A Modified Transcranial Middle Cerebral Artery Occlusion Model to Study Stroke Outcomes in Aged Mice

Summary

This protocol demonstrates a unique mouse stroke model with a medium-sized infarct and an excellent survival rate. This model allows preclinical stroke researchers to extend the ischemia duration, use aged mice, and assess long-term functional outcomes.

Abstract

In experimental stroke research, middle cerebral artery occlusion (MCAO) with an intraluminal filament is widely used to model ischemic stroke in mice. The filament MCAO model typically exhibits a massive cerebral infarction in C57Bl/6 mice that sometimes includes brain tissue in the territory supplied by the posterior cerebral artery, which is largely due to a high incidence of posterior communicating artery atresia. This phenomenon is considered a major contributor to the high mortality rate observed in C57Bl/6 mice during long-term stroke recovery after filament MCAO. Thus, many chronic stroke studies exploit distal MCAO models. However, these models usually produce infarction only in the cortex area, and consequently, the assessment of post-stroke neurologic deficits could be a challenge. This study has established a modified transcranial MCAO model in which the MCA at the trunk is partially occluded either permanently or transiently via a small cranial window. Since the occlusion location is relatively proximal to the origin of the MCA, this model generates brain damage in both the cortex and striatum. Extensive characterization of this model has demonstrated an excellent long-term survival rate, even in aged mice, as well as readily detectable neurologic deficits. Therefore, the MCAO mouse model described here represents a valuable tool for experimental stroke research.

Introduction

Nearly 800,000 people suffer a stroke in the US every year, and most of these strokes are ischemic in nature¹. Timely restoration of the cerebral blood flow with tissue plasminogen activator (tPA) and/or thrombectomy is currently the most effective treatment for stroke patients; however, the full recovery of neurologic functions in the long term is rare^2,3. Thus, searching for novel stroke therapy that targets functional improvement is an intense area of research that requires clinically relevant animal models of stroke.

The most common ischemic stroke mode....

Protocol

All procedures described in this work are conducted in accordance with the NIH guidelines for the care and use of animals in research, and the protocol was approved by the Duke Institute Animal Care and Use Committee (IACUC). Young (8-10 weeks old) and aged (22 months old) male C57Bl/6 mice were used for the present study. An overview of this protocol is illustrated in Figure 1.

1. Surgical preparation

1. Examine the mouse for gross abnor.......

Discussion

The first transcranial MCA occlusion model was established in rats in 1981^11,12, and replaced by the no-craniectomy MCAO model in 1989⁴. The initial transcranial MCA occlusion had a wide surgical field, such that the entire zygomatic arch was removed and the muscles pulled laterally. Local tissues were swollen after surgery, causing stress and decreased food intake for the animals. In our modified transcranial MCAO model, the incision is l.......

Materials

Name	Company	Catalog Number	Comments
0.25% bupivacaine	Hospira	NDC 0409-1159-18
0.9% sodium chloride	ICU Medical	NDC 0990-7983-03
2,3,5-Triphenyltetrazolium Chloride (TTC)	Sigma or any available vendor
20 G IV catheter	BD	381534	20 GA 1.6 IN
30 G needle	BD	305106
4-0 silk suture	Look	SP116	Black braided silk
8-0 suture with needle	Ethilon	2822G
Alcohol swabs	BD	326895
Anesthesia induction box	Any suitable vendor		Pexiglass make
Electrical grinder	JSDA	JD 700
High temperature cautery loop tip	Bovie	AA03
Isoflurane	Covetrus	NDC 11695-6777-2
Laser doppler perfusion monitor	Moor Instruments	moorVMS-LDF1
Lubricant eye ointment	Bausch + Lomb	339081
Mouse rectal probe	Physitemp	RET-3
Nitrous Oxide	Airgas	UN1070
Otoscope	Welchallyn	728	2.5 mm Speculum
Oxygen	Airgas	UN1072
Povidone-iodine	CVS	955338
Recovery box	Brinsea	TLC eco
Rimadyl (carprofen)	Zoetis	6100701	Injectable 50 mg/mL
Rodent ventilator	Harvard	Model 683
Temperature controller	Physitemp	TCAT-2DF
Triple antibioric & pain relief	CVS	NDC 59770-823-56
Vaporizer	RWD	R583S