Activin-Directed Differentiation of Human Embryonic Stem Cells Differentially Modulates Alveolar Epithelial Wound Repair via Paracrine Mechanism

Khondoker M Akram,Monica A Spiteri,Nicholas R Forsyth

doi:10.4236/scd.2014.43008

Abstract

Differentiated embryonic stem cells (ESC) can ameliorate lung inflammation and fibrosis in animal lung injury models; therefore, ESC, or their products, could be candidates for regenerative therapy for incurable lung diseases, such as idiopathic pulmonary fibrosis (IPF). In this study, we have investigated the paracrine effect of differentiated and undifferentiated human ESC on alveolar epithelial cell (AEC) wound repair. hESC line, SHEF-2 cells were differentiated with Activin treatment for 22 days in an embryoid body (EB) suspension culture. Conditioned media (CM) which contain cell secretory factors were collected at different time points of differentiation. CM were then tested onin vitro wound repair model with human type II AEC line, A549 cells (AEC). Our study demonstrated that CM originated from undifferentiated hESC significantly inhibited AEC wound repair when compared to the control. Whereas, CM originated from Activin-directed hESC differentiated cell population demonstrated a differential reparative effect on AEC wound repair model. CM obtained from Day-11 of differentiation significantly enhanced AEC wound repair in comparison to CM collected from pre- and post-Day-11 of differentiation. Day-11 CM enhanced AEC wound repair through significant stimulation of cell migration and cell proliferation. RT-PCR and immunocytochemistry confirmed that Day-11 CM was originated form a mixed population of endodermal/mesodermal differentiated hESC. This report suggests a putative paracrine-mediated epithelial injury healing mechanism by hESC secreted products, which is valuable in the development of novel stem cell-based therapeutic strategies.

Highlights

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing interstitial pneumonia of unknown aetiology occurring primarily in older adults, and limited to the lungs [1]
Preliminary studies suggested that adult stem cells, such as mesenchymal stem cells (MSC), might engraft to the injured lung, replace damaged epithelium and potentiate lung repair in animal models of COPD/emphysema, cystic fibrosis and IPF
It is recognised that structural engraftment of MSC in lung is generally a rare occurrence with an uncertain fate of differentiation into alveolar epithelial cells [20]

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing interstitial pneumonia of unknown aetiology occurring primarily in older adults, and limited to the lungs [1]. According to the recent hypothesis, IPF occurs due to multiple micro-injuries to alveolar epithelial cells (AEC) followed by imbalanced immune response and aberrant alveolar injury repair where inflammation does not play any vital role [2] [3]. Whilst the precise mechanism of this aberrant alveolar repair remains uncertain, multifactorial causes including repeated AEC injuries [2] [8], increased AEC apoptosis [9]-[13], dysregulated epithelial-mesenchymal cross-talk [14], polarised immune response [3], alveolar bronchiolisation [13] [15] [16] and recently demonstrated epigenetic dysregulation [17]-[19] are believed to be involved

Methods

Results

Conclusion