Convection Enhanced Delivery of Optogenetic Adeno-associated Viral Vector to the Cortex of Rhesus Macaque Under Guidance of Online MRI Images

Summary

Here, we demonstrate magnetic resonance (MR)-guided convection enhanced delivery (CED) of viral vectors into the cortex as an efficient and simplified approach for achieving optogenetic expression across large cortical areas in the macaque brain.

Abstract

In non-human primate (NHP) optogenetics, infecting large cortical areas with viral vectors is often a difficult and time-consuming task. Here, we demonstrate the use of magnetic resonance (MR)-guided convection enhanced delivery (CED) of optogenetic viral vectors into primary somatosensory (S1) and motor (M1) cortices of macaques to obtain efficient, widespread cortical expression of light-sensitive ion channels. Adeno-associated viral (AAV) vectors encoding the red-shifted opsin C1V1 fused to yellow fluorescent protein (EYFP) were injected into the cortex of rhesus macaques under MR-guided CED. Three months post-infusion, epifluorescent imaging confirmed large regions of optogenetic expression (>130 mm²) in M1 and S1 in two macaques. Furthermore, we were able to record reliable light-evoked electrophysiology responses from the expressing areas using micro-electrocorticographic arrays. Later histological analysis and immunostaining against the reporter revealed widespread and dense optogenetic expression in M1 and S1 corresponding to the distribution indicated by epifluorescent imaging. This technique enables us to obtain expression across large areas of the cortex within a shorter period of time with minimal damage compared to the traditional techniques and can be an optimal approach for optogenetic viral delivery in large animals such as NHPs. This approach demonstrates great potential for network-level manipulation of neural circuits with cell-type specificity in animal models evolutionarily close to humans. 

Introduction

Optogenetics is a powerful tool that allows for the manipulation of neural activity and the study of network connections in the brain. Implementing this technique in non-human primates (NHPs) has the potential to enhance our understanding of large-scale neural computation, cognition, and behavior in the primate brain. Although optogenetics has been successfully implemented in NHPs in recent years^{1,2,3,4,5,6,7}, a challenge that researchers....

Protocol

All procedures have been approved by the University of California, San Francisco Institutional Animal Care and Use Committee (IACUC) and are compliant with the Guide for the Care and Use of Laboratory Animals. The following procedure was performed using two adult male rhesus macaques of 8 and 7 years of age, weighing 17.5 kg and 16.5 kg (monkey G and monkey J), respectively.

NOTE: Use standard aseptic techniques for all surgical procedures.

1. Baseline Imaging

Discussion

Here, we outline a feasible and efficient technique for achieving large-scale optogenetic expression in NHP primary somatosensory and motor cortex by MR-guided CED. The use of MR-guided CED presents significant advantages over traditional methods of viral infusion in the NHP brain. One such advantage is the ability to attain expression over large areas with fewer required infusions. For instance, with conventional methods, multiple injections of 1-2 µL of the vector yield expression in a 2-3 mm diameter region

Materials

Name	Company	Catalog Number	Comments
0.2 mL High Pressure IV Tubing	Smiths Medical Inc., Dublin, OH, USA	533640
0.32 mm ID, 0.43 mm OD Silica Tubing	Polymicro Technologies	1068150027
0.45 mm ID, 0.76 mm OD Silica Tubing	Polymicro Technologies	1068150625
AAV2.5-CamKII-C1V1-EYFP	Penn Vector Core, University of Pennsylvania
ABS plastic	Stratasys, MN, USA	ABSplus-P430
Antimicrobial incise drape	3M	6650EZ	Ioban Drape
Dental Acrylic	Henry Schein, Inc.	1013117	Acrylic Bonding Agent
Elevators	VWR International, LLC.	10196-564	Langenbeck Elevator, Wide Tip
Fine suture	McKesson Medical-Surgical Inc.	1034505
Gadoteridol	Prohance, Bracco Diagnostics, Princeton, NJ	0270-1111-04
Laser for light stimulation	Omicron-Laserage, Germany	PhoxX 488-60
MR compatible 3cc syringe	Harvard apparatus, Holliston, MA, USA	59-8377
MR Imaging Software	Pixmeo	OsiriX MD 10.0
MR-Compatible Pump	Harvard apparatus, Holliston, MA, USA	Harvard PHD 2000
MR-compatible stereotaxic frame	KOPF	1430M MRI
Perifix Clamp Style Catheter Connector	B-Braun, Bethlehem, PA, USA	N/A
Plastic Screws	Plastics 1	0-80 x 1/8N	Nylon screws
Titanium screws	Crist Instrument Co., Inc.	6-YCX-0312	Self-tapping bone screws
Trephine	GerMedUSA Inc,	SKU:GV70-42
uPrinter SE 3D printer	Stratasys, MN, USA	N/A
Vitamin E Capsule	Pure Encapsulations, LLC.	DE1
Wet sterile absorbable gelatin	Pfizer Inc.	AZL0009034201	Gelfoam