Fibrosis in chronic rejection of human liver allografts: expression patterns of transforming growth factor-TGFbeta1 and TGF-beta3

Mechanisms of Tolerance Induction in Liver Transplantation: Lessons Learned from Fetomaternal Tolerance, Autoimmunity and Tumor Immunity

Since the first published report of experimental kidney transplantation in dogs in 1902, there were many experimental and clinical trials of organ transplantation, with many sacrifices. After the establishment of the surgical technique and the discovery of immunosuppressive drugs, transplantation became the definitive treatment strategy for patients with terminal organ failure. However, this is not a common therapy method due to the difficulty of solving the fundamental issues behind organ transplantation, including the shortage of donor graft, potential risks of transplant surgery and economic capability. The pre- and post-transplant management of recipients is another critical issue that may affect transplant outcome. Most liver transplant recipients experience post-transplant complications, including infection, acute/chronic rejection, metabolic syndrome and the recurrence of hepatocellular carcinoma. Therefore, the early prediction and diagnosis of these complications may improve overall and disease-free survival. Furthermore, how to induce operational tolerance is the key to achieving the ultimate goal of transplantation. In this review, we focus on liver transplantation, which is known to achieve operational tolerance in some circumstances, and the mechanical similarities and differences between liver transplant immunology and fetomaternal tolerance, autoimmunity or tumor immunity are discussed.

Consumption of barley ameliorates the diabetic steatohepatitis and reduces the high transforming growth factor β expression in mice grown in α-minimum essential medium in vitro as embryos

Non-alcoholic fatty liver disease (NAFLD), which includes the subtype non-alcoholic steatohepatitis (NASH), is a major complication of type 2 diabetic mellitus (T2DM), even among non-obese patients. However, the exact cause of NAFLD/NASH in non-obese patients with T2DM is unclear. We studied a non-obese mouse model of T2DM created through the malnourishment of embryos by culture in vitro for 48 h in α-minimum essential medium (MEM) at the two-cell stage. We compared the development of steatohepatitis in these MEM mice with control mice that were similarly cultured in standard potassium simplex-optimized medium (KSOM). We also studied the effects of 10 weeks of consumption of barley, which contains large amounts of the soluble fiber β-glucan, on the steatohepatitis of the adult MEM mice. The size of lipid droplets, the area of fibrosis, and the mRNA expression of the transforming growth factor beta (Tgfb) gene in the liver were higher in adult MEM mice fed a rice-based diet than in KSOM mice fed the same diet. However, barley consumption reduced the area of fibrosis and TGFB expression in MEM mice. In conclusion, adult mice that are cultured in MEM at the two-cell embryo stage develop steatohepatitis and T2DM, accompanied by higher hepatic TGFB expression, than KSOM controls. Furthermore, the consumption of barley during adulthood ameliorates the steatohepatitis and reduces the TGFB expression.

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The mouse preimplantation embryos cultured in αMEM in vitro developed steatohepatitis.

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Dietary barley suppressed diabetic steatohepatitis with fibrosis.

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Barley intake also reduced gene and protein expression of TGFB in livers of MEM mice.

Tgfb3 and Mmp13 regulated the initiation of liver fibrosis progression as dynamic network biomarkers

Liver fibrogenesis is a complex scar-forming process in the liver. We suggested that the liver first responded to chronic injuries with gradual changes, then reached the critical state and ultimately resulted in cirrhosis rapidly. This study aimed to identify the tipping point and key molecules driving liver fibrosis progression. Mice model of liver fibrosis was induced by thioacetamide (TAA), and liver tissues were collected at different time-points post-TAA administration. By dynamic network biomarker (DNB) analysis on the time series of liver transcriptomes, the week 9 post-TAA treatment (pathologically relevant to bridging fibrosis) was identified as the tipping point just before the significant fibrosis transition, with 153 DNB genes as key driving factors. The DNB genes were functionally enriched in fibrosis-associated pathways, in particular, in the top-ranked DNB genes, Tgfb3 negatively regulated Mmp13 in the interaction path and they formed a bistable switching system from a dynamical perspective. In the in vitro study, Tgfb3 promoted fibrogenic genes and down-regulate Mmp13 gene transcription in an immortalized mouse HSC line JS1 and a human HSC line LX-2. The presence of a tipping point during liver fibrogenesis driven by DNB genes marks not only the initiation of significant fibrogenesis but also the repression of the scar resolution.

Cellular Senescence in Liver Disease and Regeneration

Cellular senescence is an irreversible cell cycle arrest implemented by the cell as a result of stressful insults. Characterized by phenotypic alterations, including secretome changes and genomic instability, senescence is capable of exerting both detrimental and beneficial processes. Accumulating evidence has shown that cellular senescence plays a relevant role in the occurrence and development of liver disease, as a mechanism to contain damage and promote regeneration, but also characterizing the onset and correlating with the extent of damage. The evidence of senescent mechanisms acting on the cell populations of the liver will be described including the role of markers to detect cellular senescence. Overall, this review intends to summarize the role of senescence in liver homeostasis, injury, disease, and regeneration.

Targeting Senescent Cells in Fibrosis: Pathology, Paradox, and Practical Considerations

PURPOSE OF THE REVIEW

Senescent cells have the capacity to both effect and limit fibrosis. Senotherapeutics target senescent cells to improve aging conditions. Here, we review the contexts in which senescent cells mediate wound healing and fibrotic pathology and the potential utility of senotherapeutic drugs for treatment of fibrotic disease.

RECENT FINDINGS

Multi-action and temporal considerations influence deleterious versus beneficial actions of senescent cells. Acutely generated senescent cells can limit proliferation, and the senescence-associated secretory phenotype (SASP) contains factors that can facilitate tissue repair. Long-lived senescent cells that evade clearance or are generated outside of programmed remodeling can deplete the progenitor pool to exhaust regenerative capacity and through the SASP, stimulate continual activation, leading to disorganized tissue architecture, fibrotic damage, sterile inflammation, and induction of bystander senescence. Senescent cells contribute to fibrotic pathogenesis in multiple tissues, including the liver, kidney, and lung. Senotherapeutics may be a viable strategy for treatment of a range of fibrotic conditions.

Dynamic Interplay of Smooth Muscle α-Actin Gene-Regulatory Proteins Reflects the Biological Complexity of Myofibroblast Differentiation

Myofibroblasts (MFBs) are smooth muscle-like cells that provide contractile force required for tissue repair during wound healing. The leading agonist for MFB differentiation is transforming growth factor β1 (TGFβ1) that induces transcription of genes encoding smooth muscle α-actin (SMαA) and interstitial collagen that are markers for MFB differentiation. TGFβ1 augments activation of Smad transcription factors, pro-survival Akt kinase, and p38 MAP kinase as well as Wingless/int (Wnt) developmental signaling. These actions conspire to activate β-catenin needed for expression of cyclin D, laminin, fibronectin, and metalloproteinases that aid in repairing epithelial cells and their associated basement membranes. Importantly, β-catenin also provides a feed-forward stimulus that amplifies local TGFβ1 autocrine/paracrine signaling causing transition of mesenchymal stromal cells, pericytes, and epithelial cells into contractile MFBs. Complex, mutually interactive mechanisms have evolved that permit several mammalian cell types to activate the SMαA promoter and undergo MFB differentiation. These molecular controls will be reviewed with an emphasis on the dynamic interplay between serum response factor, TGFβ1-activated Smads, Wnt-activated β-catenin, p38/calcium-activated NFAT protein, and the RNA-binding proteins, Purα, Purβ, and YB-1, in governing transcriptional and translational control of the SMαA gene in injury-activated MFBs.

Localization of apoptosis proteins and lymphocyte subsets in chronic rejection of human liver allograft

In chronic liver rejection lymphocyte mediated processes lead to chronic inflammation, necrosis and repair mechanisms. The aim of the present study was to investigate the expression of apoptosis related proteins (FAS/APO-1, FAS-L, Bcl-2, Bax, TNF-α, and INF-γ). ApopTag reaction and immunohistochemistry were performed on liver samples of chronically rejected allografts and compared with normal donor livers. In chronic rejection, apoptosis was detected in pericentral hepatocytes and in the biliary epithelium. Bcl-2 was strongly expressed on lymphocytes around the bile ducts, but not on the biliary epithelium itself. Bax, FAS, TNF-α and INF-γ were present in pericentral areas. T-cells showed up around bile ducts, whereas macrophages around pericentral areas. In pericentral areas apoptosis seems to be fostered through TNF-α and INF-γ and by the lack of Bcl-2. Based on these results both downregulation and upregulation of apoptotic proteins can be observed in chronic liver allograft rejection: FAS is upregulated in biliary epithelium and zone 2, protein levels of FASL remain unchanged, BAX is upregulated in zone 3, BCL2 is downregulated in both biliary epithelium and zone 1 and both TNFa and IFN are upregulated in zone 3. Our results suggest that the balance between pro- and antiapoptotic patterns was shifted to the proapoptotic side, mainly in the centrilobular area of the hepatic lobule, and in the bile ducts. According to these findings in chronic rejection the predictive sites of apoptosis are the biliary epithelium and the pericentral areas.

Induction of chronic renal allograft dysfunction in a rat model with complete and exclusive MHC incompatibility

Chronic allograft dysfunction is one of the most important reasons for late graft loss after renal transplantation. Its etiology is multifactorial and combines immunological as well as non-immunological mechanisms. It is known from large registry data that MHC mismatches are inversely correlated to long term allograft survival. Although this is a well known aspect, the mechanisms of MHC-driven graft damage and the impact of other immunological factors leading to chronic rejection are poorly understood. In patients it is impossible to study MHC mismatches without considering non-MHC differences. Further more common animal models for chronic rejection are all characterized by non-MHC as well as MHC disparities. To exclusively study MHC mediated immunoresponses we established a rat model of renal transplantation using congenic rat strains differing in their entire MHC class I and class II, but sharing the genetic background of the LEW rat. After an initial short term of immunosuppression all animals developed renal impairment with severe albuminuria. Half of the animals died of renal failure in week 7 to 14 and showed pathological characteristics of chronic allograft damage including IF/TA and severe glomerulopathy. The majority of these recipients developed circulating donor-specific MHC alloantibodies. Allografts were significantly infiltrated with T-cells, macrophages and NK-cells. We established a MHC congenic rat model to investigate immunological mechanisms of chronic renal allograft rejection exclusively induced by a complete MHC mismatch. We demonstrated humoral as well as cellular immunoresponses leading to chronic allograft loss in 50% of animals.

Inflammation and repair in viral hepatitis C

Hepatitis C viral infection (HCV) results in liver damage leading to inflammation and fibrosis of the liver and increasing rates of hepatic decompensation and hepatocellular carcinoma (HCC). However, the host's immune response and viral determinants of liver disease progression are poorly understood. This review will address the determinants of liver injury in chronic HCV infection and the risk factors leading to rapid disease progression. We aim to better understand the factors that distinguish a relatively benign course of HCV from one with progression to cirrhosis. We will accomplish this task by discussion of three topics: (1) the role of cytokines in the adaptive immune response against the HCV infection; (2) the progression of fibrosis; and (3) the risk factors of co-morbidity with alcohol and human immunodeficiency virus (HIV) in HCV-infected individuals. Despite recent improvements in treating HCV infection using pegylated interferon alpha (PEGIFN-alpha) and ribavirin, about half of individuals infected with some genotypes, for example genotypes 1 and 4, will not respond to treatment or cannot be treated because of contraindications. This review will also aim to describe the importance of IFN-alpha-based therapies in HCV infection, ways of monitoring them, and associated complications.

Homeobox Gene Prx1 Is Expressed in Activated Hepatic Stellate Cells and Transactivates Collagen α1(I) Promoter

Hepatic stellate cells (HSCs) are mesenchymal cells of the liver, which are normally in quiescent state and synthesize tracing amounts of extracellular matrix proteins. Upon fibrogenic stimulus, HSCs become activated and increase synthesis of type I collagen 50–100 fold. Prx1 and Prx2 are two homeobox transcription factors which are required for mesenchymal tissue formation during embryogenesis. The present study shows that Prx1 mRNA is expressed in in vivo and in vitro activated HSCs, but not in quiescent HSCs. Prx1 is also expressed in fibrotic livers, while it is undetectable in normal livers. Overexpression of Prx1a in quiescent HSCs cultured in vitro induced collagen α1(I) mRNA and TGFβ3 mRNA expression. Prx1 transactivated TGFβ3 promoter 3 fold in transient transfection experiments. In the whole liver, Prx1a induced expression of collagen α1(I), α2(I), α1(III) and α-smooth muscle mRNAs, which are the markers of activation of HSCs. Prx1 also increased expression of collagen α1(I) mRNA after acute liver injury. This suggests that Prx1a promotes activation of HSCs and expression of type I collagen. Several regions in the collagen α1(I) promoter were identified which mediate transcriptional induction by Prx1. The regions are scattered throughout the promoter and individually have modest effects; however, the cumulative effect of all sequences is >50 fold. This is the first description of the effects of Prx1 in HSCs and in the liver, and identification of the two Prx1 target genes, which play a pivotal role in development of liver fibrosis, is a novel finding for liver pathophysiology.

Toona sinensis Roem (Meliaceae) leaf extract alleviates liver fibrosis via reducing TGFbeta1 and collagen

Toona sinensis Roem (TS) leaf tea as a health food for the improvement of blood sugar and hypertension has been demonstrated. Thioacetamide (TAA), a hepatotoxin, causes the progression of liver fibrosis. In this study, we tested the effects of TS leaf on TAA-induced liver injury. TAA (200mg/kg Bwt/3 days, i.p.) treated rats were orally administrated with TS leaf extract (1g/kg Bwt/10 days) three times. After 30 days treatment, the morphological data showed that TS leaf extract given to TAA-treated rats had less liver fibrosis. The GOT/GPT, collagen 1 and collagen 3 mRNAs of livers in TAA-treated rats were elevated when compared to normal rats. The improvements of GOT/GPT, collagen 1 and collagen 3 mRNAs were shown in the TS leaf extract given to TAA-treated rats. TS leaf extract given to TAA-treated rats showed higher levels of cytochrome P450 (1A1, 2A and reductase) than those of TAA-treated rats. Compared to the TAA-treated group, TGFbeta1 mRNA (RT-PCR) was decreased with an increase of TGFbetaR1 protein (western blot) in the TS leaf extract given to TAA-treated rats. The decreased tendency of FGFR2 was found in the TS leaf extract given to TAA-treated rats. The result implies that TS leaf possesses beneficial effects on liver injury through increments of detoxification and the metabolic pathway.

Effects of Everolimus on Cellular and Humoral Immune Processes Leading to Chronic Allograft Nephropathy in a Rat Model with Sensitized Recipients

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most common cause of late graft loss especially in sensitized patients. The aim of this study is to evaluate the therapeutic effect of everolimus on cellular and humoral mechanisms of chronic allograft damage in a rat model with sensitized recipients.

METHODS

F344 kidneys were transplanted to LEW.RNU rats. The athymic recipients were reconstituted with 3.5 x 10(7) or 5 x 10(7) presensitized CD4+T-lymphocytes. In the treatment group, everolimus was introduced five weeks posttransplantation. Rats were monitored for peripheral blood lymphocytes, renal function, histological changes in the graft, and the development of donor-specific alloantibodies.

RESULTS

Rats developed cell dose-dependent renal failure. Increased urinary albumin excretion and glomerulopathy were frequently accompanied by the development of donor-specific major histocompatibility complex (MHC) alloantibodies. In the everolimus group, five of six animals survived for 20 weeks with stable serum creatinine and displayed neither acute cellular rejection nor CAN. Prolonged survival was accompanied with significantly reduced tubulointerstitial cell infiltrate in the graft. Increased urinary albumin excretion was present in all, acute tubular necrosis in five of six, and glomerular sclerosis in two grafts. MHC alloantibodies were found in four of six animals.

CONCLUSION

The used rat model offers the opportunity to study the influence of everolimus on the interaction of humoral and cellular mechanisms involved in chronic renal damage. Everolimus leads to a prolongation of allograft survival, reduced cell infiltrate in the graft, and prevents tubular atrophy and interstitial fibrosis. The development of alloantibodies and albuminuria was not prevented. These data suggest that although cellular rejection is clearly suppressed, humoral mechanisms of CAN cannot be completely controlled by everolimus treatment in the sensitized rat model.

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Myofibroblast transdifferentiation in obliterative bronchiolitis: tgf-beta signaling through smad3-dependent and -independent pathways

We have shown that Smad3, an intracellular signal transducer for transforming growth factor-beta1 (TGF-beta1), is required to elicit the full histological manifestations of obliterative airway disease in a tracheal transplant model. This suggests that chronic allograft rejection results in TGF-beta1-induced Smad3 activation that leads to airway obliteration through fibroproliferation and increased matrix deposition. In other systems, these latter events are causally related to the transdifferentiation of fibroblasts into myofibroblasts, but their role in obliterative bronchiolitis (OB) after lung transplantation is unknown. We confirmed the presence of myofibroblasts inside affected airways associated with experimental OB using immunohistochemistry. Studying airway fibroblasts in vitro, we observed increased myofibroblast transdifferentiation in response to TGF-beta1, evidenced by increased alpha-smooth muscle actin mRNA and protein expression. In Smad3-null fibroblasts, TGF-beta1 induction of myofibroblast transdifferentiation was greatly diminished but not abolished, suggesting the presence of Smad3-independent pathways. Further studies revealed that small molecule inhibitors of p38 (SB203580) and MEK/ERK (U1026) further reduced the remaining effect of TGF-beta1 in Smad3-deficient fibroblasts. Together, these studies suggest that in chronic allograft rejection, TGF-beta1 stimulates myofibroblast transdifferentiation through Smad3-dependent and -independent signals, contributing to the excessive matrix deposition that characterizes obliterative bronchiolitis.

Regulation of Fibrosis by the Immune System

Inflammation and fibrosis are two inter-related conditions with many overlapping mechanisms. Three specific cell types, macrophages, T helper cells, and myofibroblasts, each play important roles in regulating both processes. Following tissue injury, an inflammatory stimulus is often necessary to initiate tissue repair, where cytokines released from resident and infiltrating leukocytes stimulate proliferation and activation of myofibroblasts. However, in many cases this drive stimulates an inappropriate pro-fibrotic response. In addition, activated myofibroblasts can take on the role of traditional APCs, secrete pro-inflammatory cytokines, and recruit inflammatory cells to fibrotic foci, amplifying the fibrotic response in a vicious cycle. Moreover, inflammatory cells have been shown to play contradictory roles in initiation, amplification, and resolution of fibrotic disease processes. The central role of the macrophage in contributing to the fibrotic response and fibrotic resolution is only beginning to be fully appreciated. In the following review, we discuss the fibrotic disease process from the context of the immune response to injury. We review the major cellular and soluble factors controlling these responses and suggest ways in which more specific and, hopefully, more effective therapies may be derived.

Chronic allograft nephropathy in athymic nude rats after adoptive transfer of primed T lymphocytes

The impact of presensitized T lymphocytes on the development of chronic allograft nephropathy (CAN) was investigated in nude athymic LEW.RNU recipients of F344 renal allografts. The recipients (n = 8) were reconstituted with 5 x 10(7) T lymphocytes primed against donor skin grafts to induce graft rejection. LEW.RNU (n = 8) and euthymic LEW recipients (n = 6) which underwent no further intervention after transplantation served as control groups. Adoptive transfer of primed T cells induced CAN in LEW.RNU rats. Their kidney function decreased progressively. After 90 days a moderate glomerulopathy, tubular atrophy and interstitial fibrosis were observed, vascular changes were only mild or absent. Cellular infiltrates were predominated by CD4+ T cells and ED1+ macrophages. Deposition of tenascin and laminin was enhanced. Grafts of euthymic recipients displayed only mild signs of CAN according to the Banff criteria. These data implicate an important role for the cellular immune response in the development of CAN.

Adoptive transfer of primed CD4+ T-lymphocytes induces pattern of chronic allograft nephropathy in a nude rat model

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most common cause of late graft loss in renal transplantation. Presensitized patients have a specifically increased risk to lose their graft. To analyze the immunological factors involved, a new experimental rat model was created with nude athymic LEW.RNU rats as recipients of F344 renal allografts.

METHODS

Adoptive transfer of CD4+ T-lymphocytes (2x, 3.5x, or 5 x 10(7) cells) primed against donor skin grafts was performed one week after transplantation. The animals were monitored for renal function, graft infiltrating cells, and the development of donor specific alloantibodies for 20 weeks or until graft loss.

RESULTS

Survival of the animals was dose dependent; rats suffered from renal failure with severe albuminuria and developed various lesions typical for CAN including interstitial fibrosis and tubular atrophy. The cell infiltrate in the graft increased with the amount of CD4+ T-cells transferred and consists predominantly of CD4+ T-cells and macrophages/monocytes. More than half of the grafts showed histological signs of glomerulopathy consistent with CAN. 9/12 rats with CAN had antibodies against the donor major histocompatibility complex (MHC)-I and in all rats donor specific anti-glomerular basement membrane (GBM) antibodies were detected.

CONCLUSION

Adoptive transfer of primed CD4+ T-cells results in a severe infiltrate of CD4+ cells in the graft and production of anti-MHC and GBM antibodies in this nude rat model. Histological changes are consistent with CAN with frequent glomerular changes. In conclusion, the induction of donor specific alloantibodies by primed CD4+ T-lymphocytes may play an important role in the pathogenesis of CAN.

Expression of CD34, alpha-smooth muscle actin, and transforming growth factor beta1 in squamous intraepithelial lesions and squamous cell carcinoma of the larynx and hypopharynx

AIM OF THE STUDY

There is increasing evidence that stromal reaction in cancer has an important diagnostic and prognostic significance. Recent studies have shown that CD34-positive stromal cells and myofibroblasts may play an important role in host response to invasive cancer. The aim of our study was to analyze the expression of CD34, alpha-smooth muscle actin (SMA), and transforming growth factor beta1 (TGFbeta1) in squamous intraepithelial lesions (SILs) and squamous cell carcinoma (SCC) of the larynx and hypopharynx, to establish their significance, and to elucidate the mechanism of myofibroblast formation.

METHODS

Immunohistochemistry was performed on samples of 42 resected larynges and 12 laryngeal biopsies of SILs and SCC using antibodies against SMA, CD34, CD31, TGFbeta1, and TGFbeta1 receptors. The expression of TGFbeta1 mRNA was detected with RNA in situ hybridization using specific oligonucleotides for TGFbeta1.

RESULTS

The stroma in normal laryngeal mucosa and SILs contained scattered CD34-positive cells, but there were no SMA-positive myofibroblasts. In contrast, the stroma of SCC contained SMA-positive myofibroblasts, but there were no CD34-positive stromal cells. This pattern of stromal reaction was also observed in the peritumoral zone. In adjacent normal tissue, there were CD34-positive stromal cells and no myofibroblasts. We found more intense TGFbeta1 expression in carcinoma cells than in the normal laryngeal epithelium and positive staining for both TGFbeta1 receptors on stromal cells of the normal mucosa. In SCC, many myofibroblasts expressed TGFbeta1 and both receptors for TGFbeta1. Expression of TGFbeta1 mRNA was similar to expression of TGFbeta1 protein.

CONCLUSION

Our study shows that disappearance of CD34-positive stromal cells and appearance of SMA-positive stromal myofibroblasts are associated with transformation of laryngeal SILs to SCC. This pattern of stromal reaction was found not only in the tumor but also in the peritumoral zone, defined as a band of host tissue between the invasive tumor front and adjacent normal tissue. Our findings also support the suggestion that overproduced TGFbeta1 in carcinoma cells mediates one of the mechanisms of transformation of stromal cells to myofibroblasts in laryngeal carcinogenesis.

Smad3 deficiency ameliorates experimental obliterative bronchiolitis in a heterotopic tracheal transplantation model

Chronic allograft rejection manifested as obliterative bronchiolitis (OB) remains the single greatest impediment to long-term survival after lung transplantation. Transforming growth factor-beta1 (TGF-beta1) has been implicated in the tissue remodeling response associated with OB. Therefore, its intracellular signal transducer, Smad3, is a prime target of investigation. Herein, we examine the role of TGF-beta1, through Smad3, in the development of OB using heterotopic tracheal transplantation in wild-type and Smad3-null mice. TGF-beta1 was detectable within infiltrating mononuclear cells early after transplantation. Later it was detected in fibroblasts and in the connective tissue accumulating within the lumen and the airway wall of the transplanted allografts. Connective tissue growth factor had a similar time and tissue distribution. Nuclear detection of Smad3 and phosphorylated Smads within intraluminal fibroblasts coincided with increased intraluminal deposition of fibronectin and collagen. When transplanted into Smad3-null mice, allografts failed to organize the intraluminal exudates despite fibroblast accumulation and showed reduced fibronectin and collagen deposition. In culture, Smad3-deficient fibroblasts expressed reduced fibronectin in response to TGF-beta1 compared to wild-type cells. Together, these studies suggest that the TGF-beta signal transducer, Smad3, is required for the development of experimental OB in transplanted tracheas.

A novel polymorphism of the gene encoding furin, a TGF-β1 activator, and the influence on cardiac allograft vasculopathy formation

BACKGROUND

Coronary vasculopathy (CV) is an important determinant of survival following cardiac transplantation. We have previously shown that G915C polymorphism of the Transforming Growth Factor-beta1 (TGF-beta1) gene strongly influences CV development. Furin is a proprotein convertase enzyme important in TGF-beta1 activation. We investigated for polymorphism within the promoter region of the gene for furin (fur). Allelic variation of the fur gene, in conjunction with TGF-beta1 polymorphism, was subsequently related to the development of CV.

METHODS AND RESULTS

The fur gene promoter region (position -1199 to +39) was analysed by SSCP and sequencing. A C/T single nucleotide substitution polymorphism at position -231* was identified. Using PCR the fur and TGFB1 genotypes were identified in 115 cardiac transplant recipients. CV was diagnosed at routine surveillance post-transplant coronary angiography. Fur polymorphism had no influence on vasculopathy development; median time to diagnosis, *C/C homozygotes, 2.27 years (2.10-4.32), *C/T heterozygotes 2.97 years (2.09-4.24), *T/T homozygotes 2.65 years (2.33-4.08), (P=0.95). Allelic variation did not influence Kaplan Meier actuarial analysis of disease onset (P=0.54). Ninety-three percent of recipients were high TGF-beta1 producers. We used fur polymorphism to substratify patients with the +915*G/G TGFB1 (high producing) allele. Fur polymorphism did not influence CV development within this TGF-beta1 high producer cohort, when analysed by time to first diagnosis and Kaplan Meier testing.

CONCLUSIONS

We have described a novel polymorphism at position -231* in the gene encoding furin. The fur -231* single nucleotide polymorphism in isolation, or in conjunction with TGFB1 polymorphism, is not useful as a genetic risk marker for cardiac transplant associated coronary vasculopathy.

Effect of Cyclical Mechanical Stretch and Exogenous Transforming Growth Factor-??1 on Matrix Metalloproteinase-2 Activity in Lamina Cribrosa Cells from the Human Optic Nerve Head

PURPOSE

Extensive remodeling of the lamina cribrosa extracellular matrix occurs in primary open angle glaucoma. The transforming growth factor-beta (TGF-beta) and matrix metalloproteinase (MMP) protein families are implicated in this process. The authors investigated (a). the effect of cyclical mechanical stretch on TGF-beta1 mRNA synthesis, TGF-beta1 protein secretion, MMP-2 protein activity and (b). the effect of exogenous TGF-beta1 on MMP-2 protein activity in human lamina cribrosa cells in vitro.

METHODS

Primary human lamina cribrosa cells grown on flexible and rigid plates were exposed to cyclical stretch (1Hz, 15%) or static conditions for 12 and 24 hours. Cells grown on 100-mm plates were exposed to human TGF-beta1 (10 ng/ml) or vehicle (4 mM HCl/1% BSA) for 24 hours. TGF-beta1 mRNA synthesis in stretched and static cells was measured using real-time polymerase chain reaction. TGF-beta1 protein secretion in stretched and static cell media was measured using enzyme linked immunosorbent assay. Gelatin zymography measured MMP-2 activity in stretched, static, TGF-beta1- treated and vehicle-treated cell media.

RESULTS

Cyclical stretch induced significant increases in TGF-beta1 mRNA synthesis after 12 hours (**P < 0.01) and TGF-beta1 protein secretion after 24 hours (*P < 0.05). Cyclical stretch significantly (*P < 0.05) increased MMP-2 activity in cell media after 24 hours. Exogenous TGF-beta 1 induced a significant (**P < 0.01) increase in cell media MMP-2 activity after 24 hours.

CONCLUSIONS

These results suggest that cyclical stretch and TGF-beta1 modulate MMP-2 activity in human lamina cribrosa cells. TGF-beta 1 and MMP-2 release from lamina cribrosa cells may facilitate matrix remodeling of the optic nerve head in primary open angle glaucoma.

Long-Term Treatment With a Specific Rho-Kinase Inhibitor Suppresses Cardiac Allograft Vasculopathy in Mice

Cardiac allograft vasculopathy (CAV) continues to be a major cause of late graft failure after cardiac transplantation. We have demonstrated that Rho-kinase, an effector of the small GTPase Rho, plays an important role in the pathogenesis of arteriosclerosis. In this study, we examined whether the Rho-kinase–mediated pathway is also involved in the pathogenesis of CAV using a specific Rho-kinase inhibitor and a dominant-negative Rho-kinase. Hearts from AKR mice were heterotopically transplanted to C3H/He (allograft) or AKR mice (isograft), and the effects of long-term oral treatment with fasudil, which is metabolized to a specific Rho-kinase inhibitor hydroxyfasudil, on CAV were examined at 2 and 4 weeks after the transplantation. Coronary remodeling in the allografts characterized by intimal thickening and perivascular fibrosis was dose-dependently suppressed in the fasudil group compared with the control group ( P <0.01, n=9 to 10). The inhibitory effects of hydroxyfasudil were mimicked by in vivo gene transfer of dominant-negative Rho-kinase ( P <0.05, n=4). Among the proinflammatory cytokines examined, those of macrophage migration inhibitory factor, interferon-γ, and transforming growth factor-β1 were upregulated in the control group and were dose-dependently inhibited in the fasudil group ( P <0.01, n=5). Vascular inflammation in the allografts, as evidenced by accumulation of inflammatory cells (macrophages and T cells), was also significantly inhibited in the fasudil group ( P <0.05, n=5 to 10). These results indicate that long-term treatment with fasudil suppresses CAV in mice, suggesting that Rho-kinase is an important therapeutic target for the prevention of CAV.

Centrilobular fibrosis in long-term follow-up of pediatric liver transplant recipients

BACKGROUND

Centrilobular fibrosis after liver transplant in adults is caused mainly by viral hepatitis, chronic rejection, and azathioprine toxicity. The aim of this study was to investigate possible etiologies and the long-term outcome of this lesion in children.

METHODS

We identified centrilobular fibrosis in 12 of 117 pediatric liver transplant recipients who were investigated for persistent elevations in aminotransferases. Etiologic factors, histologic features on serial biopsies, and clinical and biochemical changes over time were noted for 8 recipients in whom a readily identifiable cause was not apparent.

RESULTS

Centrilobular fibrosis developed a mean of 1.7 years (range: 30 days-3.6 years) posttransplantation in patients receiving cyclosporine, azathioprine, and prednisone. Centrilobular fibrosis was always associated with portal fibrosis and, in six recipients, with persistent, low-grade, cellular rejection. None demonstrated chronic cholestasis, ductopenia, or identifiable vasculopathy. Ischemic, viral, and autoimmune etiologies were excluded. Discontinuing azathioprine did not lead to biochemical or histological improvement. After changing to tacrolimus, aminotransferases normalized in three recipients and repeat biopsies in six were unchanged during a further 2 years of follow-up.

CONCLUSIONS

Centrilobular fibrosis may develop in a small number of pediatric liver transplant recipients, resulting in considerable difficulties in biopsy interpretation. It is not associated with viral hepatitis nor with classical features of chronic rejection. The prognostic significance of centrilobular fibrosis is uncertain, although no child has required retransplantation in up to 12 years of follow-up. A role for a low-grade, chronic form of cellular rejection heralded by persistent, variable, and otherwise unexplained elevations in aminotransferases is suggested.

Cytokine gene polymorphisms and acute human liver graft rejection

Interindividual differences exist in the capacity to produce cytokines. It has been reported that levels of in vitro cytokine production measured after stimulated cell culture are associated with polymorphisms in cytokine genes. Moreover, a correlation between heart, kidney, liver, and lung graft rejection or survival with cytokine gene polymorphisms has been described. In the present study, we analyzed the association of gene polymorphisms in T helper subtype 1 (T(H)1-), T(H)2-, and regulatory-type cytokines with human liver allograft rejection. Patients who received a primary liver graft from 1992 onward and were seen at the transplant outpatient clinic since then were included on this study (n = 89). Patients were HLA typed routinely. Biopsy-proven acute rejection occurred in 41 of 89 patients. After informed consent, blood was collected and DNA was obtained. Using amplification-refractory mutation system polymerase chain reaction, the following cytokine gene polymorphisms were determined: IL-2+166, IL-2-330, IL-15+13689, IL-15-80, TNF-A-308, TNFd3, IFN-G+874 (T(H)1-type cytokines), IL-4+33, IL-4-590, IL-6-174, IL-10-592, IL-10-819, IL-10-1082, IL-13+2043, IL-13-1055 (T(H)2 type cytokines), TGF-B1+869, and TGF-B1+915 (regulatory-type cytokines). Univariate analysis showed that polymorphisms of IL-10-1082, TGF-B1+869, and HLA-DR6 were significantly related to liver graft rejection. Multiple logistic regression analysis was used to assess which variables remained significantly predictive of acute rejection. Multivariate analysis showed that TGF-B1+869 and HLA-DR6 were independently associated with the occurrence of acute rejection. These findings suggest a role for the regulatory-type cytokine transforming growth factor-beta1 in human liver graft rejection.

Soluble transforming growth factor-beta type III receptor gene transfection inhibits fibrous airway obliteration in a rat model of Bronchiolitis obliterans

Post-transplant bronchiolitis obliterans (BO) is characterized by fibroproliferation and fibrous obliteration of distal airways in chronically rejected lungs. In this study, using a rat heterotopic allogeneic tracheal transplant model of BO, we evaluated the expression of transforming growth factor-beta (TGFbeta) during the development of airway fibrous obliteration. Immunohistochemical analysis revealed TGFbeta staining in infiltrating mononuclear cells at Days 2 and 7, and in the fibrous tissues until Day 21. Soluble TGFbeta receptor type III (TGFBIIIR), by blocking TGFbeta binding to its membrane receptors, functions as a TGFbeta antagonist. To study the role of TGFbeta in the development of BO, adenoviral-mediated soluble TGFBIIIR gene transfection (5 x 10(9) particles) was performed topically at the site of transplant on Day 5 after transplantation, which leads to inhibition of fibrous airway obliteration. In contrast, empty vector gene delivered through intramuscular injection, or given locally at Days 0 or 10 after tracheal transplantation had no significant effect. These results suggest that TGFbeta expressed in the allografts plays a pivotal role in the pathogenesis of BO. Soluble TGFBIIIR may competitively inhibit TGFbeta activity locally. Adenoviral-mediated soluble TGFBIIIR gene transfection should be further explored as a potential therapeutic modality for BO and other conditions involving chronic fibrosis.

Interleukin 1 and chronic rejection: possible genetic links in human heart allografts

Chronic rejection is a leading cause of graft loss in thoracic transplant recipients. Studies on the pathogenesis of chronic rejection have suggested a contributory role for certain cytokines and growth factors. The activity of these mediators is subject to genetic variation if a polymorphism alters expression, or function, of the ligand or its receptor. Here we have asked if certain cytokine and growth factor gene polymorphisms correlate with chronic rejection in recipients of thoracic allografts. In a retrospective analysis of 179 recipients of thoracic organ transplants (128 heart; 36 heart-lung; and 15 lung), polymorphisms in 8 genes that influence the inflammatory process, namely IL1B, IL1R1, IL1RN, IL6, IL10, TNFA, TGFB1 and FCGRIIA, were examined. Genotypic data from recipients who had either died or been re-transplanted as a result of chronic rejection (n = 96) were then compared to those of recipients who had a functioning graft for more than 11 years (n=83). In the heart graft recipients, only those polymorphisms that influenced expression of the IL1 receptor antagonist gene had a significant correlation with graft survival, with homozygosity for the IL1RN*1 allele being associated with rejection. The alternative, less frequent IL1RN alleles emerged as genomic predictors of long-term allograft survival. This association was especially strong when IL1 region haplotypes were considered, particularly when analysis was confined to heart transplant recipients who had had multiple acute rejection episodes (OR>20). This case-control study indicates that gene polymorphisms which influence IL1 bioactivity also influence the progression of chronic rejection in heart grafts.

Replicative senescence of biliary epithelial cells precedes bile duct loss in chronic liver allograft rejection: increased expression of p21(WAF1/Cip1) as a disease marker and the influence of immunosuppressive drugs

Early chronic liver allograft rejection (CR) is characterized by distinctive cytological changes in biliary epithelial cells (BECs) that resemble cellular senescence, in vitro, and precede bile duct loss. If patients suffering from early CR are treated aggressively, the clinical and histopathological manifestations of CR can be completely reversed and bile duct loss can be prevented. We first tested whether the senescence-related p21(WAF1/Cip1) protein is increased in BECs during early CR, and whether treatment reversed the expression. The percentage of p21+ BECs and the number of p21+ BECs per portal tract is significantly increased in early CR (26 +/- 17% and 3.6 +/- 3.1) compared to BECs in normal liver allograft biopsies or those with nonspecific changes (1 +/- 1% and 0.1 +/- 0.3; P: < 0.0001 and P: < 0.02), chronic hepatitis C (2 +/- 3% and 0.7 +/- 1; P: < 0.0001 and P: < 0.04) or obstructive cholangiopathy (7 +/- 7% and 0.7 +/- 0.6; P: < 0.006 and P: = 0.04). Successful treatment of early CR is associated with a decrease in the percentage of p21+ BECs and the number of p21+ BECs per portal tract. In vitro, nuclear p21(WAF1/Cip1) expression is increased in large and multinucleated BECs, and is induced by transforming growth factor (TGF)-beta. TGF-beta1 also increases expression of TGF-beta receptor II, causes phosphorylation of SMAD-2 and nuclear translocation of p21(WAF1/Cip1), which inhibits BEC growth. Because conversion from cyclosporine to tacrolimus is an effective treatment for early CR, we next tested whether these two immunosuppressive drugs directly influenced BEC growth in vitro. The results show that cyclosporine, but not tacrolimus, stimulates BEC TGF-beta1 production, which in turn, causes BEC mito-inhibition and up-regulation of nuclear p21(WAF1/Cip1). In conclusion, expression of the senescence-related p21(WAF1/Cip1) protein is increased in BECs during early CR and decreases with successful recovery. Replicative senescence accounts for the characteristic BEC cytological alterations used for the diagnosis of early CR and lack of a proliferative response to injury. The ability of cyclosporine to inhibit the growth of damaged BECs likely accounts for the relative duct sparing properties of tacrolimus.

Expression of recombinant extracellular domain of the type II transforming growth factor-beta receptor: utilization in a modified enzyme-linked immunoabsorbent assay to screen TGF-beta agonists and antagonists

TGF-beta is a ubiquitous protein that exhibits a broad spectrum of biological activity. The prokaryotic expression and purification of the extracellular domain of the type II TGF-beta receptor (T beta R-II-ED), without the need for fusion protein cleavage and refolding, is described. The recombinant T beta R-II-ED fusion protein bound commercially available TGF-beta 1 and displayed an affinity of 11.1 nM. In a modified ELISA, receptor binding to TGF-beta1 was inhibited by TGF-beta 3. The technique lends itself to high-throughput screening of combinatorial libraries for the identification of TGF-beta agonists and antagonists and this, in turn, may have important therapeutic implications.

Early alteration in TGF-beta mRNA expression in irradiated rat liver

PURPOSE

Radiation of the liver results in hepatic fibrosis as a late complication. TGF-beta has been implicated in the pathogenesis of fibrosis. The purpose of this study was to determine if there is early alteration in TGF-beta expression before hepatic fibrosis is evident.

METHODS AND MATERIALS

Male Sprague-Dawley rats weighing 150-175 g were used. A partial volume of liver as large as a 2 cm x 1 cm rectangle was given a single dose of 25 Gy gamma radiation. Animals were sequentially sacrificed from day 0 to day 28. Appearance of hepatic fibrosis was tested by trichrome stain. Levels of mRNA expression of TGF-beta1 and TGF-beta3 were measured by Northern blot hybridization. Change in the level of mRNA expression was analyzed by densitometry. The expression of TGF-betas was also analyzed in tissue with immunohistochemical staining.

RESULTS

In trichrome-stained liver tissues obtained through 28 days after irradiation, there was no evidence of hepatic fibrosis. The expression of mRNAs of TGF-beta1 and TGF-beta3 showed different features; The level of TGF-beta1 mRNA showed a gradual increase to the peak level of 3.6-fold at day 28, the last analyzed time. In contrast, TGF-beta3 mRNA showed an early peak of 4.8-fold at day 7 followed by a decrease to the lowest level of 1.6-fold at the last analyzed time. The expression of TGF-betas was also analyzed in tissue with immunohistochemical staining. At day 28 after radiation, increased positive staining for TGF-beta1 was observed around the central vein. Positive staining appeared mainly in nonhepatocytic cells. For TGF-beta3, the same pattern of positive staining was observed at day 7.

CONCLUSION

The results of this study suggest that the alteration in mRNA expression of TGF-beta1 and TGF-beta3 occurs very early after radiation. The contrasting difference in the mRNA expression pattern of TGF-beta1 and TGF-beta3 suggests that interaction of the TGF-betas may be involved in fibrogenesis of irradiated liver, with TGF-beta1 as a positive regulator and TGF-beta3 as a negative regulator.

Expression patterns of integrin receptors and extracellular matrix proteins in chronic rejection of human liver allografts

The beta1-integrin family of adhesion molecules is supposed to mediate cell-to-matrix interactions involved in a variety of immune reactions, especially in those associated with tissue remodelling. In an attempt to determine the role of beta1-integrins in the initiation and maintenance of fibrotic deposition observed in chronic rejection after liver transplantation, we immunohistochemically analysed the expression of different extracellular matrix components and the very late antigen (VLA) family of beta1-integrins in 11 samples of chronically rejected human liver allografts and compared results to findings in acutely rejected transplants and nontransplanted chronic inflammatory livers. In contrast to normal liver specimens, chronically rejected human liver allografts displayed a general overexpression of matrix components along sinusoids throughout the tissue and an additional characteristic accumulation in pericentral areas. Accordingly, VLA-1, -5 and -6 demonstrated a linear upregulation or de novo expression on sinusoidal lining cells, VLA-1 and VLA-4 additionally displayed concentration within pericentral fibrotic deposits. VLA-2 and -3 were only sporadically found. In accordance with findings in chronic rejection, chronic inflammatory livers showed overexpression of VLA-1, -5 and -6 within sinusoids and accumulation of VLA-1 and -4 in fibrotic septa. In contrast, acutely rejected allografts displayed slight overexpression of ECM components without characteristic accumulates, hence beta1-integrins were seen to be equally distributed throughout the parenchyma. Altogether, our analysis showed an upregulation of integrin receptors which corresponded to the extent of ECM deposition and thus suggested an important role for these molecules in the iniation of fibrosis observed in these specimens. Individual integrins showed different expression patterns within sinusoids and fibrotic areas, indicating distinct roles in differential stages of matrix accumulation, but induction patterns were generally similar in chronic inflammatory and chronically rejected livers, suggesting independence of the underlying disease.

Induction of CD4+ T Cell Alloantigen-Specific Hyporesponsiveness by IL-10 and TGF-β

Induction and maintenance of Ag-specific tolerance are pivotal for immune homeostasis, prevention of autoimmune disorders, and the goal of transplantation. Recent studies suggest that certain cytokines, notably IL-10 and TGF-β, may play a role in down-regulating immune functions. To further examine the role of cytokines in Ag-specific hyporesponsiveness, murine CD4+ T cells were exposed ex vivo to alloantigen-bearing stimulators in the presence of exogenous IL-10 and/or TGF-β. Primary but not secondary alloantigen proliferative responses were inhibited by IL-10 alone. However, the combined addition of IL-10 + TGF-β markedly induced alloantigen hyporesponsiveness in both primary and secondary MLR cultures. Alloantigen-specific hyporesponsiveness was observed also under conditions in which nominal Ag responses were intact. In adoptive transfer experiments, IL-10 + TGF-β-treated CD4+ T cells, but not T cells treated with either cytokine alone, were markedly impaired in inducing graft-vs-host disease alloresponses to MHC class II disparate recipients. These data provide the first formal evidence that IL-10 and TGF-β have at least an additive effect in inducing alloantigen-specific tolerance, and that in vitro cytokines can be exploited to suppress CD4+ T cell-mediated Ag-specific responses in vivo.