Safety of Radiation Therapy for Treatment of Malignancy in Patients with Inflammatory Bowel Disease

PURPOSE/OBJECTIVE(S)

Inflammatory bowel disease (IBD) has been considered a relative contraindication to radiation therapy (RT) due to the potential greater risk of RT-induced toxicities, however, there is limited toxicity data using modern RT techniques. This study aims to assess toxicity outcomes in patients with IBD treated with abdominal or pelvic RT.

MATERIALS/METHODS

After institutional review board approval, patients with IBD who received RT to the abdomen or pelvis were filtered from an institutional research repository and their electronic medical records were reviewed. Acute toxicity was defined as that occurring within 3 months of RT. Toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0. Univariable Cox proportional hazards regression was used to assess rates of grade ≥2 toxicity-free survival.

RESULTS

We identified 62 patients with median age of 69 years (interquartile range [IQR] 62-77) who received RT from 2006-2022. Median follow up was 15 months (IQR 4-33). Most patients were male (42; 68%) and had a diagnosis of ulcerative colitis (44; 71%). The most common primary malignancy was colorectal/anal (26; 42%). Intensity-modulated RT (IMRT) was most frequently used (38; 61%) followed by 3-dimensional conformal RT (3D-CRT) (12; 19%) and stereotactic body RT (SBRT)/brachytherapy (12; 19%). For IMRT/3D-CRT, median dose delivered was 50 Gy (IQR 49-59) in 25 fractions (IQR 25-30), and median maximum dose (Dmax) to bowel was 48 Gy (IQR 43-52); whereas for SBRT/brachytherapy, the median dose was 32 Gy (IQR 27-40) in 3 fractions (IQR 2-5) and median bowel Dmax was 32 Gy (IQR 20-37). The median biologically effective dose delivered with an assumed alpha/beta ratio of 10 (BED10) across all RT modalities was 63 Gy (IQR 60-72). After initiation of RT, 31 patients (50%) and 14 patients (23%) experienced grade ≥2 acute and late toxicity, respectively. Thirteen patients (21%) and 7 patients (11%) experienced grade 3 acute and late toxicity, respectively. No patients experienced grade >3 toxicity. Acute toxicity resulted in interruption to RT for 5 patients (8%), 2 of which did not resume RT. Four patients (6%) required adjustment to chemotherapy or IBD medication dosage as a result of their acute toxicity. Median time from RT start to acute toxicity onset was 41 days (IQR 32-46), whereas median time to onset of late toxicity was 9 months (IQR 5-15). The most common acute and late toxicities were diarrhea (21; 34%) and bowel obstruction/perforation/fistula (4; 6%), respectively. Rates of grade ≥2 toxicity-free survival overtime were not significantly associated with IBD status (active vs quiescent), delivered BED10, or bowel Dmax BED3.

CONCLUSION

In patients with IBD treated with abdominal or pelvic RT for malignancy, RT was feasible with acceptable rates of toxicity and active versus quiescent IBD status did not impact toxicity outcomes. Future research is needed to elucidate specific dose constraints when treating patients with IBD.

Impact of Employment and Insurance Status on Hope Among Patients Treated within Radiation Oncology

PURPOSE/OBJECTIVE(S)

Hope is important in serious illnesses including cancer, as it has been linked to patient well-being and quality of life. We assessed hope among patients seen in radiation oncology and aimed to determine associated socioeconomic and disease factors. We hypothesized that patients who may have less resources to cope with their illness would have lower hope scores.

MATERIALS/METHODS

The Adult Dispositional Hope Scale (AHS) is a questionnaire that aims to measures an individual's determination to accomplish goals and planning strategies to accomplish goals. We prospectively collected AHS survey scores from patients with benign or malignant disease seen in 2 radiation oncology clinics at our institution from 10/2022 to 1/2023. The AHS survey contains 12 items to measure hope through two qualities: agency (goal-directed energy) and pathways (plan to meet goals). Each item is answered using an 8-point scale. There are 4 items each for the Agency and Pathway subscales with 4 filler items for total scores ranging from 8 to 64, with higher scores reflecting higher agency and pathways thinking. Kruskal-Wallis H test and Kendall's Tau Rank Correlation were used to determine differences between categorical and continuous variables on AHS scores, respectively.

RESULTS

We included 228 patients with a median age of 62 years (range 16.9-92.6). Half were male (51%), 56% were white, and 77% had malignant disease. The primary disease subsite was CNS, GI and other in 76 (34%), 70 (31%), and 81 (36%) patients, respectively. Of patients with known occupation and insurance information, 32 (14%), 67 (29%), and 49 (22%) were not employed, employed, and retired, respectively, and 115 (50%), 85 (37%), and 20 (9%) had private insurance, Medicare, and Medical, respectively. Median agency, pathway, and total hope scores were 27 (interquartile range [IQR] 24-29), 28 (IQR 24-30), and 55 (IQR 48-58), respectively. Higher total hope scores were associated with being employed (p = 0.02), having private insurance (p<0.02), and higher ECOG scores (p<0.01). After excluding those who are not employed because they are retired (n = 99), lack of employment was significantly associated with hope (p<0.01). Characteristics such as race/ethnicity, gender, marital status, pain, symptoms from disease, malignant or benign disease, stage of disease, and treatment modalities were not associated with AHS scores.

CONCLUSION

In our study, patients with non-private insurance and being currently unemployed had lower AHS scores. The lower hope scores suggest that these patients may have fewer resources to cope with their treatments and diagnoses and may benefit from further inquiry about the need to mitigate cancer-related financial burden to improve hope levels. Further studies are needed to evaluate whether financial toxicity, which has been shown to negatively impact patient outcomes, is correlated to coping and hope.

Investigating Dosimetry and Imaging Biomarkers for Prediction of Major Adverse Cardiac Events Following Locally Advanced Non-Small Cell Lung Cancer Radiotherapy

PURPOSE/OBJECTIVE(S)

Thoracic radiotherapy (RT) may confer major adverse cardiac events (MACE) following treatment. Mean heart dose positively associates with MACE and recent studies show cardiac substructure dosimetry improves MACE prediction. Use of imaging biomarkers with cardiac substructure dose has not been studied for prediction of MACE. We sought to develop an integrated model for cardiac substructure dose and baseline coronary artery calcium (CAC) scoring and establish its relationship to MACE.

MATERIALS/METHODS

A retrospective cohort analysis was performed of consecutive patients with locally advanced non-small cell lung cancer (NSCLC) treated with definitive RT from 2006-2018 at a single institution. Demographics, medical history, cardiac events, and treatments received were recorded. Cardiac substructures were contoured, including the left descending artery (LAD), left main coronary artery (LMCA), left circumflex (LCX), right coronary artery (RCA), TotalLeft (LAD+LMCA+LCX), and TotalCor (TotalLeft+RCA). Doses were measured in 2 Gy equivalent dose. CAC was scored by visual assessment and compared to established automated Agatston scoring. Primary endpoint was MACE incidence. Receiver operating characteristic (ROC) curves assessed dose and CAC metric model performance. Threshold modeling was conducted using the log rank statistic with 95% confidence intervals measured using bootstrap resampling with 1000 iterations. Competing risk models adjusted for death were used to measure cumulative incidence of MACE as well as in univariable and multivariable risk regression modeling. Pearson correlations were used to validate CAC scoring. P-values were two tailed and considered significant at P≤0.05.

RESULTS

Of 233 eligible patients, 61.4% were male with a 68.1 years (range 34.9-90.7) median age. Median follow-up was 73.7 months (range 1.6-153.9). Median overall survival was 34.8 months. Following RT, 22.3% experienced at least one cardiac event at a median time of 21.5 months (range 1.7-118.9). Visual CAC scoring showed significant correlation with automated Agatston scoring (r = 0.72, P=1e-5). While left sided coronary arteries (TotalLeft), mean heart dose (MHD) and CAC scores individually predicted for MACE (AUC = 0.56-0.59), a multivariable model of TotalLeft CAC had the highest ROC analysis performance (AUC = 0.69). On univariable and multivariable competing risk regression analyses, TotalLeft V15 Gy >2.53 cc and CAC score >5 independently associated with MACE (P<0.05). A model incorporating age, TotalLeft CAC>5 and V15>2.53cc, showed incrementally higher MACE incidences for low (9.3%), intermediate (18.4%), and high-risk groups (27.7%) (P<0.01).

CONCLUSION

RT-induced MACE occurs in >20% of those undergoing thoracic RT in a median time of <2 years. We validate significant associations between TotalLeft RT dose and MACE and establish CAC as a predictive risk factor. These findings may serve to inform personalized RT and future cardiac risk in locally advanced NSCLC.

Detection of diagnostic and prognostic methylation-based signatures in liquid biopsy specimens from patients with meningiomas

Recurrence of meningiomas is unpredictable by current invasive methods based on surgically removed specimens. Identification of patients likely to recur using noninvasive approaches could inform treatment strategy, whether intervention or monitoring. In this study, we analyze the DNA methylation levels in blood (serum and plasma) and tissue samples from 155 meningioma patients, compared to other central nervous system tumor and non-tumor entities. We discover DNA methylation markers unique to meningiomas and use artificial intelligence to create accurate and universal models for identifying and predicting meningioma recurrence, using either blood or tissue samples. Here we show that liquid biopsy is a potential noninvasive and reliable tool for diagnosing and predicting outcomes in meningioma patients. This approach can improve personalized management strategies for these patients.

Consensus core clinical data elements for meningiomas

BACKGROUND

With increasing molecular analyses of meningiomas, there is a need to harmonize language used to capture clinical data across centers to ensure that molecular alterations are appropriately linked to clinical variables of interest. Here the International Consortium on Meningiomas presents a set of core and supplemental meningioma-specific Common Data Elements (CDEs) to facilitate comparative and pooled analyses.

METHODS

The generation of CDEs followed the four-phase process similar to other National Institute of Neurological Disorders and Stroke (NINDS) CDE projects: discovery, internal validation, external validation, and distribution.

RESULTS

The CDEs were organized into patient- and tumor-level modules. In total, 17 core CDEs (10 patient-level and 7-tumour-level) as well as 14 supplemental CDEs (7 patient-level and 7 tumour-level) were defined and described. These CDEs are now made publicly available for dissemination and adoption.

CONCLUSIONS

CDEs provide a framework for discussion in the neuro-oncology community that will facilitate data sharing for collaborative research projects and aid in developing a common language for comparative and pooled analyses. The meningioma-specific CDEs presented here are intended to be dynamic parameters that evolve with time and The Consortium welcomes international feedback for further refinement and implementation of these CDEs.

Dendrimer-Based Nanomedicine (Paramagnetic Nanoparticle, Nanocombretastatin, Nanocurcumin) for Glioblastoma Multiforme Imaging and Therapy

In brain tumors, delivering nanoparticles across the blood-brain tumor barrier presents a major challenge. Dual mode magnetic resonance imaging and fluorescent imaging probes have been developed where relaxation based Gd-DOTA or ParaCEST agents and a Near-Infrared (NIR) fluorescent dye, DL680 were conjugated on the surface of dendrimer. The in vivo and ex vivo imaging of the dual-modality contrast agent showed excellent potential utility for identifying the location of glioma tumors. Systemic delivery of the subsequent nano-sized agent demonstrated glioma-specific accumulation, probably due to the enhanced permeability and retention effect. The biodistribution studies revealed the G5 agents have accumulated in the glioma tumor and the liver while a G3 agent only accumulated in the brain tumor but not in the liver or kidney. Hydrophobic drug molecules like Combrestatin A4 (CA4) or curcumin have also been conjugated with dendrimers that provided high aqueous solubility with improved therapeutic effect.

Analysis of morphological characteristics of IDH-mutant/wildtype brain tumors using whole-lesion phenotype analysis

Background

Although IDH-mutant tumors aggregate to the frontotemporal regions, the clustering pattern of IDH-wildtype tumors is less clear. As voxel-based lesion-symptom mapping (VLSM) has several limitations for solid lesion mapping, a new technique, whole-lesion phenotype analysis (WLPA), is developed. We utilize WLPA to assess spatial clustering of tumors with IDH mutation from The Cancer Genome Atlas and The Cancer Imaging Archive.

Methods

The degree of tumor clustering segmented from T1 weighted images is measured to every other tumor by a function of lesion similarity to each other via the Hausdorff distance. Each tumor is ranked according to the degree to which its neighboring tumors show identical phenotypes, and through a permutation technique, significant tumors are determined. VLSM was applied through a previously described method.

Results

A total of 244 patients of mixed-grade gliomas (WHO II-IV) are analyzed, of which 150 were IDH-wildtype and 139 were glioblastomas. VLSM identifies frontal lobe regions that are more likely associated with the presence of IDH mutation but no regions where IDH-wildtype was more likely to be present. WLPA identifies both IDH-mutant and -wildtype tumors exhibit statistically significant spatial clustering.

Conclusion

WLPA may provide additional statistical power when compared with VLSM without making several potentially erroneous assumptions. WLPA identifies tumors most likely to exhibit particular phenotypes, rather than producing anatomical maps, and may be used in conjunction with VLSM to understand the relationship between tumor morphology and biologically relevant tumor phenotypes.

Rapid multicontrast brain imaging on a 0.35T MR-linac

PURPOSE

Magnetic resonance-guided radiation therapy (MRgRT) has shown great promise for localization and real-time tumor monitoring. However, to date, quantitative imaging has been limited for low field MRgRT. This work benchmarks quantitative T1, R2*, and Proton Density (PD)mapping in a phantom on a 0.35 T MR-linac and implements a novel acquisition method, STrategically Acquired Gradient Echo (STAGE). To further validate STAGE in a clinical setting, a pilot study was undertaken in a cohort of brain tumor patients to elucidate opportunities for longitudinal functional imaging with an MR-linac in the brain.

METHODS

STAGE (two triple-echo gradient echo (GRE) acquisitions) was optimized for a 0.35T low-field MR-linac. Simulations were performed to choose two flip angles to optimize signal-to-noise ratio (SNR) and T1-mapping precision. Tradeoffs between SNR, scan time, and spatial resolution for whole-brain coverage were evaluated in healthy volunteers. Data were inputted into a STAGE processing pipeline to yield four qualitative images (T1-weighted, enhanced T1-weighted, proton-density (PD) weighted, and simulated FLuid-Attenuated Inversion Recovery (sFLAIR)), and three quantitative datasets (T1, PD, and R2*). A benchmarking ISMRM/NIST phantom consisting of vials with variable NiCl₂ and MnCl₂ concentrations was scanned using variable flip angles (VFA) (2-60 degrees) and inversion recovery (IR) methods at 0.35 T. STAGE and VFA T1 values of vials were compared to IR T1 values. As measures of agreement with reference values and repeatability, relative error (RE) and coefficient of variability (CV) were calculated, respectively, for quantitative MR values within the phantom vials (spheres). To demonstrate feasibility, longitudinal STAGE data (pretreatment, weekly, and ~ 2 months post-treatment) were acquired in an IRB-approved pilot study of brain tumor cases via the generation of temporal and differential quantitative MRI maps.

RESULTS

In the phantom, RE of measured VFA T1 and STAGE relative to IR reference values were 7.0 ± 2.5% and 9.5 ± 2.2% respectively. RE for the PD vials was 8.1 ± 6.8% and CV for phantom R2* measurements was 10.1 ± 9.9%. Simulations and volunteer experiments yielded final STAGE parameters of FA = 50°/10°, 1 × 1 × 3 mm³ resolution, TR = 40 ms, TE = 5/20/34 ms in 10 min (64 slices). In the pilot study of brain tumor patients, differential maps for R2* and T1 maps were sensitive to local tumor changes and appeared similar to 3 T follow-up MRI datasets.

CONCLUSION

Quantitative T1, R2*, and PD mapping are promising at 0.35 T agreeing well with reference data. STAGE phantom data offer quantitative representations comparable to traditional methods in a fraction of the acquisition time. Initial feasibility of implementing STAGE at 0.35 T in a patient brain tumor cohort suggests that detectable changes can be observed over time. With confirmation in a larger cohort, results may be implemented to identify areas of recurrence and facilitate adaptive radiation therapy.

Developing Real-world Evidence-Ready Datasets: Time for Clinician Engagement

PURPOSE OF REVIEW

Real-world data (RWD) applications in healthcare that support learning health systems and pragmatic clinical trials are gaining momentum, largely due to legislation supporting real-world evidence (RWE) for drug approvals. Clinical notes are thought to be the cornerstone of RWD applications, particularly for conditions with limited effective treatments, extrapolation of treatments from other conditions, or heterogenous disease biology and clinical phenotypes.

RECENT FINDINGS

Here, we discuss current issues in applying RWD captured at the point-of-care and provide a framework for clinicians to engage in RWD collection. To achieve clinically meaningful results, RWD must be reliably captured using consistent terminology in the description of our patients. RWD complements traditional clinical trials and research by informing the generalizability of results, generating new hypotheses, and creating a large data network for scientific discovery. Effective clinician engagement in the development of RWD applications is necessary for continued progress in the field.

The Vital Role of Pathology in Improving Reproducibility and Translational Relevance of Aging Studies in Rodents

Pathology is a discipline of medicine that adds great benefit to aging studies of rodents by integrating in vivo, biochemical, and molecular data. It is not possible to diagnose systemic illness, comorbidities, and proximate causes of death in aging studies without the morphologic context provided by histopathology. To date, many rodent aging studies do not utilize end points supported by systematic necropsy and histopathology, which leaves studies incomplete, contradictory, and difficult to interpret. As in traditional toxicity studies, if the effect of a drug, dietary treatment, or altered gene expression on aging is to be studied, systematic pathology analysis must be included to determine the causes of age-related illness, moribundity, and death. In this Commentary, the authors discuss the factors that should be considered in the design of aging studies in mice, with the inclusion of robust pathology practices modified after those developed by toxicologic and discovery research pathologists. Investigators in the field of aging must consider the use of histopathology in their rodent aging studies in this era of integrative and preclinical geriatric science (geroscience).

Cause-of-Death Analysis in Rodent Aging Studies

In research studies using rats or mice, the cause of death is often not evaluated or reported. An analysis of the causes of death is particularly valuable for aging and carcinogenesis studies. Comparing causes of death among the study groups is often an important adjunct to the biochemical, molecular, clinical, and histopathologic findings. The methods for evaluating causes of death, contributing causes of death, and comorbidities have been suggested in several publications. Surprisingly, in important mouse aging studies, causes of death are often not reported. Cause-of-death assignment in preclinical rodent model aging research suffers from a lack of a standardized approach and an understanding of the value that it can add to longevity and interventional studies. While assigning single cause of death may facilitate data analysis, defining and publishing data on contributing causes (comorbidities) provides more information on associated underlying chronic conditions and health span in mouse models. This article reviews factors that affect determination of cause of death and the methods for evaluating causes of death and comorbidities. The proposed systematic pathology analysis includes assigning cause of death and comorbidities to define total disease burden. The combination of pathology with in vivo data will fully characterize the effect of tested interventions on multiple chronic diseases and health span of aging mice with improved translation to human aging and age-associated lesions.

Early-life co-administration of cockroach allergen and endotoxin augments pulmonary and systemic responses

BACKGROUND

Environmental exposures to cockroach allergen and endotoxin are recognized epidemiological risk factors for the early development of allergies and asthma in children. Because of this, it is important to examine the role of early-life concurrent inhalation exposures to cockroach allergen and endotoxin in the pathogenesis of allergic airways disease.

OBJECTIVE

We examined the effects of repeated concomitant endotoxin and cockroach allergen inhalation on the pulmonary and systemic immune responses of newborn and juvenile mice.

METHODS

C3H/HeBFeJ mice were exposed to inhaled endotoxin and cockroach allergen via intranasal instillation from day 2 to 21 after birth, and systemic and pulmonary responses were examined in serum, bronchoalveolar lavage fluid, and lung tissue.

RESULTS

Cockroach allergen exposures induced pulmonary eosinophilic inflammation, total and allergen-specific IgE, IgG(1), and IgG(2a) production, and alveolar remodelling. Co-exposures with endotoxin and cockroach allergen significantly increased serum IgE and IgG(1), lung inflammation, and alveolar wall thickness, and decreased airspace volume density. Importantly, compared with exposures with individual substances, the responses to co-exposures were more than additive.

CONCLUSIONS

Repeated inhalation exposures of neonatal and juvenile mice to endotoxin and cockroach allergen increased the pulmonary inflammatory and systemic immune responses in a synergistic manner and enhanced alveolar remodelling in the developing lung. These data underscore the importance of evaluating the effect of multiple, concurrent environmental exposures, and of using an experimental model that incorporates clinically relevant timing and route of exposures.

Secondary intracranial neoplasia in the dog: 177 cases (1986-2003)

BACKGROUND

This study investigates the frequency, location, and clinical findings associated with 177 secondary brain tumors in dogs.

HYPOTHESIS

Secondary intracranial neoplasia is more common than primary intracranial neoplasia in dogs during the time period studied, and hemangiosarcoma (HSA) is the most common secondary intracranial tumor.

ANIMALS

One hundred and seventy-seven client-owned dogs presented to the Matthew J. Ryan Veterinary Hospital between 1986 and 2003.

METHODS

Medical records were searched for a diagnosis of intracranial neoplasia in dogs who underwent complete postmortem examination. Of these dogs, those with a diagnosis of primary intracranial neoplasia were excluded.

RESULTS

Of the 177 secondary brain tumors, 51 (29%) were HSAs, 44 (25%) were pituitary tumors, 21 (12%) were lymphosarcomas, and 21 (12%) were metastatic carcinomas. The average age at diagnosis was 9.6 +/- 3.0 years. Most tumors were located in the cerebrum, and a mentation change was the most common presenting clinical sign. On postmortem examination, the same tumor that was in the brain was also present in the lung in 84 cases (47%), in the kidney in 62 cases (35%), and in the heart in 55 cases (31%).

CONCLUSIONS AND CLINICAL IMPORTANCE

Secondary intracranial neoplasia in dogs was more common than primary intracranial neoplasia during the time period studied. Many of these dogs had related disease in other body systems that was apparent on diagnostic tests such as thoracic radiography.

Effects of surfactant protein A and NaCl concentration on the uptake of Pseudomonas aeruginosa by THP-1 cells

In the present study, we characterized a model system in which we examined the effects of human surfactant protein A (SP-A) on the uptake of a common human pulmonary pathogen, Pseudomonas aeruginosa, by a human monocytic/macrophage cell line, THP-1 cells. We found that SP-A significantly increases uptake of the bacteria in a dose-dependent manner. Bacterial uptake was temperature-dependent, because an effect of SP-A on bacterial uptake was observed at 37 degrees C and not at 4 degrees C. The continued presence of SP-A during the period when the bacteria and THP-1 cells were co-incubated was necessary for enhanced uptake. Pre-incubation of the bacteria or THP-1 cells with SP-A, followed by washing, abolished the effect of SP-A on bacterial uptake. The effect of SP-A could be inhibited by high concentrations of mannose, but was not affected by the removal or addition of lipopolysaccharide (LPS). Finally, we observed that the SP-A-mediated increase in uptake of P. aeruginosa by THP-1 cells was optimal in a narrow (100 mM and 150 mM) range of NaCl concentrations. We conclude that SP-A enhances the THP-1 cell-mediated uptake of P. aeruginosa in a manner dependent on temperature, the concentration of SP-A, and the concentration of NaCl.

VEGF induces airway epithelial cell proliferation in human fetal lung in vitro

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen involved in normal and abnormal angiogenesis. VEGF mRNA and protein are abundant in distal epithelium of midtrimester human fetal lung. In the present study, we identified immunoreactivity for KDR, a major VEGF-specific receptor, in distal lung epithelial cells of human fetal lung tissue, suggesting a possible autocrine or paracrine regulatory role for VEGF in pulmonary epithelial cell growth and differentiation. Addition of exogenous VEGF to human fetal lung explants resulted in increased epithelium volume density and lumen volume density in the tissues, both morphometric parameters of tissue differentiation. Cellular proliferation demonstrated by bromodeoxyuridine uptake was prominent in distal airway epithelial cells and increased in the VEGF-treated explants. VEGF-treated explants also demonstrated increased surfactant protein (SP) A mRNA, SP-C mRNA, and SP-A protein levels compared with controls. However, SP-B mRNA levels were unaffected by VEGF treatment. [(3)H]choline incorporation into total phosphatidylcholine was increased by VEGF treatment, but incorporation into disaturated phosphatidylcholine was not affected by exogenous VEGF. Based on these observations, we conclude that VEGF may be an important autocrine growth factor for distal airway epithelial cells in the developing human lung.

In situ hybridization of SP-A mRNA in adult human conducting airways

In our study, surfactant protein (SP)-A was characterized in adult human trachea and bronchi. SP-A mRNA and protein were localized to serous cells in submucosal gland by in situ hybridization and immunohistochemistry, respectively. A 2.2 kb SP-A mRNA transcript was detected in tracheal tissues by Northern blot analysis. Primer extension analysis and gene-specific reverse transcriptase polymerase chain reaction (RT-PCR) revealed the predominance of SP-A2 mRNA. However, using nested PCR, we also detected low amounts of SP-A1 mRNA in the tracheal tissues. A approximately 35 kDa SP-A immunoreactive protein was detected in the tracheal tissues by immunoblot analysis and was shown to be modified by the addition of N-linked oligosaccharides. We conclude that submucosal glands in the conducting airways produce a novel SP-A protein with a molecular weight and post-translational modification similar to the SP-A produced in the distal lung. We speculate that this SP-A2 protein, like other serous secretions from airway submucosal glands, functions in local antimicrobial host defense mechanisms in the conducting airways.

Surfactant protein A (SP-A): the alveolus and beyond

Surfactant protein A (SP-A) is the major protein component of pulmonary surfactant, a material secreted by the alveolar type II cell that reduces surface tension at the alveolar air-liquid interface. The function of SP-A in the alveolus is to facilitate the surface tension-lowering properties of surfactant phospholipids, regulate surfactant phospholipid synthesis, secretion, and recycling, and counteract the inhibitory effects of plasma proteins released during lung injury on surfactant function. It has also been shown that SP-A modulates host response to microbes and particulates at the level of the alveolus. More recently, several investigators have reported that pulmonary surfactant phospholipids and SP-A are present in nonalveolar pulmonary sites as well as in other organs of the body. We describe the structure and possible functions of alveolar SP-A as well as the sites of extra-alveolar SP-A expression and the possible functions of SP-A in these sites.

Mice bearing deletions of retinoic acid receptors demonstrate reduced lung elastin and alveolar numbers

In mammals, including rats and mice, the development of pulmonary alveolar septa is primarily limited to late gestation and the early periods of postnatal life. Before this time, the rat lung contains a relatively large supply of endogenous retinyl ester that, together with its metabolite retinoic acid, has been shown to increase elastin gene expression and the number of alveoli. We have hypothesized that mice bearing a deletion of one or more genes encoding for retinoic acid receptors (which are DNA binding proteins that alter transcription of retinoic acid-responsive genes) may demonstrate abnormalities in retinoid-mediated alveolar formation. Our studies demonstrate that the absence of the retinoic acid receptor-gamma (RARgamma) is associated with a decrease in the steady-state level of tropoelastin messenger RNA in a subpopulation of lung fibroblasts at Postnatal Day 12. RARgamma gene deletion also resulted in a decrease in whole lung elastic tissue and alveolar number, and an increase in mean cord length of alveoli (L(m)) at Postnatal Day 28. The additional deletion of one retinoid X receptor (RXR)alpha allele resulted in a decrease in alveolar surface area and alveolar number, and an increase in L (m). These data indicate that RARgamma is required for the formation of normal alveoli and alveolar elastic fibers in the mouse, and that RAR/RXR heterodimers are involved in alveolar morphogenesis.

Antisense inhibition of epidermal growth factor receptor decreases expression of human surfactant protein A

Epidermal growth factor (EGF) stimulates surfactant protein A (SP-A) synthesis in fetal lung tissue through ligand binding to the EGF receptor. We hypothesized that inhibition of EGF receptor messenger RNA (mRNA) would block SP-A expression in human fetal lung tissue during alveolar type II cell differentiation in vitro. Midtrimester human fetal lung explants were maintained in serum-free Waymouth's medium for 3 to 5 d in the presence or absence of an antisense 18-mer phosphorothioate oligonucleotide (ON) complementary to the initiation codon region of EGF receptor mRNA. Sense and scrambled ONs similarly modified were used as additional controls. The concentration of EGF receptor mRNA was semiquantitatively determined by reverse transcriptase/polymerase chain reaction (RT-PCR). We found a significant 3-fold decrease in EGF receptor mRNA levels in the antisense-treated groups compared with the control group with no effect in the sense condition. Immunohistochemical staining revealed a decrease in the amount of staining for EGF receptor protein in distal pulmonary epithelial cells in the antisense-treated groups compared with either control or sense conditions. Treatment with antisense EGF receptor ON decreased both SP-A mRNA and protein compared with controls with no effect in the sense condition. The ONs did not affect tissue viability as measured by the release of lactate dehydrogenase. We conclude that selective degradation of EGF receptor mRNA with antisense ON treatment results in a decrease in SP-A expression in human fetal lung. These findings support the critical importance of the EGF receptor for the regulation of SP-A gene expression during human alveolar type II cell differentiation.

Neuregulin-1 and human epidermal growth factor receptors 2 and 3 play a role in human lung development in vitro

The human epidermal growth factor receptor (HER) family consists of four distinct receptors: HER1 (epidermal growth factor receptor), HER2, HER3, and HER4. Their specific activating ligands are collectively known as neuregulins (NRG). We hypothesized that one member of the NRG family, NRG-1, and the HER family would play a role in fetal lung development. To test this hypothesis, we defined NRG-1 and HER gene expression in mid-trimester human fetal lung tissue. HER2 and HER3 messenger RNA and protein were detected in the fetal lung, but HER4 expression was not detected. Immunohistochemical staining of fetal lung tissue localized HER2 and HER3 protein to the developing lung epithelium. NRG-1 expression was not found in freshly isolated human fetal lung, but it was observed in fetal lung explants after 2 d of explant culture. Immunohistochemistry of cultured human fetal lung explants revealed that NRG-1 protein was also expressed in pulmonary epithelial cells. Exposing human fetal lung to recombinant NRG-1 activated the HER receptor complex as measured by approximately 4-fold increases in receptor phosphotyrosine content. In addition, NRG-1 increased explant epithelial cell volume density approximately 2-fold (P < 0. 03); increased epithelial cell proliferation approximately 2-fold, as determined by bromodeoxyuridine labeling (P = 0.002); and reduced surfactant protein-A (SP-A) levels by 53% (P < 0.05). These data are consistent with an autocrine regulatory process mediated by NRG-1 activation of HER2/HER3 heterodimers expressed on developing human fetal lung epithelial cells. Receptor activation results in increased lung epithelial cell proliferation and volume density, and decreased SP-A production, a marker of type II pneumocyte differentiation.

Surfactant protein A in rabbit sinus and middle ear mucosa

In the present study, pulmonary surfactant protein A (SP-A) messenger RNA (mRNA) and protein were characterized in adult rabbit middle ear and maxillary sinus. Fifteen adult rabbits were used for the study: 6 with evidence of acute middle ear infections and maxillary sinusitis, 6 with infections that were successfully treated with tetracycline, and 3 that were pathogen-free. We detected SP-A mRNA in maxillary sinus and middle ear tissues by Northern blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR). The RT-PCR also revealed the presence of SP-B and SP-C mRNA in middle ear and sinus tissues. We detected SP-A protein, of molecular weight approximately 29 and 70 kd, in middle ear and sinus tissues by immunoblot analysis. Unlike the SP-A protein present in the lung, the molecular weight of the SP-A protein present in the middle ear and paranasal sinus was not altered by digestion with an enzyme that cleaves N-linked carbohydrates. Immunostaining and in situ hybridization showed that SP-A protein and mRNA, respectively, were present in surface epithelial cells of the middle ear and in epithelial cells of submucosal glands in sinus tissues. These data provide the first evidence of the presence of pulmonary surfactant proteins in the paranasal sinuses and confirm previous reports of SP-A in the middle ear epithelium.

Vascular endothelial growth factor gene expression in human fetal lung in vitro

Neonatal respiratory function depends on the development of a well-formed pulmonary capillary bed. Vascular endothelial growth factor (VEGF) is a potent inducer of endothelial cell growth and angiogenesis. High levels of VEGF protein and messenger RNA (mRNA) have been detected in the developing lung, suggesting that VEGF plays a role in the development of the pulmonary capillary bed. To begin to understand the role of VEGF in human lung development, we explored the regulation of VEGF gene expression and the localization of VEGF protein and mRNA in a model of the developing human lung. VEGF protein and mRNA were detected in midtrimester human fetal lung tissue, and their levels increased with time in explant culture. VEGF protein and mRNA were increased by the maintenance of human fetal lung explants in 2% O2 environments compared with 20% O2 environments. VEGF mRNA levels were found to be increased by cyclic adenosine monophosphate (cAMP) in explants that were incubated in 20% O2, but not in those incubated in 2% O2. Immunostaining for VEGF protein demonstrated localization primarily in airway epithelial cells in midtrimester human fetal lung tissue. Immunostaining for VEGF increased with incubation of human fetal lung explants in 2% and 20% O2. Interestingly, VEGF protein was localized primarily in the basement membrane subjacent to airway epithelial cells after 4 d of incubation in 20% O2. Incubation of tissues in the presence of dibutyryl cAMP resulted in an increase in immunostaining for VEGF, primarily in the basement membranes of prealveolar ducts in 20% O2-treated tissues. In situ hybridization studies indicated that VEGF mRNA was present in both mesenchymal cells and airway epithelial cells. These data suggest that VEGF gene expression is regulated by both oxygen and cAMP in the developing human lung. The detection of VEGF mRNA and protein in distal airway epithelial cells and the detection of VEGF protein in the basement membrane subjacent to the airway epithelial cells suggest that translocation of VEGF protein occurs after its synthesis in the epithelium. Localization of VEGF to the basement membrane of airway epithelial cells may be important for directing capillary development in the human lung.

Surfactant protein-A: new insights into an old protein--II

Pulmonary surfactant is a lipoprotein substance that lines the lungs and helps reduce surface tension. Surfactant associated protein-A (SP-A) is the most abundant non-serum protein in pulmonary surfactant. This complex glycoprotein aids in the synthesis, secretion and recycling of surfactant phospholipids, and facilitates the reduction of surface tension by surfactant phospholipids. Recent evidence has highlighted the role of SP-A in the innate immune system present in the lung. SP-A may play a major role in defense against pathogens by interacting with both infectious agents and the immune system. Factors that affect fetal lung maturation, e.g. gestational age and hormones regulate SP-A gene expression. Mediators of immune function also regulate SP-A levels. A number of lung disorders, including infectious diseases and respiratory distress syndrome are associated with abnormal alveolar SP-A levels. SP-A can no longer be called a lung-specific protein, since it has recently been detected in other tissues. In most species, SP-A is encoded by a single gene, however in humans it is encoded by two, very similar genes. Models for the structure of the human SP-A protein molecule have been proposed, suggesting that the mature alveolar SP-A molecule is composed of both gene products. The study of SP-A may provide information helpful in understanding disease processes and formulating new treatment modalities.

Insulin inhibits surfactant protein A and B gene expression in the H441 cell line

Fetuses of mothers with uncontrolled gestational diabetes have an increased risk of developing neonatal respiratory distress syndrome and are frequently hyperinsulinemic, thus it has been proposed that high levels of insulin delay fetal lung maturation. We have shown previously that insulin inhibits the accumulation of mRNA for the surfactant-associated proteins A and B (SP-A and SP-B) in human fetal lung explants maintained in vitro. To test the hypothesis that the inhibitory effects of insulin on the surfactant proteins are the result of a direct action of insulin on the lung epithelial cell, we evaluated the effects of insulin in the H441 cell line, a human pulmonary adenocarcinoma cell line that expresses SP-A and SP-B mRNA. We observed that insulin treatment for 48 h decreased SP-A mRNA and protein levels in a concentration-dependent manner when compared to controls. The inhibitory effect of insulin on SP-A mRNA levels was apparent as early as after 4 h of exposure. SP-B mRNA levels were also significantly decreased by insulin in a concentration-dependent manner. Insulin, at 2.5 microg/ml, inhibited SP-A gene transcription by approx. 67%, and inhibited SP-B gene transcription by about 32%. There was no significant effect of insulin on SP-A or SP-B mRNA stability. Thus, we have observed a pattern of insulin inhibition of SP-A and SP-B gene expression in the H441 lung epithelial cell line similar to that previously observed in human fetal lung explants, which are comprised of both epithelial and mesenchymal cells. Our findings provide further evidence that insulin may delay fetal lung maturation by inhibiting SP-A and SP-B gene expression. Furthermore, our findings suggest that the inhibitory effects of insulin are, at least partially, the result of a direct action on the lung epithelial cell.

SP-A2 gene expression in human fetal lung airways

In the present study, we characterized surfactant protein (SP)-A messenger RNA (mRNA) in mid-trimester human fetal trachea and bronchi. SP-A protein was localized by immunocytochemistry to scattered epithelial cells in the airway surface epithelium and in submucosal glands of the fetal trachea and bronchi. SP-A mRNA (2.2 kb) was detected by Northern blot analysis in human fetal trachea, as well as in primary and more distal bronchi. The levels of detectable SP-A mRNA were highest in the upper airways and were decreased in smaller bronchi in comparison. SP-A mRNA was barely detectable in the distal fetal lung tissue. In contrast, SP-A mRNA was abundant in cultured explants of distal human fetal lung tissue. SP-A1 and SP-A2 mRNA were detected by primer extension analysis in adult human lung tissue and in cultured human fetal lung explants. Only SP-A2 mRNA was detected in RNA isolated from human fetal trachea and bronchi. SP-A mRNA was localized by in situ hybridization in the fetal trachea and bronchi in scattered cells in the surface epithelium and, most prominently, in submucosal glands. Our results suggest that SP-A2, and not SP-A1, is produced in the human fetal tracheal and bronchial epithelium and in submucosal glands.

Surfactant protein-A: new insights into an old protein--Part I

Pulmonary surfactant is a lipoprotein substance that lines the lungs and helps reduce surface tension. Surfactant associated protein-A (SP-A) is the most abundant non-serum protein in pulmonary surfactant. This complex glycoprotein aids in the synthesis, secretion and recycling of surfactant phospholipids, and facilitates the reduction of surface tension by surfactant phospholipids. Recent evidence has highlighted the role of SP-A in the innate immune system present in the lung. SP-A may play a major role in defense against pathogens by interacting with both infectious agents and the immune system. Factors that affect fetal lung maturation, e.g., gestational age and hormones, regulate SP-A gene expression. Mediators of immune function also regulate SP-A levels. A number of lung disorders, including infectious diseases and respiratory distress syndrome are associated with abnormal alveolar SP-A levels. SP-A can no longer be called a lung-specific protein, since it has recently been detected in other tissues. In most species, SP-A is encoded by a single gene, however in humans it is encoded by two, very similar genes. Models for the structure of the human SP-A protein molecule have been proposed, suggesting that the mature alveolar SP-A molecule is composed of both gene products. The study of SP-A may provide information helpful in understanding disease processes and formulating new treatment modalities.

Mechanism of all trans-retinoic acid and glucocorticoid regulation of surfactant protein mRNA

The surfactant proteins (SPs) are required for the normal function of pulmonary surfactant, a lipoprotein substance that prevents alveolar collapse at end expiration. We characterized the effects of cortisol and all trans-retinoic acid (RA) on SP-A and SP-B gene expression in H441 cells, a human pulmonary adenocarcinoma cell line. Cortisol, at 10(-6) M, caused a significant inhibition of SP-A mRNA to levels that were 60-70% of controls and a five- to sixfold increase in the levels of SP-B mRNA. RA alone (10(-6) M) had no effect on SP-A mRNA levels and modestly reduced the inhibitory effect of cortisol. RA alone and the combination of cortisol and RA both significantly increased SP-B mRNA levels. RA had no effect on the rate of SP-A gene transcription or on SP-A mRNA stability. Cortisol alone and the combination of cortisol and RA significantly inhibited the rate of SP-A gene transcription but had no effect on SP-A mRNA half-life. RA at 10(-6) M had no effect on the rate of SP-B gene transcription but prolonged SP-B mRNA half-life. Cortisol alone and the combination of cortisol and RA caused a significant increase in the rate of SP-B gene transcription and also caused a significant increase in SP-B mRNA stability. We conclude that RA has no effect on SP-A gene expression and increases SP-B mRNA levels by an effect on SP-B mRNA stability and not on the rate of SP-B gene transcription. In addition, the effects of the combination of RA and cortisol were generally similar to those of cortisol alone.

O2 regulates surfactant protein A mRNA transcription and stability in human fetal lung in vitro

The effect of O2 on surfactant protein (SP) A mRNA transcription and half-life was determined in midtrimester human fetal lung tissue cultured in either 20 (control) or 70% O2. Incubation of tissues in 70% O2 resulted in a 133% increase in SP-A mRNA transcription rate compared with control tissues. The SP-A mRNA half-life was increased by 54% in lung tissues cultured in 70% O2 vs. control tissues. Western blot analysis indicated a threefold increase in SP-A in the 70% O2 condition, demonstrating that O2 regulation of SP-A mRNA levels results in corresponding changes in SP-A levels. Primer extension assays were performed to determine whether the observed increase in SP-A mRNA levels is secondary to the preferential expression of one of the human SP-A genes, SP-A1 or SP-A2. Transcripts of both the SP-A1 and SP-A2 genes were increased approximately 100% in tissues maintained in 70% O2 compared with control tissues. These data demonstrate that O2 regulates human SP-A mRNA levels by both transcriptional and posttranscriptional mechanisms. Furthermore, because there is no differential effect of O2 on the expression of SP-A1 vs. SP-A2 mRNA, the properties of these genes that mediate regulation by O2 must be conserved between the two genes.

Transient surfactant protein B deficiency in a term infant with severe respiratory failure

A 38-day-old male infant with persistent pulmonary hypertension and respiratory failure since birth was found to have a complete absence of surfactant protein B (SP-B) along with an aberrant form of SP-C in his tracheal aspirate fluid, findings consistent with the diagnosis of hereditary SP-B deficiency. Surprisingly, SP-B and SP-B messenger ribonucleic acid were present in lung biopsy tissue. However, DNA sequence analysis demonstrated a point mutation in exon 5 of one of the SP-B gene alleles. The infant's mother was found to be a carrier of this mutation. The infant's other SP-B allele did not differ from the published DNA sequence for the SP-B gene. We conclude that this patient had a transient deficiency of SP-B, in contrast to that of previously described infants with irreversible respiratory failure caused by hereditary SP-B deficiency. We recommend that infants with suspected SP-B deficiency have serial analysis of tracheal fluid samples for both SP-B and SP-C before lung biopsy, along with genetic analysis for the known SP-B mutations. We speculate that the new mutation found in one of this patient's SP-B genes was in part responsible for the transient deficiency of SP-B.

Differential regulation of SP-A1 and SP-A2 genes by cAMP, glucocorticoids, and insulin

In the human fetal lung, surfactant protein A (SP-A) is encoded by two highly similar genes, SP-A1 and SP-A2, which are developmentally and hormonally regulated. Using primer extension analysis, we evaluated the levels of SP-A1 and SP-A2 mRNA transcripts in human fetal lung explants and in a human adult lung adenocarcinoma cell line (H441 cells) cultured in the absence or presence of either dibutyryladenosine 3',5'-cyclic monophosphate (DBcAMP, 1 mM), dexamethasone (10(-7) M), or insulin (2.5 micrograms/ml). In the human fetal lung explants, the content of SP-A1 mRNA was approximately four times that of SP-A2 mRNA. DBcAMP increased SP-A1 mRNA levels by 100% and SP-A2 mRNA levels by 500%, thus reducing the ratio of SP-A1 mRNA to SP-A2 mRNA to approximately 1:1. Dexamethasone inhibited all of the SP-A1 and SP-A2 mRNA transcripts to the same extent, by approximately 70%, whereas insulin inhibited all SP-A mRNA transcripts by approximately 60%. The ratio of SP-A1 to SP-A2 mRNA in dexamethasone- or insulin-treated explants was the same as the ratio observed in controls. In the H441 cells, SP-A1 mRNA levels were approximately 1.5 times that of SP-A2 mRNA levels. DBcAMP increased both SP-A1 and SP-A2 mRNA levels by 100%. Dexamethasone inhibited SP-A1 mRNA levels in the cell line by 60%, whereas SP-A2 mRNA levels were not significantly affected. Insulin inhibited SP-A1 mRNA levels in the cell line by 40% without affecting SP-A2 mRNA levels. These findings suggest that the two human SP-A genes are regulated differently in the two model systems.

Regulation of surfactant protein gene expression by retinoic acid metabolites

Surfactant-associated proteins (SP) play an important role in the function of pulmonary surfactant. We have previously shown that SP-B mRNA is increased whereas SP-A and SP-C mRNA are decreased by all-trans-retinoic acid (RA) in a dose-dependent manner in human fetal lung explants. All-trans-RA binds primarily to the retinoic acid receptors (RARs) and 9-cis-RA binds primarily to the retinoid X receptors (RXRs). Because the fetal lung contains RXRs, we hypothesized that 9-cis-RA regulates surfactant protein gene expression in lung epithelial cells. H441 human lung adenocarcinoma cells, which synthesize SP-A and SP-B mRNA and protein, were treated with either all-trans-RA or 9-cis-RA (10(-10) to 10(-6) M) for 24 h. Neither all-trans-RA nor 9-cis-RA had an effect on SP-A mRNA levels in the H441 cells. All-trans-RA (10(-6) M) significantly increased SP-B mRNA levels in the H441 cells and 9-cis-RA had a smaller, not statistically significant effect. Human fetal lung explants were treated with 9-cis-RA for 6 d. 9-cis-RA did not significantly increase SP-B mRNA levels, significantly inhibited SP-A mRNA levels at all concentrations tested, and significantly inhibited SP-C mRNA levels at 10(-6) M in the human fetal lung explants. Both all-trans-RA (10(-6) M) and 9-cis-RA (10(-6) M) significantly increased SP-B protein levels in the human fetal lung explants. Together, these results are suggestive that all-trans-RA directly regulates SP-B gene expression in human pulmonary epithelial cells. In addition, the inhibitory effect of all-trans-RA and 9-cis-RA on SP-A mRNA levels in pulmonary epithelial cells is probably an indirect effect mediated by other cell types present in fetal lung tissue.

Fat content for nutritional labeling by supercritical fluid extraction and an on-line lipase catalyzed reaction

A method using sequential supercritical fluid extraction (SFE) and enzymatic transesterification has been developed for the rapid determination of total nutritional fat content in meat samples. SFE conditions of 12.16 MPa and 50 degrees C were utilized to extract lipid species from the sample matrix. The enzymatic transesterification of the lipids by methanol was catalyzed by an immobilized lipase isolated from Candida antarctica. Conversion of the triglycerides to fatty acid methyl esters was monitored by supercritical fluid chromatography, while the fatty acid content of the extract was determined by capillary gas chromatography (GC). Total fat, saturated fat and monounsaturated fat contents were calculated from the GC data and compared to values from traditional extraction and lipid determination methods. Both off-line SFE and automated SFE followed by on-line GC analysis using two different instruments were utilized in this study. The enzymatic-based SFE method gave comparable results to the organic solvent extraction-based method followed by conventional BF3-catalyzed esterification.

Regulation of the beta 2 subunit chain of laminin in developing rabbit fetal lung tissue

Laminins are a family of basement membrane-associated heterotrimeric proteins that are important in mediating the growth, migration, and differentiation of a variety of cell types. The beta 2 subunit chain is a component of several laminin isoforms, e.g., laminin-3, laminin-4, laminin-7, and possibly other, as yet uncharacterized laminin isoforms. Utilizing monoclonal antibodies directed against the beta 2 subunit chain of laminin, we detected this protein in fetal, neonatal, and adult lung tissues. The relative amount of laminin beta 2 subunit chain in fetal lung tissue increased as gestation proceeded, reaching its peak around the time of alveolar type II cell differentiation in the rabbit. The laminin beta 2 subunit chain was localized in early gestational age rabbit fetal lung tissue primarily in basement membranes of prealveolar ducts, airways, and smooth muscle cells of airways and arterial blood vessels. A rabbit laminin beta 2 cDNA was generated using RT-PCR and utilized as a probe in northern blot analysis to characterize the levels of laminin beta 2 mRNA in developing rabbit lung tissue. Similar to the pattern of laminin beta 2 protein induction observed in fetal lung tissue, laminin beta 2 mRNA levels were maximal late in gestation. Utilizing a laminin beta 2 chain cRNA probe and in situ hybridization, we detected laminin beta 2 mRNA in the epithelial cells of prealveolar ducts, the alveolar wall, and airways, as well as in connective tissue cells, and the smooth muscle cells of airways and blood vessels in fetal and adult lung tissues. In addition, using an in vitro explant model, we determined that alveolar type II cells are capable of synthesizing laminin beta 2 subunit mRNA and depositing this laminin subunit chain in the basement membrane beneath type II cells. The results of this study are suggestive that the laminin beta 2 chain may be involved in alveolar epithelial cell differentiation.

Localization of epidermal growth factor receptor in alveolar epithelium during human fetal lung development in vitro

Epidermal growth factor (EGF) enhances alveolar type II cell differentiation. In human fetal lung explants, EGF stimulates surfactant protein A (SP-A) synthesis. This effect may occur through a direct interaction of the ligand on EGF receptors located within distal pulmonary epithelium during alveolar type II cell differentiation. To determine if EGF receptor is present in alveolar epithelium, immunostaining for EGF receptor and in situ hybridization for EGF receptor mRNA were performed in human fetal lung explants undergoing alveolar type II cell differentiation in vitro. After 4 days in culture, EGF receptor immunostaining was present in alveolar epithelium from human fetal lung explants compared to minimal immunostaining in undifferentiated human fetal lung epithelium prior to culture. In situ hybridization revealed increased EGF receptor mRNA in differentiated type II cells from cultured explants, with minimal EGF receptor mRNA detected in undifferentiated epithelium from tissue prior to culture. Immunogold staining revealed EGF receptors on the cytoplasmic membranes of epithelial cells lining the prealveolar ducts in human fetal lung explants after 2 days in culture. Alveolar type II cell differentiation in vitro was confirmed ultrastructurally by the presence of lamellar bodies and biochemically by an increase in SP-A content. Thus, EGF receptor is found in alveolar epithelium during differentiation, which suggests an important role for EGF during human fetal lung development.

The combined effects of insulin and cortisol on surfactant protein mRNA levels

Infants of diabetic mothers are frequently hyperinsulinemic and have an increased incidence of neonatal respiratory distress syndrome, a disease caused by a deficiency in the production of pulmonary surfactant by alveolar type II cells. It has been hypothesized that insulin inhibits fetal lung type II cell differentiation. We have shown previously that insulin inhibits the accumulation of surfactant protein (SP)-A and SP-B mRNA and has no effect on SP-C mRNA levels in human fetal lung tissue maintained in vitro. We hypothesized that treatment with glucocorticoids, which are used clinically to accelerate human fetal lung maturation, would overcome the inhibitory effects of insulin on human fetal lung development. In the present study, human fetal lung explants were maintained in the presence or absence of cortisol added alone, or in insulin plus cortisol added together. Cortisol significantly decreased SP-A mRNA levels by approximately 50% at the 100 nM concentration and significantly increased levels by approximately 20% at the 1 nM concentration. Cortisol increased SP-B and SP-C mRNA levels in a dose-dependent fashion (5- and 45-fold at 100 nM cortisol, respectively). The combination of 1 nM cortisol and insulin resulted in inhibition of mRNA levels for SP-A, SP-B, and SP-C at the high insulin concentrations (approximately 50% inhibition for SP-A and SP-B and approximately 25% inhibition of SP-C mRNA levels, in the presence of 40 pmol/L x 10(-3) insulin). Surprisingly, 100 nM cortisol plus inhibitory concentrations of insulin increased SP-A mRNA levels (2-fold at 40 pmol/L x 10(-3).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of alpha 1, beta 1, and gamma 1 laminin subunits during rabbit fetal lung development

Laminin-1 is an extracellular matrix protein composed of three polypeptide chains that are designated alpha 1, beta 1, and gamma 1. We investigated the expression of laminin alpha 1, beta 1, and gamma 1 subunit chains during several stages of rabbit fetal lung development. Utilizing polyclonal antibodies directed against human placental laminin and immunoblot analysis, we found that the highest levels of laminin alpha 1, beta 1, and gamma 1 subunit chains in the fetal lung were present on day 26 of gestation (term = 31 days), coincident with the initiation of alveolar epithelial cell differentiation. Levels of the laminin chains were approximately five times higher in fetal lung at day 26 of gestation than in adult lung tissue. Different temporal patterns of laminin alpha 1, beta 1, and gamma 1 subunit chain expression were observed, data suggestive that the chains are independently regulated during lung development. Laminin was localized to the basement membranes of bronchi, bronchioles, prealveolar ducts, and blood vessels in fetal lung tissue, as shown by immunostaining with polyclonal laminin antibodies. A similar staining pattern was observed in adult lung tissue, but the alveolar wall was also stained. Laminin was also observed surrounding a few mesenchymal cells in fetal lung on day 19 of gestation; the number of positive mesenchymal cells increased with lung development. Laminin alpha 1 subunit chains, detected using a monoclonal antibody, were present in the basement membranes of bronchi, bronchioles, prealveolar ducts, and blood vessels in fetal lung tissue. No laminin alpha 1 chain staining was observed in the mesenchyme of early fetal lung tissue. Using a monoclonal antibody, laminin beta 1 subunit chains were immunolocalized in the basement membranes of bronchi, bronchioles, in prealveolar ducts, and surrounding some mesenchymal cells in fetal lung tissue. Laminin alpha 1 and beta 1 subunit chains in adult lung tissue were present in basement membranes of airways, blood vessels, and alveoli. Thus, changes in the localization and accumulation of laminin near the time of alveolar type I and type II epithelial cell differentiation suggest that laminin may play a role in mediating the differentiation of these cell types during rabbit fetal lung development.

Retinoic acid differentially regulates expression of surfactant-associated proteins in human fetal lung

Retinoic acid is known to play an essential role in maintaining the differentiation of a wide variety of epithelial cell types. However, its effects on the differentiation of lung alveolar epithelium have not been described. In the present study, we examined the effects of retinoic acid on the differentiation of human fetal lung tissue maintained in vitro. Human fetal lung explants were cultured in serum-free medium for 6 days in the absence or presence of all-trans retinoic acid at concentrations from 0.3 nM to 3 microM. Explant content of the surfactant-associated protein SP-A was measured using a specific enzyme-linked immunosorbent assay. Retinoic acid reduced SP-A protein levels in a concentration-dependent manner [analysis of variance (ANOVA), P < 0.01]. To evaluate possible cytotoxic effects of retinoic acid, culture media were assayed for lactate dehydrogenase (LDH), a cytoplasmic enzyme. LDH levels in media from retinoic acid-treated explants were not significantly different than LDH levels in media from control explants, indicating that retinoic acid is not cytotoxic in human fetal lung explants. Changes in messenger RNA (mRNA) levels for surfactant-associated proteins SP-A, SP-B, and SP-C were measured by Northern blot analysis. Retinoic acid reduced SP-A mRNA levels in a concentration-dependent manner (ANOVA, P < 0.02) and reduced SP-C mRNA levels at 3 microM. In contrast, retinoic acid increased SP-B mRNA levels in a concentration-dependent manner (ANOVA, P < 0.03). Morphometric analysis showed that retinoic acid decreased epithelial volume density in the explants by approximately 17% and increased connective tissue volume density by approximately 20% when compared to dimethyl sulfoxide vehicle controls. These data indicate that retinoic acid regulates type II cell surfactant protein gene expression in human fetal lung tissue.

Glucocorticoid regulation of surfactant-associated proteins in rabbit fetal lung in vivo

The effects of a maternally administered synthetic glucocorticoid, betamethasone, on the levels of mRNA for the surfactant proteins SP-A, SP-B, and SP-C and on the levels of SP-A protein were investigated in day 27 gestational age rabbit fetal lung tissue. Betamethasone administration to the pregnant rabbit caused approximately a twofold increase in the fetal lung level of SP-A protein and a threefold increase in fetal lung SP-A mRNA levels when compared to levels in fetuses obtained from saline-treated or uninjected animals. SP-B mRNA was increased fourfold in fetal lung tissue obtained from glucocorticoid-treated pregnant does when compared to levels in fetuses of uninjected pregnant does. However, SP-B mRNA levels in fetal lung tissue from saline-injected controls were also significantly elevated, approximately twofold, when compared to fetal lung SP-B mRNA levels in the uninjected control condition. SP-C mRNA levels in lung tissue of fetuses from both saline-injected and betamethasone-injected pregnant does were increased similarly, approximately twofold, over SP-C mRNA levels in fetal lung tissue obtained from uninjected control does. These data are suggestive that betamethasone treatment increases fetal lung SP-A and SP-B mRNA levels and that maternal stress alone can increase the expression of SP-B and SP-C mRNA in rabbit fetal lung tissue. Using in situ hybridization, SP-A mRNA was shown to be present primarily in alveolar type II cells in fetuses of control and saline-injected does. However, SP-A mRNA was easily detected in both alveolar type II cells and bronchiolar epithelial cells of rabbit fetal lung tissue following maternal betamethasone treatment. In contrast, SP-B and SP-C mRNA were present only in alveolar type II cells of lung tissue obtained from fetuses of control, saline, or betamethasone-treated does. Thus maternal administration of glucocorticoids increased SP-A protein as well as SP-A and SP-B mRNA levels in rabbit fetal lung tissue. SP-A mRNA was localized to both alveolar type II cells and in smaller amounts in bronchiolar epithelial cells of rabbit fetal lung tissue. However, SP-B and SP-C mRNA were detected only in alveolar type II cells.

Diuretic and diet effect on Menière's disease evaluated by the 1985 Committee on Hearing and Equilibrium guidelines

Fifty-four patients, diagnosed with Menière's disease and treated with diuretics and a low-salt diet, were evaluated retrospectively with the 1985 AAO/HNS Committee on Hearing and Equilibrium (CHE) guidelines for vertigo and hearing changes. The patient data base was also evaluated with other methods that helped determine the effectiveness of the 1985 AAO/HNS CHE guidelines. After 24 months of therapy, vertigo control was complete or substantial in 79% of the patients, limited or insignificant in 19%, and worse in 2% as evaluated by the CHE 1985 guidelines. Hearing improved in 35% of the patients, was unchanged in 29%, was worse in 22%, and could not be classified by CHE guidelines in 14%. Hearing was also evaluated by comparison of individual thresholds before medical therapy, and at 22 and 74 months after the start of medical therapy. We found a stabilization of low- and mid-threshold frequencies, with an average rate of hearing loss approximating 0 dB/yr with 74 months of followup. The results of this preliminary study suggest that diuretics and a low-salt diet may decrease the natural progression of sensorineural hearing loss in patients with Menière's disease. Compared with other methods of data analysis, the 1985 CHE guidelines lacked sensitivity to evaluate the hearing changes observed.

Oxygen modulates the differentiation of human fetal lung in vitro and its responsiveness to cAMP

Previously, it was found that lung explants from mid-trimester human abortuses differentiate spontaneously in organ culture in serum-free defined medium in an atmosphere of 95% air-5% CO2. Dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) treatment of human fetal lung in culture increases the rate of morphological differentiation and enhances expression of the surfactant protein A (SP-A) gene. To begin to define the factors responsible for this accelerated in vitro differentiation, we analyzed the effects of atmospheric oxygen on the morphological and biochemical development of human fetal lung in culture and on responsiveness of the cultured tissue to DBcAMP. We found that when lung explants were maintained in an atmosphere containing 1% oxygen they failed to differentiate spontaneously and no induction of SP-A gene expression was apparent. Furthermore, at 1% oxygen, DBcAMP had no effect to stimulate morphological differentiation or SP-A gene expression. When lung tissues that had been maintained for 5 days in 1% oxygen were transferred to an environment containing 20% oxygen, there was rapid morphological development and induction of SP-A gene expression. The effects on morphological development were manifest within 24 h of transfer to the 20% oxygen environment; within 72 h, a marked stimulatory effect of DBcAMP on SP-A gene expression also was observed. Our findings further suggest that the effects of oxygen on the levels of SP-A and SP-A mRNA are concentration dependent. Interestingly, the inductive effects of DBcAMP on SP-A gene expression were apparent only at oxygen concentrations > or = 10%. Morphological differentiation of the cultured human fetal lung tissue also was influenced by oxygen in a concentration-dependent manner. These findings suggest that oxygen plays an important permissive role in the spontaneous differentiation of human fetal lung in vitro.

Developmental regulation of surfactant-associated proteins in rabbit fetal lung in vivo

The developmental regulation of the rabbit surfactant-associated proteins, SP-A, SP-B, and SP-C, was investigated using Northern blot analysis. These proteins comprise approximately 10% by weight of pulmonary surfactant, a lipoprotein secreted by type II cells that reduces surface tension at the air-alveolar interface. SP-A mRNA and SP-B mRNA were first detected in rabbit fetal lung at day 24 of gestation (term = 31 days), i.e., approximately two days prior to the appearance of lamellar bodies within differentiated alveolar type II cells. The relative abundance of SP-B mRNA detected on day 24 of gestation was greater than that of SP-A mRNA. Fetal lung SP-A mRNA and SP-B mRNA levels increased rapidly during the remainder of gestation, reaching a maximum at day 31 of gestation. The relative concentrations of SP-A mRNA and SP-B mRNA were decreased in day 2 neonatal and adult lung tissues when compared to the levels present in fetal lung tissue late in gestation. A 0.5-kb rabbit SP-C cDNA was generated using the reverse transcriptase-polymerase chain reaction and was found to have high sequence homology to the human and rat SP-C cDNA nucleotide sequences. The predicted amino acid sequence for the rabbit SP-C cDNA revealed strong conservation of a hydrophobic region close to the amino terminus of the SP-C protein. Fetal lung SP-C mRNA was detected at day 19 of gestation, the earliest time point examined in this study. SP-C mRNA levels gradually increased in fetal lung tissue until day 28 of gestation and then remained level throughout the remainder of gestation and in the day 2 neonatal and adult rabbit lung tissue. These results suggest that the developmental pattern of induction of mRNA for the surfactant-associated proteins, SP-A, SP-B, and SP-C, differ from each other and are different in several respects from the developmental patterns observed in fetal lung tissue of the rat and human species.

Localization of surfactant-associated proteins SP-A and SP-B mRNA in rabbit fetal lung tissue by in situ hybridization

Pulmonary surfactant is a lipoprotein substance, comprised of approximately 80% phospholipid and approximately 10% protein, that lowers surface tension at the air-alveolar aqueous interface. Surfactant is synthesized and secreted by alveolar type II epithelial cells where it is stored intracellularly in lamellar bodies. In the present study, we used the technique of in situ hybridization to localize the mRNA for two surfactant-associated proteins, SP-A and SP-B, in developing rabbit fetal lung tissue. We found that SP-A mRNA was first localized in rabbit fetal lung alveolar type II cells on day 26 of gestation, the time at which lamellar bodies are first observed within fetal lung type II cells. On day 28 of gestation, a very small amount of SP-A mRNA was also detectable in the epithelial cells of some bronchioles. In neonatal and adult rabbit lung tissue, SP-A mRNA was primarily restricted to alveolar type II cells; however, the epithelial cells of some bronchioles contained small amounts of SP-A mRNA. SP-B mRNA was first detected in cuboidal epithelial cells in the prealveolar region of the rabbit fetal lung tissue on day 24 of gestation, i.e., at least 2 days before the appearance of SP-A mRNA and lamellar bodies within differentiated alveolar type II cells. SP-B mRNA was detected in most bronchiolar epithelial cells of the rabbit fetal lung tissue at day 28 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of cystic fibrosis transmembrane conductance regulator mRNA in human fetal lung tissue by in situ hybridization

The fetal pulmonary epithelium secretes fluid. Cl transport is presumed to provide the driving force for net fluid secretion, although the cellular mechanisms have not been well identified in the fetus. The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP- and nucleoside triphosphate-regulated Cl channel; mutations in CFTR cause cystic fibrosis. We hypothesized that if CFTR is involved in fetal lung fluid transport, the fetal pulmonary epithelium should express CFTR mRNA. We used the technique of in situ hybridization with 3H-anti-sense and, as a control, 3H-sense CFTR cRNA probes to localize CFTR mRNA in human fetal lung tissue and cultured lung explants and determine when in gestation it is expressed. Epithelial cells of both first and second trimester lung tissues expressed CFTR mRNA. A decreasing gradient of CFTR mRNA expression was present from the proximal to the distal pulmonary epithelium. Cultured second trimester lung tissue explants expressed more CFTR mRNA than the uncultured starting tissue, suggesting CFTR gene expression increased during the five days in culture. Furthermore, alveolar type II cells in cultured explants expressed CFTR mRNA, suggesting that these cells are Cl-secretory and may be involved in lung fluid transport. These data confirm that CFTR mRNA is expressed in the human fetal pulmonary epithelium, consistent with the Cl-secretory properties of the fetal lung.

Insulin regulation of messenger ribonucleic acid for the surfactant-associated proteins in human fetal lung in vitro

Respiratory distress syndrome (RDS) is primarily caused by an immaturity in the synthesis and secretion of surfactant by the fetal lung type II cell. Fetal hyperinsulinemia associated with maternal diabetes places the newborn at an increased risk of developing RDS, and therefore, it has been hypothesized that insulin inhibits type II cell differentiation. We have previously shown that insulin inhibits the accumulation of surfactant-associated protein A (SP-A), the major surfactant-associated protein, in human fetal lung explants maintained in vitro. In the present study, we used Northern blot analysis to evaluate the effects of insulin on the content of SP-A messenger RNA (mRNA) as well as on the content of mRNA for the hydrophobic surfactant-associated proteins SP-B and SP-C in human fetal lung explants maintained in vitro. Lung explants were maintained in serum-free medium with or without added insulin (0.25-2500 ng/ml) for up to 6 days. We observed that insulin, at concentrations of 25-2500 ng/ml, significantly inhibited the accumulation of SP-A mRNA when compared to controls (P less than 0.01). The inhibitory effect of insulin on SP-A mRNA accumulation was dose dependent with an approximately 75% inhibition observed at 2500 ng/ml. Insulin, at the concentration of 2500 ng/ml, significantly inhibited the accumulation of SP-B mRNA by approximately 30% when compared to control levels (P less than 0.01) but had no effect at lower concentrations. Insulin had no significant effect on SP-C mRNA levels at any concentration tested. Our findings provide evidence that insulin may delay fetal lung development by inhibiting SP-A and SP-B gene expression. A deficiency of these proteins in pulmonary surfactant may account for the increased incidence of RDS in infants of diabetic mothers.

Localization of surfactant-associated protein C (SP-C) mRNA in fetal rabbit lung tissue by in situ hybridization

Surfactant is a lipoprotein substance that is synthesized and secreted by alveolar type II epithelial cells and acts to reduce surface tension at the air-alveolar interface. SP-C is a 5,000-D molecular weight, hydrophobic, surfactant-associated protein. In the present study, we used a ribonuclease protection assay to show that SP-C mRNA is induced in rabbit fetal lung tissue early in development, increases in relative concentration as development proceeds, and is present in maximal concentration at term (31 days of gestation). We also used the technique of in situ hybridization to localize SP-C mRNA in fetal, neonatal, and adult rabbit lung tissue. SP-C mRNA was present in all of the epithelial cells of the prealveolar region of day 19 gestational age rabbit fetal lung tissue, i.e., about 7 days before the appearance of differentiated alveolar type II cells in the fetal lung tissue. By day 27 of gestation, SP-C mRNA was restricted to epithelial cells with the morphologic characteristics of alveolar type II cells. SP-C mRNA was not detected in bronchiolar epithelium at any stage of lung development. The intensity of SP-C mRNA hybridization in the prealveolar and alveolar type II epithelial cells increased as a function of gestational age and was maximal at term. The pattern of SP-C mRNA localization in neonatal and adult rabbit lung tissue was consistent with the restriction of SP-C gene expression to differentiated alveolar type II cells. Our data are suggestive that SP-C may serve some as yet unknown function early in lung development because it is present in fetal lung prealveolar epithelial cells much earlier in gestation than are differentiated, surfactant-producing alveolar type II cells.

Glucocorticoid effects on rabbit fetal lung maturation in vivo: an ultrastructural morphometric study

Maternal administration of glucocorticoids is known to stimulate fetal lung maturation. In the present study, we used microscopy and stereology to evaluate the morphological effects of maternal glucocorticoid treatment on rabbit fetal lung tissue. Betamethasone was administered to pregnant rabbits on days 25 and 26 of gestation at a dose of 0.2 mg/kg body weight. The animals were sacrificed on day 27 of gestation. Glucocorticoid treatment significantly increased the presumptive airspace in the fetal lung tissue but did not alter the relative proportion of epithelium, connective tissue, or vasculature in the tissue. In addition, glucocorticoid treatment significantly increased the proportion of type II cells in the prealveolar epithelium, increased the rate of phosphatidylcholine synthesis, and increased the content of the major surfactant-associated protein, SP-A, in the fetal lung tissue. We could detect no effect of betamethasone on lamellar body cross-sectional area, numerical density, or volume density within fetal lung type II cells. Glucocorticoid treatment of the pregnant doe caused a decrease in the volume density of intracellular glycogen and an increase in the volume density of mitochondria in fetal lung type II cells. Betamethasone treatment did not alter the distance between fetal lung epithelial cells and subadjacent connective tissue cells. However, glucocorticoid treatment increased the number of connective tissue foot processes that pierced the epithelial basal lamina. Thus, glucocorticoid treatment of the pregnant doe results in structural changes in the fetal lung tissue, an acceleration of some aspects of type II cell differentiation, and a concomitant increase in epithelial-mesenchymal interactions.

An ultrastructural, morphometric analysis of rabbit fetal lung type II cell differentiation in vivo

Rabbit lung type II cell differentiation was evaluated by use of ultrastructural, morphometric techniques. Fetal lung epithelial cells decreased in size dramatically from day 19 to day 21 of gestation. Thereafter, the cell and cytoplasmic cross-sectional area declined gradually until the neonatal time point. The tall columnar cell shape characteristic of fetal lung epithelial cells at early stages of development became cuboidal by day 24 of gestation. The number of mitochondria per micron2 cytoplasmic area in presumptive alveolar epithelial cells and the mitochondrial volume density increased toward the end of gestation. The volume density of glycogen pools within fetal lung epithelial cells reached a plateau on day 21 of gestation and then declined sharply on day 26 of gestation in lamellar body-containing, type II epithelial cells. Lamellar bodies increased in number and volume density in epithelial cells starting on day 26 of gestation and peaked with respect to these parameters in the neonatal lung tissue. Multivesicular bodies, which are thought to be a precursor to the lamellar body, became more prominent in differentiated type II cells on day 26 of gestation and increased in volume density from day 28 of gestation to the adult time point. The distance between mesenchymal and epithelial cells in fetal lung tissue declined sharply between days 24 and 26 of gestation but remained relatively constant thereafter. Foot processes extending from connective tissue cells contiguous to the epithelium were generally more numerous than those extending from the basal plasma membrane of epithelial cells at every stage of development examined. These data quantitate for the first time key ultrastructural events that occur during the differentiation of fetal lung epithelial cells in vivo.