Laser Doppler: A Tool for Measuring Pancreatic Islet Microvascular Vasomotion In Vivo

Summary

Pancreatic islet microvascular vasomotion regulates islet blood distribution and maintains the physiological function of islet β cells. This protocol describes using a laser Doppler monitor to determine the functional status of pancreatic islet microvascular vasomotion in vivo and to assess the contributions of pancreatic islet microcirculation to pancreatic-related diseases.

Abstract

As a functional status of microcirculation, microvascular vasomotion is important for the delivery of oxygen and nutrients and the removal of carbon dioxide and waste products. The impairment of microvascular vasomotion might be a crucial step in the development of microcirculation-related diseases. In addition, the highly vascularized pancreatic islet is adapted to support endocrine function. In this respect, it seems possible to infer that the functional status of pancreatic islet microvascular vasomotion might affect pancreatic islet function. Analyzing the pathological changes of the functional status of pancreatic islet microvascular vasomotion may be a feasible strategy to determine contributions that pancreatic islet microcirculation makes to related diseases, such as diabetes mellitus, pancreatitis, etc. Therefore, this protocol describes using a laser Doppler blood flow monitor to determine the functional status of pancreatic islet microvascular vasomotion, and to establish parameters (including average blood perfusion, amplitude, frequency, and relative velocity of pancreatic islet microvascular vasomotion) for evaluation of the microcirculatory functional status. In a streptozotocin-induced diabetic mouse model, we observed an impaired functional status of pancreatic islet microvascular vasomotion. In conclusion, this approach for assessing pancreatic islet microvascular vasomotion in vivo may reveal mechanisms relating to pancreatic islet diseases.

Introduction

As a parameter of the functional status of microcirculation, microvascular vasomotion takes responsibility for the delivery and exchange of oxygen, nutrients, and hormones and is crucial to the removal of metabolic products, such as carbon dioxide and cell waste¹. Microvascular vasomotion also regulates blood flow distribution and tissue perfusion, thereby affecting local microcirculatory blood pressure and responses to inflammation, which can induce edema in many diseases. Therefore, microvascular vasomotion is extremely important to maintain the physiological function of organs^2,3

Protocol

All animal experiments were executed in compliance with all relevant guidelines, regulations, and regulatory agencies. The present protocol being demonstrated was performed under the guidance and approval of the Institute of Microcirculation Animal Ethics Committee (IMAEC) at the Peking Union Medical College (PUMC).

1. Animals

1. Before the start of the experiment, keep three BALB/c mice per cage, with controlled temperature (24 ± 1 °C) and humidity (55 ± 5%), under a 12-h light-dark cycle. Allow the mice free access to regular food and water.
2. Randomly divide the mice into a non-diabetic control group and a....

Results

A photograph of the microvascular vasomotion measurement laser Doppler apparatus equipped with a semi-conductor laser diode is shown in Figure 1A. User interface software is presented in Figure 1B. Using the method mentioned above, the hemodynamic parameters of pancreatic islet microvascular vasomotion were detected for both non-diabetic control and diabetic mice. A variety of techniques, including laser Doppler flowmetry, reflec.......

Discussion

In the cases that involve microvascular dysfunction (e.g., diabetes, acute pancreatitis, peripheral microvascular diseases, etc.), some diseases lead to reduced blood flow. Other than changes in blood flow, there are important indicators, such as microvascular vasomotion, that mirror the functional status of microcirculation. The specific indicator, microvascular vasomotion, is generally defined as the oscillation of the microvascular tone in microvascular beds. In the current protocol, a microvascular .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
MoorVMS-LDF2	Moor Instruments	GI80	PeriFlux 5000 (Perimed Inc.) can be used as an alternative apparatus to harvest data
MoorVMS-PC Software	Moor Instruments	GI80-1	Software of MoorVMS-LDF2
Calibration stand	Moor Instruments	GI-cal	Calibration tool
Calibration base	Moor Instruments	GI-cal	Calibration tool
Calibration flux standard	Moor Instruments	GI-cal	Calibration tool
One Touch UltraEasy glucometer	Johnson and Johnson	#1955685	Confirm hyperglycemia
One Touch UltraEasy strips	Johnson and Johnson	#1297006	Confirm hyperglycemia
Streptozotocin	Sigma-Aldrich	S0130	Dissolve in sodium citrate buffer (pH 4.3)
Pentobarbital sodium	Sigma-Aldrich	P3761	Working concentration 3 %
Ethanol	Sinopharm Inc.	200121	Working concentration 75 %
Sucrose	Amresco	335	Working concentration 10 %
Medical gauze	China Health Materials Co.	S-7112	Surgical
Blunt-nose forceps	Shang Hai Surgical Instruments Inc.	N-551	Surgical
Surgical tapes	3M Company	3664CU	Surgical
Gauze sponge	Fu Kang Sen Medical Device CO.	BB5447	Surgical
Scalpel	Yu Lin Surgical Instruments Inc.	175C	Surgical
Skin scissor	Carent	255-17	Surgical
Suture	Ning Bo Surgical Instruments Inc.	3325-77	Surgical
Syringe and 25-G needle	MISAWA Inc.	3731-2011	Scale: 1 ml