Biomedical subjects

K B Lemström

Publications and source records attributed to K B Lemström.

At least 19 recordsLinked to original sources

PubMed2001

Prevention of cytomegalovirus infection-enhanced experimental obliterative bronchiolitis by antiviral prophylaxis or immunosuppression in rat tracheal allografts.

In this study, the prevention of rat cytomegalovirus (RCMV) infection-enhanced experimental obliterative bronchiolitis in rat tracheal allografts was investigated. RCMV infection markedly enhanced cell proliferation and histological changes of obliterative bronchiolitis, a form of chronic rejection after lung transplantation. These alterations were linked to increased interleukin (IL)-2 and tumor necrosis factor-alpha (TNF-alpha) immunoreactivity, and reduction of IL-10 expression. In recipient rats with acute RCMV infection, prophylaxis with either ganciclovir (DHPG) or hyperimmune serum (HIS) totally prevented RCMV infection-enhanced tracheal occlusion. DHPG treatment initiated during acute RCMV infection also reduced lesion development but markedly less than DHPG prophylaxis. Treatment of acute RCMV infection with HIS alone or in combination with DHPG had no significant effect on tracheal occlusion. Inhibition of the transcription of cytokines by high doses of cyclosporine A significantly reduced RCMV infection-enhanced tracheal obliteration. In rats with chronic RCMV infection, obliterative alterations were prevented by DHPG prophylaxis initiated at the time of transplantation. Prophylaxis either with DHPG or HIS did not affect the amount of infectious RCMV recovered from host salivary glands, nor were there differences seen in RCMV major immediate early DNA expression in tracheal allografts between different antiviral drug regimens. Immunohistochemical analysis of allografts revealed that inhibition of tracheal occlusion by antiviral prophylaxis was associated with a reduction in the number of ED1(+) macrophages and cells staining for Th1 cytokines and TNF-alpha, while immune modulation by cyclosporine A up-regulated IL-10 production. In conclusion, the results of the present study suggest that the CMV infection-enhanced chronic rejection develops independently of viral load but requires both immune activation and simultaneous CMV gene expression beyond immediate early genes.

Acute Disease↗

PubMed2001

Mast cells in acute and chronic rejection of rat cardiac allografts--a major source of basic fibroblast growth factor.

BACKGROUND: Studies of cardiac allograft arteriosclerosis, i.e., chronic rejection, have largely focused on mononuclear inflammatory cell infiltrates in the vascular wall and periphery of the occluded vessels. The purpose of this study was to investigate the role of mast cells in the development of acute and chronic rejection in rat cardiac allografts. METHODS: In the acute rejection model, transplant recipients were not treated with immunosuppressants, and the grafts were removed 5 days after transplantation at the time of severe acute rejection. In the chronic rejection model, the recipients were administered triple-drug immunosuppression, and the grafts were removed 90 days after transplantation. RESULTS: During acute rejection, the number of mast cells was not increased, but the localization pattern differed from that of syngeneic grafts. In acute rejection, mast cells were located in the perivascular region of the allografts, but in syngeneic grafts, mast cells had a more interstitial location. In the chronic rejection model, the cardiac allografts with severe intimal thickening showed large numbers of mast cells at perivascular sites of occluded intramyocardial vessels and in the interstitium. Linear regression analysis revealed a significant correlation between the numbers of perivascular and interstitial mast cells and the intensity of intimal thickening. The majority of mast cells showed positive immunoreactivity to basic fibroblast growth factor (bFGF). Macrophage bFGF expression was not so prominent, but macrophages were more frequent in numbers. Tumor necrosis factor-alpha expression was detected mainly in macrophages and in only a few mast cells. When the intensity of arteriosclerosis was decreased by an increase in the intensity of immunosuppression, the numbers of intragraft mast cells and other mononuclear cells, and also the production of their respective cytokines, bFGF and tumor necrosis factor-alpha, gradually diminished. CONCLUSIONS: Taken together, our data show that the intensity of intramyocardial mast cell infiltration was associated with the intensity of chronic inflammation and allograft arteriosclerotic changes, but not with acute rejection, and that mast cells, in addition to macrophages, are a major source of myocardial bFGF. The results also demonstrate that when the T-cell activation pathway is blocked using cyclosporin, the number of mast cells is decreased. Cyclosporin may have affected the cytokine production that interfered with both the mast cell-dependent initiation and the leukocyte- and mast cell-dependent amplification and progression of the immune responses influenced by mast cell-leukocyte cytokine cascades. bFGF produced by mast cells may contribute to enhanced inflammation, neovascularization, and fibrosis during cardiac allograft arteriosclerosis.

Acute Disease↗

PubMed2000

Blockade of complement inhibits obliterative bronchiolitis in rat tracheal allografts.

The role of complement activation in the development of obliterative bronchiolitis, a manifestation of chronic lung allograft rejection, was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft complement components C3 and C5b-9 (membrane attack complex) as well as IgM and IgG deposits were demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. A 7-d treatment with recombinant human soluble complement receptor type 1 (sCR1; 20 mg/kg/d, intraperitoneal), an inhibitor of both the classic and alternative complement pathways, significantly decreased epithelial necrosis and intragraft neutrophil infiltration, and reduced obliterative changes by 40%. Immunohistochemical analysis of the grafts showed that sCR1 treatment significantly decreased early C5b-9 and IgG deposits, neutrophil chemoattractant IL-8 immunoreactivity, and ICAM-1 expression. Treatment with sCR1 was associated with increased staining for Th2 cytokines, in particular IL-10, with concomitant downregulation of IL-2 and TNF-alpha immunoreactivity. In contrast, sCR1 treatment did not affect the number of graft-infiltrating CD4(+) and CD8(+) T cells, CD45(+) B cells, ED1(+) and ED3(+) macrophages, or immune activation with expression of IL-2Ralpha or MHC class II. In conclusion, this is the first study to demonstrate that blockade of complement activation attenuates the development of OB and suggests that in addition to T cell-driven responses, humoral and antigen-independent immune responses also operate in the disease process. A blockade of complement activation renders the chemokine milieu unattractive to neutrophils and also modulates the alloimmune response toward Th2 cytokines, which may have an antiproliferative role in fibroproliferative disorders.

Animals↗

PubMed1999

Cytomegalovirus infection and cardiac allograft vasculopathy.

There is a wealth of clinical and experimental evidence indicating the interaction of cytomegalovirus (CMV) infection and rejection in cardiac and other solid organ allografts. A plausible explanation for this association comes from data showing that therapy with biologicals, sepsis, and rejection, all lead to the release of TNF-alpha which, upon binding to its receptor, activates NF-kB. TNF-alpha is also able to stimulate the activity of the CMV-IE enhancer/promoter region. CMV infection of several cell lines leads to NF-kB activation. NF-kB binding sites are present in regulatory regions of various cellular and viral genes, including the IE enhancer region of CMV. In a reciprocal situation, CMV infection, most likely via gamma-interferon, leads to upregulation of MHC antigens in the transplant and, thereby, to increased transplant immunogenicity. Thus, a vicious circle is induced. We have investigated in detail the pathobiology of CMV and allograft vasculopathy (chronic rejection) in experimental animals, using aortic and cardiac allografts as well as a trachea model. The results may be summarized as follows: Infection of the recipient with rat CMV results in an early inflammatory response in the aortic and cardiac allograft vascular adventitia and intima (endothelialitis) and in the airway wall of tracheal allografts. This early inflammatory response leads to enhanced intimal thickness in aortic and cardiac allografts and enhanced luminal occlusion of tracheal allografts. Timewise, this coincides with early activation of intragraft inflammatory leukocytes and increased mRNA of various growth factors and cytokines. When the recipients receive gancyclovir, the enhanced intimal response in aortic and cardiac allografts and luminal occlusion in tracheal allografts is entirely abolished. Gancyclovir treatment dramatically reduces the inflammatory response in the allograft, and thereby growth factor synthesis in response to injury. However, gancyclovir does not prevent the expression of IE antigen of CMV, suggested to inactivate tumor suppressor protein p53 predisposing smooth muscle cells to increased growth. Taken together, the effect of CMV infection on cardiac allograft dysfunction is bidirectional and biphasic. The bidirectional nature emerges from the observations that acute CMV infection may accelerate acute rejection, and, on the other hand, acute alloimmune response-associated cytokine response may activate latent CMV infection. The biphasic effect of CMV on allograft dysfunction refers to its early and late detrimental effects, i.e. during the time of acute and chronic rejection. These two effects of CMV on allograft dysfunction emphasize the need for precise diagnosis of CMV infection in transplant recipients and pre-emptive or prophylactic anti-viral therapy. The benefits of this strategy may not be evident during the early post-transplant period, but 5-10 years after transplantation they manifest as better graft survival.

Animals↗

PubMed1999

Role of platelet-derived growth factor in obliterative bronchiolitis (chronic rejection) in the rat.

The role of platelet-derived growth factor (PDGF) in the development of obliterative bronchiolitis (OB) as a manifestation of chronic rejection was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft PDGF-Ralpha and -Rbeta mRNA expression, and in PDGF-AA and -Ralpha immunoreactivity, was demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. Treatment with CGP 53716, a protein-tyrosine kinase inhibitor selective for PDGF receptor, alone and in combination with suboptimal doses of cyclosporin A, significantly reduced myofibroproliferation and the degree of OB by more than 50%. CGP 53716 did not affect airway wall inflammatory cell proliferation, the number of graft-infiltrating CD4(+) or CD8(+) T cells, ED3(+) macrophages, or the level of immune activation determined as IL-2R and MHC class II expression. This study suggests a regulatory role for PDGF, especially for PDGF-AA and -Ralpha, in the development of obliterative bronchiolitis in this model, and demonstrates that inhibition of PDGF receptor protein-tyrosine kinase activation prevents these obliterative changes. Thus, receptor protein-tyrosine kinase inhibitors may provide a novel therapeutic strategy for the prevention of chronic rejection.

Animals↗

PubMed1997

Expression and localization of platelet-derived growth factor ligand and receptor protein during acute and chronic rejection of rat cardiac allografts.

BACKGROUND: The molecular mechanisms of cardiac allograft vasculopathy (CAV) remain largely unknown. Using rat cardiac allografts, we examined by immunohistochemistry the expression and localization of platelet-derived growth factor ligand (PDGF-AA and -BB) and receptor (R alpha and R beta) proteins during acute and chronic rejection. METHODS AND RESULTS: In acute rejection, a prominent induction of both PDGF ligand and receptor proteins occurred in the interstitial mononuclear inflammatory cells (P<.05), most of which were ED1-immunoreactive. PDGF-R beta was also induced in the capillary endothelium (P<.01). In cardiac allografts with severe intimal thickening, PDGF-AA expression was localized to the media and intima, whereas PDGF-BB expression was less prominent and was detected mainly in interstitial ED1-immunoreactive inflammatory cells. Double staining revealed that intimal cells expressing PDGF-AA were alpha-smooth muscle actin-positive but also alpha-smooth muscle actin-negative myofibroblast-like cells and to a lesser extent, ED1-immunoreactive cells. Both PDGF-R alpha and -R beta expression occurred in intimal, arterial endothelial, and interstitial mononuclear inflammatory cells. High-dose cyclosporin A (CsA) treatment significantly reduced both PDGF-AA and PDGF-R alpha expression in intimal cells. Furthermore, linear regression analysis revealed that PDGF-AA, PDGF-R alpha, and PDGF-R beta expression in intimal cells and PDGF-BB expression in interstitial mononuclear inflammatory cells correlated with intimal thickening. CONCLUSIONS: Alloimmune injury induces the expression of PDGF ligands, especially of PDGF-AA, in the graft vasculature and sufficient immunosuppression with CsA suppresses the expression of PDGF and inhibits the development of CAV. PDGF may have a substantial role in the regulation of smooth muscle cell migration and proliferation in an autocrine or paracrine manner during the development of CAV.

Acute Disease↗

PubMed1997

Adhesion molecule P-selectin and vascular cell adhesion molecule-1 in enhanced heart allograft arteriosclerosis in the rat.

BACKGROUND: The increase of P-selectin on endothelial cells (EC) overlying human atherosclerotic plaques in classic atherosclerosis was recently established. We have previously shown that vascular cell adhesion molecule-1 (VCAM-1) is extensively expressed on EC of occluded arteries during accelerated transplant arteriosclerosis. In the present study, with the use of rat heart allografts under different doses of cyclosporine A (CsA), we investigated whether the expression of P-selectin is increased during chronic rejection and possibly coexpressed with VCAM-1 on EC. METHODS AND RESULTS: Rat cardiac allografts from DA donors to WF recipients were used. Without immunosuppression, these allografts show an irreversible rejection 7 days after transplantation. In the acute rejection model, syngeneic and allogeneic grafts were harvested 5 days after transplantation. In the chronic rejection model, allograft recipients received triple-drug immunosuppression, including azathioprine, methylprednisolone, and CsA in different doses. The grafts were removed 3 months after transplantation. During acute rejection, a significant expression of P-selectin (P < .01) and VCAM-1 (P < .05) on microvascular endothelia, but not on arteries, was noticed. During intense chronic rejection (5 mg/kg CsA), arterial EC expressed P-selectin (P < .01) and VCAM-1 (P < .05) extensively. The expression of tumor necrosis factor-alpha, a cytokine inducing both P-selectin and VCAM-1 expression, was upregulated in vascular medial cells (P < .05), in intimal cells (P < .01), and in interstitial mononuclear cells (P < .05). Linear regression analysis revealed a significant correlation between arterial P-selectin (P < .01) and VCAM-1 (P < .01) expression and the intensity of intimal thickening. Also, a significant correlation and coexpression of P-selectin and VCAM-1 in epicardial arteries was demonstrated (P < .05). CONCLUSIONS: The early expression of P-selectin on microvascular EC during acute rejection may be the basis of cell adhesion and infiltration into the site of inflammation. During chronic rejection, the intensity of arterial intimal thickening was significantly correlated with the intensity of P-selectin expression on EC, in addition to that of previously reported VCAM-1 expression. Thus, P-selectin may have a crucial role in the pathogenesis of chronic rejection in the vascular wall, augmenting the immune-mediated injury against the allograft.

Acute Disease↗

PubMed1997

A dose-dependent inhibitory effect of cyclosporine A on obliterative bronchiolitis of rat tracheal allografts.

Inbred DA and WF rats were used as donors and recipients of heterotopic tracheal allografts. To investigate cellular and molecular mechanisms as well as inhibitory effects of differently acting immunosuppressive drugs on the development of obliterative bronchiolitis (OB), the recipient rats received either cyclosporine A (CsA; 1, 2, or 5 mg/kg/d), 15-deoxyspergualin (DSG; 1 or 2 mg/kg/d), or mycophenolate mofetil (MMF; 20 or 40 mg/kg/d), or were left without immunosuppression. The grafts were removed at various time points for histology and immunohistochemistry. In tracheal allografts removed from nonimmunosuppressed animals, respiratory epithelium was replaced by cuboidal or squamous cell epithelium, with markedly enhanced expression of epithelial major histocompatibility class (MHC) Class II antigens at 3 d after transplantation. This was associated with a pronounced inflammatory episode and proliferation of T cells and macrophages, with the prominence of lymphoid activation markers, MHC Class II antigens and interleukin-2R (IL-2R). Later, total epithelial necrosis developed and intense proliferation of granulation tissue occluded the airway lumen producing a condition resembling OB in humans. In syngeneic tracheal grafts, no such changes could be observed. CsA decreased the development of OB in a dose-dependent fashion, in association with downregulation of epithelial MHC Class II antigen expression, IL-2R expression, and the infiltration of T cells. The new immunosuppressive drugs DSG (suppression of the monocyte/macrophage action and lymphocyte proliferation) and MMF (blocking of the de novo pathway of purine synthesis), in the dose range tested, showed no significant effect on the development of OB. These results suggest that an acute alloimmune response to airway targets, perhaps to epithelium, is the primary cause of OB, since CsA, with a nearly exclusive effect on the transcription of immune cytokines, entirely inhibited the generation of OB, and that preventive intervention for OB must occur early in the T-cell activation pathway.

Animals↗

PubMed1997

Cytomegalovirus infection enhances experimental obliterative bronchiolitis in rat tracheal allografts.

Inbred DA (AG-B4, RT1a) and WF (AG-B2, RT1v) rat immunosuppressed with cyclosporine A (CsA) 2 mg/kg/day subcutaneously were used as donors and recipients of heterotopic rat tracheal allografts. Acute infection was established by inoculating the recipients with 10(5) plaque-forming units of rat cytomegalovirus (RCMV) intraperitoneal on the day of transplantation. Chronic RCMV infection was similarly established 8 wk before transplantation in donors alone, recipients alone, and in both donor and recipients. The control rats were left noninfected. For in vivo cell proliferation, the rats received bromedeoxyuridine intravenously 3 h before being killed. RCMV infection significantly enhanced the generation of experimental obliterative bronchiolitis (OB). First, acute RCMV infection was linked to markedly enhanced MHC class II expression on the respiratory epithelium and prominent airway wall inflammation of W3/25+ T cells (CD4+) and ED1+/ED2+ macrophages. Second, acute infection induced a fivefold increase in luminal occlusion of the trachea, due to proliferating inflammatory and alpha-smooth muscle actin+ myofibroblast-like cells. Acute RCMV infection was particularly associated with markedly increased expression of platelet-derived growth factor (PDGF) AA-isoform in various structures of the graft 10 d after transplantation. At 30 d, RCMV significantly increased PDGF alpha- and beta-receptor expression in alpha-smooth muscle actin+ cells and TNF-alpha expression in capillary endothelial cells of the fibroproliferative lesion. In chronic recipient RCMV infection, the histopathological changes were quite similar to acute infection. Chronic donor infection did not amplify the development of experimental OB. As analyzed by immunohistochemistry from the grafts and by plaque assays from salivary gland biopsies of the recipients, trace RCMV antigen expression, while no infectious RCMV could be recovered in the chronic donor infection group. In other infected groups, RCMV antigen expression was mild to moderate and salivary glands contained plenty of infectious RCMV. To conclude, our results indicate that RCMV infection enhances epithelial MHC class II expression and myofibroproliferation in heterotopic rat tracheal allografts and suggest that these changes may be induced by increased PDGF-AA and PDGF alpha-receptor expression, respectively.

Acute Disease↗

PubMed1996

Cytomegalovirus infection-enhanced chronic kidney allograft rejection is linked with intercellular adhesion molecule-1 expression.

In human kidney allografts, association of acute rejection and glomerulopathy with cytomegalovirus (CMV) infection has been demonstrated. To investigate the effect of CMV infection on the development of experimental chronic kidney allograft rejection, heterotopic kidney allografts from DA (Ag-B4, RT1a1) rat donors to WF (Ag-B2, RT1u) rat recipients were used. The animals received cyclosporine A (CsA) 5 mg/kg/day s.c. either for 1 or 12 weeks. Two groups of recipients were infected with 10(5) plaque-forming units of rat CMV (RCMV) and two other groups were left noninfected and used as controls. The grafts were removed 12 weeks after transplantation for histology and immunohistochemistry. RCMV infection significantly enhanced the development of chronic kidney allograft rejection in rats on continuous CsA the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025), the glomerular mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01), the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature, and the extent of tubular epithelial atrophy (P < 0.025). Chronic allograft damage index (CADI) was significantly increased to 4.3 +/- 0.8 in RCMV-infected allografts, compared to 0.8 +/- 0.4 in noninfected (P < 0.02). In addition, RCMV infection significantly increased the number of acute rejection episodes (serum creatinine > 200 mumol/liter, P < 0.05) and almost doubled the end-stage serum creatinine. RCMV infection significantly increased ICAM-1 expression on the vascular endothelium (P < 0.05) and tubular epithelial cells (P < 0.01), and was linked with enhanced interstitial, glomerular, and tubular inflammation. In 80% of allografts on continuous CsA, RCMV antigens could be observed in sporadic inflammatory cells one week after infection and in tubular epithelial cells at 12 weeks. In heavily inflamed allografts where the CsA treatment was discontinued at one week, enhancement of RCMV infection on the histological changes attributable to chronic kidney allograft rejection could not be demonstrated. Our results show that during CsA immunosuppression, RCMV infection enhances chronic kidney allograft rejection associated with increased interstitial inflammation as well as vascular endothelial and tubular epithelial ICAM-1 expression.

Animals↗

PubMed1996

Triple drug immunosuppression significantly reduces aortic allograft arteriosclerosis in the rat.

We evaluated the effect of triple drug immunosuppression (cyclosporine A 10 mg . kg(-1) . d(-1), methylprednisolone 0.5 mg . kg(-1) . d(-1) on the development of allograft arteriosclerosis (chronic rejection). The recipients of rat aortic allografts from the DA (AG-B4,RT1a) to the WF (AG-B2,RT1u) strain were either treated with triple drug immunosuppression (n=23) or left untreated (n=23) and used as controls. The grafts were removed 7, 14, 30, 90, and 180 days after transplantation, and vascular wall changes were evaluated by quantitative histology, [3H]thymidine autoradiography, and immunohistochemistry. Nonimmunosuppressed aortic allografts developed progressive arteriosclerotic alterations 1 to 6 months after transplantation that were virtually identical to those observed during chronic rejection in human cardiac allografts. Linear regression analysis revealed that triple drug immunosuppression with clinically relevant dosages of drugs significantly reduced intimal thickening (r=.69 versus r=.88, P<.05). Concomitantly, there was a marked reduction in the number of inflammatory cells (P<.01) and their rate of proliferation (P<.025) in the allograft adventitia during the period of acute inflammation (30 days after transplantation). Immunohistochemistry revealed that the number of helper T cells (W3/25) and monocyte/macrophages (OX42) but not cytotoxic T cells (OX8) or natural killer cells (3.2.3) was significantly (P<.05) reduced. The number of adventitial cells expressing interleukin-2 receptor (CD25) (P<.05), MHC class II (OX6) (P<.05) and leukocyte function-associated antigen-1 alpha-chain (CD11a) (P<.025) was also significantly reduced at 30 days. Triple drug immunosuppression downregulated the induction of MHC class II and intercellular adhesion molecule-1 on the graft endothelium but had no significant effect on the number of subendothelial inflammatory cells. In addition, [3H]thymidine autoradiography demonstrated that triple drug immunosuppression significantly reduced the rate of cell proliferation in the media, composed of smooth-muscle cells, 30 and 90 days after transplantation. Thus, triple drug immunosuppression efficiently reduced the development of allograft arteriosclerosis by down-regulating the inflammatory response and the level of immune++ activation in the allograft adventitia during the acute rejection period, resulting in diminished intimal thickening of the graft in the long run. These results support the concept that allograft arteriosclerosis is due to or at least initiated by immune injury of the graft.

Animals↗

PubMed1995

How cyclosporine modifies histological and molecular events in the vascular wall during chronic rejection of rat cardiac allografts.

Accelerated allograft arteriosclerosis (chronic rejection) has emerged as a major factor affecting long-term survival of human cardiac allografts. The underlying mechanism of this disorder remains unclear. The purpose of this study was to investigate the effect of cyclosporine on the development of cardiac allograft arteriosclerosis at the cellular and molecular level. Heterotopic rat cardiac allografts from DA donors to WF recipients, with a strong genetic disparity in major histocompatibility complex and non-major histocompatibility complex loci, were used. The allograft recipients received triple-drug immunosuppression consisting of methylprednisolone (0.5 mg/kg/day), azathioprine (2 mg/kg/day), and three different doses of cyclosporine A (CsA; 5, 10, and 20 mg/kg/day). The grafts were removed 3 months after transplantation and processed for histology and immunohistochemistry. Low dose CsA (5 mg/kg/day) was associated with a severe form of intimal cell accumulation and intimal thickening in epicardial arteries and in smaller intramyocardial arterioles with nearly occluded vessel lumens 3 months after transplantation. The intermediate dose CsA (10 mg/kg/day) significantly inhibited arterial intimal thickening but was not efficient in reducing intimal cell accumulation. Instead, high dose CsA (20 mg/kg/day) significantly inhibited all arteriosclerotic vascular wall changes in the allografts. Immunohistochemistry revealed that the occluded epicardial arteries of cardiac allografts with low dose CsA expressed VCAM-1 on the endothelium. Higher CsA doses significantly reduced the expression of endothelial VCAM-1. Neither ICAM-1 nor major histocompatibility complex class II were expressed. Perivascular arterial infiltrates consisting of T helper cells and monocytes/macrophages were a characteristic finding in the allograft with low dose CsA. In the allografts treated with higher doses of CsA, arterial perivascular infiltrates were seldom seen. Our results conclusively demonstrate that sufficient immunosuppression with CsA inhibits intimal thickening and intimal cell accumulation of long-surviving rat cardiac allografts in a dose-dependent fashion. Arteriosclerotic alterations associated with increased expression of arterial endothelial VCAM-1 were totally down-regulated by high doses of CsA.

Animals↗

PubMed1994

Vascular cell adhesion molecule-1 (VCAM-1) is induced during cytomegalovirus infection in vascular structures of heart allografts.

This study was designed to investigate the expression of vascular cell adhesion molecule-1 (VCAM-1) and the counter-ligand VLA-4 (CD 49d) in frozen sections of endomyocardial biopsies (EMBs) of heart allografts in relation to the onset of cytomegalovirus (CMV) infection diagnosed by CMV antigenemia. Altogether, 105 EMBs were obtained from 21 heart transplant recipients. Serial EMBs from nine patients with CMV infection, from five patients with rejection, and from seven patients with a noncomplicated postoperative course were analyzed. Associated with CMV infection, capillary expression of VCAM-1 was significantly induced when compared to control biopsies (P < 0.0001). A striking difference in the expression of VCAM-1 during rejection and CMV infection was observed: in most rejecting biopsies only a few capillaries stained faintly for VCAM-1, whereas during CMV infection, multifocal intense staining was found (P < 0.0001).

Biopsy↗

PubMed1994

Effect of ganciclovir prophylaxis on cytomegalovirus-enhanced allograft arteriosclerosis.

Clinical and experimental studies have established the accelerating role of cytomegalovirus (CMV) infection on cardiac allograft arteriosclerosis, i.e. chronic rejection. In this study, we investigated the effect of ganciclovir prophylaxis on the development of CMV-enhanced allograft arteriosclerosis. Rat aortic allografts were done from DA donors to WF recipients and either infected with 10(5) plaque-forming units of rat CMV (RCMV) 1 day after transplantation or left uninfected. RCMV-infected allografts received ganciclovir at an initial dose of 20 mg/kg and a maintenance dose of 10 mg/kg twice a day for 14 days. Grafts were removed at 7, 14 days, and 1 and 3 months after transplantation and processed for morphometry and autoradiography. The results of this study demonstrated that ganciclovir prophylaxis significantly delays and reduces RCMV-enhanced allograft arteriosclerosis in the rat.

Animals↗

PubMed1994

Cytomegalovirus infection enhances mRNA expression of platelet-derived growth factor-BB and transforming growth factor-beta 1 in rat aortic allografts. Possible mechanism for cytomegalovirus-enhanced graft arteriosclerosis.

We have recently demonstrated that rat cytomegalovirus (RCMV) infection induces an early inflammatory response in the adventitia (perivasculitis) and in the subendothelial space (endothelialitis) as well as doubles smooth muscle cell (SMC) proliferation and intimal thickening of rat aortic allografts performed from the DA (AG-B4, RT1a) to the WF (AG-B2, RT1v) strain. In this study, the impact of RCMV infection on the structure of inflammation in the allograft adventitia and on the expression of SMC growth factors in the allograft vascular wall was investigated. The recipient rats were inoculated with 10(5) plaque-forming U of RCMV Maastricht strain or left noninfected and used as controls. The allografts were removed at 7 days and 1 and 3 months after transplantation and processed for morphometry and immunohistochemistry. RNA was isolated for reverse transcriptase polymerase chain reaction (RT-PCR). RCMV infection was associated with significantly upregulated presence (P < .05) of T helper (W3/25), T cytotoxic (OX8), and natural killer (3.2.3) cells in the allograft adventitia 7 days after transplantation but not thereafter. More monocyte/macrophages (OX42) were also present in RCMV-infected allografts, but the difference was not significant. Concomitantly, RCMV infection significantly enhanced (P < .05) the expression of major histocompatibility complex class II (OX6) and almost doubled (P = NS) the expression of interleukin-2R (CD25), intercellular adhesion molecule-1 (CD54;1A29), and lymphocyte function-associated antigen-1 alpha-chain (CD11a; WT.1) in the adventitial inflammatory infiltrate. RCMV infection was linked with an early, prominent expression of both PDGF-BB mRNA at 7 days (P < .05) and at 1 month (P < .025) and of transforming growth factor-beta 1 mRNA at 7 days (P < .025) and at 1 month (P < .025) after transplantation. A less-prominent mRNA upregulation of acidic fibroblast growth factor (P < .05) was associated with RCMV infection at 7 days and at 1 month, as well as of epidermal growth factor at 1 month after transplantation, when compared with noninfected allografts, although the mRNA expression in both groups was below the levels of nontransplanted DA aortas. RCMV infection almost doubled basic fibroblast growth factor mRNA expression (P = NS) in the allograft vascular wall at 7 days and at 1 month. RCMV infection had no additional impact on insulin-like growth factor-1 mRNA expression when compared with noninfected allografts.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

Cytomegalovirus infection-enhanced allograft arteriosclerosis is prevented by DHPG prophylaxis in the rat.

BACKGROUND: Major risk factors for accelerated allograft arteriosclerosis include humoral and cellular immune response, hyperlipidemia, and viral infections. We demonstrated earlier that rat cytomegalovirus (RCMV) infection doubles smooth muscle cell proliferation and intimal thickening of rat aortic allografts. In this study, the effects of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG) on RCMV-enhanced rat allograft arteriosclerosis are investigated. METHODS AND RESULTS: Aortic allografts from the DA to the WF rat strain were used. The recipients were inoculated with 10(5) plaque-forming units of RCMV 1 day after transplantation. Two groups of RCMV-infected rats were treated with DHPG with an initial dose of 20 mg/kg IP and a maintenance dose of 10 mg/kg IP twice a day for a period of 14 days. In the DHPG prophylaxis group (n = 22), the drug administration started 1 day before infection, and in the DHPG treatment group (n = 17), 7 days after infection. One group of infected rats was left untreated (n = 21). The grafts were removed 7 and 14 days and 1, 3, and 6 months after transplantation. In the DHPG prophylaxis group, no virus could be recovered by plaque assays. In the treatment group, 50% of rats were virus-positive at 1 month and 40% at 3 months. DHPG prophylaxis prevented the infiltration of inflammatory cells and their proliferation in the adventitia of RCMV-infected recipients (P < .01), with a 60% reduction in the interleukin-2 receptor expression (P < .05) and a 30% decrease in major histocompatibility complex class II expression (P = NS). DHPG prophylaxis did not significantly alter the levels of insulin-like growth factor-1, epidermal growth factor, platelet-derived growth factor-BB, transforming growth factor-beta 1, acidic fibroblast growth factor, and basic fibroblast growth factor messages in the allograft vascular wall. Early media necrosis was reduced. Arteriosclerotic alterations and proliferation of smooth muscle cells were both reduced 50% to 70% by DHPG prophylaxis (P < .05 at 3 months). The responses in the DHPG treatment group were quite similar but less impressive and statistically nonsignificant. CONCLUSIONS: We consider it likely that DHPG inhibits arteriosclerotic alterations primarily by reducing the infectious virus and thereby the inflammatory response in the allograft vascular wall; another possibility is a direct antiproliferative effect on smooth muscle cell replication. A dose-dependent inhibitory effect of DHPG on smooth muscle cell replication was recorded in an in vitro study.

Animals↗

PubMed1994

Triple drug immunosuppression significantly reduces immune activation and allograft arteriosclerosis in cytomegalovirus-infected rat aortic allografts and induces early latency of viral infection.

The effect of triple drug immunosuppression (cyclosporine A 10 mg/kg/day+methylprednisolone 0.5 mg/kg/day+azathioprine 2 mg/kg/day) on rat cytomegalovirus (RCMV)-enhanced allograft arteriosclerosis was investigated applying WF (AG-B2, RT1v) recipients of DA (AG-B4, RT1a) aortic allografts. The recipients were inoculated intraperitoneally with 10(5) plaque-forming units of RCMV 1 day after transplantation or left noninfected. The grafts were removed on 7 and 14 days, and at 1, 3, and 6 months after transplantation. The presence of viral infection was demonstrated by plaque assays, cell proliferation by [3H]thymidine autoradiography, and vascular wall alterations by quantitative histology and immunohistochemistry. Triple drug immunosuppression reduced the presence of infectious virus in plaque assays and induced early latency of viral infection. It significantly reduced the peak adventitial inflammatory response (P < 0.05) and reduced and delayed intimal nuclear intensity and intimal thickening (P < 0.05) in RCMV-infected allografts. The proliferative response of smooth muscle cells was reduced by triple drug immunosuppression to 50% of that observed in nonimmunosuppressed RCMV-infected allografts, but still the proliferative peak response was seen at 1 month. Only low level immune activation, ie, the expression of interleukin-2 receptor (P < 0.05) and MHC class II, was observed under triple drug immunosuppression in the adventitia of RCMV-infected allografts, whereas there was no substantial change in the phenotypic distribution of inflammatory cells. In conclusion, although RCMV infection significantly enhances allograft arteriosclerosis also in immunosuppressed allografts, triple drug immunosuppression has no additional detrimental effect but rather a protective one on vascular wall histology. These results further suggest that RCMV-enhanced allograft arteriosclerosis may be an immunopathological condition linked to the host immune response toward the graft and/or the virus rather than a direct virus-induced phenomenon.

Animals↗

PubMed1993

Cytomegalovirus infection accelerates cardiac allograft vasculopathy: correlation between angiographic and endomyocardial biopsy findings in heart transplant patients.

In order to determine the impact of cytomegalovirus (CMV) infection on cardiac allograft vasculopathy (CAV), we quantitated angiograms and endomyocardial biopsy (EMB) specimens obtained from 53 heart transplant recipients. CMV infection was particularly associated with the development of discrete stenosis in major branch vessels (P < 0.03). Also, the number of diffusely affected vessel segments was significantly higher in CMV patients than in CMV-free recipients after the 2nd postoperative year (P < 0.05). The EMB histology correlated well with angiography. Significantly higher levels of arteriolar endothelial cell proliferation and intimal thickness were recorded in biopsies of CMV patients than in those of CMV-free recipients during the 1st postoperative year (P < 0.02 and P < 0.005, respectively). The CMV-associated vascular changes in EMB histology clearly preceded angiographically detectable CAV findings. Taken together, CMV infection accelerated heart allograft arteriosclerosis. The histological changes appeared prior to changes detected by coronary angiography. The CMV effect was particularly pronounced during the first 2 post-transplant years but leveled off thereafter. Thus, CMV-accelerated allograft arteriosclerosis may be linked in particular with early graft loss of CMV-infected heart transplant recipients.

Biopsy↗