Kenneth Tou En Chang

Human natural killer cells control Plasmodium falciparum infection by eliminating infected red blood cells

Significance Study of human immune responses to malaria parasite infection has been hampered by a lack of small animal models. Although immunodeficient mice supplemented with human RBCs support human parasite infection, these animals lack a human immune system. We have overcome this obstacle by developing mice that possess both human RBCs and immune system and that support multiple cycles of Plasmodium falciparum infection. We further show that human natural killer cells preferentially interact with and kill infected RBCs in a contact-dependent manner. The small animal model reported here likely will facilitate the dissection of human immune responses to malaria parasite infection and the evaluation of therapeutics and vaccines. Immunodeficient mouse–human chimeras provide a powerful approach to study host-specific pathogens, such as Plasmodium falciparum that causes human malaria. Supplementation of immunodeficient mice with human RBCs supports infection by human Plasmodium parasites, but these mice lack the human immune system. By combining human RBC supplementation and humanized mice that are optimized for human immune cell reconstitution, we have developed RBC-supplemented, immune cell-optimized humanized (RICH) mice that support multiple cycles of P. falciparum infection. Depletion of human natural killer (NK) cells, but not macrophages, in RICH mice results in a significant increase in parasitemia. Further studies in vitro show that NK cells preferentially interact with infected RBCs (iRBCs), resulting in the activation of NK cells and the elimination of iRBCs in a contact-dependent manner. We show that the adhesion molecule lymphocyte-associated antigen 1 is required for NK cell interaction with and elimination of iRBCs. Development of RICH mice and validation of P. falciparum infection should facilitate the dissection of human immune responses to malaria parasite infection and the evaluation of therapeutics and vaccines.

Mutations in Alström protein impair terminal differentiation of cardiomyocytes

Cardiomyocyte cell division and replication in mammals proceed through embryonic development and abruptly decline soon after birth. The process governing cardiomyocyte cell cycle arrest is poorly understood. Here we carry out whole exome sequencing in an infant with evidence of persistent postnatal cardiomyocyte replication to determine the genetic risk factors. We identify compound heterozygous ALMS1 mutations in the proband, and confirm their presence in her affected sibling, one copy inherited from each heterozygous parent. Next, we recognise homozygous or compound heterozygous truncating mutations in ALMS1 in four other children with high levels of postnatal cardiomyocyte proliferation. Alms1 mRNA knockdown increases multiple markers of proliferation in cardiomyocytes, the percentage of cardiomyocytes in G2/M phases, and the number of cardiomyocytes by 10% in cultured cells. Homozygous Alms1-mutant mice have increased cardiomyocyte proliferation at two weeks postnatal compared to wild-type littermates. We conclude that deficiency of Alström protein impairs postnatal cardiomyocyte cell cycle arrest.

Third-Trimester Stillbirths: Correlative Neuropathology and Placental Pathology

Although in recent years placental pathology has been the subject of a wealth of detailed descriptions and diagnostic categorization, systematic correlation of these conditions with the pathology of stillbirth has not been attempted. We examine the relationship between specific inflammatory, maternal, and fetal vascular pathologies and the central nervous system pathology and histological indicators of fetal compromise. Our design was a retrospective case series of 37 3rd-trimester intrauterine fetal deaths. In general, mixed placental pathologies were the rule, with three quarters of the placentas demonstrating combinations of maternal vascular pathology, fetal vascular pathologies, umbilical cord abnormalities, or inflammatory lesions. The range of brain pathology was limited to acute, severe congestion, white matter edema, and neuronal karyorrhexis (pontosubicular necrosis with or without neuronal karyorrhexis at other sites). Established periventricular leukomalacia was present in only 2 cases. The presence of neuronal karyorrhexis or white matter gliosis was correlated with the presence of a high-grade inflammatory lesion and with fetal thymic involution. Neuronal karyorrhexis, but not white matter gliosis, correlated as well with histologically established fetal vascular lesions in the placenta, even once the effect of inflammation was accounted for. Gliosis also correlated with inflammation, meconium staining, and thymic involution. Central nervous system injury may be the end result of complex placental pathologies, and neuronal injury may be a consequence of the fetal inflammatory response. The correspondence between the time courses of histological features of chorioamnionitis, neuronal karyorrhexis, and thymic involution points to irreversible central nervous system injury being common 12–48 hours prior to in utero demise.

The role of ischemia in necrotizing enterocolitis

AIM The role of ischemia in the pathogenesis of necrotizing enterocolitis (NEC) remains unclear. We used immunohistochemical markers of hypoxia to identify presence/absence of ischemia in NEC and spontaneous intestinal perforation (SIP) with clinical correlation. METHODS Immunohistochemical staining was performed on 24 NEC and 13 SIP intestinal resection specimens using 2 hypoxia markers, hypoxia inducible factor 1α (HIF-1α) and glucose transporter 1 (GLUT1) and inflammatory markers, leukocyte common antigen (LCA) and myeloperoxidase. Ischemic score (0-6) from the sum of the HIF-1α and GLUT1 staining intensity grades was devised (positive ≥3). Inflammation was graded from the sum of LCA and myeloperoxidase grading. Relevant clinical information was obtained from hospital case records. RESULTS Fourteen NEC specimens had positive ischemic score (4.6±1.2). The remaining 10 NEC (ischemic score 0.7±0.8) and all 13 SIP samples (ischemic score 0.5±0.5) were ischemic-negative. The ischemic-positive cases had classic NEC with multiple areas of bowel necrosis; were associated with later onset, enteral feeding and pneumatosis. In contrast, all ischemic-negative NEC were short-segment NEC with perforation. Their clinical profile was similar to the SIP cases with younger gestational age at birth, early onset, association with ibuprofen/indomethacin usage but not with feeding and pneumatosis. Ischemic scores are correlated with inflammation scores in mucosa but not submucosa. CONCLUSIONS Ischemia as assessed with immunohistochemical markers HIF-1α and GLUT1, has a primary role in pathogenesis of classic NEC only, not in SIP or short-segment NEC with perforation. Better categorization of the different types of NEC can direct appropriate prevention and treatment strategies.

Mitogenic cardiomyopathy: A lethal neonatal familial dilated cardiomyopathy characterized by myocyte hyperplasia and proliferation

Pediatric cardiomyopathies are a heterogenous group of conditions of which dilated cardiomyopathies are the most common clinicomorphologic subtype. However, the etiology and pathogenesis of many cases of dilated cardiomyopathies remain unknown. We describe a series of 5 cases of a rare but clinically and histologically distinctive dilated cardiomyopathy that was uniformly lethal in early infancy. The 5 cases include 2 pairs of siblings. There was parental consanguinity in 1 of the 2 pairs of siblings. Death occurred in early infancy (range, 22-67 days; mean, 42 days) after a short history of general lethargy, decreased feeding, respiratory distress, or cyanosis. There was no specific birth or early neonatal problems. Autopsy revealed congestive cardiac failure and enlarged, dilated hearts with ventricular dilatation more pronounced than atrial dilatation, and endocardial fibroelastosis. Histology showed prominent hypertrophic nuclear changes of cardiac myofibers and markedly increased myocyte mitotic activity including occasional atypical mitoses. Immunohistochemical staining for Mib1 showed a markedly increased proliferative index of 10% to 20%. Ancillary investigations, including molecular studies, did not reveal a primary cause for the cardiomyopathies. This distinctive dilated cardiomyopathy characterized by unusual histologic features of myocyte nuclear hypertrophy and marked mitotic activity is lethal in early infancy. Its occurrence in 2 pairs of siblings suggests familial inheritance. Although the underlying molecular pathogenesis remains to be elucidated, it is important to recognize this distinctive entity for purposes of genetic counseling.

Characterisation of liver pathogenesis, human immune responses and drug testing in a humanised mouse model of HCV infection

Objective HCV infection affects millions of people worldwide, and many patients develop chronic infection leading to liver cancers. For decades, the lack of a small animal model that can recapitulate HCV infection, its immunopathogenesis and disease progression has impeded the development of an effective vaccine and therapeutics. We aim to provide a humanised mouse model for the understanding of HCV-specific human immune responses and HCV-associated disease pathologies. Design Recently, we have established human liver cells with a matched human immune system in NOD-scid Il2rg−/− (NSG) mice (HIL mice). These mice are infected with HCV by intravenous injection, and the pathologies are investigated. Results In this study, we demonstrate that HIL mouse is capable of supporting HCV infection and can present some of the clinical symptoms found in HCV-infected patients including hepatitis, robust virus-specific human immune cell and cytokine responses as well as liver fibrosis and cirrhosis. Similar to results obtained from the analysis of patient samples, the human immune cells, particularly T cells and macrophages, play critical roles during the HCV-associated liver disease development in the HIL mice. Furthermore, our model is demonstrated to be able to reproduce the therapeutic effects of human interferon alpha 2a antiviral treatment. Conclusions The HIL mouse provides a model for the understanding of HCV-specific human immune responses and HCV-associated disease pathologies. It could also serve as a platform for antifibrosis and immune-modulatory drug testing.

Absence of the interstitial cells of Cajal in a child with chronic pseudoobstruction

Absence or altered distribution of the interstitial cells of Cajal (ICCs) has been described in association with intestinal pseudoobstruction in adults. We report the first pediatric case with regional absence of ICCs in the distal small bowel and colon associated with intestinal pseudoobstruction. This report highlights that abnormalities of the ICCs in intestinal pseudoobstruction should be considered early in the diagnostic workup of children with intestinal pseudoobstruction.

Novel Karyotypes and Cyclin D1 Immunoreactivity in Clear Cell Sarcoma of the Kidney

Pathological diagnosis of clear cell sarcoma of the kidney (CCSK) is challenging as it resembles blastemal Wilms tumor (WT) and other pediatric sarcomas, and does not have any distinctive immunophenotype. The YWHAE-FAM22 translocation t(10;17)(q22;p13) has been reported in a subset of CCSK. This translocation also occurs in high-grade endometrial sarcoma, in which it is associated with cyclin D1 overexpression. Hence we seek to determine YWHAE-FAM22 translocation status and cyclin D1 immunoreactivity in a series of local CCSK cases. Of 8 CCSK cases from 7 patients identified, no CCSK had the YWHAE-FAM22 fusion transcript by reverse transcriptase–polymerase chain reaction. Novel karyotypes were identified for 2 cases: 1 had t(2;13)(q13; q22) and the other t(3:17)(q29;p11.2). Excluding a case with poor tissue section antigenicity, 7 of 7 CCSKs (100%) showed diffuse and strong nuclear cyclin D1 staining. Cyclin D1 immunohistochemistry was also performed on tissue microarrays of other pediatric renal tumors: blastemal areas of 18 WT cases were negative; 6 rhabdoid tumors and 1 metanephric adenoma showed patchy and weak staining; 3 mesoblastic nephromas and 18 of 29 neuroblastomas had positive staining. Cyclin D1 immunohistochemistry helps distinguish CCSK from blastemal WT and metanephric adenoma and rhabdoid tumors, but not from neuroblastomas and mesoblastic nephromas. Cyclin D1 overexpression in CCSK is not contingent on YWHAE-FAM22 translocation, and cyclin D1 inhibition may potentially be explored as a targeted therapeutic strategy in CCSK.

Identification of MET genomic amplification, protein expression and alternative splice isoforms in neuroblastomas

Background Crizotinib, a dual anaplastic lymphoma kinase (ALK) and mesenchymal-epithelial transition (MET) tyrosine kinase inhibitor, is currently being evaluated for the treatment of neuroblastoma. Its effects are thought to be mediated mainly via its activity against ALK. Although MET genomic/protein expression status might conceivably affect crizotinib efficacy, this issue has hitherto not received attention in neuroblastomas. Aims/Methods MET genomic and protein expression status was characterised by silver in situ hybridisation and immunohistochemistry (IHC) respectively, in a cohort of 54 neuroblastoma samples. MET splice isoforms were characterised in 15 of these samples by quantitative PCR. Results One case (1/54; prevalence 1.85%) displayed MET genomic amplification, while another case (1/54; prevalence 1.85%) displayed strong membranous MET protein expression (IHC score 3+). Alternative exon 10-deleted and exon 14-deleted MET splice isoforms were identified. Conclusions MET amplification and protein expression, although low in prevalence, are present in neuroblastomas. This has implications when crizotinib is employed as a therapeutic agent in neuroblastomas. Additionally, the existence of alternatively spliced MET isoforms may have clinical and biological implications in neuroblastomas.

Delineation of Natural Killer Cell Differentiation from Myeloid Progenitors in Human

Understanding of natural killer (NK) cell development in human is incomplete partly because of limited access to appropriate human tissues. We have developed a cytokine-enhanced humanized mouse model with greatly improved reconstitution and function of human NK cells. Here we report the presence of a cell population in the bone marrow of the cytokine-treated humanized mice that express both NK cell marker CD56 and myeloid markers such as CD36 and CD33. The CD56+CD33+CD36+ cells are also found in human cord blood, fetal and adult bone marrow. Although the CD56+CD33+CD36+ cells do not express the common NK cell functional receptors and exhibit little cytotoxic and cytokine-producing activities, they readily differentiate into mature NK cells by acquiring expression of NK cell receptors and losing expression of the myeloid markers. Further studies show that CD33+CD36+ myeloid NK precursors are derived from granulo-myelomonocytic progenitors. These results delineate the pathway of human NK cell differentiation from myeloid progenitors in the bone marrow and suggest the utility of humanized mice for studying human hematopoiesis.