required for neuroprotective benefit since delivery of lentivirus-proSAAS to the striatum is as effective as nigral delivery in protecting against nigral AAV- α-Syn- induced motor deficits. This is significant because it suggests that proSAAS delivery to the DA terminals in the more accessible caudate-putamen is a viable therapeutic strategy for PD. It is currently unknown if the protection afforded at the DA terminal level requires proSAAS release from neuron terminals making synaptic contact with DA terminals or whether a more diffuse delivery of proSAAS would be effective. The translational significance of this question lies in the several benefits offered by a genetically modified astrocytic cell transplantation approach to proSAAS delivery over direct viral inoculation, including: 1) avoidance of insertional mutagenesis; 2) ability to incorporate larger, controlled expression constructs; 3) benefits provided by supportive astrocytes 4) enhanced tissue penetration afforded by cellular ramifications. We have therefore produced human induced pluripotent stem cell (iPSC)-derived neuroprogenitor cells (iNPCs) expressing proSAAS and will test their efficacy in both cell culture and in vivo PD models. Rat primary DA neurons will be co-cultured with iNPC-proSAAS or control iNPCs and exposed to human α-Syn-expressing AAV or α-Syn preformed fibrils, with DA neuron survival and p129-aSyn staining as the output measures (Aim 1a). In parallel, iNPC-proSAAS will be co-cultured with human iPSC-derived DA neurons from patients with young-onset PD (YOPD) to test their effectiveness in attenuating previously demonstrated elevated endogenous soluble α-Syn protein levels (Aim 1b). The effectiveness of iNPC-proSAAS striatal transplantation in providing neuroprotection will be tested using in rat unilateral nigral AAV-haSyn and aSyn preformed fibril PD models. Positive results would confirm that proSAAS offers protection to DA neurons in a non-cell-autonomous fashion and support progression to iNPC-proSAAS IND-enabling studies.