Shuichiro Uehara

NK Cells Can Trigger Allograft Vasculopathy: The Role of Hybrid Resistance in Solid Organ Allografts

Progressive arterial stenosis (cardiac allograft vasculopathy (CAV)) is a leading cause of long-term failure of organ transplants. CAV remains intractable, in part because its mechanisms are insufficiently understood. A central proposition is that MHC-driven alloimmune processes play a necessary role in CAV, as shown by the absolute requirement for histoincompatibility between donor and recipient for its production. Two immunological pathways have been implicated involving reactivity to donor MHC Ags by either T or B cells. In this study, we use a novel system of semiallogeneic cardiac transplants between parental donors and F1 hybrid recipients to provide evidence that NK cells, members of the innate immune system, also contribute to the generation of CAV in mice. This finding marks the first demonstration that the hybrid resistance phenomenon occurs in solid organ allografts. Extension of these experiments to recipients deficient in T cells demonstrates that this third pathway of CAV, the NK cell-triggered pathway, involves the recruitment of T cells not responsive to donor alloantigens. Finally, transplants performed with donors or recipients deficient in IFN-γ revealed that recipient-derived IFN-γ is necessary for CAV formation in parental to F1 transplants, suggesting a possible effector mechanism by which NK cells can promote CAV. Together, these results define a previously unknown pathway toward CAV and assign a novel role to NK cells in organ allograft rejection.

Chronic cardiac transplant arteriopathy in mice: relationship of alloantibody, C4d deposition and neointimal fibrosis.

Murine heterotopic cardiac allografts were used to reveal some of the fundamental interrelationships between donor‐specific alloantibodies (DSA), chronic transplant arteriopathy (CTA) and capillary C4d deposition. B10.BR recipients of B10.A hearts developed transient DSA and C4d deposition that peaked on day 7 and became undetectable at day 56 while CTA developed progressively. Male cardiac grafts in female recipients showed similar degrees of CTA at day 56 but never developed DSA or C4d deposition, indicating that T cell‐mediated mechanisms are sufficient to produce CTA. Passive transfer of monoclonal IgG2a anti‐H‐2Kk into B6.RAG1 KO recipients of B10.BR hearts over 14–28 days led to progressive CTA. If treatment was stopped on day 14, lesions showed little progression and had no C4d deposition or detectable DSA on day 42. If treatment was stopped on day 28 when the lesions were fully developed, no regression occurred over the next 28 days, even though C4d deposition and circulating antibody became undetectable. Therefore, a minimum threshold of antibody exposure is needed to cause CTA. Once the CTA develops, C4d may become negative after DSA disappears. Thus, serial samples are needed in clinical studies to ascertain the relevance of alloantibody to the lesions of chronic graft rejection.

Complement Independent Antibody‐Mediated Endarteritis and Transplant Arteriopathy in Mice

Complement fixation, as evidenced by C4d in the microvasculature, is a widely accepted criterion of antibody‐mediated rejection. Complement fixation has been shown to be essential in acute antibody‐mediated rejection, but its role in chronic rejection has not been addressed. Previous studies showed that passive transfer of complement fixing monoclonal IgG2a anti‐H‐2Kk into B6.RAG1−/− KO recipients of B10.BR hearts led to progressive chronic transplant arteriopathy (CTA) over 14–28 days, accompanied by C4d deposition. The present studies were designed to test whether complement was required for these lesions. We report that a noncomplement fixing donor‐specific alloantibody (DSA, monoclonal IgG1 anti‐H‐2Kk) injected into B6.RAG1‐/‐ KO recipients of B10.BR hearts also promotes CTA, without C4d deposition. Furthermore, a passive transfer of DSA (monoclonal IgG2a anti‐H‐2Kk) initiated endarteritis followed by CTA in B6.RAG1−/‐ mice genetically deficient in the third component of complement (RAG1−/−C3−/−). These studies indicate that antibody to class I MHC antigens can trigger chronic arterial lesions in vivo without complement participation, in contrast to acute antibody‐mediated rejection. This pathway may be relevant to C4d‐negative chronic rejection sometimes observed in patients with DSA, and argues that lack of C4d deposition does not exclude antibody‐mediated chronic rejection.

Macrophage Depletion Suppresses Cardiac Allograft Vasculopathy in Mice

Cardiac allograft vasculopathy (CAV) is a major source of late posttransplant mortality. Although numerous cell types are implicated in the pathogenesis of CAV, it is unclear which cells actually induce the vascular damage that results in intimal proliferation. Because macrophages are abundant in CAV lesions and are capable of producing growth factors implicated in neointimal proliferation, they are leading end‐effector candidates. Macrophages were depleted in a murine heterotopic cardiac transplant system known to develop fulminant CAV lesions. C57BL/6 hearts were transplanted into (C57BL/6 × BALB/c)F1 recipients, which then received anti‐macrophage therapy with intraperitoneal carrageenan or i.v. gadolinium. Intraperitoneal carrageenan treatment depleted macrophages by 30–80% with minimal effects upon T, B or NK cells as confirmed by flow cytometry and NK cytotoxicity assays. Carrageenan treatment led to a 70% reduction in the development of CAV, as compared to mock‐treated controls (p = 0.01), which correlated with the degree of macrophage depletion. Inhibition of macrophage phagocytosis alone with gadolinium failed to prevent CAV. Macrophages may represent the end‐effector cells in a final common pathway towards CAV independent of T‐cell or B‐cell alloreactivity and exert their injurious effects through mechanisms related to cytokine/growth factor production rather than phagocytosis.

Increased expression of multidrug resistance-associated genes after chemotherapy in pediatric solid malignancies.

BACKGROUND/PURPOSE The overexpression of multidrug resistance (MDR)-associated genes in primary untreated tumors has been proven to be associated with worse prognosis in various pediatric malignancies. This study compared the expression of 3 MDR-associated genes, MDR1, MDR-associated protein 1 (MRP1), and lung resistance-related protein (LRP), in pediatric tumors before and after chemotherapy to elucidate the mechanism of MDR during chemotherapy. METHODS Surgical specimens of both primary and chemotherapy-treated tumors were obtained from 24 patients with pediatric malignancies (neuroblastoma [NB] 8; hepatoblastoma [HB] 8; Wilms tumor [WT] 4; rhabdomyosarcoma [RB] 4). The expression of MDR1, MRP1, and LRP was evaluated using the immunohistochemical staining. RESULTS In primary tumors, MDR1 expression was observed in 6 NBs, 8 HBs, 3 WTs, and 3 RBs. MRP1 expression was observed in 3 NBs and 1 HB. LRP expression was not detected in any of the primary tumors. After chemotherapy, MDR1 expression was observed to increase in 5 NBs, 4 HBs, 2 WTs, and 3 RBs. MRP1 expression was newly observed or increased in 7 NBs, 4 HBs, and 3 RBs. LRP expression was newly observed in 3 HBs and 2 WTs. CONCLUSIONS These results indicate that these 3 MDR-associated genes were upregulated after chemotherapy in various pediatric malignancies. These findings may be useful to understand the mechanism of drug resistance in pediatric malignancies.

Aldehyde Dehydrogenase 1 (ALDH1) Is a Potential Marker for Cancer Stem Cells in Embryonal Rhabdomyosarcoma

Cancer stem cells (CSCs) are defined as a small population of cancer cells with the properties of high self-renewal, differentiation, and tumor-initiating functions. Recent studies have demonstrated that aldehyde dehydrogenase 1 (ALDH1) is a marker for CSCs in adult cancers. Although CSCs have been identified in some different types of pediatric solid tumors, there have been no studies regarding the efficacy of ALDH1 as a marker for CSCs. Therefore, in order to elucidate whether ALDH1 can be used as a marker for CSCs of pediatric sarcoma, we examined the characteristics of a population of cells with a high ALDH1 activity (ALDH1high cells) in rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children. We used the human embryonal RMS (eRMS) cell lines RD and KYM-1, and sorted the cells into two subpopulations of ALDH1high cells and cells with a low ALDH1 activity (ALDH1low cells). Consequently, we found that the ALDH1high cells comprised 3.9% and 8.2% of the total cell population, respectively, and showed a higher capacity for self-renewal and tumor formation than the ALDH1low cells. With regard to chemoresistance, the survival rate of the ALDH1high cells was found to be higher than that of the ALDH1low cells following treatment with chemotherapeutic agents for RMS. Furthermore, the ALDH1high cells exhibited a higher degree of pluripotency and gene expression of Sox2, which is one of the stem cell markers. Taken together, the ALDH1high cells possessed characteristics of CSCs, including colony formation, chemoresistance, differentiation and tumor initiation abilities. These results suggest that ALDH1 is a potentially useful marker of CSCs in eRMS.

Clinical application of indocyanine green (ICG) fluorescent imaging of hepatoblastoma

BACKGROUND/PURPOSE Although the usefulness of intraoperative indocyanine green (ICG) fluorescent imaging for the resection of hepatocellular carcinoma has been reported, its usefulness for the resection of hepatoblastoma remains unclear. This study clarifies the feasibility of intraoperative ICG fluorescent imaging for the resection of hepatoblastoma. METHODS In three hepatoblastoma patients, a primary tumor, recurrent tumor, and lung metastatic lesions were intraoperatively examined using a near-infrared fluorescence imaging system after the preoperative administration of ICG. RESULTS ICG fluorescent imaging was useful for the surgical navigation in hepatoblastoma patients. In the first case, the primary hepatoblastoma exhibited intense fluorescence during right hepatectomy, but no fluorescence was detected in the residual liver. In the second case, a recurrent tumor exhibited fluorescence between the residual liver and diaphragm. A complete resection of the residual liver, with a partial resection of the diaphragm, followed by liver transplantation was performed. In the third case with multiple lung metastases, each metastatic lesion showed positive fluorescence, and all were completely resected. These fluorescence-positive lesions were pathologically proven to be viable hepatoblastoma cells. CONCLUSION Intraoperative ICG fluorescence imaging for patients with hepatoblastoma was feasible and useful for identifying small viable lesions and confirming that no remnant tumor remained after resection.

Forskolin, a Hedgehog signal inhibitor, inhibits cell proliferation and induces apoptosis in pediatric tumor cell lines.

The Hedgehog (Hh) signaling pathway regulates the development of many organs in mammals. Recent studies have indicated that the activation of the Hh signaling pathway contributes to the growth of various adult cancers. However, little is known about its role in the development of pediatric malignancies. The present study was undertaken to examine the expression and functional involvement of Hh signal transcription factors in pediatric tumor cells in order to determine their potential as therapeutic targets. We utilized real-time RT-PCR to investigate the expression of Glioma-associated oncogene homolog 1 (Gli1) in various pediatric tumor cell lines, including rhabdomyosarcoma, neuroblastoma and hepatoblastoma. The mRNA expression of Gli1 was markedly increased in rhabdomyosarcoma (RMS-YM, RD, RH30) cell lines, and moderately increased in neuroblastoma (NB19) and hepatoblastoma (Huh6) cell lines. The proliferation of these cell lines was dose dependently inhibited by Forskolin, a specific Hh signal inhibitor. In addition, Forskolin-induced growth suppression was associated with the down-regulation of C-Myc. Moreover, the blockade of Hh signaling with Forskolin enhanced cell apoptosis in a dose-dependent manner. These results demonstrated that Hh signal activation frequently occurs in neuroblastoma, hepatoblastoma and rhabdomyosarcoma cell lines. The inhibition of Hh signaling suppressed proliferation and increased apoptosis in these tumor cells. These findings suggest that the Hh signaling pathway plays an important role in tumorigenesis and is a potential molecular target of new treatment strategies for these pediatric malignant tumors.

Apelin is a marker of the progression of liver fibrosis and portal hypertension in patients with biliary atresia

PurposeApelin, the endogenous ligand of the angiotensin-like-receptor 1 (APJ), is thought to play an important role in liver disease. This study investigated the apelin expression in different stages of biliary atresia (BA) and investigated whether it is associated with the progression of disease.MethodsLiver tissues were obtained from patients at Kasai’s procedure (KP), the follow-up stage after KP (Post-KP) and at liver transplantation (LT). Immunohistochemistry for apelin and its receptor APJ and real-time quantitative reverse transcriptase polymerase chain reaction for apelin mRNA expression were conducted.ResultsThe immunohistochemical study revealed that apelin was mainly localized in the perivenular areas of control liver tissue, and slightly detected in the hepatic stellate cells (HSC) and hepatocytes, whereas intense apelin immunoreactivity was detected in perivenular areas, HSC and hepatocytes of LT liver tissue. The apelin mRNA expression level was significantly higher in the LT group than in the KP and Post-KP group. Significant linear correlations were observed between the apelin mRNA level and liver fibrosis, serum total bilirubin and the grade of esophageal varices.ConclusionsThe hepatic apelin–APJ system is markedly activated in the progression of BA, especially in end-stage cirrhosis. The apelin expression level accurately reflects the severity of hepatic fibrosis and esophageal varices and therefore could be used as a prognostic factor in BA patients.

Three-Stage Reconstruction of the Airway and Alimentary Tract in a Case of Tracheal Agenesis

In the few surviving cases of tracheal agenesis, infants have not been capable of oral intake because the esophagus was used as a substitute for the trachea. We performed a three-stage reconstruction of the airway and alimentary tract in an infant with tracheal agenesis. This procedure involved a double cervical esophagostomy followed by an anastomosis of the upper mid-esophagus and carinal trachea. Finally, the esophagus was reconstructed by an anastomosis of the cervical esophagus to the lower esophagus. This novel procedure may become a highly effective surgical treatment for some infants in critical condition due to tracheal agenesis.