Cell-based Platform for Gene Delivery to the Brain - ABSTRACT
Parkinson’s disease (PD) affects more than a million individuals in the U.S. with up to 60,000 new cases
diagnosed each year. Currently, there are no treatments that can halt or reverse the course of PD; only palliative
therapies, such as replacement strategies for missing neurotransmitters, exist. The pathobiology of PD is
associated with the loss of dopaminergic (DA) neurons. Thus, the successful delivery of neurotrophic factors, in
particular, glial cell line-derived neurotrophic factor (GDNF), that promote neuronal survival and reverse the
progression of PD is of great importance. Regrettably, the blood brain barrier (BBB) remains a seemingly
insurmountable obstacle to the routine use of systemically administered macromolecules - including GDNF 1.
To circumvent this problem, we propose using genetically modified peripheral blood monocytes (PBM) for
systemic gene delivery to the brain. It is well established that specialized cells of the immune system, including
monocytes, macrophages, and T cells, can easily penetrate the BBB and migrate rapidly to sites of brain
inflammation and degeneration 2,3. Our research has previously demonstrated that macrophages transfected ex
vivo with therapeutic protein-encoding DNA plasmid (pDNA), can deliver therapeutic gene in intoxicated mice
with acute brain inflammation, and in the transgenic mice, Parkin-Q311X(A). Mechanistic studies revealed that
genetically modified macrophages release extracellular vesicles, exosomes, packed with protein-encoding
genetic material, pDNA and mRNA, as well as a transcription factor involved in the encoded gene expression.
Importantly, multiple lines of evidence for therapeutic efficacy were observed in PD mouse models, including
decreased brain inflammation, significant neuroprotection, and improved locomotor functions.
Planned studies include the evaluation of brain bioavailability for engineered PBM and GDNF gene transfer in
Parkin-Q311X(A) mouse model (SA1). To enforce outcomes of the new formulation, PBM will be differentiated
to a specific subset of “alternatively activated” (M2) macrophages with regenerative functions. The mechanism
of macrophage-mediated gene transfer including involvement cell-cell interactions and/or exosomes secreted by
GDNF-transfected PBM will be elucidated (SA2). We will then assess the therapeutic potential of this novel
product by measuring its anti-inflammatory and neuroprotective effects and, lastly, by extensive behavioral
analysis in Parkin-Q311X(A) mice (SA3). To provide translational link, human induced pluripotent stem cells
(iPSCs) with almost unlimited expandability will be tested. Furthermore, to obtain a universal cell-carrier, iPSCs
with knockout MHC class II (MHC-II) receptor will be utilized.
Our studies will provide fundamental insights into how PBM interact with brain cells and facilitate
horizontal gene transfer upon neurodegeneration, potentially opening up other cell-based gene delivery
systems to the CNS and beyond.
