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Onset Time and Durability of Huntingtin Suppression in Rhesus Putamen After Direct Infusion of Antihuntingtin siRNA.

Grondin R, Ge P, Chen Q, Sutherland JE, Zhang Z, Gash DM, Stiles DK, Stewart GR, Sah DW, Kaemmerer WF - Mol Ther Nucleic Acids (2015)

Bottom Line: After a 1-week washout period, monkeys received radiolabeled siRNA targeting huntingtin.After 1 or 3 days of siRNA delivery, monkeys were either terminated, or their pumps were shut off and they were terminated 10 or 24 days later.These findings indicate the rapid onset and durability of siRNA-mediated target gene suppression observed in other organs also occurs in the brain, and support the use of episodic delivery of siRNA into the brain for treatment of Huntington's disease and possibly other neurodegenerative diseases.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA.

ABSTRACT
One possible treatment for Huntington's disease involves direct infusion of a small, interfering RNA (siRNA) designed to reduce huntingtin expression into brain tissue from a chronically implanted programmable pump. Here, we studied the suppression of huntingtin mRNA achievable with short infusion times, and investigated how long suppression may persist after infusion ceases. Rhesus monkeys received 3 days of infusion of Magnevist into the putamen to confirm catheter patency and fluid distribution. After a 1-week washout period, monkeys received radiolabeled siRNA targeting huntingtin. After 1 or 3 days of siRNA delivery, monkeys were either terminated, or their pumps were shut off and they were terminated 10 or 24 days later. Results indicate that the onset of huntingtin mRNA suppression in the rhesus putamen occurs rapidly, achieving a plateau throughout the putamen within 4 days. Conversely, loss of huntingtin suppression progresses slowly, persisting an estimated 27-39 days in the putamen and surrounding white matter. These findings indicate the rapid onset and durability of siRNA-mediated target gene suppression observed in other organs also occurs in the brain, and support the use of episodic delivery of siRNA into the brain for treatment of Huntington's disease and possibly other neurodegenerative diseases.

No MeSH data available.


Related in: MedlinePlus

Study design and distribution of infusates. (a) Diagram of the experimental groups and time course of events in the study. Diamonds indicate MRIs taken after implantation of the delivery hardware and at later points in the study. Groups 4 and 5 had their pumps completely turned off after 4 days of infusion. (b) Distribution of Magnevist after 3 days of delivery to the putamen at a rate of 0.3 µl per minute. (c) siRNA distribution in the same monkey after 3 days of delivery to the putamen at a rate of 0.3 µl per minute, visualized by autoradiography. The autoradiography is color-coded for siRNA concentrations. Magenta represents a potentially “efficacious” level of siRNA (≥ 0.65 mg of siRNA per gram of tissue). At this coronal plane, there was near complete coverage of the putamen with some spread to adjacent structures, in particular some tracking of infusate dorsally into cortex. Scale bars = 1 cm.
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fig1: Study design and distribution of infusates. (a) Diagram of the experimental groups and time course of events in the study. Diamonds indicate MRIs taken after implantation of the delivery hardware and at later points in the study. Groups 4 and 5 had their pumps completely turned off after 4 days of infusion. (b) Distribution of Magnevist after 3 days of delivery to the putamen at a rate of 0.3 µl per minute. (c) siRNA distribution in the same monkey after 3 days of delivery to the putamen at a rate of 0.3 µl per minute, visualized by autoradiography. The autoradiography is color-coded for siRNA concentrations. Magenta represents a potentially “efficacious” level of siRNA (≥ 0.65 mg of siRNA per gram of tissue). At this coronal plane, there was near complete coverage of the putamen with some spread to adjacent structures, in particular some tracking of infusate dorsally into cortex. Scale bars = 1 cm.

Mentions: Fifteen adult female rhesus monkeys were implanted with intracranial catheters primed with 5 mmol/l Magnevist in phosphate-buffered saline (PBS) and connected to abdominally implanted infusion pumps. All animals were infused with Magnevist from their implanted pump at a rate of 0.3 μl per minute for 3 days. In all animals, the catheter needle tips were found to be within a 2 mm radius of the target location in the putamen based on the postoperative MRI taken immediately after catheter placement (on day −10). Also, all catheters were patent based on Magnevist visualization in the brain via the MRI taken 3 days postsurgery (on day −7). After an intervening 7-day infusion of PBS at a rate of 0.1 μl per minute (for “washout” of the Magnevist), the pump reservoir was filled (on day 0) with radiolabeled anti-HTT siRNA for all animals but a PBS control group (n = 3), and the infusion continued at a rate of 0.3 μl per minute for 2 or 4 days. The purpose of these time periods was to yield 1- and 3-day infusions of the siRNA into the brain, given that the time required for the siRNA to reach the brain from the abdominal pump, at a rate of 0.3 μl/minute, is about 24 hours. At the end of this infusion, either the monkeys were terminated, or the infusion was stopped for a period of 10 or 24 days at which point the animals were terminated (Figure 1a). All 15 catheters were determined to be patent at the time of the animal's necropsy based on a postmortem check of fluid delivery through the catheter from the pump.


Onset Time and Durability of Huntingtin Suppression in Rhesus Putamen After Direct Infusion of Antihuntingtin siRNA.

Grondin R, Ge P, Chen Q, Sutherland JE, Zhang Z, Gash DM, Stiles DK, Stewart GR, Sah DW, Kaemmerer WF - Mol Ther Nucleic Acids (2015)

Study design and distribution of infusates. (a) Diagram of the experimental groups and time course of events in the study. Diamonds indicate MRIs taken after implantation of the delivery hardware and at later points in the study. Groups 4 and 5 had their pumps completely turned off after 4 days of infusion. (b) Distribution of Magnevist after 3 days of delivery to the putamen at a rate of 0.3 µl per minute. (c) siRNA distribution in the same monkey after 3 days of delivery to the putamen at a rate of 0.3 µl per minute, visualized by autoradiography. The autoradiography is color-coded for siRNA concentrations. Magenta represents a potentially “efficacious” level of siRNA (≥ 0.65 mg of siRNA per gram of tissue). At this coronal plane, there was near complete coverage of the putamen with some spread to adjacent structures, in particular some tracking of infusate dorsally into cortex. Scale bars = 1 cm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561652&req=5

fig1: Study design and distribution of infusates. (a) Diagram of the experimental groups and time course of events in the study. Diamonds indicate MRIs taken after implantation of the delivery hardware and at later points in the study. Groups 4 and 5 had their pumps completely turned off after 4 days of infusion. (b) Distribution of Magnevist after 3 days of delivery to the putamen at a rate of 0.3 µl per minute. (c) siRNA distribution in the same monkey after 3 days of delivery to the putamen at a rate of 0.3 µl per minute, visualized by autoradiography. The autoradiography is color-coded for siRNA concentrations. Magenta represents a potentially “efficacious” level of siRNA (≥ 0.65 mg of siRNA per gram of tissue). At this coronal plane, there was near complete coverage of the putamen with some spread to adjacent structures, in particular some tracking of infusate dorsally into cortex. Scale bars = 1 cm.
Mentions: Fifteen adult female rhesus monkeys were implanted with intracranial catheters primed with 5 mmol/l Magnevist in phosphate-buffered saline (PBS) and connected to abdominally implanted infusion pumps. All animals were infused with Magnevist from their implanted pump at a rate of 0.3 μl per minute for 3 days. In all animals, the catheter needle tips were found to be within a 2 mm radius of the target location in the putamen based on the postoperative MRI taken immediately after catheter placement (on day −10). Also, all catheters were patent based on Magnevist visualization in the brain via the MRI taken 3 days postsurgery (on day −7). After an intervening 7-day infusion of PBS at a rate of 0.1 μl per minute (for “washout” of the Magnevist), the pump reservoir was filled (on day 0) with radiolabeled anti-HTT siRNA for all animals but a PBS control group (n = 3), and the infusion continued at a rate of 0.3 μl per minute for 2 or 4 days. The purpose of these time periods was to yield 1- and 3-day infusions of the siRNA into the brain, given that the time required for the siRNA to reach the brain from the abdominal pump, at a rate of 0.3 μl/minute, is about 24 hours. At the end of this infusion, either the monkeys were terminated, or the infusion was stopped for a period of 10 or 24 days at which point the animals were terminated (Figure 1a). All 15 catheters were determined to be patent at the time of the animal's necropsy based on a postmortem check of fluid delivery through the catheter from the pump.

Bottom Line: After a 1-week washout period, monkeys received radiolabeled siRNA targeting huntingtin.After 1 or 3 days of siRNA delivery, monkeys were either terminated, or their pumps were shut off and they were terminated 10 or 24 days later.These findings indicate the rapid onset and durability of siRNA-mediated target gene suppression observed in other organs also occurs in the brain, and support the use of episodic delivery of siRNA into the brain for treatment of Huntington's disease and possibly other neurodegenerative diseases.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA.

ABSTRACT
One possible treatment for Huntington's disease involves direct infusion of a small, interfering RNA (siRNA) designed to reduce huntingtin expression into brain tissue from a chronically implanted programmable pump. Here, we studied the suppression of huntingtin mRNA achievable with short infusion times, and investigated how long suppression may persist after infusion ceases. Rhesus monkeys received 3 days of infusion of Magnevist into the putamen to confirm catheter patency and fluid distribution. After a 1-week washout period, monkeys received radiolabeled siRNA targeting huntingtin. After 1 or 3 days of siRNA delivery, monkeys were either terminated, or their pumps were shut off and they were terminated 10 or 24 days later. Results indicate that the onset of huntingtin mRNA suppression in the rhesus putamen occurs rapidly, achieving a plateau throughout the putamen within 4 days. Conversely, loss of huntingtin suppression progresses slowly, persisting an estimated 27-39 days in the putamen and surrounding white matter. These findings indicate the rapid onset and durability of siRNA-mediated target gene suppression observed in other organs also occurs in the brain, and support the use of episodic delivery of siRNA into the brain for treatment of Huntington's disease and possibly other neurodegenerative diseases.

No MeSH data available.


Related in: MedlinePlus