Supplementary Material for: Pathways of Infusate Loss during Convection-Enhanced Delivery into the Putamen Nucleus

<b><i>Background:</i></b> New strategies aiming to treat Parkinson’s disease, such as delivery of trophic factors via protein infusion or gene transfer, depend upon localized intracerebral infusion, mainly into the putamen nucleus. Convection-enhanced delivery (CED) has been proposed as a method to improve intracerebral distribution of therapies. Yet analysis of controversial results during the clinical translation of these strategies suggests that intracerebral misdistribution of infusate may have affected the outcomes by limiting the amount of treatment into the target region. <b><i>Objectives:</i></b> This study aimed to identify possible pathways of infusate loss and their relative impact in the success of targeted CED into the postcommissural ventral putamen nucleus. <b><i>Methods:</i></b> Thirteen adult macaque monkeys received intraputaminal CED infusions of 100 µl of 2.0 mM gadoteridol and bromophenol blue (0.16 mg/ml) solution at a rate of 1.0 µl/min under intraoperative magnetic resonance imaging (MRI) guidance. Quantitative maps of infusate concentration were computed at 10-min intervals throughout the procedure in a 3-Tesla MRI scanner. The fraction of tracer lost from the putamen as well as the path of loss were evaluated and quantified for each infusion. <b><i>Results:</i></b> All injections (total 22) were successfully placed in the ventral postcommissural putamen nucleus. Four major paths of infusate loss from the putamen were observed: <i>overflow</i> across putamen boundaries, <i>perivascular flow</i> along large blood vessels, <i>backflow</i> along the inserted catheter and <i>catheter tract leakage</i> into the vacated catheter tract upon catheter removal. Overflow loss was observed within the first 30 µl of infusion in all cases. Measurable tracer loss following the path of an artery out of the putamen was observed in 15 cases, and in 8 of these cases, the loss was greater than 10% of infusate. Backflow that exited the putamen was observed in 4 cases and led to large loss of infusate (80% in 1 case) into the corona radiata. Loss into the vacated catheter tract amounted only to a few microliters. <b><i>Conclusions:</i></b> Our analysis demonstrates that after controlling for targeting, catheter type, infusion rate and infusate, the main issues during surgical planning are the identification of appropriate infusate volume that matches the target area, as well as mapping the regional vasculature as it may become a pathway for infusate loss. Most importantly, these results underscore the significance of presurgical planning for catheter placement and infusion, and the value of imaging guidance to ensure targeting accuracy

Neurodegeneration prevented by lentiviral vector delivery of GDNF in primate models of Parkinson's disease.

Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients

Tetrapyrrole Metabolism in Arabidopsis thaliana

Higher plants produce four classes of tetrapyrroles, namely, chlorophyll (Chl), heme, siroheme, and phytochromobilin. In plants, tetrapyrroles play essential roles in a wide range of biological activities including photosynthesis, respiration and the assimilation of nitrogen/sulfur. All four classes of tetrapyrroles are derived from a common biosynthetic pathway that resides in the plastid. In this article, we present an overview of tetrapyrrole metabolism in Arabidopsis and other higher plants, and we describe all identified enzymatic steps involved in this metabolism. We also summarize recent findings on Chl biosynthesis and Chl breakdown. Recent advances in this field, in particular those on the genetic and biochemical analyses of novel enzymes, prompted us to redraw the tetrapyrrole metabolic pathways. In addition, we also summarize our current understanding on the regulatory mechanisms governing tetrapyrrole metabolism. The interactions of tetrapyrrole biosynthesis and other cellular processes including the plastid-to-nucleus signal transduction are discussed