Role of Eosinophils in the Proliferation of Airway Smooth Muscle (ASM) Cells

Role of Eosinophils in the Proliferation of ASM Cells in Asthma

Being a key player in Asthma, eosinophils constitute a potential target to interfere with the series of biological events leading to Asthma pathogenesis. In this proposal, the investigators hypothesize that the interaction between eosinophils and airway smooth muscle cells (ASM) cells plays an important role in airway remodeling. Hence the investigators will investigate the role of eosinophils in enhancing ASM cells proliferation resulting in airways remodeling. The investigators will also investigate the mechanism behind this phenomenon. This will then pave the way for medical (drug) interference at one or several sites in order to prevent one of the main potential reasons behind airway remodeling, namely eosinophil-derived ASM proliferation.

Rational and hypothesis Asthma is a chronic inflammatory disorder of the lung airways that is associated with airway remodeling and hyperresponsiveness (AHR). Its is well documented that the smooth muscle mass in asthmatic airways is increased due to hypertrophy and hyperplasia of the ASM cells. Moreover, eosinophils have been proposed in different studies to play a major role in airway remodeling. The association between increased eosinophil numbers and asthma severity has been well documented. Here, we hypothesized that the interaction between eosinophils and ASM cells plays an important role in airway remodeling and that eosinophils modulate the airways through enhancing ASM cell proliferation.

Objectives of the study The aim of this study is to examine the effect of eosinophils on ASM cell proliferation using eosinophils isolated from asthmatic subjects.

Specific aim 1. Effect of co-culture of ASM cells with eosinophils on ASM cell proliferation.

In this specific aim, the effect of eosinophil on ASM cell proliferation will be studied by co-culturing eosinophils isolated from asthmatic and healthy patients with ASM cells in vitro. This will be done using non-stimulated eosinophils or eosinophils activated with Interleukin-5 (IL-5)and Interleukin-3 (IL-3). ASM proliferation will be monitored by determining the levels of the proliferation marker Ki-67 expression in ASM cells.

Specific aim 2. Understanding the mechanism by which eosinophils enhance ASM proliferation.

In this specific aim, we will study the mechanism by which eosinophils enhance the proliferation of ASM cells. To study if this effect of eosinophils is done through direct contact with ASM cells, we will co-culture ASM cells with eosinophils membrane fractions. Moreover, we will examine the effect of cytokines and extracellular matrix (ECM) proteins produced by eosinophils on smooth muscle cells

Asthma: Patient Selection (Inclusion Criteria)

1. Subjects with documented clinical history of asthma for a period of at least 6 months prior to study entry (and a minimum of one clinic follow-up visit since initial diagnosis)
2. Willing to provide written informed consent and in the judgment of the investigator, individuals who are able to understand the informed consent process.
3. Subjects with documented clinical history (in preceding 12 months) of airway reversibility of at least 12% based on Forced Expiratory Volume (FEV1), measured pre and post inhalation of a β-2 agonist (2 puffs of albuterol using a measured dose inhaler with spacer) OR
4. Individuals with strong history of asthma but with waning, or no current symptoms may be included in the study if their asthma was well controlled using an asthma medication. Principal investigator must verify or know the clinical history of an individual before accepting him as an asthmatic individual.
5. Able to perform Spirometry/FEV1 correctly.

Exclusion Criteria

1. Age < 5 years
2. Smoking for 20 years, 1 pack/day or more.
3. Congestive heart failure.
4. Chronic Obstructive Pulmonary Disease (COPD).
5. Chronic lung disease other than asthma and COPD.
6. Bronchiectasis.