Immunohistochemical evidence for the occurrence of similar epithelial phenotypes during lung development and radiation-induced fibrogenesis

PURPOSE

Processes of fibrosis, wound healing and tissue regeneration have in common the fact that proliferation and differentiation of cells involved in the restoration of normal-tissue architecture resemble to a certain degree the embryonic development of the corresponding tissue. The present review focuses on the phenotypic changes of alveolar epithelial cells during fibrogenesis and describes similarities in the expression pattern of epithelial antigens during lung development.

METHODS

For comparative studies, immunohistochemical investigations of different experimental fibrosis models were performed.

RESULTS

For several epithelial proteins, such as the CD44 adhesion molecule, the enzymes carbanhydrase II and cathepsin D, as well as the lectin galectin-3, a transient epithelial immunoreactivity have been detected. What all four examples have in common is that a part of the foetal antigenic profile reappears under conditions of injury and during the development of pulmonary fibrosis.

CONCLUSIONS

The re-expression of foetal antigens in fibrotic samples with a spatio-temporal pattern, as detected by immunocytochemical techniques, indicates that some mechanisms or factors exist, which similarly regulate the differentiation of the epithelium during ontogenesis and in the remodelling process during fibrogenesis.

Preservation of intraalveolar surfactant in a rat lung ischaemia/reperfusion injury model

Ischaemia/reperfusion (I/R) injury, a major problem in clinical lung transplantation, is associated with surfactant dysfunction. The present study aimed to test the hypothesis that preservation related improvements in post-ischaemic lung function are associated with improved ultrastructural preservation of pulmonary surfactant. Rat lungs were flush perfused with modified Euro-Collins solutions (ECS), stored for 2 h at 4 degrees C, and reperfused for 40 min. Lungs were preserved with conventional (ECS 115: 115 mmol x L(-1) K+), medium-K+ (ECS 40: 40 mmol x L(-1) K+), or low-K+ (ECS 10: 10 mmol x L(-1) K+) ECS. Functional parameters were monitored during reperfusion (n=10 per group). After reperfusion, left lungs were prepared for electron microscopical and stereological analysis of surfactant (n=5 per group). In all three experimental groups notable I/R injury developed which was lowest in ECS 40 as indicated by significantly less intraalveolar oedema, higher perfusate oxygenation, and lower peak inspiratory pressure. This was associated with a significantly superior preservation of the ultrastructure of the surface active surfactant subtype tubular myelin in ECS 40 compared with ECS 115 and ECS 10. Stereological analysis revealed that the relative amount of tubular myelin was highest in ECS 40 (mean+/-SEM; 6.2+/-0.8%) compared with ECS 115 (3.0+/-1.0%) and ECS 10 (2.7+/-1.6%). Analysis of surfactant in its natural location within the organ showed that the severity of ischaemia/reperfusion injury correlates with differences in intraalveolar surfactant composition. Improved post-ischaemic respiratory function achieved by medium-K+ Euro-Collins solution is associated with superior ultrastructural preservation of tubular myelin. It is concluded that the integrity of surface active tubular myelin represents an important criterion for the assessment of lung preservation quality.

Keratinocyte growth factor-induced hyperplasia of rat alveolar type II cells in vivo is resolved by differentiation into type I cells and by apoptosis

Keratinocyte growth factor (KGF) is a potent mitogen of alveolar epithelial type II cells (AEII). AEII hyperplasia is resolved within several days following intratracheal instillation of KGF by unknown mechanism(s). AEII hyperplasia was induced in rat lungs by intrabronchial instillation of 5 mg recombinant human (rh)KGF x kg body weight(-1) or an equivalent amount of diluent. Epithelial architecture, cell proliferation, transformation of AEII into type I cells (AEI) and apoptosis were investigated by means of immunohistochemistry, stereology, double immunofluorescence microscopy, electron microscopy and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) technique in lungs fixed 1, 2, 3 and 7 days after treatment. After 1 day of rhKGF instillation, an increase was observed in the nuclear antigen Ki-67, a proliferation marker detected by the antibody MIB-5-expressing surfactant protein (SP)-B, -C, -D-positive AEII. The incidence of mitosis was increased by day 2, resulting in AEII micropapillae with intense basolateral expression of the exon 6 containing isoform (v6) of CD446 (CD44v6), a marker for AEII. By day 3, monolayers of AEII exhibiting lateral CD44v6 covered 45% of the alveolar surface. After 7 days, there were numerous intermediate AEII/AEI cells characterized by a flat elongated shape, staining for SP-D, apical appearance of AEI marker Lycopersicon esculentum lectin and lateral staining for AEII marker CD44v6. Increased numbers of TUNEL-positive epithelial cells were seen at days 2-7. In conclusion, restoration of normal alveolar epithelium after instillation of recombinant human keratinocyte growth factor is accomplished by terminal differentiation and apoptosis of hyperplastic alveolar epithelial type II cells in vivo.

Ultrastructural alterations in intraalveolar surfactant subtypes after experimental ischemia and reperfusion

Ischemia and reperfusion (I/R) result in surfactant dysfunction. Whether the impairment of surfactant is a consequence or a cause of intraalveolar edema formation is still unknown. The cumulative effects of lung perfusion, ischemic storage, and subsequent reperfusion on surfactant ultrastructure and pulmonary function were studied in a rat isolated perfused lung model. The left lungs were fixed for electron microscopy by vascular perfusion either immediately after excision (control; n = 5) or after perfusion with modified Euro-Collins solution (EC), storage for 2 h at 4 degrees C in EC, and reperfusion for 40 min (n = 5). A stereological approach was chosen to discriminate between intraalveolar surfactant subtypes of edematous regions and regions free of edema. Intraalveolar edema seen after I/R in the EC group occupied 36 +/- 6% (mean +/- SEM) of the gas exchange region as compared with control lungs (1 +/- 1%; p = 0.008). Relative intraalveolar surfactant composition showed a decrease in surface active tubular myelin (3 +/- 1 versus 12 +/- 0%; p = 0.008) and an increase in inactive unilamellar forms (83 +/- 2 versus 64 +/- 5%; p = 0.008) in the EC group. These changes occurred both in edematous (tubular myelin, 3 +/- 1%; unilamellar forms, 88 +/- 6%) and in nonedematous regions (tubular myelin, 4 +/- 3%; unilamellar forms, 77 +/- 5%). The ultrastructural changes in surfactant were associated with an increase in peak inspiratory pressure during reperfusion. In conclusion, surfactant alterations seen after I/R are not directly related to the presence of edema fluid in the alveoli. Disturbances in intraalveolar surfactant after I/R are not merely the result of inactivation due to plasma protein leakage but may instead be responsible for an increased permeability of the blood-air barrier, resulting in a vicious cycle of intraalveolar edema formation and progressing surfactant impairment.

Experimental induction of AGEs in fetal L132 lung cells changes the level of intracellular cathepsin D

The effect of the carbonyl compound glyoxal on the induction of advanced glycation end products (AGEs) in the fetal epithelial lung cells L132 was investigated using immunohistochemical, immunoelectron microscopic, and biochemical methods. It was found that glyoxal treatment resulted in morphological changes of the cells and in the membranous and cytosolic localization of AGEs such as methyl-glyoxal-derived compounds, N-(carboxymethyllysine) (CML) and imidazolone. The formation of AGEs was accompanied with a change in the intracellular expression of cathepsin D and a loss of enzymatic activity.

Combined use of prostacyclin and higher perfusate temperatures further enhances the superior lung preservation by Celsior solution in the isolated rat lung

BACKGROUND

The poor tolerance of the lung to ischemia and reperfusion (IR) still represents one of the limitations in clinically successful lung transplantation. Modified Euro-Collins (EC) is routinely used in lung preservation, but alternative solutions have been developed for improvement of pulmonary preservation. Celsior is an extracellular solution that has significantly reduced the IR-induced pulmonary damage in animal studies. So far, no extensive experimental studies exist concerning the influence of Celsior on pulmonary gas exchange following IR.

METHODS

In an extracorporeal rat lung model 10 lungs, each, were preserved with Celsior (CE) and Celsior/prostacyclin (CEPC, 6 microg/100 ml) at 4 degrees and 15 degrees C, each, and compared to low-potassium Euro-Collins (EC-40, 40 mmol/liter potassium). After 2 hours of ischemia lungs were reventilated and reperfused using a roller pump. Oxygenation in terms of oxygen partial tension in the left atrial effluent, pulmonary vascular resistance (PVR), peak inspiratory pressure, and wet/dry ratio were monitored for 50 minutes. Furthermore, edema formation was evaluated by light microscopy. Statistical analysis was performed using ANOVA models.

RESULTS

Compared to the EC-40 group, oxygenation was increased and amount of edema was reduced in most Celsior-preserved organs (p<0.032) with exception of the CEPC group at 4 degrees C (p = 0.06). Additional application of prostacyclin did not have any significant effect on oxygenation in the Celsior group. However, after temperature elevation of the CEPC perfusate to 15 degrees C, a superior partial tension of oxygen was observed (p<0.023) in contrast to the 4 degrees C groups CE and CEPC. The lowest PVR was found in the CE 4 degrees C group (p<0.02).

CONCLUSIONS

Celsior provides better lung preservation than EC-40 solution. Application of prostacyclin at higher perfusate temperatures results in additional functional improvement. In vivo experiments and ultrastructural analysis are warranted for further evaluation of Celsior in lung preservation.

Alterations in the immunohistochemical distribution patterns of vascular endothelial growth factor receptors Flk1 and Flt1 in bleomycin-induced rat lung fibrosis

To investigate the role of vascular endothelial growth factor (VEGF) in fibrogenesis, the distribution patterns of the VEGF receptors Flt1 and Flk1 were studied by immunohistochemistry, double immunofluorescence, and immunoelectron microscopy in normal (n=2) and bleomycin-treated (n=21) adult rats. Lungs were studied at 5, 24, 28, 35, and 42 days after treatment (p.t.). Flt1, Flk1, and VEGF immunoreactivity localised predominantly to the pulmonary epithelium. In control lungs, Flt1 immunoreactivity was present in ciliated bronchial epithelium and type 2 pneumocytes, Flk1 in Clara cells, and VEGF in Clara cells and type 2 pneumocytes. Flk1 localised to mast cells, present in the peribronchovascular and pleural interstitium only. Flt1- and Flk1-mRNAs were observed in Clara cells and type 2 pneumocytes. Bleomycin-induced fibrogenesis was characterised by a decrease in Flk1 immunoreactivity of Clara cells, and an increase in VEGF-immunoreactive myofibroblasts and type 2 pneumocytes by day 5 p.t., followed by a progressive accumulation of Flk1-immunoreactive mast cells by day 24 p.t. in fibrotic lesions containing VEGF-immunoreactive myofibroblasts. After 42 days, fibrotic regions were densely populated by mast cells. Since mast cells are known to be chemotactically attracted by VEGF, we suggest that VEGF/Flk1 represents the molecular link between proliferation of myofibroblasts, accumulation of mast cells, and the burst of fibrosis at sites of initial lesions in bleomycin-induced fibrosis.

Pulmonary ischemia/reperfusion injury: a quantitative study of structure and function in isolated heart-lungs of the rat

Early graft dysfunction after lung transplantation is a significant and unpredictable problem. Our study aimed at a detailed investigation of structure-function correlations in a rat isolated heart-lung model ofischemia/ reperfusion injury. Variable degrees of injury were induced by preservation with potassium-modified Euro-Collins solutions, 2 hr of cold ischemia, and 40 min of reperfusion. Pulmonary artery pressure (Ppa), pulmonary vascular resistance (PVR), peak inspiratory pressure (PIP), and perfusate gases (deltaPO2, deltaPCO2) were recorded during reperfusion. Right lungs were used to calculate W/D-weight ratios. Nineteen experimental and six control left lungs were fixed for light and electron microscopy by vascular perfusion. Systematic random samples were analyzed by stereology to determine absolute and relative volumes of lung structures, the amount of interstitial and intraalveolar edema, and the extent of epithelial injury. Lectin- and immunohistochemistry using established epithelial cell markers were performed in three animals per group to reveal sites of severe focal damage. Experimental lungs showed a wide range in severity of ischemia/ reperfusion injury. Intraalveolar edema fluid amounted to 77-909 mm3 with a mean of 448+/-250 mm3 as compared with 22+/-22 mm3 in control lungs (P<0.001). Perfusate oxygenation (deltaPO2) decreased from 30.5+/-15.2 to 21.7+/-15.2 mm Hg (P=0.05) recorded after 5 and 40 minutes of reperfusion. In experimental lungs, a surface fraction of 1% to 58% of total type I pneumocyte surface was damaged. Intraalveolar edema per gas exchange region (Vv ape,P) and deltaPO2 were related according to deltaPO2 = 96 - 60 x log10(Vv ape,P) [mm Hg]. The extent of epithelial injury did not correlate with deltaPO2 nor with intraalveolar edema, but increased significantly with PVR. Lectin- and immunohistochemistry revealed focal severe damage to the alveolar epithelium at the border of perivascular cuffs.

Improvement of rat lung structure and function after preservation with celsior

Ischemia/reperfusion-induced increase in pulmonary microvascular permeability was shown to be reduced after preservation with Celsior. We investigated reimplantation-induced lung injury in isolated, reperfused rat lungs after preservation via the pulmonary artery with Celsior, Celsior + prostacyclin, and reduced-potassium (40 mmol) Euro-Collins solution (40 ml/kg/body wt each) followed by 2 h of cold ischemia. Arterial and veneous oxygen tensions were recorded during 50 min of in vitro reperfusion after which the lungs (10 right lungs per experimental group) were fixed by vascular perfusion. The tissue was further processed for microscopy, and histological changes were quantified stereologically. Lung preservation with Celsior resulted in a significantly higher volume of air-filled alveolar space with a large proportion of widely distended alveoli compared with the other groups. In the Euro-Collins group the fraction of atelectatic alveoli exceeded that observed in Celsior-preserved lungs. In accordance, the difference between arterial and venous oxygen tensions was significant among Euro-Collins- and Celsior-protected lungs, with improved oxygenation values in the Celsior group. In contrast, addition of prostacyclin to Celsior treatment resulted in rather variable structural as well as functional data. There were no differences in the volumes of intraalveolar edema among the groups tested. However, the volume of alveolar tissue was increased in the Euro-Collins group. In conclusion, compared with Euro-Collins and Celsior + prostacyclin solutions, preservation with Celsior resulted in improved structural characteristics which in combination with improved oxygenation parameters supports the prospective advantage of Celsior in clinical organ preservation.

Stereological estimation of the volume weighted mean volumes of alveoli and acinar pathways in the rat lung to characterise alterations after ischaemia/reperfusion

The aim of this study was to characterise pulmonary reimplantation injury in isolated, perfused rat lungs following 2 h of cold ischaemia, and 50 min. of in vitro reperfusion. The effects of 2 differently composed lung preservation solutions (low potassium Euro-Collins and Celsior; each n = 5) were examined in comparison with untreated, nonischaemic control lungs (n = 3). After fixation by vascular perfusion and tissue collection by systematic random sampling, the volume weighted mean volume (Vv) of alveoli and acinar pathways was estimated by light microscopic stereology using the method of point sampled intercepts in plastic embedded, Azan-stained material. Significantly higher Vv of alveoli and acinar paths was found in the Celsior group than in Euro-Collins preserved lungs. However, in the controls the size of acinar pathways was similar to Celsior preserved lungs whereas alveolar size was comparable to preservation with Euro-Collins. The between-animal coefficient of variation of alveoli was very low in controls and Celsior preserved but higher in the Euro-Collins group. Size distribution of alveoli and acinar paths in 15 size classes was largely homogeneous in all groups tested. In the Euro-Collins group the fractions of both class 1-alveoli and class 1-acinar paths significantly exceeded those of the other groups. Widely expanded alveoli (size classes 13-15) only occurred after preservation with Celsior whereas wider acinar paths (size class 15) were found in the Celsior group and in the controls. It is concluded that lung preservation with low-potassium Euro-Collins and Celsior solutions may act differently on distinct spaces in the distal gas-exchange regions of lungs. This may be due to selective effects on pulmonary surfactant activity and on elastic tissue elements in the alveolar ducts, respectively. Additionally, the method of point sampled intercepts is considered to be an efficient tool to evaluate the effects of different preservation solutions on lung parenchyma.

Differential immunolocalization of VEGF in rat and human adult lung, and in experimental rat lung fibrosis: light, fluorescence, and electron microscopy

Vascular endothelial growth factor (VEGF) is a cytokine with main angiogenetic functions in embryonic development and tumor-formation. In the adult lung, reports of the localization of VEGF were controversial. A precise cell typing of VEGF-positive pulmonary cells is still lacking. Nothing is known about a potential role in pulmonary fibrosis. Immunohistochemistry (IH), double immunofluorescence microscopy (DIF), and immunoelectron microscopy (IEM) were used to study the differential distribution of VEGF in paraffin-embedded (IH, DIF) and in cryo-substituted, Lowicryl-embedded (IEM) specimens of normal rat and human lungs and fibrotic rat lungs. Fibrosis was induced by intratracheal bleomycin treatment. IH and DIF showed that VEGF was present in surfactant protein (SP) D-positive alveolar type II pneumocytes, bronchiolar Clara cells, smooth muscle (SM) cells, and alpha-SM actin-positive myofibroblasts of normal rat and human lungs. Fibrotic lesions in bleomycin-treated rat lungs were rich in VEGF-positive cells presenting with a heterogeneous phenotype (mainly SP-D-positive type II pneumocytes, alpha-SM actin-positive myofibroblasts). There were no signs of angiogenesis. Post-embedding immunogold labeling using protein A-gold and IgG-gold technique revealed a specific localization of VEGF to mitochondria, Clara cell secretory granules, and capillary interendothelial cell junctions. The predominant localization of VEGF to bronchiolar and alveolar epithelial and alpha-SM actin-positive cells, and the marked increase of VEGF-positive type II pneumocytes and myofibroblasts in fibrotic lung lesions, indicate that in adult lungs VEGF is involved in processes other than angiogenesis.

Receptor for advanced glycation endproducts (RAGE) exhibits highly differential cellular and subcellular localisation in rat and human lung

The transmembrane receptor (RAGE) of advanced glycation endproducts (AGEs), is abundantly present in the lung. Although the interaction of AGEs and RAGE plays an important role in vasculopathies, particularly in diabetes, the lung is not a classical target organ of diabetes. Thus, the role of RAGE in the lung is still obscure. This study sought to precisely localise RAGE in the lungs of rat and human by immunohistochemistry, double immunofluorescence and immunoelectron microscopy using a polyclonal antiserum developed against human recombinant RAGE. Anti-RAGE immunoreactivity was prominent in alveolar epithelial type I pneumocytes, while it was absent from type II pneumocytes and capillary endothelium. Cell type specificity was demonstrated by colocalisation with well established cell markers. Quantitative immunoelectron microscopy of cryo-substituted, Lowicryl-embedded rat and human specimens demonstrated a unique labelling pattern of RAGE in that it selectively localised to the basal cell membrane of type I pneumocytes. Labelling pattern was independent of the mode of fixation. Equivalent labelling densities were calculated from a fibrotic rat lung 3 months after irradiation. This highly selective localisation of RAGE to the basal face of type I pneumocytes and its absence from capillary endothelium might explain the resistance of the lung to typical diabetic complications.

Influence of the potassium concentration on functional and structural preservation of the lung: where is the optimum?

BACKGROUND

Low-potassium solutions have been shown to improve lung preservation. The optimal potassium concentration, however, has not been investigated systematically. The purpose of this study was to evaluate the effect of solutions with different potassium concentrations on functional and structural preservation after flush-perfusion and ischemia. We used our established extracorporeal working heart-lung model and a modification of this model with isolated pulmonary perfusion at defined flow rates.

METHODS

In two sets of experiments 42 rat heart-lung blocks (experiment I and II: n=7/group) were used. Lungs were flush-preserved with 20 ml Euro-Collins solution (EC115; K+ 115 mmol/L), potassium-reduced Euro-Collins solution (EC40; K+ 40 mmol/L), or low-potassium Euro-Collins solution (EC10; K+ 10 mmol/L) and stored for 2 hours at 10 degrees C. Reperfusion was performed for 40 minutes with Krebs-Henseleit solution containing washed bovine red blood cells (38%) while the lungs were ventilated with room air. In experiment I pulsatile perfusion of the lungs was achieved by the working right side of the heart. In experiment II lungs were perfused at defined flow rates by a roller pump. Postischemic function was assessed by means of oxygenation capacity and pulmonary vascular resistance. The degree of structural damage to the air-blood barrier was assessed by quantitative stereologic light and electron microscopic evaluation.

RESULTS

In both experiments after 40 minutes reperfusion oxygenation capacity was significantly higher in EC40 than in EC115 and EC10, whereas pulmonary vascular resistance was significantly higher in EC115 than in EC40 and EC10. Quantitative histologic examination showed surprisingly modest damage to the endothelial side of the air-blood barrier but a considerable degree of damage to the epithelium in both experiments. The alterations in the pump-perfused isolated lung experiments exceeded those of the pulsatile perfused heart-lung experiments. The comparative analysis of the study groups revealed a minor degree of epithelial swelling and fragmentation in EC40 than in EC115 and EC10, respectively.

CONCLUSIONS

The results obtained with two modifications of an extracorporeal model indicate that flush perfusion of the lung with a potassium-reduced solution results in better functional and structural preservation than flush perfusion with either high- or low-potassium solutions. The optimum may lie in the vicinity of 40 mmol/L. Further studies are necessary to verify these initial findings.

Early alterations in intracellular and alveolar surfactant of the rat lung in response to endotoxin

The aim of this study was to characterize early ultrastructural, biochemical, and functional alterations of the pulmonary surfactant system induced by Salmonella minnesota lipopolysaccharide (LPS) in rat lungs. Experimental groups were: (1) control in vitro, 150 min perfusion; (2) LPS in vitro, 150 min perfusion, infusion of 50 microg/ml LPS after 40 min; (3) control ex vivo, 10 min perfusion; (4) LPS ex vivo, lungs perfused for 10 min from rats treated for 110 min with 20 mg/kg LPS intraperitoneally. Morphometry of type II pneumocytes showed that LPS increased stored surfactant. Lamellar bodies were increased in size, but decreased in numerical density, suggesting that giant lamellar bodies observed in LPS-treated lungs may result from fusion of normal bodies. Structural analysis of alveolar surfactant composition showed that LPS elicited an increase in lamellar body-like and multilamellar forms. Bronchoalveolar lavage (BAL) material from LPS-treated lungs was decreased in phospholipids. BAL bubble surfactometer analysis showed a reduction in hysteresis area caused by LPS. We conclude that LPS leads to alterations of intracellular and alveolar surfactant within 2 h: fusion of lamellar bodies, reduction in surfactant secretion, and changes in alveolar surfactant transformation, composition, and function, which may contribute to the development of respiratory distress.

Ultrastructural pathology of the alveolar type II pneumocytes of human donor lungs. Electron microscopy, stereology, and microanalysis

Alveolar type II pneumocytes (PII) were studied in 12 human donor lungs perfused with modified Euro-Collins solution during single-lung transplantation (SLTx). While one lung was transplanted, the contralateral donor lung (cDL) was fixed at the time of SLTx for examination by electron microscopy, stereology, and microanalysis. Three groups were then formed: group A (n = 7), cDL without contusions, uneventful early postoperative course; group B (n = 3), cDL with conclusions, uneventful early postoperative course; group C (n = 2), cDL without contusions, early postoperative respiratory dysfunction. The major findings were that the presence of contusions had no effect on PII ultrastructure and that intracellular surfactant-storing lamellar bodies of cDL in group C were characterized by a higher volume-to-surface ratio (VsR) and larger area per cell profile than group A. Correlation analysis based on pooled data (groups A and C) showed that ischaemic time had little effect on PII ultrastructure and bore no relationship to postoperative clinical variables. The duration of preoperative donor intubation had a pronounced influence on ultrastructure and postoperative clinical variables. The stereologically estimated amount of intracellular surfactant and mitochondrial VsR were the only ultrastructural parameters that were significantly associated with early postoperative oxygenation. Lamellar bodies were the only ultrastructural components found to have a significant relationship to postoperative intubation time. The ultrastructural integrity of type II pneumocytes of human donor lungs is an important determinant of early respiratory function following clinical lung transplantation.

Influence of incubation time and rinsing buffer on the distribution of the tracer lanthanum in canine heart muscle

Lanthanum (La) is an extracellular tracer, which stains the interstitial space and the cell surface. This study investigates to what extent the distribution of lanthanum in the myocardium of cardioplegically arrested non-ischaemic hearts was influenced by (a) different incubation times in La containing fixative, (b) different kinds of buffer for rinsing and postfixation dilution and (c) different degree of cellular oedema. Myocytes exhibiting La surface staining, with and without intracellular La, were quantified and the volume density of myofibrils (VVMf) as a parameter for the degree of cellular oedema was determined morphometrically. Samples were taken immediately after cardiac arrest induced by coronary perfusion with a cardioplegic solution. Tissue blocks 1 mm3 in size were fixed by immersion for different time periods in a fixation solution containing 1.1% La(NO3)3. Fixation was followed by rinsing in cacodylate or phosphate buffer. The postfixation solution also contained either cacodylate or phosphate buffer. For La detection electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS), was used. Our results show: (i) the volume densities do not differ significantly in specimens rinsed and postfixed in cacodylate or phosphate buffers; (ii) the percentage of myocytes with La surface staining depends on the incubation time in La containing fixative, independent of the rinsing buffer; (iii) the percentage of myocytes with intracellular La correlates significantly with the VVMf; (iv) the incubation time with La containing fixative does not significantly affect the intracellular La staining of slightly swollen cells; and (v) intracellular La distribution patterns differ in cacodylate- and phosphate-buffered specimens. Thus, La tracer methods in conjunction with microanalysis are valuable tools to detect alterations in membrane permeability not visible by conventional transmission electron microscopy (cTEM) in non-ischaemic hearts exhibiting a well preserved ultrastructure.

Effects of ischaemia and preservation on the ultrastructure of the bronchiolar epithelium. A quantitative electron microscopic study of human and canine lungs

In ten cases of clinical human single-lung transplantation, the nontransplanted Euro-Collins-preserved contralateral lungs were examined using electron microscopy to determine the effects of ischaemia on the bronchiolar epithelium. Existing structural damage at the time of transplantation was characterized using this approach, and nine nonpreserved canine single lungs were also investigated to identify the impact of ischaemia. The study revealed a significant correlation between the duration of ischaemia and the mitochondrial surface-to-volume ratio, which can serve as a morphometric criterion for mitochondrial damage, in canine lungs. However, this correlation was not found in the human donor lungs. Further examination of human donor lungs showed slight to moderate damage to the endoplasmic reticulum and nuclear chromatin. In addition, various degrees of damage to mitochondrial structure, ranging from inconspicuous to severe, were found. The mitochondrial surface-to-volume ratio can be considered to be a suitable criterion for the quantification of ischaemic damage of the bronchiolar epithelium under experimental conditions. Ultrastructural analysis of human donor lungs revealed intact bronchiolar epithelial cell structures at the time of transplantation, reflecting adequate organ preservation with Euro-Collins solution.

Cellular distribution patterns of lanthanum and morphometry of rat hearts exposed to different degrees of ischemic stress

BACKGROUND

The element lanthanum (La) can be used as a tracer for verification of membrane permeability. The aim of this study was to establish whether 1) distribution of La in the myocardium of rat hearts depends on the degree of ischemic stress and 2) morphometrically determined cell and mitochondrial swelling correlates with the La distribution.

MATERIALS AND METHODS

Isolated beating rat hearts were arrested by coronary perfusion with the cardioplegic solution Custodiol (controls) or by aortic cross clamping followed by exposure to different degrees of ischemic stress. The solutions for perfusion-and postfixation as well as for rinsing contained 1.1% La(NO3)3. Cellular and mitochondrial swelling were determined morphometrically and myocytes exhibiting intracellular La were quantified and stated as percentage of test fields.

RESULTS

Immediately after cardiac arrest La was present as precipitates only in a few myocytes adjacent to the outer mitochondrial membrane as seen by cTEM and ESI. In such cells La was also detected by EELS in mitochondrial matrix and myofibrils. Advanced ischemic stress led to an increase of the percentage of myocytes containing detectable intracellular La. After 45 min ischemia at 30 degrees C, myocytes and mitochondria showed a remarkable edema and different intracellular distribution patterns of La. After 90 min of ischemia at 20 degrees C interruptions of sarcolemma could only be detected in a few of the swollen myocytes. Roundish La granules were seen in the myofibrils. The percentage of myocytes containing intracellular La and the extent of cellular and mitochondrial swelling showed a significant correlation.

CONCLUSIONS

Patterns of intracellular La distribution depend on the degree of ischemic stress and correspond to the degree of cellular as well as mitochondrial edema. These results point at a direct relation between alterations of membrane permeability and development of edema.

Morphometric characterisation of the fine structure of human type II pneumocytes

BACKGROUND

Pulmonary type II pneumocytes have been examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and morphometry in numerous mammals. Until now, the fine structure of the human type II pneumocyte has not been studied by means of morphometry.

METHODS

Eleven human donor lungs, which could not be made available for a suitable recipient, were preserved with Euro Collins solution (ECS) according to clinical organ preservation techniques. The lungs were fixed via the airways. Systematic random samples were analyzed by SEM, TEM, and classical stereological methods.

RESULTS

Type II pneumocytes showed normal fine structural characteristics. Morphometry revealed that although inter-individual variation due to some oedematous swelling was present, the cells were in a normal size range as indicated by an estimated mean volume of 763 +/- 64 microns 3. The volume densities were: nucleus 21.9 +/- 2.2%, mitochondria 5.8 +/- 0.9%, lamellar bodies 9.8 +/- 3.6%, and remaining cytoplasmic components 62.4 +/- 2.9% of the cell volume. Since the inter-individual variations in the volume densities referred to the cell may, to variable degrees, reflect the variation in the reference space, the volume densities referred to the constant test point system and the respective volume-to-surface ratios were used for inter-individual comparisons. These parameters indicate that lamellar bodies were independent of cellular swelling, while mitochondria < nucleus < remaining cytoplasmic components increased in size with increasing cell size.

CONCLUSIONS

Two to 7.5 hours of cold ischemia following ECS preservation do not deteriorate the fine structure of type II pneumocytes of human donor lungs. For reliable assessment of fine structural variations, morphometric parameters are required that are independent of variations in cell size.

Functional and fine structural changes in isolated rat lungs challenged with endotoxin ex vivo and in vitro

The aim of this study was to relate changes in rat lung functions caused by the endotoxin lipopolysaccharide (LPS) to alterations in structure. The following four experimental groups were used: 1), control in vitro, perfusion for 150 minutes; 2), LPS in vitro, perfusion for 150 minutes and infusion of 5 mg of LPS after 40 minutes; 3), control ex vivo, perfusion for 10 minutes; and 4), LPS ex vivo, lungs perfused for 10 minutes from rats treated for 110 minutes with 20 mg/kg LPS intraperitoneally. Histologically, blood-derived leukocytes were detectable only in lungs from group 4, where neutrophils were found in capillaries, interstitium, and endothelial pouches. LPS treatment increased pulmonary resistance and decreased pulmonary compliance in group 4 (ex vivo), and, to a greater extent, in group 2 (in vitro). In these two groups, formation of giant lamellar bodies in the type II pneumocytes was observed. By histological examination, the bronchoconstriction induced by LPS in vitro was localized to the terminal bronchioles. At 2 hours after LPS treatment, no edema and no change in precapillary and postcapillary resistance, capillary pressure, vascular compliance, capillary permeability, and the wet/dry ratio was observed. Thus, our major findings are that LPS induced constriction of the terminal bronchioles in vitro, formation of giant lamellar bodies in type II pneumocytes ex vivo and in vitro, and trapping of neutrophils in endothelial pouches in vivo.

Evaluation of lanthanide tracer methods in the study of mammalian pulmonary parenchyma and cardiac muscle by electron energy-loss spectroscopy

Lanthanum (La) has widely been used as a tracer to study the integrity of plasma membranes. With conventional transmission electron microscopy (cTEM), the absence of electron scattering deposits from the cytoplasm has generally been assumed to reflect an intact cell membrane. However, the application of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS) reveals that electron scattering deposits may be present which do not contain La. However, La could be detected in regions of pulmonary parenchyma and cardiac muscle that were devoid of electron scattering deposits. Therefore, to exclude misinterpretations based on cTEM the application of microanalytical techniques is strongly recommended for the study of the integrity of plasma membranes by means of La tracers. In addition, ESI and EELS are shown to distinguish between different tracers in simultaneous applications of La and terbium (Tb) which were used at the different faces of the pulmonary air-blood barrier. The analysis of the distribution of both tracers which form electron scattering deposits, indistinguishable by cTEM, may help us to understand the different functional significances of cellular alterations of both cellular borders of the barrier. As was shown for La, however, strictly controlled conditions are mandatory during the fixation procedure because an increase in the incubation time to more than 1 h in samples of pulmonary parenchyma may result in the occurrence of La deposits within the cytoplasm. In the absence of electron scattering deposits, the presence of La in glycogen granules and ribosome-containing areas of various types of alveolar septal cells even after 15 min incubation indicates that the absence of deposits does not necessarily correspond to the absence of the tracer.

Electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) of multilamellar bodies and multilamellar body-like structures in tannic acid-treated alveolar septal cells

We used electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) to compare multilamellar bodies (MLB) of Type II alveolar epithelial cells with MLB-like structures that are present in various alveolar septal cells after fixation with tannic acid. Despite their structural similarity in conventional transmission electron microscopy, the phosphorus signal recorded by both ESI and EELS was considerably higher in multilamellar bodies than in MLB-like structures. This indicates that they are different in chemical composition.

Euro-Collins flush perfusion in human lung preservation--ultrastructural studies of the preservation quality of the contralateral donor lung in clinical single lung transplantation

The quality of pulmonary preservation after Euro-Collins flush perfusion was assessed by means of morphometric analysis based on transmission electron microscopy. In five patients undergoing single lung transplantation, the contralateral donor lung that could not be matched for another recipient was studied by means of light microscopy and transmission electron microscopy. While one of the donor lungs was transplanted, the contralateral lung was fixed by airway instillation at the same time and subsequently processed for microscopic examination. Although light microscopy showed an excellent quality of organ preservation, transmission electron microscopy revealed the presence of fine to medium alterations at the level of the air-blood-barrier. In the five contralateral donor lungs, different degrees of the cellular alterations were recorded by morphometric analysis, which correlated with differences observed in the early postoperative course of the patients receiving the other lung, respectively. Although in four of five patients the clinical course showed no complications and extubation was performed within 36 hours after the operation, one patient required artificial ventilation over a period of 10 days because of impaired oxygenation of the transplanted lung. In this patient, morphometric analysis of the air-blood-barrier showed a significantly (p < 0.02) smaller surface fraction of normal type 1 pneumocytes, a significantly (p < 0.05) smaller volume density of the capillary endothelial cells, and a significantly (p < 0.01) higher volume density of type 2 pneumocytes. The alterations of the alveolar epithelium have to be interpreted as a result of influences occurring during the donor's medical history rather than being an effect of preservation and/or ischemia.

Scanning and transmission electron microscopy of human donor lungs: fine structure of the pulmonary parenchyma following preservation and ischemia

In six cases of clinical single-lung transplantation, the contralateral donor lungs were studied by means of scanning (SEM) and transmission (TEM) electron microscopy. SEM and TEM revealed an overall good to excellent preservation of the pulmonary parenchyma. Since the donor double lung blocks, which were preserved by means of pulmonary arterial perfusion with modified Euro-Collins solution, were separated immediately prior to transplantation, transplanted and contralateral lungs had been subjected to identical influences. Comparing the arterial oxygenation achieved in the recipient 6 h after transplantation with the structural data of the corresponding contralateral donor lung, the degree of epithelial alterations appeared to be most important in determining postoperative lung function. Concerning the assessment of the quality of the alveolar epithelium, gradings performed independently by means of SEM and TEM yielded largely corresponding scores, while a significant shortcoming of SEM was the very limited access to the endothelial surface. Taking into account the relevance of epithelial injury in determining postoperative lung function, SEM can provide clinically relevant data more quickly than TEM. To quantify the fine structural alterations of human donor lungs, however, TEM-based morphometry is required.