Creation of Two Saccular Elastase-Digested Aneurysms with Different Hemodynamics in One Rabbit

Summary

This protocol describes the steps for the creation of a rabbit model with two elastase-digested aneurysms with different hemodynamics (stump and bifurcation constellation). This allows the testing of novel endovascular devices in aneurysms with different angioarchitecture and hemodynamic conditions within a single animal.

Abstract

Preclinical animal models with hemodynamic, morphologic, and histologic characteristics close to human intracranial aneurysms play a key role in the understanding of the pathophysiological processes and the development and testing of new therapeutic strategies. This study aims to describe a new rabbit aneurysm model that allows the creation of two elastase-digested saccular aneurysms with different hemodynamic conditions within the same animal.

Five female New Zealand white rabbits with a mean weight of 4.0 (± 0.3) kg and mean age of 25 (±5) weeks underwent microsurgical stump and bifurcation aneurysm creation. One aneurysm (stump) was created by right common carotid artery (CCA) exposure at its origin at the brachiocephalic trunk. A temporary clip was applied at the CCA origin and another, 2 cm above. This segment was treated with a local injection of 100 U of elastase for 20 min. A second aneurysm (bifurcation) was created by suturing an elastase-treated arterial pouch into the end-to-side anastomosis of the right CCA to left CCA. Patency was controlled by fluorescence angiography immediately after creation.

The average duration of surgery was 221 min. The creation of two aneurysms in the same animal was successful in all rabbits without complication. All aneurysms were patent immediately after surgery except for one bifurcation aneurysm, which showed an extreme tissue reaction due to elastase incubation and an immediate intraluminal thrombosis. No mortality was observed during surgery and up to one-month follow-up. Morbidity was limited to a transient vestibular syndrome (one rabbit), which recovered spontaneously within one day.

Demonstrated here for the first time is the feasibility of creating a two-aneurysm rabbit model with stump and bifurcation hemodynamic characteristics and highly degenerated wall conditions. This model allows the study of the natural course and potential treatment strategies on the basis of aneurysm biology under different flow conditions.

Introduction

Intracranial aneurysm is a severe condition with a mortality rate after rupture reaching 50% and long-term disability in 10-20% of patients¹. The last decade has seen a rapid development of endovascular treatment options but, at the same time, also an increasing rate of recurrence with up to 33% of aneurysm recanalization after coiling^2,3. To better understand the pathophysiology underlying aneurysm occlusion and recanalization, as well as for the development and testing of new endovascular devices, there is currently a need for reliable preclinical models whose hemodynamic, morphologic....

Protocol

NOTE: The experiment was approved by the Local Committee for Animal Care of the Canton Bern, Switzerland (Application Number BE108/16), and all animal care and procedures were performed in accordance with institutional guidelines and 3R principles^15,16. Data are reported according the ARRIVE guidelines. Peri-operative management was conducted by a board-certified veterinarian anesthesiologist. For the study, female New Zealand white rabbits, with a mean weight of 4.0 (± 0.3) kg and mean age of 25 (±5) weeks, were housed at a room temperature of 22-24 °C with a 12-h light/dark cycle with free acc....

Results

The creation of a stump and a bifurcation aneurysm was successful in all 5 New Zealand white rabbits without intraoperative complications. No mortality was observed during surgery or during the follow-up period of 24 ± 2 days. One rabbit experienced postoperative complications with a vestibular syndrome and a blindness of the right side. The animal recovered completely and spontaneously after 24 h. This complication did not interfere with its normal activities (free movements, water and food intake, interactions with oth.......

Discussion

The most common technique for aneurysm creation involves the creation of a stump aneurysm at the origin of the right CCA, either through an open or an endovascular method. The model has been validated to be a stable non-growing aneurysm that remains open with time^20,21. The second possible technique involves the microsurgical creation of an arterial bifurcation aneurysm by anastomosing the right CCA on the left one and suturing an aneurysm pouch on the bifurcatio.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
4-0 resorbable suture	Ethicon Inc., USA	VCP292ZH
4-0 resorbable suture	Ethicon Inc., USA	VCP304H
6-0 non absorbable suture	B. Braun, Germany	C0766070
9-0 non absorbable suture	B. Braun, Germany	G1111140
Adrenaline	Amino AG	1445419	any generic
Amiodarone	Helvepharm AG	5078567	any generic
Anesthesia machine	Dräger		any other
Aspirin	Sanofi-Aventis (Suisse) SA	622693	any generic
Atropine	Labatec Pharma SA	6577083	any generic
Bandpass filter blue	Thorlabs	FD1B	any other
Bandpass filter green	Thorlabs	FGV9	any other
Biemer vessel clip (2x)	B. Braun Medical AG, Aesculap, Switzerland	FD560R	any other
Bipolar forceps			any other
Bispectral index (neonatal)			any other
Blood pressure cuff (neonatal)		any other
Bycilces spotlight			any other
Clamoxyl	GlaxoSmithKline AG	758808	any generic
Dexmedetomidine	Ever Pharma	136740-1	any generic
Elastase	Sigma Aldrich	E7885
Electrocardiogram electrodes
Ephedrine	Amino AG	1435734
Esmolol	OrPha Swiss GmbH	3284044
Fentanyl (intravenous use)	Janssen-Cilag AG	98683
Fentanyl (transdermal)	Mepha Pharma AG	4008286
Fluoresceine	Curatis AG	5030376
Fragmin	Pfizer PFE Switzerland GmbH	1906725
Heating pad or heating forced-air warming system
Isotonic sodium chloride solution (0.9%)	Fresenius KABI	336769
Ketamine	Pfizer PFE Switzerland GmbH	342261
lid retractor			Approach
Lidocaine	Streuli Pharma AG	747466
Longuettes
Metacam	Boehringer Ingelheim	P7626406	Medication
Methadone	Streuli Pharma AG	1084546	Sedaton
Micro-forceps  curved	Ulrich Swiss, Switzerland	U52-015-15
Micro-forceps  straight 2x	Ulrich Swiss, Switzerland	U52-010-15
Microscissors	Ulrich Swiss , Switzerland	U52-327-15
Midazolam	Accord Healthcare AG	7752484
Needle 23 G			arteriotomy
Needle holder
O2-Face mask
Operation microscope	Wild Heerbrugg
Papaverin	Bichsel		topical application
Povidone iodine	Mundipharma Medical Company		any generic
Prilocaine-lidocaine creme	Emla
Propofol	B. Braun Medical AG, Switzerland		General anesthesia
Pulse oxymeter
Rectal temperature probe (neonatal)
Ringer Lactate	Bioren Sintetica SA		Infusion
Ropivacain	Aspen Pharma Schweiz GmbH	1882249	Local anesthesia
Scalpell	Swann-Morton	210
Small animal shaver
Soft tissue forceps
Soft tissue spreader
Stainless steel sponge bowls
Sterile micro swabs
Stethoscope
Surgery drape
Surgical scissors
Syringes 1 mL, 2 mL, and 5 mL
Tris-Buffer	Sigma Aldrich	93302	Elastase solution
Vascular clip applicator	B. Braun, Germany	FT495T
Vein and arterial catheter 22 G
vessel loop			Approach
video camera or smartphone
Vitarubin	Streuli Pharma AG	6847559
Yasargil titan standard clip (2x)	B. Braun Medical AG, Aesculap, Switzerland	FT242T