Soo-Min Jung

A Genome-Wide Association Study Identifies Potential Susceptibility Loci for Hirschsprung Disease

Hirschsprung disease (HSCR) is a congenital and heterogeneous disorder characterized by the absence of intramural nervous plexuses along variable lengths of the hindgut. Although RET is a well-established risk factor, a recent genome-wide association study (GWAS) of HSCR has identified NRG1 as an additional susceptibility locus. To discover additional risk loci, we performed a GWAS of 123 sporadic HSCR patients and 432 unaffected controls using a large-scale platform with coverage of over 1 million polymorphic markers. The result was that our study replicated the findings of RET-CSGALNACT2-RASGEF1A genomic region (rawP = 5.69×10−19 before a Bonferroni correction; corrP = 4.31×10−13 after a Bonferroni correction) and NRG1 as susceptibility loci. In addition, this study identified SLC6A20 (adjP = 2.71×10−6), RORA (adjP = 1.26×10−5), and ABCC9 (adjP = 1.86×10−5) as new potential susceptibility loci under adjusting the already known loci on the RET-CSGALNACT2-RASGEF1A and NRG1 regions, although none of the SNPs in these genes passed the Bonferroni correction. In further subgroup analysis, the RET-CSGALNACT2-RASGEF1A genomic region was observed to have different significance levels among subgroups: short-segment (S-HSCR, corrP = 1.71×10−5), long-segment (L-HSCR, corrP = 6.66×10−4), and total colonic aganglionosis (TCA, corrP>0.05). This differential pattern in the significance level suggests that other genomic loci or mechanisms may affect the length of aganglionosis in HSCR subgroups during enteric nervous system (ENS) development. Although functional evaluations are needed, our findings might facilitate improved understanding of the mechanisms of HSCR pathogenesis.

Experience with laparoscopic-assisted anorectal pull-through in 25 males with anorectal malformation and rectourethral or rectovesical fistulae: postoperative complications and functional results

INTRODUCTION LAARP (laparoscopic-assisted anorectal pull-through) has become an established operation for anorectal malformation (ARM) with rectourethral or rectovesical fistula. The aim of this study was to review post-LAARP operation complications and midterm functional results. METHODS Between 2003 and 2010, we performed 28 LAARPs in ARM patients with rectourethral or rectovesical fistula. We retrospectively analyzed the clinical outcomes in 25 male patients with rectourethral or vesical fistulae. RESULT The mean age of the patients at the time of LAARP was 2.7 ± 1.4 months. The most common ARM type was rectoprostatic urethral fistula (n=16). Few immediate postoperative complications (urinary tract infection (1), ileus (1), and one case of pneumonia) occurred. Rectal mucosal prolapse developed and was excised 6 months later in 13 (52%) patients. Urethral diverticulum occurred in one patient with a rectobulbar urethral fistula. Immediate postoperative high rectal tone developed in six patients during the early study period (2003-2004). Six of the 12 patients older than 3 years had voluntary bowel movement and no soiling. CONCLUSION LAARP was a safe procedure. Shorter dissection of rectum in the intra-abdominal space may be helpful in preventing rectal mucosal prolapse. Intermittent rectal tube insertion may be useful for the patient with high rectal tone in the immediate postoperative period. LAARP is not recommended for the bulbar fistula with a long common wall.

Posteromedial diaphragmatic hernia following pediatric liver transplantation.

Moon S‐B, Jung S‐M, Kwon C‐H, Kim S‐J, Joh J‐W, Seo J‐M, Lee S‐K. Posteromedial diaphragmatic hernia following pediatric liver transplantation.

The phenotypic characteristic of liver-derived stem cells from adult human deceased donor liver.

Liver transplantation is the only effective treatment for end-stage liver disease. Because of the limited donor availability, attention has been focused on the possibility to restore liver mass and function through cell transplantation. Stem cells are a promising source for liver repopulation after cell transplantation, but whether or not the adult liver contains hepatic stem cells is highly controversial. Several studies have suggested the presence of stem cells in the adult normal human liver. However, a population with stem cell properties has not yet been isolated. The purpose of this study was to identify and characterize progenitor cells in normal adult human liver. We isolated and expanded human liver stem cells (HLSCs) from a donated liver not suitable for liver transplantation or characterizing them by fluorescence-activated cell sorter, polymerase chain reaction, and immunofluorescence assay. HLSCs expressed the mesenchymal stem cell markers CD29, CD73, CD44, CD90, CD105, and CD166 but not the hematopoietic stem cell markers CD34, CD45, and CD117. HLSCs were also positive for vimentin and nestin, a stem cell marker. The absence of staining for cytokeratin-19, CD117, and CD34 indicated that HLSCs were not oval stem cells. In addition, HLSCs expressed CD26, and in a small percentage of cells, cytokeratin-8 and cytokeratin-18, indicating a partial commitment to hepatic cells. We concluded that HLSCs expressed several mesenchymal but not hematopoietic stem cell markers as well as CD26 and CK18, indicating a partial commitment to hepatic cells.

Differentiation and Major Histocompatibility Complex Antigen Expression in Human Liver–Derived Stem Cells

Stem cells are a promising source for liver repopulation after cell transplantation, but whether the adult liver contains hepatic stem cells is controversial. The purpose of this study was to characterize the properties and expression profile of major histocompatibility complex (MHC) antigens on the surface of human-derived stem cells. Human liver-derived stem cells (HLSC7) were isolated from the nontumorous tissue of a patient who underwent a resection of an hepatic hemangioendothelioma. We characterized HLSC7 using a fluorescence-activated cell sorter, polymerase chain reactions, and immunofluorescence assays. HLSC7 expressed mesenchymal but not hematopoietic stem cell markers. HLSC7 underwent osteogenic, chondrogenic, and hepatogenic differentiation when cultured in appropriate differentiation media. However, HLSC7 did not differentiate into adipocytes. In addition, HLSC7 did not express MHC class II (HLA-DP, -DQ, and -DR) antigens. However, they did express MHC class I antigens. These results suggest that human liver-derived stem cells express MHC class I antigens and thus may be rejected on transplantation. Therefore, in addition to studies on stem cell differentiation, one must overcome immunologic barriers for successful clinical application of this therapy.

Potential association between ITPKC genetic variations and Hirschsprung disease

Hirschsprung disease (HSCR) is a congenital and complex disorder characterized by intestinal obstruction due to the absence of enteric neurons along variable lengths of the hindgut. Our recent genome-wide association study (GWAS) has revealed regional associations with HSCR at several loci of inositol-trisphosphate 3-kinase C (ITPKC). For fine mapping, we additionally selected and genotyped a total of 12 single nucleotide polymorphisms (SNPs) of ITPKC in 187 HSCR patients and 283 unaffected controls, and performed a further combined imputation analysis based on genotype data from this second stage of fine mapping and our previous GWAS stage, totaling 902 subjects (187 HSCR cases and 715 controls). As a result, several SNPs (minimum P = 0.004) and a haplotype (P = 0.02) were found to be significantly associated with HSCR. In further in silico analyses to ascertain the potential functions of the significant variants, the change from the common allele to the rare allele of the highly conserved nonsynonymous rs76785336 showed a difference in mRNA folding structure. In the case of intronic SNPs, rs2607420 with a high consensus value was predicted to be a new splice site. Although this study has limitations (such as lack of functional evaluations, small number of cases, and further need of replication in other cohorts), our findings suggest that genetic variants of ITPKC may have a potential association with HSCR susceptibility and/or developmental diseases related to enteric nervous system development.