Matthew T. Santore

Platelets regulate lymphatic vascular development through CLEC-2–SLP-76 signaling

Although platelets appear by embryonic day 10.5 in the developing mouse, an embryonic role for these cells has not been identified. The SYK-SLP-76 signaling pathway is required in blood cells to regulate embryonic blood-lymphatic vascular separation, but the cell type and molecular mechanism underlying this regulatory pathway are not known. In the present study we demonstrate that platelets regulate lymphatic vascular development by directly interacting with lymphatic endothelial cells through C-type lectin-like receptor 2 (CLEC-2) receptors. PODOPLANIN (PDPN), a transmembrane protein expressed on the surface of lymphatic endothelial cells, is required in nonhematopoietic cells for blood-lymphatic separation. Genetic loss of the PDPN receptor CLEC-2 ablates PDPN binding by platelets and confers embryonic lymphatic vascular defects like those seen in animals lacking PDPN or SLP-76. Platelet factor 4-Cre-mediated deletion of Slp-76 is sufficient to confer lymphatic vascular defects, identifying platelets as the cell type in which SLP-76 signaling is required to regulate lymphatic vascular development. Consistent with these genetic findings, we observe SLP-76-dependent platelet aggregate formation on the surface of lymphatic endothelial cells in vivo and ex vivo. These studies identify a nonhemostatic pathway in which platelet CLEC-2 receptors bind lymphatic endothelial PDPN and activate SLP-76 signaling to regulate embryonic vascular development.

Maternal alloantibodies induce a postnatal immune response that limits engraftment following in utero hematopoietic cell transplantation in mice

The lack of fetal immune responses to foreign antigens, i.e., fetal immunologic tolerance, is the most compelling rationale for prenatal stem cell and gene therapy. However, the frequency of engraftment following in utero hematopoietic cell transplantation (IUHCT) in the murine model is reduced in allogeneic, compared with congenic, recipients. This observation supports the existence of an immune barrier to fetal transplantation and challenges the classic assumptions of fetal tolerance. Here, we present evidence that supports the presence of an adaptive immune response in murine recipients of IUHCT that failed to maintain engraftment. However, when IUHCT recipients were fostered by surrogate mothers, they all maintained long-term chimerism. Furthermore, we have demonstrated that the cells responsible for rejection of the graft were recipient in origin. Our observations suggest a mechanism by which IUHCT-dependent sensitization of the maternal immune system and the subsequent transmission of maternal alloantibodies to pups through breast milk induces a postnatal adaptive immune response in the recipient, which, in turn, results in the ablation of engraftment after IUHCT. Finally, we showed that non-fostered pups that maintained their chimerism had higher levels of Tregs as well as a more suppressive Treg phenotype than their non-chimeric, non-fostered siblings. This study resolves the apparent contradiction of induction of an adaptive immune response in the pre-immune fetus and confirms the potential of actively acquired tolerance to facilitate prenatal therapeutic applications.

Stem cell and genetic therapies for the fetus

Advances in prenatal diagnosis have led to the prenatal management of a variety of congenital diseases. Although prenatal stem cell and gene therapy await clinical application, they offer tremendous potential for the treatment of many genetic disorders. Normal developmental events in the fetus offer unique biologic advantages for the engraftment of hematopoietic stem cells and efficient gene transfer that are not present after birth. Although barriers to hematopoietic stem cell engraftment exist, progress has been made and preclinical studies are now underway for strategies based on prenatal tolerance induction to facilitate postnatal cellular transplantation. Similarly, in-utero gene therapy shows experimental promise for a host of diseases and proof-in-principle has been demonstrated in murine models, but ethical and safety issues still need to be addressed. Here we review the current status and future potential of prenatal cellular and genetic therapy.

Hepaticoduodenostomy vs hepaticojejunostomy for reconstruction after resection of choledochal cyst.

PURPOSE Roux-en-Y hepaticojejunostomy (HJ) is currently the favored reconstructive procedure after resection of choledochal cysts. Hepaticoduodenostomy (HD) has been argued to be more physiologically and technically easier but is feared to have associated complications. Here we compare outcomes of the 2 procedures. METHODS A retrospective chart review identified 59 patients who underwent choledochal cyst resection within our institution from 1999 to 2009. Demographic and outcome data were compared using t tests, Mann-Whitney U tests, and Pearson χ(2) tests. RESULTS Fifty-nine patients underwent repair of choledochal cyst. Biliary continuity was restored by HD in 39 (66%) and by HJ in 20 (34%). Open HD patients required less total operative time than HJ patients (3.9 vs 5.1 hours, P = .013), tolerated a diet faster (4.8 days compared with 6.1 days, P = .08), and had a shorter hospital stay (7.05 days for HD vs 9.05 days for HJ, P = .12). Complications were more common in HJ (HD = 7.6%, HJ = 20%, P = .21). Three patients required reoperation after HJ, but only one patient required reoperation after HD for a stricture (HD = 2.5%, HJ = 20%, P = .037). CONCLUSIONS In this series, HD required less operative time, allowed faster recovery of bowel function, and produced fewer complications requiring reoperation.

Enhancing recovery in pediatric surgery: a review of the literature

BACKGROUND Enhanced recovery after surgery (ERAS), guidelines entail a strategy of perioperative management proven to hasten postoperative recovery and reduce complications in adult populations. Relatively few studies have investigated the applicability of this paradigm to pediatric populations. Our objective was to perform a systematic review of existing evidence regarding the use and efficacy of enhanced recovery protocols (ERPs) in the pediatric population. MATERIALS AND METHODS Data were collected through a PubMed/MEDLINE literature search. Study eligibility criteria included a pediatric population and implementation of at least four components of published ERAS Society recommendations. RESULTS One retrospective and four prospective cohort studies evaluating children undergoing gastrointestinal, urologic, and thoracic surgeries were identified. The overall quality of reporting was fair with few studies acknowledging limitations and bias and inconsistent outcome reporting. Studies included six or fewer interventions compared to 20 recommended interventions in most adult ERAS Society guidelines. None of the studies were well controlled. Nevertheless, these studies suggest that ERPs applied to the appropriate pediatric surgical populations may be associated with decreased length of stay, decreased narcotic use, and no detectable increase in complications. CONCLUSIONS There is a paucity of high-quality literature evaluating implementation of ERPs in pediatric populations. The limited literature available indicates that ERPs would be safe and potentially effective. More studies are needed to assess the efficacy of ERPs in pediatric surgery.

Prenatal Stem Cell Transplantation and Gene Therapy

At the present time, the most likely and eminent application of stem cell therapy to the fetus is in utero hematopoietic stem cell transplantation (IUHCT), and this stem cell type will be discussed as a paradigm for all prenatal stem cell therapy. The authors feel that the most likely initial application of IUHCT will use adult HSC derived from bone marrow (BM) or peripheral blood (PB), and will focus this article on this specific approach. The article also reviews the experimental data that support the capacity of IUHCT to induce donor-specific tolerance.

Laparoscopic hepaticoduodenostomy versus open hepaticoduodenostomy for reconstruction after resection of choledochal cyst.

BACKGROUND Laparoscopic surgical techniques have been applied for reconstruction after choledochal cyst resection. The aim of our study was to report the technical details of laparoscopic hepaticoduodenostomy and to compare outcomes between the open and laparoscopic approaches at our institution. METHODS We performed a retrospective analysis of children with choledochal cyst who underwent hepaticoduodenostomy between August 2005 and May 2009. Patients were divided into open and laparoscopic groups based on the surgical approach. We analyzed demographic and clinical characteristics to compare the outcomes in these 2 groups. RESULTS From August 2005 to May 2009, 21 patients underwent choledochal cyst excision with hepaticoduodenostomy reconstruction. Six patients underwent laparoscopic hepaticoduodenostomy and 15 underwent open hepaticoduodenostomy reconstruction. There were no significant differences in age or gender, characterization of the cyst, presentation, or preoperative laboratory results. There were no significant differences in operative time, days to full enteral nutrition, or time to discharge between the 2 groups. There were no differences in postoperative complications between the 2 groups. CONCLUSION A laparoscopic approach to choledochal cyst resection and hepaticoduodenostomy is feasible and safe.

Pediatric thoracic trauma: Current trends

Pediatric thoracic trauma is relatively uncommon but results in disproportionately high levels of morbidity and mortality when compared with other traumatic injuries. These injuries are often more devastating due to differences in children׳s anatomy and physiology relative to adult patients. A high index of suspicion is of utmost importance at the time of presentation because many significant thoracic injuries will have no external signs of injury. With proper recognition and management of these injuries, there is an associated improved long-term outcome. This article reviews the current literature and discusses the initial evaluation, current management practices, and future directions in pediatric thoracic trauma.

Focused assessment with sonography for trauma in children after blunt abdominal trauma: A multi-institutional analysis

Introduction The utility of focused assessment with sonography for trauma (FAST) in children is poorly defined with considerable practice variation. Our purpose was to investigate the role of FAST for intra-abdominal injury (IAI) and IAI requiring acute intervention (IAI-I) in children after blunt abdominal trauma (BAT). Methods We prospectively enrolled children younger than 16 years after BAT at 14 Level I pediatric trauma centers over a 1-year period. Patients who underwent FAST were compared with those that did not, using descriptive statistics and univariate analysis; p value less than 0.05 was considered significant. FAST test characteristics were performed using computed tomography (CT) and/or intraoperative findings as the gold standard. Results Two thousand one hundred eighty-eight children (age, 7.8 ± 4.6 years) were included. Eight hundred twenty-nine (37.9%) received a FAST, 340 of whom underwent an abdominal CT. Ninety-seven (29%) of these 340 patients had an IAI and 27 (7.9%) received an acute intervention. CT scan utilization after FAST was 41% versus 46% among those who did not receive FAST. The frequency of FAST among centers ranged from 0.84% to 94.1%. There was low correlation between FAST and CT utilization (r = −0.050, p < 0.001). Centers that performed FAST at a higher frequency did not have improved accuracy. The test performance of FAST for IAI was sensitivity, 27.8%; specificity, 91.4%; positive predictive value, 56.2%; negative predictive value, 76.0%; and accuracy, 73.2%. There were 81 injuries among the 70 false-negative FAST. The test performance of FAST for IAI-I was sensitivity, 44.4%; specificity, 88.5%; positive predictive value, 25.0%; negative predictive value, 94.9%; and accuracy, 85.0%. Fifteen children with a negative FAST received acute interventions. Among the 27 patients with true positive FAST examinations, 12 received intervention. All had an abnormal abdominal physical examination. No patient underwent intervention before CT scan. Conclusion As currently used, FAST has a low sensitivity for IAI, misses IAI-I and rarely impacts management in pediatric BAT. LEVEL OF EVIDENCE Prognostic and epidemiologic study, level II; diagnostic tests or criteria study, level II; therapeutic/care management study, level III.

Identifying Children at Very Low Risk for Blunt Intra-Abdominal Injury in Whom CT of the Abdomen Can Be Avoided Safely

BACKGROUND Computed tomography is commonly used to rule out intra-abdominal injury (IAI) in children, despite associated cost and radiation exposure. Our purpose was to derive a prediction rule to identify children at very low risk for IAI after blunt abdominal trauma (BAT) for whom a CT scan of the abdomen would be unnecessary. STUDY DESIGN We prospectively enrolled children younger than 16 years of age who presented after BAT at 14 Level I pediatric trauma centers during 1 year. We excluded patients who presented more than 6 hours after injury or underwent abdominal CT before transfer. We used binary recursive partitioning to derive a prediction rule identifying children at very low risk of IAI and IAI requiring acute intervention (IAI-I) using clinical information available in the trauma bay. RESULTS We included 2,188 children with a median age of 8 years. There were 261 patients with IAI (11.9%) and 62 patients with IAI-I (2.8%). The prediction rule consisted of (in descending order of significance): aspartate aminotransferase >200 U/L, abnormal abdominal examination, abnormal chest x-ray, report of abdominal pain, and abnormal pancreatic enzymes. The rule had a negative predictive value of 99.4% for IAI and 100.0% for IAI-I in patients with none of the prediction rule variables present. The very-low-risk population consisted of 34% of the patients and 23% received a CT scan. Computed tomography frequency ranged from 4% to 96% by center. CONCLUSIONS A prediction rule using history and physical examination, chest x-ray, and laboratory evaluation at the time of presentation after BAT identifies children at very low risk for IAI for whom CT can be avoided.