Alveolar epithelial cells undergo epithelial-mesenchymal transition in acute interstitial pneumonia: a case report
- Hongbo Li†1,
- Jinjin Zhang†2,
- Xiaodong Song2,
- Tao Wang1,
- Zhi Li1,
- Dong Hao1,
- Xiaozhi Wang1,
- Qingyin Zheng3,
- Cuiping Mao2,
- Pan Xu2 and
- Changjun Lv1Email author
© Li et al.; licensee BioMed Central Ltd. 2014
Received: 4 November 2013
Accepted: 9 April 2014
Published: 23 April 2014
Acute interstitial pneumonia is a rare interstitial lung disease that rapidly progresses to respiratory failure or death. Several studies showed that myofibroblast plays an important role in the evolution of diffuse alveolar damage, which is the typical feature of acute interstitial pneumonia. However, no evidence exists whether alveolar epithelial cells are an additional source of myofibroblasts via epithelial-mesenchymal transition in acute interstitial pneumonia.
In this report, we present a case of acute interstitial pneumonia in a previously healthy 28-year-old non-smoking woman. Chest high-resolution computed tomography scan showed bilateral and diffusely ground-glass opacification. The biopsy was performed on the fifth day of her hospitalization, and results showed manifestation of acute exudative phase of diffuse alveolar damage characterized by hyaline membrane formation. On the basis of the preliminary diagnosis of acute interstitial pneumonia, high-dose glucocorticoid was used. However, this drug showed poor clinical response and could improve the patient’s symptoms only during the early phase. The patient eventually died of respiratory dysfunction. Histological findings in autopsy were consistent with the late form of acute interstitial pneumonia.
The results in this study revealed that alveolar epithelial cells underwent epithelial-mesenchymal transition and may be an important origin of myofibroblasts in the progression of acute interstitial pneumonia. Conducting research on the transformation of alveolar epithelial cells into myofibroblasts in the lung tissue of patients with acute interstitial pneumonia may be beneficial for the treatment of this disease. However, to our knowledge, no research has been conducted on this topic.
KeywordsAcute interstitial pneumonia Epithelial-mesenchymal transition Myofibroblast
Acute interstitial pneumonia (AIP), also known as Hamman-Rich syndrome, is a fulminating interstitial lung disease characterized by acute respiratory failure. The clinical features presented by majority of patients are described as a flulike prodrome including sore throat, headache, cough, dyspnea, and often fever with abrupt onset and short duration .
The histological hallmark of AIP was defined as diffuse alveolar damage (DAD), which is a nonspecific reaction in the lung to many injurious agents. The pathologic progress of DAD can be separated into three phases: acute exudative phase, which is characterized by interstitial edema, hyaline membrane, and acute interstitial inflammation accumulation ; proliferative phase, which is characterized by interstitial thickening and the appearance of granulation tissue in alveolar spaces ; and fibrotic phase, which is characterized by enlarged fibrotic septa and laminated intra-alveolar fibrosis .
The primary focus of therapy is supportive care. However, the use of glucocorticoids and immunosuppressive therapies is only effective in some cases. The case-fatality ratio remains high (>60 percent) despite intensive treatment and the majority of patients die within six months of presentation . Thus, the pathologic process of the disease should be urgently explored, and a new therapeutic target should be identified.
Epithelial-mesenchymal transition (EMT), defined by the loss of epithelial characteristics and the acquisition of a mesenchymal phenotype, is essential for the progress of embryonic development . Numerous studies revealed that the abnormal activation of EMT programs plays an important role in tissue fibrosis, cancer invasion, and metastasis [7–9]. However, the emergence and importance of EMT in lungs of patients with AIP remain unclear.
In this report, we present the case of a 28-year-old female diagnosed with AIP through histological and radiological lung examinations. Pathological and ultrastructural findings at open lung biopsy and autopsy showed that alveolar epithelial cells underwent EMT which may be beneficial for early intervention of AIP.
AIP is one of the six subtypes of major idiopathic interstitial pneumonia according to the American Thoracic Society/European Respiratory Society classification . Given that many diseases could mimic AIP, multidisciplinary diagnosis, which requires a combination of clinical, radiological, and pathological findings, is needed. The case reported a patient with typical appearances of AIP. Apart from supplemental oxygen and mechanical ventilation, the patient received high-dose intravenous methylprednisolone for 5 d and normal dose of methylprednisolone for several days. However, the treatment could not contribute to the patient’s survival. The data from this case confirmed the occurrence of EMT in AIP and maybe beneficial for the treatment of this disease.
The process of lung injury with subsequent development of scar tissue in idiopathic pulmonary fibrosis has been likened to an abnormal wound healing model. A similar construct may be applied to AIP . In theory, intervention before the deposition of mature collagen should allow the restoration of normal lung architecture. The marked expansion of myofibroblast numbers within the alveolar septa responds for the subsequent collagen production in the proliferative and fibrotic AIP . Consistent with this conclusion, we also detected an amount of myofibroblast in the patient’s lung tissue. This myofibroblast may be related to the AIP process.
Previous observations revealed that injured epithelial cells could gradually lose their epithelial cell markers and polarity, thus expressing mesenchymal markers and acquiring single-cell motility , which was defined as EMT. During EMT, cytoskeletal reprogramming establishes the presence of α-SMA stress fibers in epithelial cells . Through this transition, alveolar epithelial cells serve as an importance source of myofibroblasts during tissue injury response. Kalluri et al.  reported that under inflammatory stress, 30% of myofibroblasts can arise via EMT, whereas resident fibroblasts contribute only 23% in the kidney. Several articles reported that EMT may participate in various lung diseases, such as developmental disorders, fibrotic tissue remodeling, and lung cancer in humans [16–18]. Harada et al.  demonstrated the presence of EMT in patients with usual interstitial pneumonia pattern. However, Yamada et al.  obtained conflicting results and did not detect double-positive cells for E-cadherin, ICAM-1, LEA CD44v9, SP-A, α-SMA, or vimentin in lung tissues from patients with idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia. Therefore, the evidence of myofibroblasts originating from epithelial cells through EMT in interstitial pneumonia remains controversial. Our ultrastructural data supported the existence of EMT in the lung tissue of patients with AIP. We also found that SPC and α-SMA, which are markers for alveolar epithelial cells and myofibroblasts, respectively , coexisted in the patient’s sections. The EMT program in epithelial cells is identified to be switched on by many transcription factors. For example, Snail, a major transcription factor governing EMT , could regulate the expression of genes related to epithelial and mesenchymal phenotype . We found that the expression of Snail in the lung tissue of the patient was upregulated in the proliferative phase of AIP compared with the exudative phase of AIP.
In conclusion, the results of this study confirmed that alveolar epithelial cells underwent EMT, which maybe an important origin of myofibroblasts in the progression of AIP. Although pathological manifestation may vary from one case of AIP to another, our finding partly indicated the possibility and importance of EMT in AIP and provided a potential therapeutic method of preventing EMT in AIP.
Written informed consent was obtained from the lung of the patient for publication of this Case Report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal form.
Acute interstitial pneumonia
High-resolution computed tomography
Diffuse alveolar damage
Surfactant associated protein
α-Smooth muscle actin.
This study was supported by Taishan Scholar Project to Fang Han and National Natural Science Foundation of China (NO. 81273957, NO.31300288), Important Project of Science and Technology of Shandong Province (NO.2010GWZ20254, NO. 2011GHY11501), Natural Science Foundation of Shandong Province (NO.ZR2009EM006, ZR2012HQ042), Project of Science and Technology of Education Department of Shandong Province (NO.J11FL87).
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