Divisions of 1 Pulmonary Medicine and 2 Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039
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ABSTRACT |
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Transgenic mice overexpressing
human transforming growth factor- (TGF-
) develop emphysema and
fibrosis during postnatal alveologenesis. To assess dose-related
pulmonary alterations, four distinct transgenic lines expressing
different amounts of TGF-
in the distal lung under control of the
surfactant protein C (SP-C) promoter were characterized. Mean lung
homogenate TGF-
levels ranged from 388 ± 40 pg/ml in the
lowest expressing line to 1,247 ± 33 pg/ml in the highest
expressing line. Histological assessment demonstrated progressive
alveolar airspace size changes that were more severe in the higher
expressing TGF-
lines. Pleural and parenchymal fibrosis were only
detected in the highest expressing line (line 28), and
increasing terminal airspace area was associated with increasing
TGF-
expression. Hysteresis on pressure-volume curves was
significantly reduced in line 28 mice compared with other
lines of mice. There were no differences in bronchoalveolar lavage
fluid cell count or differential that would indicate any evidence of
lung inflammation among all transgenic lines. Proliferating cells were
increased in line 28 without alterations of numbers of type
II cells. We conclude that TGF-
lung remodeling in transgenic mice
is dose dependent and is independent of pulmonary inflammation.
pulmonary fibrosis; emphysema; epidermal growth factor receptor
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INTRODUCTION |
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TRANSFORMING GROWTH
FACTOR- (TGF-
) is a polypeptide member of
the epidermal growth factor (EGF) family, which includes the EGF,
amphiregulin and heparin-binding EGF. Synthesized as a 160-amino acid
precursor polypeptide, mature 50-amino acid TGF-
peptide is released
through proteolytic cleavage by specific elastase-like enzymes
(3). TGF-
mRNA is present throughout prenatal lung development (12). In human fetal and postnatal lungs,
TGF-
immunolocalizes to airway and alveolar epithelial cells and
vascular smooth muscle (14). Although TGF-
is clearly
produced in many cells in the developing lung, the precise
physiological role for TGF-
is not completely understood. In vitro,
TGF-
increases the proliferation of rabbit type II alveolar and
cultured lung fibroblasts (2, 13), which suggests that
TGF-
is involved in the propagation of cell populations in the lung
during development.
Although TGF- appears to be active in lung development, there is
evidence that TGF-
also participates in diseases where there is
significant lung remodeling. Strandjord and colleagues (14) demonstrated increased immunostaining for TGF-
in
pulmonary epithelial cells of infants dying from respiratory distress
syndrome or bronchopulmonary dysplasia (BPD). Lung biopsies from
patients with idiopathic pulmonary fibrosis demonstrate increased
TGF-
staining in the vascular endothelium, type II pneumocytes, and fibroblasts compared with controls (1). Lungs from
patients with end-stage cystic fibrosis (CF) contain increased
immunostaining for TGF-
in alveolar macrophages, airway epithelial
cells, and diseased submucosal areas compared with healthy controls
(5). Increased immunostaining with the proliferation
marker Ki67 was detected in submucosal regions of the CF lungs, which
suggests that TGF-
may be partially responsible for lung remodeling
via increased proliferation of interstitial cells. The orderly
production of TGF-
during lung development may be reactivated during
disease processes that lead to lung remodeling.
Transgenic mice overexpressing high levels of TGF- in the distal
lung under control of the surfactant protein C (SP-C) promoter demonstrate enlarged alveolar airspaces with pleural and peribronchial fibrosis (8) due to abnormal development during postnatal
alveolarization (6). To determine the levels of TGF-
that induce alveolar emphysema and fibrosis and to assess mechanisms by
which TGF-
causes lung remodeling, four lines of SP-C transgenic
mice with distinct levels of transgene expression were compared for the extent of cellular proliferation, airspace enlargement, pulmonary fibrosis, and pulmonary function. Increased levels of transgenic TGF-
were associated with increasingly severe morphological and physiological alterations in the lung.
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METHODS |
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Transgenic mice and Southern blot analysis.
Methods for generating transgenic mice that express human TGF- under
control of the human SP-C 3.7-kb promoter-enhancer sequence were
previously described (8). Four founder lines (lines
6108, 4, 2, and 28) on the FVB/N
background strain were evaluated compared with an FVB/N nontransgenic
control. All mice studied were transgene heterozygotes. Transgenic mice
were identified by a diagnostic 1.4-kb band on genomic Southern blots
of PstI-digested genomic tail DNA as previously described
(8). Studies were approved by the Institutional Animal
Care and Use Committee of the Children's Hospital Research Foundation
and the University of Cincinnati Medical Center (Cincinnati, OH).
Quantitation of TGF- expression.
The lungs from 2-mo-old mice from each transgenic line and the
nontransgenic control were removed and the mice were euthanized. Lung
tissue was homogenized in 2 ml of PBS (pH 7.2) and centrifuged at 1,500 g, and the supernatant was stored at
70°C. Human TGF-
levels were determined using a quantitative murine sandwich
enzyme-linked immunosorbent assay (ELISA) kit (Oncogene Research
Products, Cambridge, MA) according to the manufacturer's directions.
All plates were read on a microplate reader (Molecular Devices, Menlo
Park, CA) and analyzed with the use of a computer-assisted analysis
program (Softmax, Molecular Devices). Only assays having standard
curves with a calculated regression line value >0.95 were accepted for analysis.
Pulmonary histology and immunohistochemistry. Two-month-old mice from each group were euthanized with intraperitoneal pentobarbital sodium. The tracheae were cannulated and the lungs were inflated (1 min at 25 cmH2O) with 4% paraformaldehyde in PBS (pH 7.2). After 24 h of immersion, the lungs were washed in PBS, dehydrated in graded alcohol and xylene, and embedded in paraffin (60°C). Paraffin-embedded lungs were sectioned (5 µm) and placed on Polysine glass slides (Erie Scientific, Portsmouth, NH). The slides were deparaffinized with xylene and rehydrated with graded alcohol washes and PBS. The sections were stained with hematoxylin and eosin and Gomori trichrome stain.
For immunohistochemical detection of 5-bromo-2'-deoxyuridine (BrdU), 2-wk-old animals from each line were injected with BrdU-labeling reagent (0.1 ml/100 g body wt; Zymed Laboratories, San Francisco, CA) 2 h before death. BrdU incorporated into DNA was detected using anti-BrdU monoclonal antibody and a BrdU staining kit (Zymed Laboratories). BrdU staining for each animal was performed on three randomly selected fields from serial sections at ~2.0-mm intervals. Staining was analyzed only in the distal lung in the alveolar region, and the proliferation index was determined by counting the total number of BrdU-stained nuclei and dividing by the total number of nuclei in each field. Antibodies and procedures for immunostaining to detect proSP-C have been described previously (17). The total number of type II cells per field and the percentage of type II cells per nuclei were determined from random fields in three serial sections. As with BrdU detection, staining and analysis were performed only in the distal lung in the alveolar region. To further identify subpopulations of proliferating cells, lung tissue sections were double-stained with proliferating cell nuclear antigen (PCNA) and proSP-C. Briefly, tissue sections were dehydrated and then stained first for proSP-C using methods briefly described (17). To distinguish PCNA nuclear staining from proSP-C, development of SP-C was modified by using alkaline phosphatase substrate reagent and counterstaining with vector red. This adaptation caused proSP-C to stain red in the cell cytoplasm. Tissue was then fixed with 4% paraformaldehyde. PCNA staining was performed using a staining kit with a biotinylated monoclonal antibody as per the manufacturer's recommendations. PCNA cells were identified with a dark-brown nuclear stain.Morphometry. Mice were killed at 2 mo of age for morphometric studies. Lung tissue sections stained with hematoxylin and eosin were prepared as described (see Pulmonary histology and immunohistochemistry). Two serial sections at ~2.0-mm intervals were studied for each animal. Three representative fields of lung were studied per slide. The studied section was visually scanned, and fields were selected to contain terminal airspaces. Fields with large conducting airways, longitudinal sections of alveolar ducts, or blood vessels were not selected.
Morphometric measurements for terminal airspace area were collected using Image-1/Metamorph Imaging System version 2 for Microsoft Windows (Universal Imaging) and using methods previously described (6). Briefly, calibrations for ×4, ×10, and ×20 images were determined by acquiring images of a ruler (in micrometers) at these powers, which allows the computer to calculate the number of pixels per micrometer at each power. Images were corrected for tears in airspace walls. The airspaces were distinguished from tissue based on intensity, and the computer measured the number of pixels in each airspace. These measurements were then converted and recorded in square micrometers.Pressure-volume curve. Mice were sedated with pentobarbital sodium (100 mg/kg ip) and placed in a box containing 100% oxygen to ensure complete collapse of the alveoli by oxygen absorption after spontaneous breathing ceased. The mice were euthanized by exsanguination. The trachea was cannulated and connected by a syringe to a pressure sensor (mouse pulmonary testing system) via a three-way connector. After the diaphragm was opened, the lungs were inflated in 75-µl increments every 10 s to a maximum pressure and were similarly deflated (15). Lung volume is expressed as milliliters per kilogram of body weight. Hysteresis was measured by counting the intersections of the squares and multiplying by the area of the square.
Bronchoalveolar lavage fluid cell count, differential count, and lung homogenate proinflammatory cytokines. After the mice were euthanized, the tracheae were cannulated and the lungs were lavaged three times with 1 ml of Hanks' balanced salt solution [containing (in mM) 137 NaCl, 5.4 KCl, 0.44 KH2PO4, 0.34 Na2HPO4, 4.2 NaHCO3, and 5.6 glucose]. Bronchoalveolar lavage (BAL) fluid was pooled and immediately cooled to 4°C. Differential cell counts were performed on Diff-Quik-stained (Baxter Diagnostics, McGaw Park, IL) cytospin (Cytospin 3, Shandon Scientific) slides of cells from 200 µl of BAL fluid; 200 cells/slide were counted. The remaining BAL fluid was then centrifuged at 1,300 rpm for 10 min. Cells were resuspended in PBS, and 10 µl of cells were mixed with 10 µl of 0.4% trypan blue and placed on a hemocytometer. White blood cells were counted on a grid and normalized to cells per milliliter.
Tumor necrosis factor-Statistical analysis.
Pressure-volume curve measurements were compared using ANOVA and
subsequent Student-Newman-Keuls test. Differences in TGF- lung
homogenate levels, cell counts, BrdU, and type II cell indexes were
compared using ANOVA. Differences in terminal airspace areas between
strains of mice were determined using an ANOVA conducted with an
-level of 0.05. Scores from the individual mice were nested within
groups to reduce extraneous variance. The analysis was performed with
the SAS 6.12 statistical software (SAS Institute, Cary, NC) general
linear model according to the manufacturer's recommended procedure.
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RESULTS |
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Concentration of human TGF- in lung homogenates.
Human TGF-
levels were different between each transgenic line, with
a threefold increase in the amount of TGF-
produced between the
lowest expressing line 6108 and the highest expressing line 28 (Table 1). All values
were also normalized to mean nontransgenic levels to control for
endogenous mouse TGF-
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Histological and morphometric changes related to TGF-
expression.
Lines 6108 and 4 demonstrate minimal alveolar
airspace enlargement compared with nontransgenic mice (Fig.
1); the mean airspace areas were almost
identical between line 6108 (510 ± 10 µm2) and line 4 (509 ± 11 µm2; Fig. 2). Although
airspace area in lines 6108 and 4 was increased compared with that in nontransgenic control mice (417 ± 8 µm2), these differences did not reach statistical
significance. For line 2 mice, the alveoli appeared
emphysematous compared with nontransgenic, line 6108, and
line 4 mice (Fig. 1). The mean airspace area was
significantly increased in line 2 mice (1,447 ± 77 µm2) compared with nontransgenic control, line
6108, and line 4 mice. Line 28 lungs
appeared most remodeled, and the pleural and septal thickening
identified in these mice were not detected in the other transgenic
lines (Fig. 1). In addition to the thickened pleura, there were
occasional scattered areas of peribronchial and perivascular fibrosis
(data not presented). Airspace area for line 28 mice (5,843 ± 319 µm2) was significantly greater than
for the other transgenic and nontransgenic mice.
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Altered pressure-volume curves.
As shown in Fig. 3, there were no
differences in opening or maximal pressures between nontransgenic,
line 6108, and line 4 mice. These three lines of
mice had normal opening pressures of ~15 cmH2O. In
line 2 and line 28 mice, the lung volume
increased as the pressure increased, whereas these mice did not show
obvious increases in opening pressure. Line 2 mice had
significantly higher lung volumes at maximum pressure than other
groups. The volume at 15 cmH2O on the inflation limb of
line 2 and line 28 mice pressure-volume curves
was more than twofold higher than that in control, line 6108, and line 4 mice. Hysteresis was significantly
reduced in line 28 mice compared with all other transgenic
lines or control mice (Fig. 3).
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TGF- enhanced BrdU labeling and type II cell staining.
Incorporation of BrdU into DNA was used to estimate cell proliferation
in the different lines of transgenic mice. Significantly increased BrdU
was detected only in line 28 mice, which demonstrated a
threefold increase compared with control or the other transgenic lines
(Table 2). BrdU labeling among line
28 mice was detected primarily in respiratory epithelial cells in
the lung periphery, although proliferating cells were detected in
fibrosing areas in the peribronchial, perivascular, and lung pleura
(Fig. 4). Double
staining with PCNA and proSP-C in line 28 sections confirmed that many of the proliferating cells were type II cells (Fig. 4).
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TGF--induced alterations are not associated with pulmonary
inflammation.
To determine whether TGF-
-induced lung remodeling was associated
with inflammation, BAL fluid cell counts and lung homogenate proinflammatory cytokines were measured. There were no significant differences noted in the total cell counts or the lung differential counts among transgenic lines compared with nontransgenic mice (Table
3). Proinflammatory cytokine lung
homogenate levels were measured in five nontransgenic control and five
line 28 mice. No significant differences were detected for
each cytokine between nontransgenic and line 28 mice.
Measured levels for nontransgenic and line 28 mice were,
respectively, as follows: TNF-
, 16.4 ± 3 and 12.8 ± 1 pg/ml; IL-1
, 52.7 ± 10 and 31.1 ± 6 pg/ml; and MIP-2,
4.6 ± 1 and 3.7 ± 2 pg/ml.
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DISCUSSION |
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The present study demonstrates that increased TGF- expression
in the lung produces incremental histological changes related to the
level of transgenic human TGF-
expression. The two lower expressing
TGF-
lines (lines 6108 and 4) demonstrated
mild alveolar airspace enlargement, with the alveolar airspace area
~25% larger than the nontransgenic alveolar airspace; however, these
values were not statistically significant. With the higher levels of TGF-
expression produced by line 2 mice, the alveoli were
uniformly enlarged, and the airspace areas were three times larger than for nontransgenic mice. The highest expressing line, line
28, demonstrated significant lung remodeling with markedly
enlarged alveolar airspace area as previously reported
(6). Airspace areas were 14 times larger than control
areas. Line 28 mice were the only transgenic line to
demonstrate fibrosis, which was apparent on the pleural surface,
alveolar septa, and peribronchial and perivascular regions. The degree
of airspace remodeling was directly related to the level of human
TGF-
expression, and the highest levels also induced pulmonary fibrosis.
Alterations in opening pressures and maximal volumes corresponded to
the severity of lung remodeling. There were no differences detected in
the pressure-volume curves in line 6108 and line
4 mice compared with controls, and hence there were no detectable physiological effects of the mild emphysema in these lines. Line 2 mice did not have higher opening pressure but did have higher lung volumes at maximum pressure than all the other groups. It is
likely that the alveoli in line 2 mice are more distensible, but the molecular basis for these changes is not known. Lungs of
high-level-expressing lines have altered elastin structure (8), and it is possible that a subtle alteration in
elastin could also be present in other TGF- transgenic lines. For
line 28 mice, the lung volumes were slightly larger than in
control, line 6108, and line 4 mice but not as
large as for line 2 mice. The most likely explanation for
lower lung volumes in line 28 mice compared with line
2 mice is that the pleural fibrosis in line 28 reduced
lung expansion at the higher inflation volumes. Line 28 mice
were the only line of mice to demonstrate significantly increased
hysteresis that most likely reflects the more distensible emphysematous alveoli.
TGF- is a known mitogen for a variety of cells in the lung including
type II epithelial cells and fibroblasts (2, 13). To begin
investigating the mechanisms by which TGF-
expression induces lung
remodeling and the subsequent physiological effects, we examined the
proliferative index in the distal alveolar region where TGF-
is
expressed. We observed a mild yet statistically insignificant increase
in BrdU-labeled cells in the lower-expressing lines, whereas for
line 28 mice, BrdU-labeled cells were more abundant than in
the other transgenic lines and three times greater than in
nontransgenic mice. Cells demonstrating proliferation in line
28 mice included type II cells and interstitial cells. We did not
specifically identify these other proliferating cells, but they appear
to include fibroblasts and occasional macrophages. Because line
28 is the only transgenic line to develop histological evidence of
fibrosis and significant increases in proliferating subsets of cells,
these findings suggest that there is a threshold level of TGF-
expression in the lung, after which there is increased cellular
proliferation. Increased numbers of interstitial cells could lead to
increased collagen deposition in the lung. The precise molecular
signaling mechanism whereby TGF-
expression induces fibrosis in the
transgenic mice is not understood. We have previously generated
transgenic mice where EGF receptor signaling was disrupted in type II
cells. These transgenic mice expressed a mutated EGF receptor sequence
that lacked a portion of the intracytoplasmic domain but contained the
transmembrane and extracellular ligand-binding domain under control of
the SP-C promoter (a mutated EGF receptor) (7). When
bitransgenic mice were generated with the line 28 TGF-
transgene and the SP-C mutated EGF receptor transgene, there was no
histological evidence of fibrosis. Because the mutated EGF receptor was
expressed in type II cells, these findings suggest that line
28-induced fibrosis develops not through a direct paracrine effect
from TGF-
acting on interstitial cells but rather through an
undefined signaling pathway between type II cells and interstitial cells.
The mechanism for emphysema in the transgenic lines is also unclear. We
have previously demonstrated in line 28 mice that emphysema
develops in the immediate postnatal period when saccules are
subdividing into alveoli (6). There are also histological abnormalities of elastin (8) that may disrupt the orderly
secondary septation of saccules, thus resulting in more disorganized,
emphysematous alveoli. However, two lines of evidence suggest that
TGF--induced emphysema is not directly a result of increased
proliferation. First, we were unable to demonstrate increased
proliferation in line 2 mice despite significant
histological and morphometric emphysema. Second, if the emphysema was
secondary to increased proliferation of alveolar cells, we hypothesized
that we would detect an increase in the type II cell population of the
lung relative to other cells. Our analysis of type II cells
demonstrated no changes in the percentage of type II cells as a
proportion of total cell nuclei among all transgenic lines compared
with nontransgenic controls. Ganser and colleagues (4)
demonstrated that mouse lung explants produced a marked dilation of
tubular end buds and reduced branching when treated with TGF-
.
Increased activity of a type IV collagenase-gelatinase (possibly matrix metalloproteinase-2) was detected, which suggests that TGF-
induces proteinase-elastase activity. We have previously reported that in
TGF-
transgenic mice, elastin fibers appear to be less abundant and
blunted in the bronchiolar regions and alveolar septa compared with
normal nontransgenic lungs (8). TGF-
produced in the transgenic mouse lung may induce or activate matrix-degrading enzymes
that subsequently disrupt or degrade the elastin network and inhibit
the formation of normal alveoli during postnatal alveologenesis.
Previous experimental data indicate that TGF- is induced after
various forms of lung injury. TGF-
is released from alveolar macrophages stimulated by endotoxin in vitro (11). Rodent
lungs injured with intratracheal administration of asbestos,
naphthalene, or bleomycin produce increased TGF-
mRNA transcripts or
protein in the airway and alveolar epithelium as well as the
interstitium (9, 10, 16). In the transgenic lines, lung
remodeling was not related to or induced by lung inflammation. There
were no differences in the total white cell counts or differential
counts in the BAL fluid cells between any of the transgenic and control mice, nor were there any differences in selected proinflammatory lung
homogenate cytokines between nontransgenic and line 28 mice. TGF-
expression in the lung does not induce further inflammation but
rather induces direct changes in the lung architecture that are
independent of inflammation.
The postnatal lung remodeling of TGF- transgenic mice may have
clinical relevance with regard to lung diseases of infancy and
childhood, specifically BPD and CF. Premature lungs are injured after
birth from a variety of causes including barotrauma, reduced surfactant, and infection. These premature lungs develop inflammation and significant lung remodeling during the chronic phases of repair. Some of the pathological features of BPD resemble the lung remodeling seen in transgenic TGF-
mice, including emphysematous alveoli and
fibrosis of the pleural surface. Immunohistochemistry of infants who
died from BPD demonstrates a prominence of EGF, TGF-
, and EGF
receptor in the diseased areas of the lung (14). Analysis of the lungs of patients with end-stage CF demonstrated marked TGF-
staining in inflamed airway epithelium and fibrosing submucosal areas
(5). Hence the findings of increased TGF-
and EGF and the similarities in some features of lung remodeling seen in BPD and CF
and in the TGF-
transgenic mice suggest that injury-induced TGF-
expression leads to morphological and functional abnormalities of the lung.
In summary, this study demonstrates that TGF- expression in the lung
can induce changes in the lung architecture in a dose-response fashion
that are independent of lung inflammation. Because TGF-
is known to
be released in disease states where there is subsequent lung
remodeling, it is likely that TGF-
is a component of the complex
cascade of growth factors and cytokines that cause postnatal lung remodeling.
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ACKNOWLEDGEMENTS |
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We thank Judy Bean for assistance with statistics, Marie Chappel for manuscript preparation, Sherri Profitt and Susan Wert for morphology and histology, and Jeff Whitsett for helpful advice and critical reading of the manuscript.
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FOOTNOTES |
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This work was sponsored by National Heart, Lung, and Blood Institute Grant KO8-HL-04172.
Address for reprint requests and other correspondence: W. D. Hardie, Division of Pulmonary Medicine, Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229-3039 (E-mail: bill.hardie{at}chmcc.org).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 22 March 2001; accepted in final form 18 July 2001.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Baughman, RP,
Lower EE,
Miller MM,
Bejarano PA,
and
Heffelfinger SC.
Overexpression of transforming growth factor- and epidermal growth factor-receptor in idiopathic pulmonary fibrosis.
Sarcoidosis Vasc Diffuse Lung Dis
16:
57-61,
1999[ISI][Medline].
2.
Derynck, R.
Transforming growth factor-.
Cell
54:
593-595,
1988[ISI][Medline].
3.
Derynck R, Roberts AB, Winkler ME, Chen EY, and Goeddel DV. Human
transforming growth factor-: precursor, structure, and expression in
E. coli. Cell 38: 287-297.
4.
Ganser, GL,
Stricklin GP,
and
Matrisian L.
EGF and TGF- influence in vitro lung development by the induction of matrix-degrading metalloproteinases.
Int J Dev Biol
35:
453-461,
1991[Medline].
5.
Hardie, WD,
Bejarano PA,
Miller MA,
Yankaskas JR,
Ritter JH,
Whitsett JA,
and
Korfhagen TR.
Immunolocalization of transforming growth factor- and epidermal growth factor receptor in lungs of patients with cystic fibrosis.
Pediatr Dev Pathol
2:
415-423,
1999[ISI][Medline].
6.
Hardie, WD,
Huelsman K,
Bruno M,
Iwamoto H,
Carrigan P,
Leikauf G,
and
Korfhagen T.
Effects of TGF- during postnatal alveolarization in transgenic mice.
Am J Pathol
151:
1075-1083,
1997[Abstract].
7.
Hardie, WD,
Kerlakian CB,
Bruno MD,
Huelsman KM,
Wert SE,
Glasser SW,
Whitsett JA,
and
Korfhagen TR.
Reversal of lung lesions in transgenic TGF- mice by expression of mutant EGF-R.
Am J Respir Cell Mol Biol
15:
499-508,
1996[Abstract].
8.
Korfhagen, TR,
Swantz RJ,
Wert SE,
McCarty JM,
Kerlakian CB,
Glasser SW,
and
Whitsett JA.
Respiratory epithelial cell expression of human transforming growth factor- induces lung fibrosis in transgenic mice.
J Clin Invest
93:
1691-1699,
1994[ISI][Medline].
9.
Liu, J,
Morris G,
Lei W,
Corti M,
and
Brody A.
Up-regulated expression of transforming growth factor- in the bronchiolar-alveolar duct regions of asbestos-exposed rats.
Am J Pathol
149:
205-217,
1996[Abstract].
10.
Madtes, DK,
Busby HK,
Strandjord TP,
and
Clark JG.
Expression of transforming growth factor- and epidermal growth factor receptor is increased following bleomycin-induced lung injury in rats.
Am J Respir Cell Mol Biol
11:
540-551,
1994[Abstract].
11.
Madtes, DK,
Raines EW,
Sakariassen KS,
Assoian RK,
Sporn MB,
Bell GI,
and
Ross R.
Induction of transforming growth factor- in activated human alveolar macrophages.
Cell
53:
285-293,
1988[ISI][Medline].
12.
Ruocco, S,
Lallemand A,
Tournier JM,
and
Gaillard D.
Expression and localization of epidermal growth factor, transforming growth factor-, and localization of their common receptor in fetal human lung development.
Pediatr Res
39:
448-455,
1996[Abstract].
13.
Ryan, RM,
Mineo-Kuhn MM,
Kramer CM,
and
Finkelstein JN.
Growth factors alter neonatal type II alveolar epithelial cell proliferation.
Am J Physiol Lung Cell Mol Physiol
266:
L17-L22,
1994
14.
Strandjord, TP,
Clark JG,
Guralnick DE,
and
Madtes DK.
Immunolocalization of transforming growth factor-, epidermal growth factor (EGF), and EGF-receptor in normal and injured developing human lung.
Pediatr Res
38:
851-856,
1995[Abstract].
15.
Tokieda, K,
Ikegami M,
Wert SE,
Baatz JE,
Zou Y,
and
Whitsett JA.
Surfactant protein B corrects oxygen-induced pulmonary dysfunction in heterozygous surfactant protein B-deficient mice.
Pediatr Res
46:
708-714,
1999[Abstract].
16.
Van Winkle, LS,
Isaac JM,
and
Plopper CG.
Distribution of epidermal growth factor receptor and ligands during bronchiolar epithelial repair from naphthalene-induced Clara cell injury in the mouse.
Am J Pathol
151:
443-459,
1997[Abstract].
17.
Zhou, L,
Lim L,
Costa RH,
and
Whitsett JA.
Thyroid transcription factor-1, hepatocyte nuclear factor-3, surfactant protein B, C, and Clara cell secretory protein in developing mouse lung.
J Histochem Cytochem
44:
1183-1193,
1996