Joaquin J. Estrada

Fibroblast growth factor 10 is critical for liver growth during embryogenesis and controls hepatoblast survival via β‐catenin activation

Fibroblast growth factor (FGF) signaling and β‐catenin activation have been shown to be crucial for early embryonic liver development. This study determined the significance of FGF10‐mediated signaling in a murine embryonic liver progenitor cell population as well as its relation to β‐catenin activation. We observed that Fgf10−/− and Fgfr2b−/− mouse embryonic livers are smaller than wild‐type livers; Fgf10−/− livers exhibit diminished proliferation of hepatoblasts. A comparison of β‐galactosidase activity as a readout of Fgf10 expression in Fgf10+/LacZ mice and of β‐catenin activation in TOPGAL mice, demonstrated peak Fgf10 expression from E9 to E13.5 coinciding with peak β‐catenin activation. Flow cytometric isolation and marker gene expression analysis of LacZ+ cells from E13.5 Fgf10+/LacZ and TOPGAL livers, respectively, revealed that Fgf10 expression and β‐catenin signaling occur distinctly in stellate/myofibroblastic cells and hepatoblasts, respectively. Moreover, hepatoblasts express Fgfr2b, which strongly suggests they can respond to recombinant FGF10 produced by stellate cells. Fgfr2b−/−/TOPGAL+/+ embryonic livers displayed less β‐galactosidase activity than livers of Fgfr2b+/+/TOPGAL+/+ littermates. In addition, cultures of whole liver explants in Matrigel or cell in suspension from E12.5 TOPGAL+/+mice displayed a marked increase in β‐galactosidase activity and cell survival upon treatment with recombinant FGF10, indicating that FGFR (most likely FGFR2B) activation is upstream of β‐catenin signaling and promote hepatoblast survival. Conclusion: Embryonic stellate/myofibroblastic cells promote β‐catenin activation in and survival of hepatoblasts via FGF10‐mediated signaling. We suggest a role for stellate/myofibroblastic FGF10 within the liver stem cell niche in supporting the proliferating hepatoblast. (HEPATOLOGY 2007.)

Esophageal atresia/tracheoesophageal fistula in very low-birth-weight neonates: improved outcomes with staged repair

INTRODUCTION The surgical management of esophageal atresia with distal tracheoesophageal fistula (EA/TEF) involves early division of the TEF and primary esophageal anastomosis. However, in premature infants, the morbidity associated with primary repair remains high, and the optimal surgical approach has not been well defined. METHODS Medical records of very low-birth-weight infants (<1500 g) with EA/TEF from June 1987 to 2008 were retrospectively reviewed. Patients were separated into 2 groups: (1) primary repair and (2) ligation and division of TEF followed by delayed repair of EA. Demographics, anastomotic, and postoperative complications were compared. RESULTS Twenty-five premature infants with EA/TEF were identified. Sixteen patients (64%) underwent primary repair, and 9 (36%) were repaired in a staged manner. The leak rate confirmed by esophagram was significantly higher after primary repair (50%) compared to staged repair (0%) (P = .034). Strictures occurred significantly more often in the primary repair (81%) vs the staged repair (33%) group (P = .036). Postoperative pneumonia and sepsis were significantly higher in patients treated with primary repair (P = .028). CONCLUSION Staged repair of EA/TEF in very low-birth-weight premature infants results in a significantly lower rate of anastomotic complications and overall morbidity and should be considered the preferred surgical approach in this group of patients.

β-catenin regulates mesenchymal progenitor cell differentiation during hepatogenesis.

BACKGROUND Understanding the pathways regulating mesenchymal progenitor cell fate during hepatogenesis may provide insight into postnatal liver injury or liver bioengineering. While β-Catenin has been implicated in the proliferation of fetal hepatic epithelial progenitor cells, its role in mesenchymal precursors during hepatogenesis has not been established. MATERIALS AND METHODS We used a murine model of conditional deletion of β-Catenin in mesenchyme using the Dermo1 locus (β-Catenin(Dermo1)) to characterize the role of β-Catenin in liver mesenchyme during hepatogenesis. RESULTS Lineage tracing using a LacZ reporter indicates that both hepatic stellate cells and pericytes derive from mesenchymal Dermo1 expressing precursor cells. Compared to control littermate livers, β-Catenin(Dermo1) embryonic livers are smaller and filled with dilated sinusoids. While the fraction of mesenchymally-derived cells in β-Catenin(Dermo1) embryos is unchanged compared to littermate controls, there is an increase in the expression of the mesenchymal markers, DESMIN, α-SMA, and extracellular deposition of COLLAGEN type I, particularly concentrated around dilated sinusoids. Analysis of the endothelial cell compartment in β-Catenin(Dermo1)/Flk1(lacZ) embryos revealed a marked reorganization of the intrahepatic vasculature. Analysis of various markers for the endodermally-derived hepatoblast population revealed marked alterations in the spatial expression pattern of pan-cytokeratin but not E-cadherin, or albumin. β-Catenin(Dermo1) phenocopies mesenchymal deletion of Pitx2, a known regulator of hepatic mesenchymal differentiation both during both organogenesis and postnatal injury. CONCLUSIONS Our data implicate mesenchymal β-Catenin signaling pathway in the differentiation of liver mesenchymal progenitor cells during organogenesis, possibly via Pitx2. Hepatic mesenchymal β-Catenin signaling, in turn, modulates the development of both endothelium and endodermally-derived hepatoblasts, presumably via other downstream paracrine pathways.

Subcutaneous Fixation of Gastrostomy Tube Is Superior to Temporary Fixation

PURPOSE The placement of gastrostomy tubes (GTs) in infants and children to provide enteral access over the past decade has shifted toward a minimally invasive, safer direction with the development of various new techniques. We have developed a modified technique, utilizing subcutaneous (S.C.) tunneling stay sutures to prevent complications, such as GT dislodgment and wound infection. The aim of this study was to identify and describe complications of the modified procedure and compare it with the standard laparoscopic GT placement. MATERIALS AND METHODS A retrospective 4-year review of 153 patients who underwent laparoscopic GT placement was conducted. Eighty-nine patients underwent the modified S.C. tunneled technique, and 64 patients had standard U-stitch with temporary fixation. RESULTS The overall complication rate was significantly higher with the temporary fixation group (20%) versus the modified technique group (2.5%). Six patients from the temporary group and 2 patients from the modified group developed cellulitis. Seven patients underwent reoperation secondary to GT dislodgment in the temporary group. No patients were identified with tube-related pressure necrosis or procedure-related deaths. CONCLUSION S.C. placement of stay sutures in the modified technique is associated with a lower complication rate than temporary fixation. The modified technique should be the preferred approach when performing laparoscopic GT insertion.

Natural Progression of Biochemical Markers of Biliary Tract Obstruction in Patients with Gallstone Pancreatitis

The presenting pattern and natural progression of biochemical markers of biliary tract obstruction in patients with gallstone pancreatitis have not been elucidated. We analyzed serial values of bilirubin levels following admission to discharge in 143 patients. Ninety-four of patients demonstrated a Decrescendo (falling) pattern of bilirubin levels from admission until normalization at 21 hours (median). Forty-nine patients demonstrated a Crescendo-Decrescendo (initially rising) pattern with peak levels of bilirubin occurring at 39 hours after admission followed by a subsequent normalization after a median of 119 hours. Patients in the Decrescendo group were significantly younger (33 versus 41 years, P = .02) and more patients had experienced symptoms for greater than 48 hours (65% versus 47%, P = .05). Ten percent of patients in the Decrescendo group and 29% of patients in the Crescendo-Decrescendo group underwent ERCP (P = .02). Normalization of biochemical markers after ERCP was significantly delayed in both groups compared to no ERCP. Older patients present earlier, with higher bilirubin levels and normalize slower than younger patients, perhaps due to fibrosis of the ampulla and decreased compliance of the common bile duct. Patients who disobstruct spontaneously (90%) normalize quicker than patients undergoing ERCP.