Peritubular Capillary Injury during the Progression of Experimental Glomerulonephritis in Rats
RYUJI OHASHI,
HIROSHI KITAMURA and
NOBUAKI YAMANAKA
Department of Pathology, Nippon Medical School, Tokyo,
Japan.
Correspondence to Dr. Ryuji Ohashi, Department of Pathology, Nippon Medical
School, 1-1-5 Sendagi, Bunkyoku, Tokyo 113-8602, Japan. Phone: +81 3 3822
2131; Fax: +81 3 5685 3067; E-mail:
r-ohashi{at}nms.ac.jp
Abstract. The functional and morphologic changes occurring inthe
peritubular capillaries (PTC) of the kidney during the progressionof renal
disease are not yet completely understood. In thisstudy, the features of PTC
disruption observed in a rat anti-glomerularbasement membrane-induced
glomerulonephritis (GN) model werecharacterized. Contributions to the
progression of the diseasemade by other interstitial components, including
ED-1-positivemacrophages and CD3-positive T cells, were also investigated.
Within7 d of inducing GN, severe necrotizing glomerular injuries were
observed.Thrombomodulin staining revealed that within 3 to 8 wk, therewas a
significant (P < 0.001) decline in the number of PTC,accompanied
by a marked accumulation of macrophages, T cells,and fibrotic material. By
the end of this period, most PTC wereseverely damaged or lost, and
tubulointerstitial scarring wasnoted in the affected areas. Furthermore, PTC
endothelial cellapoptosis occurred concomitantly, as shown by application of
terminaldeoxynucleotidyl transferasemediated dUTP-biotin nick end labeling
methodsand electron microscopy. It was presumed that the PTC injurywas
mediated possibly by the infiltrating macrophages and Tcells, which, together
with destruction of the PTC structure,correlated significantly with the
impairment of renal function.These findings suggest that PTC disruption and
the subsequentregression of the capillary network may contribute to the
developmentof the tubulointerstitial injury largely responsible for therenal
dysfunction in progressive GN.
Since Henle et al. first reported that tubulointerstitial fibrosis
ratherthan glomerular changes is responsible for renal dysfunction
(1),there have been many
studies stressing the importance of interstitialinjury in the progression of
renal disease
(2,3,4).
A varietyof factors contributing to the progression of tubulointerstitial
lesionshave recently been reported, including macrophages that playa pivotal
role in the tubulointerstitial lesions
(5,6,7,8).
Tcell-mediated immune response have also been demonstrated andare now
recognized to be a principal cause of interstitial injury
(5,9,10,11,12).
Thus,it seems that the mechanisms of tubulointerstitial injury aregradually
becoming clear.
Among the various components making up the tubulointerstitialregions of
the kidney, the peritubular capillaries (PTC), whichare a network of
interstitial vessels, are thought to play amajor role in maintaining renal
function and hemodynamics. Infact, several studies of human biopsy specimens
have shown thatPTC may be all or partially lost from cortical areas
exhibitingtubulointerstitial injury. Moreover, the degree of loss is strongly
relatedto the progression of the disease
(13,14,15).
Despite theseobservations, the role of PTC has tended to be deemphasizedin
recent studies of renal disease. In particular, no studiesof the time course
of progressive glomerulonephritis (GN) haveyet been carried out to resolve
the role played by PTC damagein the impairment of renal function.
In the present study, we characterized the PTC disruption occurringin the
anti-glomerular basement membrane (GBM) GN model of Wistar-Kyotorats that
proceeds to end-stage kidney disease, exhibiting severenecrotizing
proliferative GN and marked interstitial fibrosis
(16).Because visualization of
PTC is difficult by routine light microscopy,PTC structures were identified
using an antibody (Ab) raisedagainst thrombomodulin (TM), a known endothelial
cell marker
(17,18).
TMlabeling on endothelial cells was confirmed by using a secondendothelial
cell marker, anti-rat endothelial cell Ab, RECA-1
(19).Furthermore, apoptotic
PTC endothelial cells were recognizedby the characteristic nuclear DNA
fragmentation using terminaldeoxynucleotidyl transferase (TdT)-mediated
dUTP-biotin nickend labeling (TUNEL). Macrophages and T cells were identified
usinganti-ED-1 and anti-CD3 Ab, respectively. Finally, the relationship
betweenPTC disruption and renal function during the progression ofGN was
analyzed.
Experimental Design
Progressive GN was induced in groups of male Wistar-Kyoto rats(100 g body
wt; Charles River Japan, Kanagawa, Japan) with asingle intravenous injection
of 50 µg IgG/100 g body wtof rabbit anti-rat GBM Ab (courtesy of Dr.
Yasuhiro Natori,International Medical Center of Japan, Tokyo)
(18). Five ratseach were
sacrificed on days 3 and 7, and then 2, 3, 4, 6, and8 wk after administration
of the anti-GBM Ab. Five uninjectedrats each were sacrificed on day 0 and
after 4 and 8 wk, respectively,served as controls.
Histologic Examination
Kidneys were removed, fixed in 4% buffered paraformaldehyde,embedded in
paraffin sections (2.5 µm thick), and stainedwith periodic acid-Schiff
(PAS) and periodic acid-methenaminesilver for histologic examination. To
detect the endothelialcells of the glomerular and peritubular capillaries,
the tissuewas labeled with polyclonal rabbit anti-rat TM Ab (courtesyof Dr.
Stern, Columbia University)
(17), previously biotinylated
accordingto the method of Shimizu et al.
(18). To detect macrophages,
panT cells, and type IV collagen, tissues were respectively labeledwith
anti-rat ED-1 Ab
(20,21),
anti-human CD3 Ab (Dako, Glostrup,Denmark), and anti-human type IV collagen
Ab (Southern BiotechnologyAssociates, Birmingham, AL). The anti-CD3 Ab was
confirmed toreact with rat pan T cells using rat spleen.
Specifically, labeling was accomplished by deparaffinizing thetissue
sections and treating first for 30 min with 0.3% H2O2in
methanol, and then incubating for 60 min with either avidin-biotinylated
anti-TMAb (1:400 dilution), anti-ED-1 Ab (1:100), anti-CD3 Ab (1:100),or
anti-type IV collagen Ab (1:200). The TM-labeled tissue sectionswere then
incubated for 60 min with avidin-biotin peroxidasecomplex (Dako) and
visualized using 3,3'-diaminobenzidine (DAB)in 0.05 mol/L Tris buffer.
The ED-1-, CD3-, and type IV collagen-labeledsections were incubated for 60
min with peroxidase-conjugatedgoat anti-mouse IgG or mouse anti-goat IgG
(1:100; Dako) andvisualized using H2O2 containing DAB
buffer.
To confirm TM labeling on endothelial cells, some tissue sampleswere
frozen on dry ice-acetone and stored at -75°C. Cryostatsections (4 µm)
were later labeled using the mouse monoclonalanti-rat endothelial cell Ab,
RECA-1 (Serotec Ltd., Oxford,United Kingdom). Sections were incubated with
rhodamine-labeledgoat anti-mouse IgG antibody and were observed with a
fluorescencemicroscope.
For electron microscopy, tissues were fixed in 2.5% glutaraldehydein
phosphate buffer, pH 7.4, post-fixed with 1% osmium tetroxide,dehydrated, and
embedded in Epon 812. Ultrathin sections werestained with uranyl acetate and
lead citrate, and then examinedwith a Hitachi H7100 electron microscope.
Identification of Apoptosis
Apoptotic cells were identified based on the presence of fragmentednuclear
DNA in histologic sections labeled using the TUNEL method
(22).Deparaffinized
2.5-µm-thick sections were incubated withproteinase K (100/ml) for 15 min
at room temperature. Afterblocking endogenous peroxidase by immersion in 2%
H2O2 in distilledwater, sections were rinsed in TdT
buffer (30 mmol/L Tris/HClbuffer, pH 7.2, 140 mmol/L sodium cacodylate, 1
mmol/L cobaltchloride) and then incubated for 60 min at 37°C with TdT
(1:100)and biotinylated dUTP (1:200) in TdT buffer. The biotinylatednuclei
were visualized using avidin-peroxidase and H2O2- and
NiCl-containingDAB. Apoptotic endothelial cells were identified by double
labelingusing TUNEL and anti-TM Ab. Initially, sections were labeledusing
the TUNEL protocol described above, after which the sectionswere blocked for
20 min each in 0.1% avidin (AVIDIN D, VectorLaboratories, Burlingame, CA) and
0.01% biotin (d-BIOTIN; SigmaChemical Co., St. Louis, MO) in
phosphate-buffered saline
(23).The sections were then
incubated with biotinylated rabbit anti-ratTM Ab and avidin-biotin peroxidase
complex and visualized withH2O2-DAB. Negative controls
were produced by omitting dUTP orTdT from the TUNEL protocol, by substitution
of biotinylatedanti-TM with biotinylated normal rabbit IgG and by pretreating
preparationswith anti-TM Ab before TUNEL.
Quantification of Glomerular Alteration
For each kidney sample, more than 30 glomerular cross sectionswere
examined for the following: (1) glomerular capillary regression
(i.e.,the number of glomerular capillary lumina surrounded by
TM-positivecells); (2) total number of macrophages (i.e.,
the number ofED-1-positive cells); (3) total number of pan T cells
(i.e.,the number of CD3-positive cells); and (4)
glomerulosclerosisprogression (i.e., the area positive for type IV
collagen).In each case, quantities were expressed per glomerular cross
section.The type IV collagen-positive area was measured by means ofa Luzex
IIIU digital image analyzer (Nireco, Tokyo, Japan) andexpressed as percentage
of total cross sectional area.
Quantification of PTC and Interstitial Alteration
In each sample, 40 randomly selected fields (0.065 mm2) were
examinedfor the following under x400 magnification: (1) PTC
regression(i.e., the number of TM-positive lumina); (2)
total number ofmacrophages (i.e., the number of ED-1-positive
cells); (3) totalnumber of pan T cells (i.e., the number of
CD 3-positive cells);and (4) degree of interstitial injury
(i.e., the area of thecortical interstitium). Numbers of PTC,
macrophages, and panT cells were expressed per mm2. The area of
the cortical interstitiumwas measured by means of a Luzex IIIU digital image
processoranalyzer and expressed as percentage of total cortical area.
Renal Function Studies
The urine of all animals was obtained during 12-h overnightcollections
using metabolic cages, after which the animals werekilled. Blood samples were
obtained from control and GN ratsat the time of death. Blood urea nitrogen
and serum creatininelevels were measured using the modified Folin-Wu and the
urease-ultravioletmethods, respectively. The protein excreted into the urine
wasquantified using the pyrogallol red-molybdenum method.
Statistical Analyses
All values were expressed as the mean ± SD or SEM. Comparisonswere
made using the Mann—Whitney test for the following:(1) values
on day 3 and after week 1 versus the day 0 controls;(2)
values after week 2, 3, or 4 versus the week 4 controls;and
(3) values after week 6 or 8 versus the week 8 controls.
Correlationsbetween groups were calculated using Pearson's test.
Glomerular Alteration in Progressive GN
By 3 to 7 d after injection of the anti-GBM Ab, necrotizingand
mesangiolytic lesions of glomeruli were observed along withmassive exudative
changes (Figure 1B). The number
of TM-positiveglomerular capillary lumina was reduced due to destruction of
thecapillary network (Figure
2A), accompanied by a notable macrophageinfiltration
(Figure 2C).
Figure 1. Morphologic alteration of the glomerulus and the interstitium in
anti-glomerular basement membrane (GBM) glomerulonephritis (GN) in
Wistar-Kyoto rats. (A) Control rat on week 8. (B) Seven days after induction
of disease, segmental necrotizing and mesangiolytic lesions of the glomerulus
occur with exudative changes. (C) Four weeks after induction of disease, the
numbers of glomerular capillary lumina continue to decline due to global
destruction of the capillary network. The interstitium is becoming fibrotic
and eventually expanded. (D) Eight weeks after induction of disease, the
glomerulus has become sclerotic, and the numbers of glomerular capillaries and
endothelial cells have been reduced within sclerotic lesions. Dilation of the
interstitium due to marked fibrosis is noted. Periodic acid-methenamine silver
stain. Magnification, x200.
Figure 2. Correlation between the number of thrombomodulin (TM)-positive peritubular
capillary (PTC) lumina (A), TM-terminal deoxynucleotidyl transferase-mediated
dUTP-biotin nick end labeling (TUNEL)-positive PTC lumina (B), ED-1-positive
macrophages (C), CD3-positive T cells (D), and area of the interstitium (E)
during the course of the experiment. [UNK] and , number in experimental
and control groups, respectively. Values are expressed as mean ± SD in
A and C through E, and as mean ± SEM in B. *P <
0.05; **P < 0.001 versus control.
Necrotizing GN persisted from day 7 to week 4. During this period,the
destruction of capillary network progressed with accumulationof mesangial
matrix. The number of macrophages per glomerularcross section decreased as
inflammation declined, whereas changesin the number of glomerular pan T cells
were very mild duringthe course of the disease
(Figure 2D).
From week 4, destruction of the capillary network became evident,
glomerularinflammation almost disappeared, and macrophages were rarely
observed.The accumulation of mesangial matrix continued to progress
(Figure 2E),however, resulting
in global glomerulosclerosis by week8
(Figure 1D).
PTC and Interstitial Alteration in Progressive GN
Although most glomeruli exhibited notable changes shortly afterinduction
of GN, changes of the interstitium were still notapparent on day 3, and no
significant changes in the appearanceor number of TM-positive PTC lumina were
seen (Figure 3A). Byday 7, a
small number of macrophages (Figure
3B) and pan T cellsappeared in the interstitium. The macrophages
were particularlynumerous around Bowman's capsule, whereas the T cells were
mainlyseen in the interstitium of the deeper cortex
(Figure 4A).
Figure 3. Serial sections showing PTC disruption accompanying anti-GBM-mediated GN in
Wistar-Kyoto rats. Disease progression is reflected by effects on TM-positive
PTC endothelial cells (A, C, and E) and ED-1-positive macrophages (B, D, and
F). (A and B) Seven days after disease induction, the appearance and number of
PTC remain unchanged, although the influx of macrophages is becoming apparent
(arrows). (C and D) Four weeks after disease induction, PTC lumina appear
compressed or misshapen with mild expansion of the interstitium (arrow). In
the affected area of the interstitium, the influx of macrophages is noted
(arrow). (E and F) Eight weeks after disease induction, PTC lumina are no
longer identifiable in some areas of the expanded interstitium (arrowheads).
Most of the remaining PTC lumina are either compressed or dilated. In the
vicinity of the injured PTC lumina, markedly dilated or atrophic tubules are
noted. Local infiltration of macrophages into the expanded interstitium is
shown. Magnification, x200.
Figure 4. CD3-positive T cells in the interstitium at day 7 (A) and week 3 (B). (A)
CD3-positive T cells primarily appear in the deeper cortex. (B) They disperse
dominantly in the interstitium, while only a few are seen within the
glomerulus. Magnification, x200.
During the period between day 7 and week 4, TM-positive PTClumina appeared
compressed and misshapen due to mild expansionof the interstitium caused by
edema and fibrosis (Figure 3C),
andthere was a marked influx of macrophages into the corresponding
interstitium(Figure 3D).
Dilation of PTC lumina was noted in other regions.Increased numbers of
macrophages and T cells were disperseddiffusely throughout most of the
cortical interstitium. By week3, T cell numbers had reached a maximum
(Figures 4B and
5D),while macrophage
infiltration was maximal by week 4 (Figure
5C).
Figure 5. Correlation between the number of TM-positive endothelial cells (A), TM and
TUNEL-positive cells (B),ED-1-positive macrophages (C), CD3-positive T cells
(D), and type IV collagen-positive area (E) per glomerular cross section
during the course of the experiment. [UNK] and , number in experimental
and control groups, respectively. Values are expressed as mean ± SD in
A and C through E, and as mean ± SEM in B. *P <
0.05; **P < 0.001 versus control.
From week 4, the number of PTC lumina retaining their originalshapes was
significantly decreased (P < 0.001), and mostof the interstitium
was expanded due to accumulation of fibroticmaterials compared to week 4
controls (P < 0.001). By week8, increases in areas of the
interstitium (27.2 ± 4.2%of the cortical interstitium) and reductions
in TM-positivePTC lumina were clearly apparent and highly significant
comparedto week 8 controls (Figure 5, A
and E) (P < 0.001, respectively).In some interstitial
regions, TM-positive PTC lumina were absent,having been displaced by fibrotic
material, and most remainingPTC lumina were compressed, disintegrated, or
dilated (Figure 3E).Dilation
of tubules was also noted in the vicinity of injuredPTC lumina. Macrophage
infiltration was diminishing in correspondinginterstitial areas
(Figure 3F), but in other
cortical regions,inflammatory cell numbers were unchanged.
Figure 6 shows thatthere is
statistically significant correlation between the numberof TM-positive PTC
lumina and the area of the cortical interstitiumat week 8 (r = 0.79,
P < 0.001). To confirm the findingsof TM, PTC lumina were stained
with a second marker of endothelialcell, RECA-1, using frozen sections in
which antigens were preservedbetter than in paraffin sections. Immunostaining
showed similarpatterns, with a loss of PTC staining in areas of
tubulointerstitialscarring at the later stage of the disease
(Figure 7).
Figure 6. Relationship between the number of TM-positive PTC lumina and the area of
the cortical interstitium in 40 randomly selected fields (0.065 mm2
per field) at week 8. Pearson's correlation coefficient is shown (r =
0.79, P < 0.001).
Figure 7. Immunostaining with RECA-1 in frozen sections. Most of PTC lumina are
misshapen but they can still be recognized at week 4 (A). Note the lack of
staining in areas of tubulointerstitial scarring at week 8 (B) compared to
staining in an endothelial cell of the small artery (arrow). Magnification,
x200.
Apoptotic cells were seen in PTC between weeks 3 and 8. Mostof the
apoptotic cells were identified as endothelial cellsby positive anti-TM
labeling and TUNEL (Figures 5B
and 8). Afew apoptotic cells
within PTC were not labeled by anti-TM Ab;these cells were considered
infiltrating mononuclear cells.Electron microscopic analysis revealed that at
this stage, thebasement membrane of PTC was partially disrupted and
fragmented,desquamated endothelial cells were present within PTC lumina,and
PTC lumina were barely detectable due to their completeloss of original shape
(Figure 9, A through E). At the
sametime, the interstitium was widened and filled with infiltratingcells and
fibrotic material (Figure
9F).
Figure 8. Apoptotic PTC endothelial cells double-labeled with both TUNEL (black) and
anti-TM antibody (brown) at week 3 (A) and week 8 (B). A double-labeled
apoptotic cell (arrow) is seen within a capillary lumen. Magnification,
x600.
Figure 9. Morphologic alteration in injured PTC endothelial cells and lumina 6 wk (A
through D) and 8 wk (E and F) after induction of disease. (A) An endothelial
cell and basement membrane are partially disrupted (arrow). Apoptotic bodies
that have been ingested by a mononuclear cell in the lumen are seen in the
lumen (asterisk). Magnification, x4000. (B) An endothelial cell
(asterisk) is activated and swollen, and its fenestration cannot be
recognized. Magnification, x6000. (C and D) Typical apoptotic
endothelial cells characterized by condensation of nuclear chromatin (C,
asterisk) and crescentic condensed nucleus and nuclear fragments (D,
asterisk). Magnification, x7000. (E) Basement membrane of PTC is
partially destroyed (arrow) and an endothelial cell is desquamated (asterisk).
Magnification, x3000. (F) Interstitium is widened and filled with
infiltrating cells and fibrotic material. PTC lumina can rarely be identified.
Magnification, x1000.
Renal Function Study
Blood urea nitrogen and serum creatinine levels significantlyincreased
after 7 d and 2 wk, respectively (Figure
10, A and B).They both gradually increased for the entire
experimentresulting in chronic renal failure. Most of the animals became
proteinuricat day 3, and urinary protein levels continued to increase until
theend of the disease (Figure
10C).
Figure 10. Changes in parameters of renal function in experimental and control animals
during the course of the experiment. Blood urea nitrogen (BUN) level (A),
serum creatinine level (B), and urinary protein excretion level (C). [UNK] and
, number in experimental and control groups, respectively. Values are
expressed as mean SD. *P < 0.05 versus
control.
Relationship between Glomerular and Interstitial Disruption and Renal
Function
Tables 1 and
2 show relations between
glomerular and interstitialalteration, and renal function during the disease.
It is notablethat the PTC number shows significant correlation with all three
indicatorsof renal function tested.
In the present study, we characterized features of the PTC disruption
duringthe progression of GN that have perhaps not attracted adequate
attentiongiven the large number of studies on tubulointerstitial injury.In
addition, we attempted to elucidate the contribution madeby PTC disruption to
the development of renal disease and tothe impairment of renal function.
The PTC network is directly originated from efferent arteriolesof the
glomeruli. It could be postulated, therefore, that ifglomeruli are injured
substantially, as in our GN model, theresultant reduction in blood flow from
the glomeruli to thePTC would be expected to lead to disruption or regression
ofthe PTC. Our findings cannot be explained solely by this sequenceof
events, however. Beginning relatively early in the progressionof the GN, the
numbers of TM-positive PTC lumina began to decreasein many areas of the
interstitium, and some apoptotic endothelialcells were identified. In
addition, ultrastructural analysisrevealed that as PTC lumina became
misshapen and basement membranespartially disintegrated, PTC endothelial
cells became activatedor degenerated and subsequently detached. At a later
stage,a number of PTC apparently disappeared, replaced by fibroticelements
and numerous infiltrating inflammatory cells. Althoughrecent studies
primarily describe PTC injury as obliterationof its lumen
(14,15),
our findings show that PTC destructionduring the course of progressive GN is
better characterizedby endothelial cell injury and loss of structure.
A notable finding of this study is that PTC endothelial cellsundergo
apoptosis. Although the significance remains controversial,vascular
endothelial cell apoptosis is known to occur aftercell injury or activation
(24). Furthermore,
macrophage-dependentvascular endothelial cell apoptosis may trigger capillary
regressionby blocking blood flow at the site of apoptosis, in turn triggering
apoptosisof the remaining endothelial cells and resulting in regressionof
the entire capillary (25). In
our study, accumulation ofED-1-positive macrophages was predominantly noted
in areas wherePTC injury was evident, suggesting the involvement of
macrophagesin PTC endothelial cell injury as well as in the subsequent
disintegrationof the entire capillary structure.
CD3-positive pan T cells first appeared in the interstitiumon day 7 and
reached a peak by week 3, whereas accumulationof macrophages was not maximal
until week 4. This findings suggestthat macrophage accumulation was mediated
by T cells, consistentwith recent reports
(26,27).
Cytotoxicity mediated by T cellsmay occur within the glomerulus of the
anti-GBM-induced GN model,where T cells functioned as natural killer cells
without expressionof pan T cell ligands
(16). In our model, most of
interstitialT cells were CD3-positive, indicating that they were not
cytotoxicnatural killer cells. Therefore, we presume that interstitialT
cells function to mediate interstitial inflammation ratherthan induce direct
cytotoxicity.
We showed previously that glomerular capillary regression maylead to the
development of glomerulosclerosis
(18). Here, weattempted to
determine the extent to which PTC regression contributesto tubulointerstitial
scarring. Although precise details ofthat process have not been elucidated,
tubulointerstitial scarringhas been regarded as a major determinant in the
progressionof renal diseases
(28). We found that marked
interstitial fibrosis,tubular atrophy, and consequent tubulointerstitial
scarringwere colocalized within areas of PTC injury. Furthermore, statistical
analysisrevealed that there is a significant correlation between thedegree
of PTC injury and that of interstitial injury. BecausePTC are essential for
maintaining proper renal hemodynamicsand for supplying oxygen to the entire
kidney, it is possiblethat PTC injury causes localized hypoxia, leading to
regressionand scarring of the tubulointerstitium. Therefore, we concludethat
PTC regression may contribute to the development of thetubulointerstitial
scarring in progressive GN.
PTC disruption and the subsequent tubulointerstitial injuryappear to
promote the continued progression of the tubulointerstitialinjury.
Accordingly, the appearance of macrophages in the interstitiumcorrelated with
PTC disruption and impaired renal function.We suggest that the present study
reaffirms the importance ofthe PTC itself and its involvement with other
interstitial componentsin determining the level of renal functionality.
However, therelationship between tubulointerstitial injury and progressive
lossof glomerular function has not been fully investigated. It hasbeen
hypothesized that when resident glomerular cells are injured,as in GN, they
secrete cytokines that activate interstitialcells and induce inflammatory
cell infiltration (29). Fine
etal. proposed that injured or occluded PTC might increase
glomerularcapillary pressure and thus lead to glomerulosclerosis
(30).Our findings indicate
that the progression of glomerulosclerosiscoincides with that of the PTC and
interstitial injury, suggestingthat there may be cross-talk between the
glomerulus and theinterstitium during disease development. Further
investigationsto clarify this issue are now in progress in our
laboratory.
In summary, we demonstrated that the injury and loss of PTCoccur in
tubulointerstitial scarring in a progressive GN model.Such PTC injury is
characterized by endothelial cell apoptosisand the subsequent destruction of
the capillary structures.This process can be mediated by infiltrating
macrophages, andthe involvement of T cells is also suggested. The progression
ofPTC disruption coincides with the alteration of other interstitial
components,most of which strongly correlate with the impairment of renal
function.We conclude that PTC disruption and the subsequent regressionof the
capillary network contribute to the development of thetubulointerstitial
injury largely responsible for the renaldysfunction occurring in progressive
GN.
Acknowledgments
The authors are grateful to Drs.D.Stern and Y.Yuzawa for providingthe
anti-TM antibody, Drs.Y.Natori and N.Nakao for providingthe anti-GBM
antibody. We also wish to thank Professor Y.Sugisaki,Drs.A.Shimizu,
M.Ishizaki and Y.Masuda for their advice andtechnical assistance.
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Received for publication April 15, 1999.
Accepted for publication June 22, 1999.
Top
Abstract
Introduction
, number in experimental
and control groups, respectively. Values are expressed as mean ± SD in
A and C through E, and as mean ± SEM in B. *P <
0.05; **P < 0.001 versus control.
