Serum KL-6 and Surfactant Proteins A and D in Pediatric Interstitial Lung Disease

Serum biomarkers in neuroendocrine cell hyperplasia of infancy

BACKGROUND

Neuroendocrine cell hyperplasia of infancy (NEHI) is a form of childhood interstitial lung disease of unknown origin associated with hyperplasia of pulmonary neuroendocrine cells (PNECs). Diagnosis is based on the characteristic clinical picture and typical radiological imaging, and, in some cases, on lung biopsies. To date, no biochemical indicators of the disease have been identified.

AIM

We aimed to determine biomarkers that could be useful in the management of children diagnosed with NEHI.

METHODS

Patients with NEHI and healthy children were enrolled. Concentrations of serum biomarkers secreted by PNECs (calcitonin gene-related peptide and gastrin-releasing peptide) and biomarkers of the destruction of alveolar capillary membrane (surfactant proteins A and D [SP-A and SP-D]; glycoprotein Krebs von den Lungen-6 [KL-6]; metalloproteinases 7 and 9 [MMP-7 and MMP-9]; tissue inhibitor of metalloprotease 1) were measured.

RESULTS

Fifty-two children with NEHI and 23 healthy children were included in the study. The median age of children with NEHI was 3.9 years. There were no differences in serum levels of biomarkers secreted by PNECs between groups. KL-6 levels were significantly higher in children with NEHI than in healthy ones (median 119.6 vs. 92.1 U/mL, p = 0.003); however, concentrations of KL-6 were low in both groups. No significant differences existed between groups for the remaining biomarkers associated with the destruction of the alveolar-capillary membrane.

CONCLUSIONS

Measurement of serum biomarkers released by PNECs and those associated with the destruction of the alveolar-capillary membrane does not appear to be useful in the management of children with NEHI.

Surfactant protein disorders in childhood interstitial lung disease

Surfactant, which was first identified in the 1920s, is pivotal to lower the surface tension in alveoli of the lungs and helps to lower the work of breathing and prevents atelectasis. Surfactant proteins, such as surfactant protein B and surfactant protein C, contribute to function and stability of surfactant film. Additionally, adenosine triphosphate binding cassette 3 and thyroid transcription factor-1 are also integral for the normal structure and functioning of pulmonary surfactant. Through the study and improved understanding of surfactant over the decades, there is increasing interest into the study of childhood interstitial lung diseases (chILD) in the context of surfactant protein disorders. Surfactant protein deficiency syndrome (SPDS) is a group of rare diseases within the chILD group that is caused by genetic mutations of SFTPB, SFTPC, ABCA3 and TTF1 genes.Conclusion: This review article seeks to provide an overview of surfactant protein disorders in the context of chILD. What is Known: • Surfactant protein disorders are an extremely rare group of disorders caused by genetic mutations of SFTPB, SPTPC, ABCA3 and TTF1 genes. • Given its rarity, research is only beginning to unmask the pathophysiology, inheritance, spectrum of disease and its manifestations. What is New: • Diagnostic and treatment options continue to be explored and evolve in these conditions. • It is, therefore, imperative that we as paediatricians are abreast with current development in this field.

The potential of biomarkers of fibrosis in chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the major long-term cause of morbidity and mortality after lung transplantation. Both bronchiolitis obliterans syndrome and restrictive lung allograft syndrome, two main types of CLAD, lead to fibrosis in either the small airways or alveoli and pleura. Pathological pathways in CLAD and other types of fibrosis, for example idiopathic pulmonary fibrosis, are assumed to overlap and therefore fibrosis biomarkers could aid in the early detection of CLAD. These biomarkers could help to differentiate between different phenotypes of CLAD and could, in comparison to biomarkers of inflammation, possibly distinguish an infectious event from CLAD when a decline in lung function is present. This review gives an overview of known CLAD specific biomarkers, describes new promising fibrosis biomarkers currently investigated in other types of fibrosis, and discusses the possible use of these fibrosis biomarkers for CLAD.

Krebs von den Lungen-6 and surfactant protein-A in interstitial pneumonia with autoimmune features

Interstitial pneumonia with autoimmune features (IPAF) is a special subtype of interstitial lung disease that has received worldwide attention. Krebs von den Lungen-6 (KL-6) and surfactant protein-A (SP-A) can be used as an important biomarker of interstitial lung disease, but its exact relationship with IPAF is poorly understood.A total of 65 IPAF patients were included in the study and were followed up for 52 weeks. The KL-6 and SP-A were evaluated by chemiluminescence enzyme immunoassay. The above indicators were tested at 2 time points, baseline (the first admission of patients) and 52 weeks. We also collected the indicators of antinuclear antibodies and rheumatoid factor. Based on high-resolution computed tomography evaluations, patients were divided into: aggravation, stable, and improvement group. At same time, 30 age-matched normal people as normal control were recruited, the same information was collected. Correlations among the groups were compared and analyzed.The KL-6 and SP-A level in IPAF patients were significantly higher than normal controls (fold increase = 11.35 and 1.39, both P < .001) and differed significantly at baseline and 52 weeks in IPAF (difference ratio = 37.7% and 21.3%, P < .05, both). There were significant differences at baseline and 52 weeks (r values of aggravation, improvement, and stable groups for KL-6 were 0.705, 0.770, and 0.344, P = .001, .001, and .163, and for SP-A the r value were 0.672, 0.375, and 0.316, P = .001, .126, and .152). In aggravation group, KL-6 and SP-A were correlated with CT scores (both P < .05). Diffusing capacity of the lung for carbon monoxide (DLCO) and forced vital capacity (FVC), % predicted showed a progressive downward trend, with a significant difference at baseline and 52 weeks in IPAF patients (difference ratio = 23.8% and 20.6%, both P < .05). There was a significant correlation between KL-6 and FVC % predicted and DLCO (both P < .05), SP-A showed negatively correlated with DLCO, but not significantly correlated with FVC % predicted (P < .05 and .47).This study demonstrated that KL-6 and SP-A can reflect disease progression, and both 2 play a key role at reflection of lung epithelial cell injury and fibrosis degree in IPAF.

Serum Krebs von den Lungen-6 level predicts disease progression in interstitial lung disease

Disease progression (DP) in interstitial lung disease (ILD) is variable and difficult to predict. In previous reports, serum Krebs von den Lungen-6 (KL-6) was suggested to be useful in diagnosing and predicting survival in ILD. The aim of our study was to investigate the usefulness of serum KL-6 as a predictor of DP in ILD. Clinical data of 199 patients with ILD (idiopathic pulmonary fibrosis: 22.8%) were prospectively collected and serum KL-6 levels were measured. DP was defined as a relative decline in forced vital capacity (FVC) ≥ 10%, acute exacerbation, or death during follow-up. The median follow-up period was 11.1 months. The mean age of the subjects was 62.2 years, and 59.8% were male. DP occurred in 21.6% of patients. The progressed group showed lower FVC, lower diffusing capacity for carbon monoxide, lower the minimum oxygen saturation during the 6-minute walk test, higher fibrosis scores on high-resolution computed tomography, and higher KL-6 levels (826.3 vs. 629.0 U/mL; p < 0.001) than those of the non-progressed group. In receiver operating characteristic curve analysis, serum KL-6 levels were a significant predictor of DP in ILD (area under the curve = 0.629, p = 0.009, and the optimal cut-off level was 811 U/mL). In multivariable Cox analysis, high serum KL-6 levels (≥ 800 U/mL) were only independently associated with DP in ILD (HR 2.689, 95% CI 1.445–5.004, P = 0.002). Serum KL-6 levels might be useful to predict DP in patients with ILD.

Vitamin D levels are prognostic factors for connective tissue disease associated interstitial lung disease (CTD-ILD)

OBJECTIVE

Vitamin D deficiency was associated with CTD-ILD and reduced lung function. We sought to confirm that lower Vitamin D level would be related to shorter survival times.

RESULTS

The CTD-ILD patients had lower Vitamin D level(P<0.05). Among patients with CTD-ILD who have improved lung function after treatment, elevation of Vitamin D level was positively associated with ΔFVC (%), ΔFEV1(%) and ΔDLCO-SB (%). The median survival time of patients with high serum 25(OH)D level was significantly longer than the patients with low 25(OH)D level group (16.5 months vs14.0 months, P=0.007). The Vitamin D was identified as an independent prognostic factor with a hazard ratio of 0.869 (95% CI 0.772-0.977, P =0.019).

CONCLUSIONS

Vitamin D level was lower in patients with CTD-ILD and associated with poor prognosis. Continuous levels of Vitamin D may be an important serum biomarker of prognosis.

METHODS

85 CTD-ILD patients, 71 Idiopathic pulmonary fibrosis (IPF) patients and 78 healthy control patients were included in the study. In the subgroup analysis, the CTD-ILD patients were divided into anti-MDA5 antibody-positive group and anti-MDA5 antibody-negative group according to the serum autoantibodies results. The survival analysis evaluated effect of Vitamin D level on disease prognosis.

Surfactant protein D as a marker for pulmonary complications in pediatric patients with sickle cell disease: Relation to lung function tests

BACKGROUND

Surfactant protein D (SP-D) is considered a candidate biomarker for lung integrity and for disease progression.

AIM

We determined the level of SP-D in children and adolescents with SCD and assessed its possible relation to pulmonary complications and lung function.

METHODS

Serum SP-D levels were assessed in 50 SCD patients compared with 30 healthy controls. High-resolution computerized tomography (HRCT) of the chest was done. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁ ), FEV₁ /FVC% and forced expiratory flow rate during 25-75% of expiration (FEF25-75%) were determined.

RESULTS

SP-D was significantly higher in SCD patients than controls, particularly patients with sickle cell anemia than those with sickle β-thalassemia. SP-D levels were significantly associated with increasing severity of interstitial lung disease. The highest SP-D levels were observed among patients with restrictive lung disease followed by mixed type then obstructive lung disease. SP-D was positively correlated to HbS and serum ferritin while negatively correlated to duration of hydroxyurea treatment and parameters of pulmonary functions. ROC curve analysis revealed that SP-D cutoff value 720 ng/mL could significantly detect the presence of abnormal pulmonary function among SCD patients with 82% sensitivity and 88% specificity. Logistic regression analysis showed that SP-D is an independent factor related to abnormal pulmonary function in SCD.

CONCLUSIONS

SP-D may be a promising biomarker for screening of SCD patients for risk of later pulmonary complications.

Surfactant protein D is a useful biomarker for monitoring acute lung injury in rats

PURPOSE

The purpose of this study is to investigate the serial changes in the SP-D concentrations of serum and bronchoalveolar lavage fluid (BALF) in a bleomycin-induced lung injury rat model and compare them with the levels of conventional biochemical markers.

MATERIALS AND METHODS

Male Wister rats were anesthetized and intratracheally administered bleomycin (1.0 mg/kg). We evaluated the histological changes and SP-D expression of their lung tissues. We also measured the concentrations of SP-D, albumin, and lactate dehydrogenase (LDH) and the numbers of various types of cells in BALF, and the serum levels of SP-D and conventional markers, including LDH, high mobility group box 1, monocyte chemoattractant protein-1, and C-reactive protein.

RESULTS

The BALF SP-D level increased and peaked on day 3, and then gradually decreased. These variations were significantly correlated with the changes in the BALF albumin level and granulocyte cell count. The serum SP-D level increased from day 5, peaked on day 10, and then gradually decreased until day 28. The changes in the serum SP-D level accurately reflected the extent of the histological changes caused by the lung injury. On the other hand, the serum levels of conventional biomarkers were only elevated for a few days or did not change during the study period.

CONCLUSIONS

The SP-D level is the most useful marker of the severity of lung injuries. These results suggest that the measurement of SP-D levels is an additional tool for monitoring acute lung injuries in rats.

Genetic disorders of surfactant protein dysfunction: when to consider and how to investigate

Genetic mutations affecting proteins required for normal surfactant protein function are a rare cause of respiratory disease. The genes identified that cause respiratory disease are surfactant protein B, surfactant protein C, ATP binding cassette number A3 and thyroid transcription factor-1. Surfactant protein dysfunction syndromes are highly variable in their onset and presentation, and are dependent on the genes involved and environmental factors. This heterogeneous group of conditions can be associated with significant morbidity and mortality. Presentation may be in a full-term neonate with acute and progressive respiratory distress with a high mortality or later in childhood or adulthood with signs and symptoms of interstitial lung disease. Genetic testing for these disorders is now available, providing a non-invasive diagnostic test. Other useful investigations include radiological imaging and lung biopsy. This review will provide an overview of the genetic and clinical features of surfactant protein dysfunction syndromes, and discuss when to suspect this diagnosis, how to investigate it and current treatment options.

Biomarkers in Pediatric ARDS: Future Directions

Acute respiratory distress syndrome (ARDS) is common among mechanically ventilated children and accompanies up to 30% of all pediatric intensive care unit deaths. Though ARDS diagnosis is based on clinical criteria, biological markers of acute lung damage have been extensively studied in adults and children. Biomarkers of inflammation, alveolar epithelial and capillary endothelial disruption, disordered coagulation, and associated derangements measured in the circulation and other body fluids, such as bronchoalveolar lavage, have improved our understanding of pathobiology of ARDS. The biochemical signature of ARDS has been increasingly well described in adult populations, and this has led to the identification of molecular phenotypes to augment clinical classifications. However, there is a paucity of data from pediatric ARDS (pARDS) patients. Biomarkers and molecular phenotypes have the potential to identify patients at high risk of poor outcomes, and perhaps inform the development of targeted therapies for specific groups of patients. Additionally, because of the lower incidence of and mortality from ARDS in pediatric patients relative to adults and lack of robust clinical predictors of outcome, there is an ongoing interest in biological markers as surrogate outcome measures. The recent definition of pARDS provides additional impetus for the measurement of established and novel biomarkers in future pediatric studies in order to further characterize this disease process. This chapter will review the currently available literature and discuss potential future directions for investigation into biomarkers in ARDS among children.

The proteomics of lung injury in childhood: challenges and opportunities

Proteomics, the large-scale study of the structure and function of proteins of a cell or organism, is a rapidly developing area of biomedical research which is perfectly suited to the study of pediatric lung injury, where a variety of samples are easily, and repeatedly, accessible including plasma (reflecting a whole body response) and broncheoalveolar lung fluid (reflecting the lungs response). When applied to pediatric lung injury, proteomics could be used to develop much needed early biomarkers of lung injury, elucidate pathological pathways and determine protein alterations associated with specific disease processes. However despite the obvious benefits and need, proteomics is rarely utilized in studies of pediatric injury. This review primarily reports on the last decade of pediatric research into proteomes associated with specific respiratory diseases including bronchopulmonary dysplasia, respiratory infection, cystic fibrosis and asthma whilst also reflecting on the challenges unique to proteomic studies of the pediatric respiratory disease population. We conclude that the number of key pathological differences between the pediatric and adult study populations inhibit inference of results from adult studies onto a pediatric population and necessitate studies of the pediatric proteome. Furthermore the disparity amongst pediatric lung disease in terms of age at onset and underlying pathological mechanism (genetic, immunological, intervention-based, developmental arrest, inhaled toxin) will require proteomic studies which are well designed, with large disease specific patient sets to ensure adequate power as well as matched controls. Regardless of causative agent, pulmonary biomarkers are needed to predict the clinical course of pediatric lung disease, status, progression and response to treatment. Identification of early biomarkers is particularly pertinent in order to understand the natural history of disease and monitor progression so prevention of ongoing lung injury and impact on childhood can targeted.

Serum Krebs Von Den Lungen-6 as a Biomarker for Early Detection of Bronchiolitis Obliterans Syndrome in Children Undergoing Allogeneic Stem Cell Transplantation

Bronchiolitis obliterans syndrome (BOS) is a devastating complication after allogeneic stem cell transplantation (allo-SCT). Early identification of high-risk patients is pivotal for success. Lung proteins, KL-6, CCSP, SP-A, and SP-D, measured in the serum may identify high-risk patients for BOS earlier than pulmonary function tests (PFTs) can identify changes or clinical symptoms. Lung proteins were measured in patients' serum at baseline and at 1, 3, 6, 9, 12, 18, and 24 months after transplantation along with history, clinical examination, and PFTs. Serum levels of lung proteins were also measured in healthy control subjects. The primary endpoint was the development of BOS confirmed by pathological biopsy or National Institutes of Health criteria. Between September 2009 and September 2011, 39 patients were enrolled. Six children developed BOS at a median time of 200 days (range, 94 to 282). KL-6 levels were low in control subjects, at a median of .1 U/mL (range, .1 to 1.5). Pre-SCT and 1-month KL-6 levels were significantly higher in surviving patients who developed BOS (n = 6) versus those who did not (n = 18) (pre-SCT: mean, 32.6 U/mL [IQR, 9.7 to 89.3] versus 5.8 U/mL [IQR, 2.1 to 12.6], P = .03; at 1 month: mean, 52.5 U/mL [IQR, 20.2 to 121.3] versus 11.4 U/mL [IQR, 5.7 to 36.0], P = .04). Three- and 6-month KL-6 levels continued to be higher in BOS group but were not statistically significant. CCSP, SP-A, and SP-D were not predictive. KL-6 measured in the serum of children receiving allo-SCT may identify patients at high risk for the development of BOS. These patients will benefit from intensive surveillance protocol and early therapy before irreversible lung damage.

Correlation of serum KL-6 and CC16 levels with neurodevelopmental outcome in premature infants at 12 months corrected age

The aim of this study was to evaluate KL-6 and CC16 levels and their correlation with neurodevelopmental outcome among very low birth weight pre-term infants at 12 months corrected age. This prospective cohort study was performed from 2011 to 2013 by enrolling pre-term neonates of gestational age ≤ 32 weeks and birth weight ≤ 1500 g. Serum KL-6 and CC16 levels were determined 7 days after birth and their correlation with neurodevelopment was evaluated using Gesell Mental Developmental Scales. Of the 86 eligible pre-term infants, 63 completed follow-up, of which 15 had bronchopulmonary dysplasia. At 12 months corrected age, 49 infants had favorable outcomes and 14 infants had poor neurodevelopmental outcome. KL-6 levels were higher and CC16 levels were lower in infants with poor neurodevelopmental outcome compared with those infants who had favourable neurodevelopmental outcome. Serum KL-6 levels less than 90.0 ng/ml and CC16 levels greater than 320.0 pg/ml at 7 days of life were found to be predictive of a favourable outcome at 12 months corrected age. These biological markers could predict neurodevelopmental outcome at 12 months corrected age in very low birth weight premature infants, and help the clinician plan early therapeutic interventions to minimize or avoid poor neurodevelopmental outcome.

Factors influencing the measurement of plasma/serum surfactant protein D levels by ELISA

Background

Extensive variations in human surfactant protein D (SP-D) levels in circulation as measured by ELISA exist in the published literature. In order to determine the source of these variations, factors influencing the measurement by ELISA were explored.

Materials and Methods

Peripheral blood from healthy individuals was collected into various vacutainers during the same blood draw. Recombinant SP-D was diluted into different matrices and used for a standard curve. Samples were analyzed by capture ELISA using one of two distinct detection antibodies.

Results

The type of matrix had some effects on detection of recombinant SP-D. The type of anticoagulant used and dilution factor had very little effect, except for in plasma collected in EDTA vacutainers. The extent of variation in published values seemed to be due to the ELISA configuration employed, and, in agreement with this, we found that by switching the detection antibody, there was a 50% decrease in the extrapolated SP-D value of serum and plasma samples. Storage of samples resulted in slight changes in measured SP-D levels.

Conclusions

The ELISA configuration employed to measure circulating levels of SP-D has a significant effect on the extrapolated values. In both configurations tested, the use of EDTA as a coagulant resulted in inconsistent values, and we, therefore, suggest the avoidance of this anticoagulant when assaying for SP-D by ELISA. While the demonstrated effects of several factors on measurement of SP-D may not account for all the disparities amongst the previous studies, they stress that variations in methodologies for measuring the same protein can result in very inconsistent results.

Hereditary interstitial lung diseases manifesting in early childhood in Japan

BACKGROUND

Genetic variations associated with interstitial lung diseases (ILD) have not been extensively studied in Japanese infants.

METHODS

Forty-three infants with unexplained lung dysfunction were studied. All 43, 22, and 17 infants underwent analyses of surfactant protein (SP)-C gene (SFTPC) and ATP-binding cassette A3 gene (ABCA3), SP-B gene (SFTPB), and SP-B western blotting, respectively. Two and four underwent assessment of granulocyte macrophage colony-stimulating factor-stimulating phosphorylation of signal transducer and activator of transcription-5 (pSTAT-5) and analyses of FOXF1 gene (FOXF1), respectively.

RESULTS

ILD were diagnosed clinically in nine infants: four, three, and two had interstitial pneumonitis, hereditary pulmonary alveolar proteinosis (hPAP), and alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), respectively. Genetic variations considered responsible were detected in six (67%) of the nine infants with ILD: three with hPAP (SFTPC p.Leu45Arg and p.Gln145fs, and ABCA3 p.Arg1583Trp/p.Val1495CysfsX21), two with interstitial pneumonitis (SFTPC p.Lys63Glu and p.Ser72Asn/p.Gly100Ala), and one with ACD/MPV (FOXF1 p.Leu300ArgfsX79). None showed SFTPB mutations or defects in pSTAT-5. The 17 bronchoalveolar lavage or tracheal aspirates contained enough SP-B protein.

CONCLUSION

The SP-C abnormality was most prevalent, and SP-B deficiency was rare in Japanese infants with hereditary ILD.

A comparison of KL-6 and Clara cell protein as markers for predicting bronchopulmonary dysplasia in preterm infants

OBJECTIVES

To evaluate the predictive characteristics of KL-6 and CC16 for bronchopulmonary dysplasia (BPD) in preterm infants, either independently or in combination.

STUDY DESIGN

This prospective cohort study was performed from 2011 to 2013 with preterm neonates of gestational age ≤32 weeks and birth weight ≤1500 g. Serum KL-6 and CC16 levels were determined 7 and 14 days after birth.

RESULTS

Seventy-three preterm infants were studied. BPD was identified in 24 of these infants. After adjusting for potential confounders, serum KL-6 concentrations were found to be elevated in BPD infants at both time points relative to non-BPD infants, while serum CC16 concentrations were lower at 14 days. At both 7 d and 14 d of life the predictive power of KL-6 levels exceeded that of CC16 (area under receiver operating characteristic curve: at 7 d, 0.91 cf. 0.73, P = 0.02; at 14 d, 0.95 cf. 0.85, P = 0.05). The combination of these markers enhanced the sensitivity further.

CONCLUSIONS

Serum KL-6 levels higher than 79.26 ng/mL at 14 days postpartum in preterm infants predict the occurrence of BPD. CC16 was less predictive than KL-6 at this time point, but KL-6 and CC16 together enhanced the prediction.

Diffuse lung disease in children: summary of a scientific conference

A multi-disciplinary scientific conference focused on diffuse and interstitial lung diseases in children was held in La Jolla, CA in June 2012. The conference brought together clinicians (including Pediatric and Adult Pulmonologists, Neonatologists, Pathologists, and Radiologists), clinical researchers, basic scientists, government agency representatives, patient advocates, as well as children affected by diffuse lung disease (DLD) and their families, to review recent scientific developments and emerging concepts in the pathophysiology of childhood DLD. Invited speakers discussed translational approaches, including genetics and proteomics, epigenetics and epigenomics, models of DLD, including animal models and induced pluripotent stem cells, and regenerative medicine approaches. The presentations of the invited speakers are summarized here.

Serum heat shock protein 47 levels are elevated in acute interstitial pneumonia

Background

Heat shock protein (HSP) 47, a collagen-specific molecular chaperone, is involved in the processing and/or secretion of procollagen. We hypothesized that HSP47 could be a useful marker for fibrotic lung disease. The aim of this study was to evaluate serum levels of HSP47 in patients with various idiopathic interstitial pneumonias (IIPs).

Methods

Subjects comprised 9 patients with acute interstitial pneumonia (AIP), 12 with cryptogenic organizing pneumonia (COP), 16 with nonspecific interstitial pneumonia (NSIP), 19 with idiopathic pulmonary fibrosis (IPF), and 19 healthy adult volunteers.

Results

Patients with AIP had serum HSP47 levels that were significantly higher than those of COP, NSIP or IPF patients and those of healthy volunteers. In contrast, serum levels of HSP47 among patients with COP, NSIP, IPF, and healthy volunteers did not differ significantly. Receiver operating characteristic curves revealed that the cut-off level for HSP47 that resulted in the highest diagnostic accuracy for discriminating between AIP and COP, NSIP, IPF, and healthy controls was 859.3 pg/mL. The sensitivity, specificity, and diagnostic accuracy were 100.0%, 98.5%, and 98.7%, respectively.

Conclusion

The present results demonstrate that, among patients with various IIPs, serum levels of HSP47 were elevated specifically in patients with AIP.

A novel lung injury animal model using KL-6-measurable human MUC1-expressing mice

KL-6, an epitope of MUC1 mucin expressed on type II pneumocytes and bronchiolar epithelia in humans, is a sensitive serum marker for interstitial pneumonia. However, an in vivo model for KL-6 has not been established because no KL-6 epitope is expressed in animals other than humans and apes. To investigate whether KL-6 is detectable in human MUC1-expressing (hMUC1-exp) mice and whether KL-6 level reflects the degree of lung injury, we examined serum and bronchoalveolar lavage fluid (BALF) levels of KL-6 and surfactant protein-D (SP-D) in either lipopolysaccharide (LPS)- or bleomycin (BLM)-induced lung injury models. KL-6 was expressed on type II pneumocytes and bronchiolar epithelial cells in naïve hMUC1-exp mice. Serum KL-6 levels in these mice were comparable to those in humans, and KL-6 levels in BALF were significantly higher than those in sera. In the LPS model, KL-6 levels in sera and BALF were slightly increased, although SP-D levels were markedly increased. During the inflammatory phase in the BLM model, KL-6 levels in sera were greatly increased, but those in BALF were decreased. Serum KL-6 levels were positively correlated with BALF albumin levels, a representative marker for increased the alveolar-capillary permeability. SP-D levels in sera and BALF were significantly increased compared to the corresponding levels in the LPS model. The increase in serum KL-6 levels appeared to be associated with the disruption of alveolar-capillary barrier after BLM-induced lung injury. This hMUC1-exp mouse can be used for assessment of KL-6 in vivo during lung injury.

The elevation of serum napsin A in idiopathic pulmonary fibrosis, compared with KL-6, surfactant protein-A and surfactant protein-D

Background

Napsin A, an aspartic protease, is mainly expressed in alveolar type-II cells and renal proximal tubules and is a putative immunohistochemical marker for pulmonary adenocarcinomas. This study sought to determine whether napsin A could be measured in the serum to evaluate its relationship to idiopathic pulmonary fibrosis (IPF) and determine whether renal dysfunction might affect serum napsin A levels.

Methods

Serum levels of napsin A were measured in 20 patients with IPF, 34 patients with lung primary adenocarcinoma, 12 patients with kidney diseases, and 20 healthy volunteers. Surfactant protein (SP)-A, SP-D, and Krebs von den Lungen-6 (KL-6) levels in serum and pulmonary function tests were also evaluated in IPF patients.

Results

Circulating levels of napsin A were increased in patients with IPF, as compared with healthy controls, and they correlated with the severity of disease. Moreover, the serum napsin A levels were not elevated in patients with pulmonary adenocarcinoma or renal dysfunction. The distinguishing point between IPF and the controls was that the area under the receiver operating characteristic curve (ROC) of napsin A was larger than that of KL-6, SP-A, or SP-D.

Conclusion

These findings suggest that serum napsin A may be a candidate biomarker for IPF.

Pulmonary Collectins in Diagnosis and Prevention of Lung Diseases

Pulmonary surfactant is a complex mixture of lipids and proteins, and is synthesized and secreted by alveolar type II epithelial cells and bronchiolar Clara cells. It acts to keep alveoli from collapsing during the expiratory phase of the respiratory cycle. After its secretion, lung surfactant forms a lattice structure on the alveolar surface, known as tubular myelin. Surfactant proteins (SP)-A, B, C and D make up to 10% of the total surfactant. SP-B and SPC are relatively small hydrophobic proteins, and are involved in the reduction of surface-tension at the air-liquid interface. SP-A and SP-D, on the other hand, are large oligomeric, hydrophilic proteins that belong to the collagenous Ca²⁺-dependent C-type lectin family (known as “Collectins”), and play an important role in host defense and in the recycling and transport of lung surfactant (Awasthi 2010) (Fig. 43.1). In particular, there is increasing evidence that surfactant-associated proteins A and -D (SP-A and SP-D, respectively) contribute to the host defense against inhaled microorganisms (see 10.1007/978-3-7091-1065_24 and 10.1007/978-3-7091-1065_25). Based on their ability to recognize pathogens and to regulate the host defense, SP-A and SP-D have been recently categorized as “Secretory Pathogen Recognition Receptors”. While SP-A and SP-D were first identified in the lung; the expression of these proteins has also been observed at other mucosal surfaces, such as lacrimal glands, gastrointestinal mucosa, genitourinary epithelium and periodontal surfaces. SP-A is the most prominent among four proteins in the pulmonary surfactant-system. The expression of SP-A is complexly regulated on the transcriptional and the chromosomal level. SP-A is a major player in the pulmonary cytokine-network and moreover has been described to act in the pulmonary host defense. This chapter gives an overview on the understanding of role of SP-A and SP-D in for human pulmonary disorders and points out the importance for pathology-orientated research to further elucidate the role of these molecules in adult lung diseases. As an outlook, it will become an issue of pulmonary pathology which might provide promising perspectives for applications in research, diagnosis and therapy (Awasthi 2010).

Serum KL-6 and surfactant protein D in children with 2009 pandemic H1N1 influenza infection

BACKGROUND

A global pandemic influenza A (H1N1) outbreak occurred in 2009. Rapid progress of respiratory distress is one of the characteristic features of pandemic influenza A (H1N1) infection. The physiologic mechanism causing hypoxia in pandemic influenza A (H1N1) infection, however, has not been elucidated.

METHODS

The serum levels of KL-6 and surfactant protein D (SP-D) were evaluated in 21 cases of pandemic influenza A (H1N1) infection associated with chest radiographic abnormality in order to estimate alveolar involvement. The clinical features were also analyzed.

RESULTS

All of the patients had high fever, and rapidly progressed to respiratory distress within several days of disease onset. Despite mild radiographic abnormality in these patients, dyspnea was severe and they had low blood oxygen saturation levels. Many of the patients had a history of allergic diseases including asthma. Serum KL-6 and SP-D levels on admission were 191 ± 69 U/mL and 32.6 ± 18.9 ng/mL, respectively. These two levels were still below the upper normal limit 1 week later. There were no clear relationships between specific clinical symptoms and KL-6 or SP-D levels. All patients were treated with oseltamivir and/or zanamivir, and improved without mechanical ventilation management.

CONCLUSION

KL-6 and SP-D elevation were not significant in pandemic influenza A (H1N1) infection associated with chest radiographic abnormality. In pandemic influenza A (H1N1) infection, alveolar involvement was estimated to be little, and severe respiratory distress was probably caused by obstruction of peripheral bronchi.

Serum KL-6 level and the development of bronchiolitis obliterans syndrome in lung transplant recipients

KL-6 is a glycoprotein expressed by pulmonary epithelial cells, and its serum level has been used as a marker of disease activity in a variety of respiratory illnesses. Previously, we showed that KL-6 was elevated in lung transplant recipients diagnosed with BOS. In this study, we followed serum KL-6 levels and lung functions prospectively in lung transplant recipients who were within the first five-yr post-transplant and had no evidence of BOS at the time of study entry. Mean peak KL-6 levels were 596.16 ± 309.32 U/mL in the nine recipients who developed BOS compared to 352.41 ± 140.68 in 36 recipients who did not (p = 0.05). Six of the nine patients with BOS had an absolute rise in KL-6 above baseline level >200 U/mL compared to two of the 37 who had the same increase in KL-6 but did not develop BOS. Using the 200 U/mL elevation of KL-6 from baseline as a threshold for a positive test would produce a sensitivity of 67%, specificity of 95%, PPV of 75%, and a NPV of 92%. In addition, mean KL-6 levels of patients during acute rejection were not significantly elevated compared to the prerejection mean KL-6 levels (p = 0.71). We conclude that serum KL-6 is a relatively specific marker of BOS in lung transplant recipients.

Evaluation and management of pulmonary disease in ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is a rare autosomal recessive disorder caused by mutations in the ATM gene, resulting in faulty repair of breakages in double-stranded DNA. The clinical phenotype is complex and is characterized by neurologic abnormalities, immunodeficiencies, susceptibility to malignancies, recurrent sinopulmonary infections, and cutaneous abnormalities. Lung disease is common in patients with A-T and often progresses with age and neurological decline. Diseases of the respiratory system cause significant morbidity and are a frequent cause of death in the A-T population. Lung disease in this population is thought to exhibit features of one or more of the following phenotypes: recurrent sinopulmonary infections with bronchiectasis, interstitial lung disease, and lung disease associated with neurological abnormalities. Here, we review available evidence and present expert opinion on the diagnosis, evaluation, and management of lung disease in A-T, as discussed in a recent multidisciplinary workshop. Although more data are emerging on this unique population, many recommendations are made based on similarities to other more well-studied diseases. Gaps in current knowledge and areas for future research in the field of pulmonary disease in A-T are also outlined.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

Fatal familial lung disease caused by ABCA3 deficiency without identified ABCA3 mutations

OBJECTIVE

To test the hypothesis that some functionally significant variants in the gene encoding member A3 of the ATP Binding Cassette family (ABCA3) are not detected using exon-based sequencing approaches.

STUDY DESIGN

The first of 2 female siblings who died from neonatal respiratory failure was examined for mutations with sequence analysis of all ABCA3 exons and known regulatory elements within the 5' untranslated region. Lung tissue from both siblings was immunostained for ABCA3 and examined with electron microscopy. Segregation of ABCA3 alleles was determined with analysis of polymorphisms in the parents and all children.

RESULTS

No mutations were identified with ABCA3 sequence analysis in the first affected infant. Affected siblings were concordant for their ABCA3 alleles, but discordant from those of their unaffected siblings. ABCA3 protein was not detectable with immunostaining in lung tissue samples from both affected infants. Electron microscopy demonstrated small, dense lamellar bodies, characteristically seen with ABCA3 mutations.

CONCLUSIONS

The segregation of ABCA3 alleles, absence of ABCA3 immunostaining, lung pathology, and ultrastructural findings support genetic ABCA3 deficiency as the cause of lung disease in these 2 infants, despite the lack of an identified genetic variant.

Serum markers in interstitial pneumonia with and without Pneumocystis jirovecii colonization: a prospective study

Background

In patients with chronic respiratory disease, Pneumocystis jirovecii (P. jirovecii) colonization is observed, and may influence disease progression and systemic inflammation. Pneumocystis pneumonia causes interstitial changes, so making a diagnosis of PCP in patients who have interstitial pneumonia (IP) with P. jirovecii colonization is sometimes difficult based on radiography.

Methods

This study investigated the prevalence of P. jirovecii colonization in IP patients and assessed pulmonary injury due to P. jirovecii colonization by measurement of serum markers (KL-6, SP-A, SP-D, and (1→3) β-D-glucan (β-D-glucan)) and the peripheral lymphocyte counts, prospectively. A total of 75 patients with idiopathic pulmonary fibrosis (n = 29), collagen vascular-related interstitial pneumonia (n = 19), chronic bronchitis or pneumonia (n = 20), and Pneumocystis pneumonia (n = 7) were enrolled in this prospective study. P. jirovecii DNA was detected in sputum samples, while serum markers and the lymphocyte count were measured in the peripheral blood.

Results

IP patients (idiopathic pulmonary fibrosis and collagen vascular-related IP) who received oral corticosteroids had a high prevalence of P. jirovecii colonization (23.3%). In IP patients, oral corticosteroid therapy was a significant risk factor for P. jirovecii colonization (P < 0.05). Serum markers did not show differences between IP patients with and without P. jirovecii colonization. The β-D-glucan level and lymphocyte count differed between patients with Pneumocystis pneumonia or P. jirovecii colonization.

Conclusion

Serum levels of KL-6, SP-A, SP-D, and β-D-glucan were not useful for detecting P. jirovecii colonization in IP patients. However, the serum β-D-glucan level and lymphocyte count were useful for distinguishing P. jirovecii colonization from pneumocystis pneumonia in IP patients.

Juvenile dermatomyositis: clinical characteristics and the relatively high risk of interstitial lung disease

To clarify the clinical features of juvenile dermatomyositis (JDM) in Japanese cases, we retrospectively evaluated the characteristics of 16 children with JDM that were treated at Saitama Children's Medical Center between 1985 and 2004. The age at disease onset ranged from 3.5 to 14.1 years old (7 boys, mean age 7.9 years; 9 girls, mean age 9.2 years). In 14 patients more than two muscle enzymes were elevated at diagnosis. The antinuclear antibody at diagnosis was positive in all girls but one, while it was positive in only two boys (2/7; P<0.01). Three patients were complicated with interstitial lung disease (ILD) (18.8%) and their serum KL-6 levels were already elevated on admission. Our findings suggest that serum KL-6 levels seemed to be sensitive to the detection of ILD in an early phase, and the relatively high frequency of JDM-associated ILD indicated that a careful evaluation of the lungs was therefore required in any individuals with JDM. Of 16 patients, two boys showed a favorable improvement and prognosis without relapse for over 9 years after the termination of treatment. Overall, in girls, there is a tendency to be a delay in the diagnosis/treatment for JDM, and this disease also demonstrated a severe course.

Circulating surfactant protein D as a potential lung-specific biomarker of health outcomes in COPD: a pilot study

BACKGROUND

There is a paucity of surrogate lung-specific biological markers that can be used to track disease progression and predict clinical outcomes in chronic obstructive pulmonary disease (COPD). The principal aim of this pilot study was to determine whether circulating surfactant protein D (SPD) or Clara Cell protein-16 (CC16) levels are associated with lung function or health status in patients with severe COPD.

METHODS

We studied 23 patients with advanced COPD. Lung function measurements, Chronic Respiratory Disease Questionnaire (CRQ) scores, and serum levels of SPD, CC16, and C-reactive protein (CRP) were determined at baseline and at 3 months.

RESULTS

At baseline, FEV(1) was inversely associated with serum SPD levels (P = 0.045) but not with CC16 (P = 0.675) or CRP levels (P = 0.549). Over a 3 month period, changes in SPD levels correlated significantly with changes in CRQ scores (adjusted P = 0.008) such that patients who had the largest declines in serum SPD levels experienced the largest gains in health status. The association was particularly notable between circulating SPD level and the dyspnea domain of the CRQ score (P = 0.018). Changes in CC16 or CRP levels did not correlate with changes in CRQ scores.

CONCLUSION

Changes in serum SPD levels tracked well with changes in health status over a 3 month period in patients with severe COPD. These data suggest that circulating SPD levels may be useful biomarkers to track health outcomes of COPD patients.

Immunohistochemical distribution of SP-D, compared with that of SP-A and KL-6, in interstitial pneumonias

The immunohistochemical distribution of SP-D was compared with that of SP-A and KL-6 using a monoclonal antibody in lung tissues of 15 cases of collagen vascular disease-associated interstitial pneumonia (CVD-IP), 4 cases of hypersensitivity pneumonitis (CHP), and 6 cases of other diseases to determine their differences in distribution. In this study, the main targets were alveolar epithelial cells, especially those in the regenerating stage, as well as lymph vessels and stroma. The cytoplasm of type II alveolar epithelial cells and Clara cells was positive for SP-D, with sharp margins; interestingly, however, during the process of regeneration large positive cells were intermingled with relatively small negative cells, even in the same row of cells. In sharp contrast, staining for SP-A and KL-6 was positive in the cytoplasm of all the regenerating alveolar epithelial cells, as well as Clara cells. Staining for KL-6 was usually positive in the surface of air spaces in linear fashion. Staining for SP-A was also positive in elastic fibers in vascular walls. In areas of destruction of pulmonary structures, loose stroma and the endothelial cells of lymph vessels as well as their contents were distinctly positive for SP-A and/or KL-6 but not SP-D. Judging from these results in pulmonary tissues of CVD-IP and HP, SP-D might be a marker for maturity of regenerating epithelial cells. Both SP-A and KL-6 were detected in intimate relationship to the stage of regeneration of alveolar epithelial cells and were expressed before SP-D. In addition, the lymph vessels play a very important role in transfer of KL-6 into the bloodstream.

Plasma KL-6 predicts the development and outcome of bronchopulmonary dysplasia

Circulating KL-6 is a specific indicator of pulmonary injury affecting the alveolar epithelium and interstitium. Our preliminary study suggested the usefulness of plasma KL-6 as a marker of bronchopulmonary dysplasia (BPD). To confirm the diagnostic value of KL-6 for BPD as well as to determine the reference range, we conducted a larger prospective study in 135 preterm infants <32 wk GA. Among the infants without oxygen dependence at a postconceptional age of 36 wk, the plasma KL-6 level showed no significant association with GA at any time. Among 42 infants <28 wk GA, plasma KL-6 levels were significantly higher in those with moderate/severe BPD compared with those with no/mild BPD. A plasma level of 199 U/mL at 1 wk or 232 U/mL at 2 wk was an excellent predictor of moderate/severe BPD <28 wk GA (positive predictive value of 83% and 80%, respectively). Unlike nonspecific markers of inflammation or fibrosis, KL-6 objectively reflects the severity of pulmonary injury irrespective of the treatment or the radiographic changes. Therefore, not only as a good marker, measurement of KL-6 may also help to provide new insights into the pathogenesis of BPD.

Serum KL-6 as a Marker for Bronchiolitis Obliterans Syndrome after Lung Transplantation

Bronchiolitis obliterans (BO) is the pathologic manifestation of chronic allograft rejection in lung transplant recipients and specific diagnosis requires invasive tests. BO causes progressive obstruction of the small airways. The term bronchiolitis obliterans syndrome (BOS) is a clinical surrogate for the histopathologic diagnosis of BO and is measured by lung function testing. KL-6 is a glycoprotein expressed on pulmonary epithelial cells and it is present in the serum of normal individuals in small amounts. Serum KL-6 has been shown to be a useful marker of disease activity in interstitial lung diseases. We demonstrated that serum levels of KL-6 are elevated in lung transplant recipients with BOS when compared with those without BOS and healthy controls. Our results indicate that serum KL-6 measurement has the potential to serve as a noninvasive diagnostic test for the detection of BO in lung transplant recipients.

Surfactant protein D in human lung diseases

The lung is continuously exposed to inhaled pollutants, microbes and allergens. Therefore, the pulmonary immune system has to defend against harmful pathogens, while an inappropriate inflammatory response to harmless particles must be avoided. In the bronchoalveolar space this critical balance is maintained by innate immune proteins, termed surfactant proteins. Among these, surfactant protein D (SP-D) plays a central role in the pulmonary host defence and the modulation of allergic responses. Several human lung diseases are characterized by decreased levels of bronchoalveolar SP-D. Thus, recombinant SP-D has been proposed as a therapeutical option for cystic fibrosis, neonatal lung disease and smoking-induced emphysema. Furthermore, SP-D serum levels can be used as disease activity markers for interstitial lung diseases. This review illustrates the emerging role of SP-D translated from in vitro studies to human lung diseases.

The role of serum KL-6 measurement in common pediatric respiratory infections

KL-6 is a useful marker for interstitial pneumonia of various origins. However, the role of KL-6 in common pediatric respiratory infections is largely unknown. In order to determine whether the KL-6 level is elevated during respiratory infection, and whether KL-6 is a useful biomarker for the disease activity, we evaluated serum KL-6 levels in 132 children with various respiratory infections. KL-6 levels were significantly higher in patients with measles, influenza, or respiratory syncytial virus infection than in the control subjects. On the other hand, KL-6 levels in patients with bacterial infections such as mycoplasma, chlamydia, or pertussis were comparable to the control values. In patients with viral infections, high KL-6 levels, as defined by the mean plus 2 standard deviations of the control group, significantly correlated with low SpO(2) or days of O(2) administration, but did not correlate with C-reactive protein or white blood cell counts. These results indicate that measurement of serum KL-6 levels is helpful for the management of common pediatric respiratory infections.

Serum biomarkers in interstitial lung diseases

The use of biomarkers in medicine lies in their ability to detect disease and support diagnostic and therapeutic decisions. New research and novel understanding of the molecular basis of the disease reveals an abundance of exciting new biomarkers who present a promise for use in the everyday clinical practice. The past fifteen years have seen the emergence of numerous clinical applications of several new molecules as biologic markers in the research field relevant to interstitial lung diseases (translational research). The scope of this review is to summarize the current state of knowledge about serum biomarkers in interstitial lung diseases and their potential value as prognostic and diagnostic tools and present some of the future perspectives and challenges.