| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
From 1 Retina Associates, Boston, Massachusetts; and 2 Schepens Eye Research Institute, Harvard Medical School, Boston, Massachusetts; and the 3 Fred Hutchinson Cancer Research Center, Seattle, Washington.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
METHODS. The approach was to compare the extent of PVR induced by cells that do or do not express the receptors for PDGF and therefore differ in their ability to respond to PDGF.
RESULTS. Mouse embryo fibroblasts derived from PDGF receptor knock-out embryos
that do not express either of the two PDGF receptors induced PVR poorly
when injected into the eyes of rabbits that had previously undergone
gas vitrectomy. Re-expression of the PDGF ß receptor in these cells
did not improve the ability of the cells to cause PVR. In contrast,
injection of cells expressing the PDGF 
receptor resulted in stage 3
or higher PVR in 8 of 10 animals.
CONCLUSIONS. These findings show that PDGF makes an important contribution to the
development of PVR in this animal model. Furthermore, there is a marked
difference between the two receptors for PDGF, and it is the PDGF
receptor that is capable of driving events that lead to
PVR.
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In an attempt to understand the basis of this disease, a number of investigators have focused on the composition of the ERM. It is largely fibrous material, containing retinal pigment epithelial (RPE) cells and, to a lesser extent, glial cells.6 7 8 There are numerous growth factors associated with the ERM and/or secreted by the RPE cells.9 10 11 Expression of platelet-derived growth factor (PDGF)-AA, one of the three isoforms of PDGF, is increased in RPE cells within the ERM of human patients.12 Animal models also show increased PDGF-AA expression in RPE cells after either retinal detachment or laser damage.13 14 Because RPE cells also express the receptors for PDGF,9 it is possible that retinal insult triggers a PDGF-mediated autocrine loop in RPE cells. This idea is supported by the observation that the growth of cultured human RPE cells can be partially blocked by neutralizing antibodies to PDGF.13
PDGF is a dimeric polypeptide that occurs in several different forms:
PDGF-BB, PDGF-AB, and PDGF-AA.15
16
The different isoforms
of PDGF appear to have distinct functions, because knocking out each of
the genes for PDGF leads to distinct phenotypes.17
18
This
is, at least in part, because there are two different PDGF receptor
(PDGFR) subunits, and the composition of the receptor (which is a
ligand-inducible dimer of two subunits) is determined by the isoform of
PDGF. For instance, PDGF-BB is the universal ligand, and it assembles
and ßß homodimers and ß heterodimers, whereas PDGF-AA
activates only homodimers. Once activated, the PDGFR initiates
signal relay cascades that drive biologic responses, such as chemotaxis
and proliferation. Although these data strongly implicate PDGF (and in
particular PDGF-AA) as a contributor to the pathologic events leading
to PVR, it is likely that PDGF is not the only growth factor involved.
We have recently found that the receptor for hepatocyte growth factor
is expressed by RPE cells and that it stimulates migration of cultured
RPE cells. Furthermore, ERMs from patients with PVR are strongly
positive for the hepatocyte growth factor receptor.19
In
addition, others have found that RPE cells secrete vascular endothelial
growth factor (VEGF), express receptors for VEGF, and respond
mitogenically and chemotactically to VEGF.10
11
20
Consequently, VEGF may also play a role in PVR. Together, these
findings have lead to the hypothesis that formation of the ERM is at
least in part driven by growth factor-mediated proliferation and
chemotaxis of RPE cells.1
2
5
21
Although many growth
factors have been implicated in PVR, the relative contribution of even
the best candidate (PDGF) has not been tested.
In this study, we directly tested the hypothesis that PDGF is important
for PVR in a rabbit model of the disease. This was accomplished by
using a novel approach of comparing the PVR potential of cells that
differed in the ability to respond to PDGF. Our findings strongly
implicate the PDGFR in our animal model of PVR. Importantly, the
PDGFR is selectively activated by PDGF-AA, the isoform that has been
strongly tied to PVR in humans. Finally, our data demonstrate that the
contribution of the receptor for a single growth factor can
dramatically influence the incidence of disease.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
and ßPDGFR cDNA were subcloned into the pLXSHD and
pLXSH retroviral vectors,22
respectively, and the
resultant plasmids were introduced into PA137 cells, an amphotropic
virus-producing cell line, as previously described.23
The
virus was used to infect F cells, mouse embryo fibroblasts that are
nullizygous for both of the PDGFRs. These cells were derived as
follows: E 9.5 embryos were recovered from timed matings of PDGFR
alpha+/-, PDGFR beta+/- X
PDGFR alpha+/-, and PDGFR
beta+/- mice,24
25
which were on a
hybrid (C57BL6x129sv) background. Embryos were dissociated for 5
minutes with 0.25% trypsin and 1 mM EDTA at 37°C. The cells were
then plated on 30-mm gelatinized dishes and immortalized by infection
with retroviral vector harboring the simian virus 40 large T
antigen.26
Cells were passaged at a 1:10 dilution every 3
days. After infection of the cells with the PDGFR viruses, the cells
were selected in the presence of 5 mM histidinol (PDGFR) or 200
µg/ml hygromycin (ßPDGFR). Coexpression of both receptors was
achieved by infecting the PDGFR cells (F) with the ßPDGFR
virus, and the cells were grown in the presence of both histidinol and
hygromycin.
Western Blot Analysis
To determine the level to which the PDGFRs were expressed, cells
were grown to confluence, washed twice with 20 mM Hepes (pH =7.4) and
150 mM NaCl (HS) and lysed in EB (10 mM Tris-HCl [pH 7.4], 5 mM EDTA,
50 mM NaCl, 50 mM NaF, 1% Triton X-100, 20 µg/ml aprotinin, and 1 mM
phenylmethylsulfonyl fluoride). The lysates were centrifuged for 15
minutes at 13,000 rpm (refrigerated microfuge; Savant Instruments,
Farmingdale, NY), the protein content of the clarified lysates was
determined with the BCA protein assay (Pierce, Rockford, IL), and then
30 µg protein was resolved by 10% sodium dodecyl
sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The proteins
were transferred onto membranes (Immobilon; Amersham, Arlington
Heights, IL), and the membrane was subjected to western blot analysis
using anti-PDGFR (27P/80.8) or anti-ßPDGFR (30A) antibodies, as
previously described.27
28
To measure PDGF-dependent Erk activation, cells were grown to 80% to 90% confluence, starved in Dulbecco’s modified Eagle’s medium (DMEM) plus 0.1% calf serum for 24 hours and then stimulated with 40 ng/ml of PDGF-AA or PDGF-BB for 5 minutes. The cells were washed with HS plus 2 mM sodium orthovanadate and lysed in EB plus 2 mM sodium orthovanadate. The clarified lysates were subjected to BCA protein assay, and 30 µg protein was resolved on 7.5% SDS-PAGE and transferred onto membranes. Membranes were probed with primary anti phosphoErk antibodies (1:500 dilution; New England Biolabs, Beverly, MA) and then with a horseradish peroxidase–conjugated goat anti-mouse secondary antibody (1:5000; Amersham). The signal was detected by enhanced chemiluminescence (Amersham). Western blot analysis with antibodies against the GTPase activating protein of Ras (RasGAP) was performed as previously described.29
[3H]Thymidine Uptake
Cells were plated in 24-well dishes at 6 x
104 cells per well in DMEM plus 10% fetal bovine
serum (FBS) and incubated at 37°C for 24 hours. Cells were washed
twice with phosphate-buffered saline (PBS) and then incubated in DMEM
plus 2 mg/ml BSA for 48 hours. Buffer (10 mM acetic acid and 2 mg/ml
BSA), PDGF AA (50 ng/ml), PDGF-BB (50 ng/ml), or FBS (10%) was added
for 18 hours, and then the cells were pulsed with
[3H]thymidine (0.8 µCi/ml) for 4 hours. Cells were
washed with ice-cold PBS, then with 5% trichloroacetic acid and lysed
in 0.25N NaOH. Lysates were transferred into scintillation vials
containing 50 µl of 6 N HCl and 4 ml of scintillation cocktail (ICN,
Costa Mesa, CA). Incorporated radioactivity was determined by
scintillation counting. Each experimental condition was assayed in
triplicate. Two independent experiments were performed and produced
similar results.
Rabbit Surgery
Eighty pigmented rabbits in eight groups of 10 were used. The
groups consisted of animals that were injected with either of the four
cell lines (F, F, Fß, or Fß), in the presence or absence of
platelet-rich plasma (PRP). All rabbits were anesthetized with an
intramuscular injection of 0.5 ml chloropromazine HCl (25 mg/ml) and 1
ml ketamine HCl (100 mg/ml) per kilogram. In all cases, only one of the
eyes was subjected to treatment. Gas compression of the vitreous was
accomplished according to standard procedures.30
.31
Briefly, 0.4 ml perfluoropropane (C3F8) gas was injected into the
vitreous through a 30-gauge needle 4 mm posterior to the limbus. A
paracentesis created by a 30-gauge needle at the limbus was used to
remove 0.2 ml of vitreous to restore normal eye pressure. The gas was
removed on the third day after the injection. To prepare the cells for
injection, dishes of confluent cells were trypsinized, washed, and
resuspended in DMEM at a final concentration of 1 million cells/ml.
Immediately after the removal of the C3F8 gas, 100,000 cells in 0.1 ml
DMEM were slowly injected into the vitreous cavity through a 30-gauge
needle, 4 mm posterior to the limbus. PRP was prepared by collecting
venous rabbit blood in the presence of 3.8% sodium citrate, the whole
blood was centrifuged, and the supernatant was the PRP. In experiments
in which PRP was used, 0.1 ml of the PRP was injected by a second,
independent injection. The fundus was checked after the injection for
iatrogenic tears or retinal detachment. One animal was excluded from
the study because of the occurrence of retinal detachment after an
iatrogenic retinal tear. Rabbit eyes with small, limited retinal tears
that did not result in retinal detachment by the end of the study
period remained in the study. In a separate study we found that PVR did
not develop in animals that received such a tear but had not been
injected with cells (Anthony Andrews and Kameran Lashkari, unpublished
observations, 1998).
Examination of the Rabbits
The rabbits were examined by slit lamp biomicroscopy and indirect
ophthalmoscope with a +30-D fundus lens through a dilated pupil (1%
cyclopentolate HCl eye drops and 2.5% phenylephrine HCl eye drops,
0.05 ml of each). Each animal was examined at the outset of the
experiment to rule out the presence of any pre-existing anterior and
posterior segment ocular abnormalities. All procedures were performed
under aseptic conditions and pursuant to the regulations of the ARVO
Statement for the use of Animals in Ophthalmic and Vision Research. The
rabbits were examined by the same examiner on days 1, 3, 5, and 7 and
weekly thereafter using the indirect ophthalmoscope. Clinical
observations were recorded according to the Fastenberg
classification,32
33
and sketches were made. The animals
were killed on day 28. Eyes that received a grading of Fastenberg stage
3 or higher were enucleated, bissected, and examined in gross. Selected
specimens, including the one with the iatrogenic tear, were embedded in
paraffin, sectioned, stained with hematoxylin and eosin, and examined
by light microscopy.
Statistical Analysis
To determine whether the differences among groups of rabbits were
statistically significant we performed the Mann–Whitney test for
nonparametric ordinal data. The responses of rabbits injected with the
F cells were compared with the responses of rabbits injected with cells
that were expressing the PDGFRs. P < 0.05 was
considered to show a statistically significant difference.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
PDGFR-expressing cells (F) with the ßPDGFR virus. The
infected cells were selected in drug-containing medium, and mass
populations of cells were analyzed for expression of the introduced
receptor. Confluent cultures of cells were lysed, the insoluble
material was removed by centrifugation, and the resultant lysates were
subjected to western blot analysis using antibodies that specifically
recognize either of the two PDGFRs. In these studies the parental F
cells were included as a negative control. Two positive control cell
lines were also included. One was rabbit conjunctival primary
fibroblasts, which are often used in the PVR rabbit
model.33
34
35
36
The second was PhWT cells, which are a
mouse embryo fibroblast cell line that expresses each of the PDGFRs at
levels that are usually found in fibroblasts (approximately 100,000
receptors/cell).37
As shown in Figure 1 A, the PDGFR was readily detected in the F cells as well as the
cells infected with both of the PDGFR viruses (Fß). The level of
the PDGFR in the F was comparable to that seen in conjunctival
fibroblasts, and approximately three to four times less than the level
of the PDGFR in the PhWT. The PDGFR in the Fß cells was
roughly two times higher than in F cells. In contrast, no PDGFR
was detected in either the parental F cells, or in the cells infected
with the ßPDGFR. The cells that had been infected with the ßPDGFR
virus expressed the ßPDGFR, and the levels were comparable to the
conjunctival fibroblasts and PhWT cells (Fig. 1B)
. Thus, both of the
PDGFRs were expressed to physiologically relevant levels, and periodic
assessment of the cells indicated that expression was stable for at
least 6 months.
|
PDGFR, whereas PDGF-BB is the universal
ligand, and it activates all PDGFRs. After stimulation, the cells were
lysed, and the clarified lysates were subjected to western blot
analysis using a phospho-specific Erk antibody. As shown in Figure 2
A, exposure of F cells to either form of PDGF did not activate Erk,
because these cells have no PDGFRs (Fig. 1)
. Engagement of either the
or ß PDGFR resulted in activation of Erk, and the response was
consistently slightly stronger in the Fß cells. Simultaneous
activation of both of the receptors, by stimulating the Fß cells
with PDGF-BB, did not lead to much more of a response. The lower panel
of Figure 2A
is a western blot of an unrelated protein in the cell
lysates and is included to verify that there were similar amounts of
cell lysate in all the samples. Additional studies revealed that
exposure to PDGF stimulated comparable levels of tyrosine
phosphorylation of the introduced receptors (data not shown). These
studies indicate that the introduced receptors were capable of
triggering characteristic biochemical events such as receptor
autophosphorylation and coupling to the Erk pathway.
|
PDGFR was able
to initiate entry of cells into the S phase, and the response was
approximately 45% to 50% of the response seen with 10% FBS. The
ßPDGFR also stimulated DNA synthesis and was routinely somewhat
better than the PDGFR. This observation is consistent with the work
of other groups that reported that the ßPDGFR is more potent than the
PDGFR at driving cell cycle progression in
fibroblasts.39
40
41
Simultaneous activation of both the
receptors (by PDGF-BB in Fß cells) resulted in a response
comparable to that seen when only the ßPDGFR was activated (exposure
of Fß cells to PDGF-BB). Taken together, the data in Figure 2
show
that the ßPDGFR was slightly more potent than the PDGFR and that
both of the receptors coupled to signal relay pathways and initiate
biologic responses. In addition, simultaneous activation of both of the
receptors did not dramatically change the response, compared with
activation of either receptor alone.
Comparison of Cell Lines for Their Ability to Induce PVR
To test the PVR induced by the various cell lines, we used a
well-established rabbit model. Rabbits were first subjected to gas
vitrectomy, then either F, F, Fß, or Fß cells were injected,
and the eyes were monitored for development of membranes and retinal
detachment for 28 days. The data presented in Figure 3
are the results at day 28, and although PVR at the earlier time points
was less severe, there were no additional trends between the cell lines
(data not shown). All PVR in the clinical Fastenberg classifications of
stage 3 or higher was confirmed on gross and light microscopic
examination of the sectioned specimens. Light microscopy confirmed the
presence of retinal membranes and retinal detachment in the embedded
specimens.
|
PDGFR (F cells) resulted in a modest
trend toward the more severe stages of PVR; however, this increase was
not statistically significant (P = 0.104). Cells
expressing the ßPDGFR (Fß cells) did not induce more severe PVR
than the parental cells. In contrast, stage 3 or higher PVR developed
in 9 of 10 rabbits when cells coexpressing the two PDGFRs (Fß
cells) were injected. These findings indicate that expression of both
of the PDGFRs greatly increased the incidence of PVR. Because there was
not an exogenous source of PDGF in these experimental conditions, it
appears that there is enough PDGF in the rabbit eye to activate the
injected cells.
We were somewhat surprised that the F cells were unable to induce PVR.
With the exception of the PDGF receptors, these cells should express
all other cell surface receptors found on fibroblasts, and fibroblasts
efficiently induce PVR in this animal model.32
35
42
Therefore, either the PDGFRs are critical for PVR, or there is not a
sufficient concentration of growth factors in the injected eye to cause
disease. To distinguish between these two possibilities, we altered the
experimental protocol by injecting PRP together with the cells.
Previous investigations have found that injection of PRP greatly
accelerates the progression of PVR.35
42
This is
presumably because of the many factors within the PRP, one of which is
PDGF.43
The PRP did not have a pronounced effect on the
onset of the disease (data not shown). However, it greatly potentiated
the ability of the F cells to induce PVR: Eight of 10 rabbits had
stage 3 or higher (Fig. 3B
; the difference between F and F was
statistically significant). In contrast, PRP did not improve the
ability of the Fß cells to cause disease. The Fß cells were also
able to induce PVR under these conditions. The findings indicate that
the signal sent by the PDGFR was critical for inducing PVR in this
animal model.
To document and verify PVR, the rabbit eyes were photographed, and then
the animals were killed and the eyes enucleated and examined by gross
and light microscopy. Figure 4
A shows a normal retina (left) and mild fibrous proliferation on the
surface of the retina at day 28 in an animal that was injected with
Fß cells and no PRP. PVR in this animal was classified as Fastenberg
stage 1. On the right is the eye of a rabbit that was injected with
F cells together with PRP. There was extensive fibrous proliferation
and consequent total retinal detachment. PVR in this animal was
classified as Fastenberg stage 5. During the entire course of the
study, the appearance of the membranes did not reflect the type of
cells that were injected. We also examined the membranes histologically
and found that the membranes were attached to the surface of the retina
and that they were composed mostly of fibrous tissue, with a lesser
cellular component. In addition, the retina appeared intact, and no
cellular invasion was seen (Fig. 4B)
.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
PDGFR in PVR.
Because this receptor is selectively activated by PDGF-AA, our data
support and extend the data of others collected from animal models or
humans, that PDGF-AA may play an important role in PVR. We injected mouse cells into rabbits, and consequently, the injected cells could have been rejected. Throughout the course of the study the vitreous of the eyes that were injected did not become cloudy or turbid (Anthony Andrews, unpublished observations, 1998), consistent with the idea the eyes were not becoming uveitic. A possible explanation is that the eye is an immune-privileged site and can tolerate foreign cells. Importantly, other investigators have also used heterologous cells to study PVR in rabbits without any apparent immunologic complications.32
Cells that did not express PDGFR were only marginally able to induce PVR (Fig. 3) . This was an unexpected result, because PVR can be induced by the injection of a variety of cell types, including several different types of fibroblasts.32 42 The cells used in these studies were normal mouse embryo fibroblasts (with the exception of the absence of PDGFRs), which are responsive to numerous growth factors. For instance, they grew well in tissue culture medium supplemented with 10% FBS, in which lysophosphatidic acid is the major mitogen. In addition, expression of either or both of the PDGFRs did not markedly improve the growth of these cells in serum, indicating that PDGF is not the only mitogen for these cells. The inability to induce PVR was most surprising when the F cells were coinjected with PRP, a rich source of numerous growth factors. Thus, although many growth factors have been implicated in PVR, the results of our studies indirectly indicate that PDGF plays a particularly important role, at least in this animal model of the disease.
Our data not only showed that PDGF is important in PVR but also began
to identify the relative contribution of each of the PDGFR subunits. In
the presence of PRP, the F cells induced PVR much better than cells
without any PDGFRs (Fig. 3B)
. This indicates that presence of the
PDGFR greatly increased the likelihood of PVR. There was a
particularly wide range in stages of PVR in the group of animals
injected with the F cells, but no PRP (Fig. 3A)
. Because ocular
injury stimulates expression of PDGF,9
a possible
explanation is that the surgical procedures induced expression of PDGF
to various degrees in individual rabbits within the group. Thus when
animals were injected with cells that have a high PVR potential (F
cells), the amount of PDGF (or other growth factors) could be the
determining factor in the severity of the disease.
In contrast to the F cells, the cells expressing the ßPDGFR
largely did not induce the severe stages of PVR in the presence or
absence of PRP. The inability of the ßPDGFR to mediate this response
is not because this receptor was nonfunctional (Fig. 2)
. The ßPDGFR
initiated signal relay cascades and promoted cell cycle progression at
least as well as the PDGFR (Fig. 2)
. Furthermore, it is unlikely
that the ßPDGFR did not promote PVR because of the absence of
PDGF-BB, because this form of PDGF is readily found in the platelets of
nonprimates44
and consequently should have been present in
the PRP.
The data showing cells coexpressing both of the PDGFRs are the most
difficult to interpret for two reasons. First, three types of receptor
dimers can form, and ßß homodimers and ß heterodimers,
and it is therefore not possible to know which type of receptors is
responsible for mediating an effect. This caveat highlights the utility
of having matched sets of cells that individually express each of the
PDGFRs, in which only one type of receptor dimer is possible. The
second problem is that PRP seemed to suppress the ability of the
Fß cells to drive the most severe forms of PVR (Fig. 3)
, although
the difference between these two groups did not reach statistical
significance. One explanation is that the PRP contains high levels of
PDGF-BB, leading to activation of all possible types of PDGFRs and that
one or more of these PDGFRs prevent PVR. Given that the ßPDGFR did
not induce disease, we speculate that the ßPDGFR (ßß homodimers)
or ß heterodimers suppress PVR that is induced through PDGFR.
It is also likely that other variables make an important contribution
to the overall effect. For instance, transforming growth factor ß,
which is present in the vitreous and retina,45
has been
shown to induce secretion of PDGF-AA in fibroblasts.46
Furthermore, it is plausible that at least some of the other growth
factors that have been implicated in PVR are also making a
contribution. Additional experimentation will be required to
investigate these possibilities further.
The idea that the PDGFRs make unequal contributions to PVR is
surprising, because the and ßPDGFRs are able to initiate cell
signaling, cell movement, and cell proliferation, responses that are
intrinsic to PVR. However, mice nullizygous for each of the receptors
display distinct abnormalities, suggesting that the and ßPDGFRs
play distinct roles during embryogenesis.16
Furthermore,
although PDGF is implicated in a variety of diseases, the relative
contribution of the two receptors is nonidentical.16
Thus,
the two PDGFRs appear to have distinct roles in both the normal and
pathologic processes.
It is likely that at least part of the reason why the two receptors
drive distinct biologic responses is because they initiate nonidentical
signal relay cascades. Indeed, although there are many similarities in
the signaling events initiated by the two PDGFRs, a number of
fundamental differences are beginning to emerge.47
48
49
The
availability of a panel of PDGFR mutants that are defective in
initiating one or more signal relay cascades will enable us to identify
the signaling enzymes that contributed to the progression and
establishment of PVR in this animal model. This information may provide
new targets for therapeutic intervention as well as prevention of PVR.
Finally, an important area for future investigation is to relate our
results in this animal model to the disease in humans.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
Submitted for publication February 5, 1999; revised April 16, 1999; accepted June 3, 1999.
Commercial relationships policy: N.
Corresponding author: Andrius Kazlauskas, Schepens Eye Research Institute, Harvard Medical School, 20 Staniford Street, Boston MA 02114. E-mail: kazlauskas{at}vision.eri.harvard.edu
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
and a 64-kilodalton protein, respectively Mol Cell Biol 13,133-143 and ß platelet-derived growth factor (PDGF) receptors J Biol Chem 268,9287-9295-subunit mutant and reconstituted cell lines demonstrate that transforming growth factor-ß can be mitogenic through PDGF A-chain-dependent and -independent pathways J Biol Chem 269,13951-139551 and phosphatidylinositol 3 kinase are the downstream mediators of the PDGF receptor’s mitogenic signal Cell 73,321-334[Medline][Order article via Infotrieve]
This article has been cited by other articles:
|
|
 |
|
  H. Lei, G. Velez, P. Hovland, T. Hirose, D. Gilbertson, and A. Kazlauskas Growth Factors Outside the PDGF Family Drive Experimental PVR Invest. Ophthalmol. Vis. Sci., July 1, 2009; 50(7): 3394 - 3403. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Lei and A. Kazlauskas Growth Factors Outside of the Platelet-derived Growth Factor (PDGF) Family Employ Reactive Oxygen Species/Src Family Kinases to Activate PDGF Receptor {alpha} and Thereby Promote Proliferation and Survival of Cells J. Biol. Chem., March 6, 2009; 284(10): 6329 - 6336. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Yang, S. Yuzawa, and J. Schlessinger Contacts between membrane proximal regions of the PDGF receptor ectodomain are required for receptor activation but not for receptor dimerization PNAS, June 3, 2008; 105(22): 7681 - 7686. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Lei, G. Velez, P. Hovland, T. Hirose, and A. Kazlauskas Plasmin Is the Major Protease Responsible for Processing PDGF-C in the Vitreous of Patients with Proliferative Vitreoretinopathy Invest. Ophthalmol. Vis. Sci., January 1, 2008; 49(1): 42 - 48. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Li, A. Maminishkis, F. E. Wang, and S. S. Miller PDGF-C and -D Induced Proliferation/Migration of Human RPE Is Abolished by Inflammatory Cytokines Invest. Ophthalmol. Vis. Sci., December 1, 2007; 48(12): 5722 - 5732. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Lei, P. Hovland, G. Velez, A. Haran, D. Gilbertson, T. Hirose, and A. Kazlauskas A Potential Role for PDGF-C in Experimental and Clinical Proliferative Vitreoretinopathy Invest. Ophthalmol. Vis. Sci., May 1, 2007; 48(5): 2335 - 2342. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-J. Chen and Z.-Z. Ma N-Cadherin Expression in a Rat Model of Retinal Detachment and Reattachment Invest. Ophthalmol. Vis. Sci., April 1, 2007; 48(4): 1832 - 1838. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Svegliati Baroni, M. Santillo, F. Bevilacqua, M. Luchetti, T. Spadoni, M. Mancini, P. Fraticelli, P. Sambo, A. Funaro, A. Kazlauskas, et al. Stimulatory autoantibodies to the PDGF receptor in systemic sclerosis. N. Engl. J. Med., June 22, 2006; 354(25): 2667 - 2676. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Weick, P. Wiedemann, A. Reichenbach, and A. Bringmann Resensitization of P2Y Receptors by Growth Factor-Mediated Activation of the Phosphatidylinositol-3 Kinase in Retinal Glial Cells Invest. Ophthalmol. Vis. Sci., April 1, 2005; 46(4): 1525 - 1532. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. F. James, R. L. Beauchamp, N. Manchanda, A. Kazlauskas, and V. Ramesh A NHERF binding site links the {beta}PDGFR to the cytoskeleton and regulates cell spreading and migration J. Cell Sci., June 15, 2004; 117(14): 2951 - 2961. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J Troger, S Sellemond, G Kieselbach, M Kralinger, E Schmid, B Teuchner, Q A Nguyen, E Schretter-Irschick, and W Gottinger Inhibitory effect of certain neuropeptides on the proliferation of human retinal pigment epithelial cells Br. J. Ophthalmol., November 1, 2003; 87(11): 1403 - 1408. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. V. Hoch and P. Soriano Roles of PDGF in animal development Development, October 15, 2003; 130(20): 4769 - 4784. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Saishin, Y. Saishin, K. Takahashi, M.-S. Seo, M. Melia, and P. A. Campochiaro The Kinase Inhibitor PKC412 Suppresses Epiretinal Membrane Formation and Retinal Detachment in Mice with Proliferative Retinopathies Invest. Ophthalmol. Vis. Sci., August 1, 2003; 44(8): 3656 - 3662. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Milenkovic, M. Weick, P. Wiedemann, A. Reichenbach, and A. Bringmann P2Y Receptor-Mediated Stimulation of Muller Glial Cell DNA Synthesis: Dependence on EGF and PDGF Receptor Transactivation Invest. Ophthalmol. Vis. Sci., March 1, 2003; 44(3): 1211 - 1220. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. H. Van Aken, O. De Wever, L. Van Hoorde, E. Bruyneel, J.-J. De Laey, and M. M. Mareel Invasion of Retinal Pigment Epithelial Cells: N-cadherin, Hepatocyte Growth Factor, and Focal Adhesion Kinase Invest. Ophthalmol. Vis. Sci., February 1, 2003; 44(2): 463 - 472. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Ikuno and A. Kazlauskas An In Vivo Gene Therapy Approach for Experimental Proliferative Vitreoretinopathy Using the Truncated Platelet-Derived Growth Factor {alpha} Receptor Invest. Ophthalmol. Vis. Sci., July 1, 2002; 43(7): 2406 - 2411. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Ikuno, F.-L. Leong, and A. Kazlauskas PI3K and PLC{gamma} Play a Central Role in Experimental PVR Invest. Ophthalmol. Vis. Sci., February 1, 2002; 43(2): 483 - 489. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Ikuno and A. Kazlauskas TGF{beta}1-Dependent Contraction of Fibroblasts Is Mediated by the PDGF{alpha} Receptor Invest. Ophthalmol. Vis. Sci., January 1, 2002; 43(1): 41 - 46. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. A. Drixler, I. H. M. B. Rinkes, E. D. Ritchie, F. W. Treffers, T. J. M. V. van Vroonhoven, M. F. B. G. Gebbink, and E. E. Voest Angiostatin Inhibits Pathological but Not Physiological Retinal Angiogenesis Invest. Ophthalmol. Vis. Sci., December 1, 2001; 42(13): 3325 - 3330. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Ikuno, F.-L. Leong, and A. Kazlauskas Attenuation of Experimental Proliferative Vitreoretinopathy by Inhibiting the Platelet-Derived Growth Factor Receptor Invest. Ophthalmol. Vis. Sci., September 1, 2000; 41(10): 3107 - 3116. [Abstract] [Full Text]
|
|
|
|
|
|
S. Rosenkranz, Y. Ikuno, F. L. Leong, R. A. Klinghoffer, S. Miyake, H. Band, and A. Kazlauskas Src Family Kinases Negatively Regulate Platelet-derived Growth Factor alpha Receptor-dependent Signaling and Disease Progression J. Biol. Chem., March 24, 2000; 275(13): 9620 - 9627. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
