Surfactant homeostasis is maintained in vivo during keratinocyte growth factor-induced rat lung type II cell hyperplasia

Breaking the in vitro alveolar type II cell proliferation barrier while retaining ion transport properties

Alveolar type (AT)I and ATII cells are central to maintaining normal alveolar fluid homeostasis. When disrupted, they contribute to the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome. Research on ATII cells has been limited by the inability to propagate primary cells in vitro to study their specific functional properties. Moreover, primary ATII cells in vitro quickly transdifferentiate into nonproliferative "ATI-like" cells under traditional culture conditions. Recent studies have demonstrated that normal and tumor cells grown in culture with a combination of fibroblast (feeder cells) and a pharmacological Rho kinase inhibitor (Y-27632) exhibit indefinite cell proliferation that resembled a "conditionally reprogrammed cell" phenotype. Using this coculture system, we found that primary human ATII cells (1) proliferated at an exponential rate, (2) established epithelial colonies expressing ATII-specific and "ATI-like" mRNA and proteins after serial passage, (3) up-regulated genes important in cell proliferation and migration, and (4) on removal of feeder cells and Rho kinase inhibitor under air-liquid interface conditions, exhibited bioelectric and volume transport characteristics similar to freshly cultured ATII cells. Collectively, our results demonstrate that this novel coculture technique breaks the in vitro ATII cell proliferation barrier while retaining cell-specific functional properties. This work will allow for a significant increase in studies designed to elucidate ATII cell function with the goal of accelerating the development of novel therapies for alveolar diseases.

Ultrastructural pathology of rat lung injury induced by ischemic acute kidney injury

Ischemic acute kidney injury (AKI) is a common complication during inpatient hospitalization, and often induces acute lung injury (ALI). A lot of studies have concentrated on the relevance between AKI and ALI, but the underlying mechanisms of AKI- associated ALI have remained unclear until now. One reason is that evidence of the ultrastructural pathology of AKI-associated ALI has been scarce and needed to be accumulated. The aims of present study are to observe ultrastructural changes, and to reveal leukocyte trafficking of ALI induced by ischemic AKI in rats. For this purpose light microscopy (LM) and electron microscopy (EM), as well as morphometric analysis, were employed in present study. LM observations revealed distinct regions of collapsed alveoli, hemorrhage in alveoli, and interstitial edema in AKI-induced ALI. EM examinations provided facts that alveolar epithelial cells, including type I and type II cells, were necrotic, and endothelia cells undergoing apoptosis as well as interstitial cells undergoing necroptosis were noted in AKI lungs. In addition, shrinkage and decreased or disappeared lamellar bodies were evident in alveolar type II cell of AKI rat lungs. Leukocyte numerical density on area (NA) in AKI lungs was significantly more than that in sham lungs. Based on the morphological criteria from EM examinations and morphometric analysis, a conclusion was that necrosis, including necroptosis, and apoptosis were involved in damaged lung induced by AKI. And inflammation also contributed to acute lung injury of rats with AKI.

Effects of recombinant human keratinocyte growth factor on surfactant, plasma, and liver phospholipid homeostasis in hyperoxic neonatal rats

Respiratory distress and bronchopulmonary dysplasia (BPD) are major problems in preterm infants that are often addressed by glucocorticoid treatment and increased oxygen supply, causing catabolic and injurious side effects. Recombinant human keratinocyte growth factor (rhKGF) is noncatabolic and antiapoptotic and increases surfactant pools in immature lungs. Despite its usefulness in injured neonatal lungs, the mechanisms of improved surfactant homeostasis in vivo and systemic effects on lipid homeostasis are unknown. We therefore exposed newborn rats to 85% vs. 21% oxygen and treated them systemically with rhKGF for 48 h before death at 7 days. We determined type II pneumocyte (PN-II) proliferation, surfactant protein (SP) mRNA expression, and the pulmonary metabolism of individual phosphatidylcholine (PC) species using [D(9)-methyl]choline and tandem mass spectrometry. In addition, we assessed liver and plasma lipid metabolism, addressing PC synthesis de novo, the liver-specific phosphatidylethanolamine methyl transferase (PEMT) pathway, and triglyceride concentrations. rhKGF was found to maintain PN-II proliferation and increased SP-B/C expression and surfactant PC in both normoxic and hyperoxic lungs. We found increased total PC together with decreased [D(9)-methyl]choline enrichment, suggesting decreased turnover rather than increased secretion and synthesis as the underlying mechanism. In the liver, rhKGF increased PC synthesis, both de novo and via PEMT, underlining the organotypic differences of rhKGF actions on lipid metabolism. rhKGF increased the hepatic secretion of newly synthesized polyunsaturated PC, indicating improved systemic supply with choline and essential fatty acids. We suggest that rhKGF has potential as a therapeutic agent in neonates by improving pulmonary and systemic PC homeostasis.

rhKGF stimulates lung surfactant production in neonatal rats in vivo

Surfactant deficiency and bronchopulmonary dysplasia (BPD), major obstacles in preterm infants, are addressed with pre- and postnatal glucocorticoids which also evoke harmful catabolic side-effects. Keratinocyte growth factor (KGF) accelerates surfactant production in fetal type II pneumocytes (PN-II), protects epithelia from injury and is deficient in lungs developing BPD, highlighting its potential efficacy in neonates. Neonatal rats were treated with recombinant human (rh)KGF, betamethasone, or their combination for 48 hr prior to sacrifice after which body weight, surfactant, and tissue phosphatidylcholines (PC) were investigated at postnatal d3, d7, d15, and d21. Pneumocyte proliferation, surfactant protein (SP) expression and SP-B/C in lung lavage fluid (LLF) were also determined at d7 and d21 to identify broader surfactant changes occurring at the beginning and end of the initial alveolarization phase. While all treatments increased secreted surfactant PC, BM compromised animal growth whereas rhKGF did not. At d3 rhKGF was more effective in male compared to female rats. Single treatments became less effective towards d21. Neither treatment altered PC composition in LLF. BM inhibited PN-II proliferation and increased surfactant PCs at the expense of tissue PCs. rhKGF however increased surfactant PCs without decreasing other PC species. Whereas SP-B/C gene expression was induced by all treatments, the changes in secreted SP-B/C mirrored those observed for surfactant PC. Our results encourage investigation of the mechanisms by which rhKGF improves surfactant homoeostasis, and detailed examination of its efficacy in neonatal lung injury models with a view to implementing it as a non-catabolic surfactant-increasing therapeutic in neonatal intensive care.

Pulmonary effects of keratinocyte growth factor in newborn rats exposed to hyperoxia

Acute lung injury and compromised alveolar development characterize bronchopulmonary dysplasia (BPD) of the premature neonate. High levels of keratinocyte growth factor (KGF), a cell-cell mediator with pleiotrophic lung effects, are associated with low BPD risk. KGF decreases mortality in hyperoxia-exposed newborn rodents, a classic model of injury-induced impaired alveolarization, although the pulmonary mechanisms of this protection are poorly defined. These were explored through in vitro and in vivo approaches in the rat. Hyperoxia decreased by 30% the rate of wound closure of a monolayer of fetal alveolar epithelial cells, due to cell death, which was overcome by recombinant human KGF (100 ng/ml). In rat pups exposed to >95% O2 from birth, increased viability induced by intraperitoneal injection of KGF (2 microg/g body wt) every other day was associated with prevention of neutrophil influx in bronchoalveolar lavage (BAL), prevention of decreases in whole lung DNA content and cell proliferation rate, partial prevention of apoptosis increase, and a markedly increased proportion of surfactant protein B-immunoreactive cells in lung parenchyma. Increased lung antioxidant capacity is likely to be due in part to enhanced CAAT/enhancer binding protein alpha expression. By contrast, KGF neither corrected changes induced by hyperoxia in parameters of lung morphometry that clearly indicated impaired alveolarization nor had any significant effect on tissue or BAL surfactant phospholipids. These findings evidence KGF alveolar epithelial cell protection, enhancing effects on alveolar repair capacity, and anti-inflammatory effects in the injured neonatal lung that may account, at least in part, for its ability to reduce mortality. They argue in favor of a therapeutic potential of KGF in the injured neonatal lung.

Treatment with keratinocyte growth factor does not improve lung allograft survival in the rat

PURPOSE

Lung allografts are threatened by primary graft dysfunction, infections, and rejection. Novel therapies protecting pulmonary allografts are badly needed. Keratinocyte growth factor (KGF) protects the lung against a variety of injurious stimuli and exerts anti-inflammatory effects. The aim of the study was to test the potential of recombinant truncated KGF (DeltaN23-KGF, palifermin) to attenuate pulmonary allograft rejection.

MATERIALS AND METHODS

Intratracheal instillation of 5 mg/kg DeltaN23-KGF was performed twice in donor rats on days 3 and 2 before explantation of the lung. In control animals, an equivalent volume of vehicle was instilled. Left lungs were transplanted in the fully allogeneic Dark Agouti to Lewis rat strain combination and in the less stringent Fischer 344 to Wistar Kyoto combination. Allograft recipients were additionally treated with DeltaN23-KGF post-transplantation. Graft outcome, leukocytic infiltration, and major histocompatibility complex (MHC) class II antigen expression was analyzed.

RESULTS

In both rat strain combinations, DeltaN23-KGF treatment did not improve pulmonary allograft outcome. Graft infiltration by macrophages and T lymphocytes remained unchanged. In addition, we demonstrated that MHC class II antigens were more abundant in KGF-treated allografts compared to control-treated grafts, which probably results in an increased alloreactivity.

CONCLUSION

In conclusion, intratracheal DeltaN23-KGF treatment is not effective to prevent acute pulmonary allograft rejection.

Distribution of intracellular and secreted surfactant during postnatal rat lung development

Pulmonary surfactant prevents alveolar collapse via reduction of surface tension. In contrast to human neonates, rats are born with saccular lungs. Therefore, rat lungs serve as a model for investigation of the surfactant system during postnatal alveolar formation. We hypothesized that this process is associated with characteristic structural and biochemical surfactant alterations. We aimed to discriminate changes related to alveolarization from those being either invariable or follow continuous patterns of postnatal changes. Secreted active (mainly tubular myelin (tm)) and inactive (unilamellar vesicles (ulv)) surfactant subtypes as well as intracellular surfactant (lamellar bodies (lb)) in type II pneumocytes (PNII) were quantified before (day (d) 1), during (d 7), at the end of alveolarization (d 14), and after completion of lung maturation (d 42) using electron microscopic methods supplemented by biochemical analyses (phospholipid quantification, immunoblotting for SP-A). Immunoelectron microscopy determined the localization of surfactant protein A (SP-A). (1) At d 1 secreted surfactant was increased relative to d 7-42 and then decreased significantly. (2) Air spaces of neonatal lungs comprised lower fractions of tm and increased ulv, which correlated with low SP-A concentrations in lung lavage fluid (LLF) and increased respiratory rates, respectively. (3) Alveolarization (d 7-14) was associated with decreasing PNII size although volume and sizes of Lb continuously increased. (4) The volume fractions of Lb correlated well with the pool sizes of phospholipids in lavaged lungs. Our study emphasizes differential patterns of developmental changes of the surfactant system relative to postnatal alveolarization.

Effects of keratinocyte growth factor on intra-alveolar surfactant fixed in situ: Quantitative ultrastructural and immunoelectron microscopic analysis

Quantitative (immuno) transmission electron microscopy using design-based stereology was performed on specimens collected by means of systematic uniform random sampling of rat lungs, which were fixed by vascular perfusion to stabilize intra-alveolar surfactant in situ. This procedure ensures that the data recorded are representative of the whole organ. Ultrathin sections of specimens embedded at low temperature in Lowicryl HM20 were labeled by indirect immuno-gold staining for surfactant protein A. We observed that, 3 days after treatment of lungs in vivo with truncated keratinocyte growth factor (DeltaN23-KGF), a potent mitogen of alveolar epithelial type II cells, surfactant protein A associated with the tubular myelin fraction of intra-alveolar surfactant was increased by 47% in comparison with buffer-treated control lungs. Despite the marked type II cell hyperplasia, the relative amount of ultrastructural surfactant subtypes was not significantly affected. Because surfactant protein A reduces the sensitivity to inhibition of the biophysical activity of surfactant by exudating plasma proteins, we propose that pretreatment of lungs with DeltaN23-KGF ameliorates adverse effects observed in acute lung injury following, for example, ischemia and reperfusion.

Involvement of distal airways in a chronic model of experimental asthma

BACKGROUND

Bronchial asthma is characterized by chronic airway inflammation and airway remodelling which occurs in both proximal and distal airways. These changes are associated with development of airway hyper-responsiveness and airflow limitation.

OBJECTIVE

This study was aimed to analyse whether chronic inhalative allergen challenges in mice lead to morphological and physiological changes comparable with this phenotype.

METHODS

For this purpose, BALB/c mice were systemically sensitized to ovalbumin (OVA) followed by aerosol allergen challenges on 2 consecutive days per week for 12 weeks.

RESULTS

In chronically challenged mice, tissue inflammation in proximal as well as distal airways was observed with a predominance of lymphocytes within the cellular infiltrate. In contrast, inflammation in the airway lumen decreased over time. These changes were associated by a shift in bronchoalveolar lavage-cytokine levels from IL-4, IL-5 and TNF-alpha production (during the acute phase) towards markedly increased levels of TGF-beta during the chronic phase. Goblet cell hyperplasia and subepithelial fibrosis occurred throughout the airway tree. In terms of lung function, chronically challenged mice developed persistent bronchial hyper-responsiveness and progressive airflow limitation. Six weeks after OVA aerosol discontinuation, airway inflammation still persisted although lung function was normalized.

CONCLUSION

These data indicate that our model of chronic aerosol allergen challenges leads to a phenotype of experimental asthma with participation of distal airways and persistence of inflammation thereby resembling many morphological and physiological aspects of human bronchial asthma.

Improved lung preservation relates to an increase in tubular myelin-associated surfactant protein A

Background

Declining levels of surfactant protein A (SP-A) after lung transplantation are suggested to indicate progression of ischemia/reperfusion (IR) injury. We hypothesized that the previously described preservation-dependent improvement of alveolar surfactant integrity after IR was associated with alterations in intraalveolar SP-A levels.

Methods

Using immuno electron microscopy and design-based stereology, amount and distribution of SP-A, and of intracellular surfactant phospholipids (lamellar bodies) as well as infiltration by polymorphonuclear leukocytes (PMNs) and alveolar macrophages were evaluated in rat lungs after IR and preservation with EuroCollins or Celsior.

Results

After IR, labelling of tubular myelin for intraalveolar SP-A was significantly increased. In lungs preserved with EuroCollins, the total amount of intracellular surfactant phospholipid was reduced, and infiltration by PMNs and alveolar macrophages was significantly increased. With Celsior no changes in infiltration or intracellular surfactant phospholipid amount occurred. Here, an increase in the number of lamellar bodies per cell was associated with a shift towards smaller lamellar bodies. This accounts for preservation-dependent changes in the balance between surfactant phospholipid secretion and synthesis as well as in inflammatory cell infiltration.

Conclusion

We suggest that enhanced release of surfactant phospholipids and SP-A represents an early protective response that compensates in part for the inactivation of intraalveolar surfactant in the early phase of IR injury. This beneficial effect can be supported by adequate lung preservation, as e.g. with Celsior, maintaining surfactant integrity and reducing inflammation, either directly (via antioxidants) or indirectly (via improved surfactant integrity).

Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) has been recognized for almost half a century. At least three separate pathophysiologic mechanisms may lead to the characteristic feature of PAP: the excessive accumulation of surfactant lipoprotein in pulmonary alveoli, with associated disturbance of pulmonary gas exchange. The prognosis for adult patients with PAP varies, but disease-specific survival rate exceeds 80% at 5 years. The survival rates for adult PAP patients seem to have increased progressively in the four decades since the initial clinical description of this condition. The last decade has brought new advances in laboratory and clinical research that are lifting a veil not only on PAP but also on general aspects of pulmonary surfactant biology and innate immune defense.

Molecular targeting in radiotherapy of lung cancer

Molecular targeting is a promising option to increase the radiation response of tumours and to decrease normal tissue reactions, i.e. to achieve therapeutic gain. Molecular targeting substances in themselves are not curative while radiation is a highly efficient cytotoxic agent, with local recurrences often occurring from only few surviving clonogenic cells. High-dose radiotherapy therefore offers optimal conditions to evaluate the potential of specific biology-driven drugs for oncology. This review summarises the current status of preclinical and clinical research on combined radiation with examples of molecular targeting substances relevant for the treatment of NSCLC (EGFR, COX-2, VEGFR, KGF, TGF-beta, BBI).

Keratinocyte growth factor transiently alters pulmonary function in rats

Keratinocyte growth factor (KGF) is a mitogen for pulmonary epithelial cells. Intratracheal administration of KGF to adult rats results in alveolar epithelial type II and bronchiolar epithelial cell proliferation. While cellular responses to KGF have been intensively studied, functional consequences regarding lung function are unknown. Therefore, in this study, we sought to investigate whether KGF alters pulmonary function variables. Rats received either recombinant human KGF (rHuKGF) (5 mg/kg) or vehicle intratracheally. Before and on days 3 and 7 after treatment, pulmonary function was determined by body plethysmography. Subsequently, lung histological changes were quantified. rHuKGF induced a transient proliferation of alveolar and bronchiolar epithelial cells. The extent of type II cell hyperplasia was significantly correlated with a transient reduction in tidal volume and an increase in breathing frequency. In addition, quasi-static compliance, total lung capacity, and vital capacity were reduced after rHuKGF instillation, suggesting the development of a transitory restrictive lung disorder. Moreover, reduced expiratory flow rates and forced expiratory volumes, as well as increased functional residual capacity after rHuKGF but not vehicle, suggest obstructive lung function changes. In conclusion, the induction of alveolar and bronchiolar epithelial cell proliferation by KGF is paralleled by moderate functional consequences that should be taken into account when the therapeutic potential of KGF is tested.