BHLHE40 drives protective polyfunctional CD4 T cell differentiation in the female reproductive tract against Chlamydia.

The protein basic helix-loop-helix family member e40 (BHLHE40) is a transcription factor recently emerged as a key regulator of host immunity to infections, autoimmune diseases and cancer. In this study, we investigated the role of Bhlhe40 in protective T cell responses to the intracellular bacterium Chlamydia in the female reproductive tract (FRT). Mice deficient in Bhlhe40 exhibited severe defects in their ability to control Chlamydia muridarum shedding from the FRT. The heightened bacterial burdens in Bhlhe40-/- mice correlated with a marked increase in IL-10-producing T regulatory type 1 (Tr1) cells and decreased polyfunctional CD4 T cells co-producing IFN-γ, IL-17A and GM-CSF. Genetic ablation of IL-10 or functional blockade of IL-10R increased CD4 T cell polyfunctionality and partially rescued the defects in bacterial control in Bhlhe40-/- mice. Using single-cell RNA sequencing coupled with TCR profiling, we detected a significant enrichment of stem-like T cell signatures in Bhlhe40-deficient CD4 T cells, whereas WT CD4 T cells were further down on the differentiation trajectory with distinct effector functions beyond IFN-γ production by Th1 cells. Altogether, we identified Bhlhe40 as a key molecular driver of CD4 T cell differentiation and polyfunctional responses in the FRT against Chlamydia.

IFNγ and Antibody Synergize To Enhance Protective Immunity against Chlamydia Dissemination and Female Reproductive Tract Reinfections.

CD4 T cell-dependent IFNγ production and antibody are the two best known effectors for protective immunity against Chlamydia female reproductive tract (FRT) infection. Nevertheless, mice lacking either IFNγ or B cells can clear the vast majority of Chlamydia from the FRT, while suffering from varying degrees of disseminated infection. In this study, we investigated whether IFNγ and B cells play complementary roles in host defense against Chlamydia and evaluated their relative contributions in systemic and mucosal tissues. Using mice deficient in both IFNγ and B cells (IFNγ-/- x µMT), we showed that mice lacking both effectors were highly susceptible to lethal systemic bacterial dissemination following Chlamydia muridarum intravaginal infection. Passive transfer of immune convalescent serum, but not recombinant IFNγ, reduced bacterial burden in both systemic and mucosal tissues in IFNγ-/- x µMT mice. Notably, over the course of primary infection, we observed a reduction of bacterial shedding of more than 2 orders of magnitude in IFNγ-/- x µMT mice following both C. muridarum and C. trachomatis FRT infections. In contrast, no protective immunity against C. muridarum reinfection was detected in the absence of IFNγ and B cells. Together, our results suggest that IFNγ and B cells synergize to combat systemic Chlamydia dissemination, while additional IFNγ and B cell-independent mechanisms exist for host resistance to Chlamydia in the lower FRT.

Novel viral RNA genomes of the vine mealybug Planococcus ficus.

The vine mealybug, Planococcus ficus (Signoret, 1875), is the most important insect pest in growing areas of the grapevine Vitis vinifera L. in several countries, including Mexico. In Mexico, Baja California (B.C.) is the region with the highest production of V. vinifera L. grapes for industrial purposes. Recently, the diversity of viruses infecting insects only (insect-specific viruses) has been broadly explored to elucidate further ecological viral-host interactions in many insect species, which in some cases has resulted in the application of virus-based biological control agents for insect pests. However, a survey of the Pl. ficus virome has not been done yet. In the present study, we pooled Pl. ficus individuals collected through different vineyards of Ensenada, B.C., Mexico and analysed them by meta-transcriptomics. Novel nearly complete genomes of five RNA viruses were retrieved. These viruses were related to the Iflaviridae and Reoviridae families, and to the Picornavirales and Tolivirales orders. A new isolate belonging to the Dicistroviridae family was also found. Phylogenetic analyses showed that these putative viral genomes group with viruses having hemipteran (including a mealybug species) or other insect hosts, or with viruses associated with insects. Our results suggest that the identified novel RNA viruses could be insect-specific viruses of Pl. ficus. This work is the first insight into the Pl. ficus virome; it guarantees further studies aimed to characterize those viruses with potential for application in biological control of this economically important insect.

Liver Transplantation as Definitive Treatment of Post-cholecystectomy Bile Duct Injury: Experience in a High-volume Repair Center.

OBJECTIVE: To analyze the perioperative and long-term outcomes of patients undergoing LT due to BDI in a tertiary care center. BACKGROUND: BDI is associated with significant morbidity and long-term impact on quality of life. LT represents the only possibility of a cure in patients with BDI who develop SBC. METHODS: Retrospective cohort study from a prospective LT database. Between 2008 and 2019, patients with SBC due to BDI after cholecystectomy and requiring LT were identified. Perioperative and long-term outcomes were analyzed. RESULTS: Among 354 LT, 12 patients underwent LT to treat post-cholecystectomy BDI and accounted for 3.4% of all LT. The median time from BDI to SBC diagnosis was 9.3 years (2.4-14). The mean time from SBC to inclusion on the waitlist was 2.4years (± 2.2). Postoperative complications occurred in 11 patients (91.6%); mainly infectious (9/12 patients, 75%), followed by renal complications (4/12 patients, 33.3%). Only 2 patients developed major complications, which were the patients who died, resulting in a 90-day mortality of 16.7%. After a mean follow-up of 40.3 months (± 42.2) survival at 1, 3, and 5 years was 83%. CONCLUSIONS: Although BDI is an unusual indication for LT worldwide, it accounted for 3.4% of all LT in our center. Although postoperative mortality remains high, LT is the only possibility of a cure, with acceptable long-term outcomes. Early referral to a tertiary care center is essential to avoid long-term complications of BDI, such as SBC.

Innate IFN-γ Is Essential for Systemic Chlamydia muridarum Control in Mice, While CD4 T Cell-Dependent IFN-γ Production Is Highly Redundant in the Female Reproductive Tract.

Protective immunity against the obligate intracellular bacterium Chlamydia has long been thought to rely on CD4 T cell-dependent gamma interferon (IFN-γ) production. Nevertheless, whether IFN-γ is produced by other cellular sources during Chlamydia infection and how CD4 T cell-dependent and -independent IFN-γ contribute differently to host resistance have not been carefully evaluated. In this study, we dissected the requirements of IFN-γ produced by innate immune cells and CD4 T cells for resolution of Chlamydia muridarum female reproductive tract (FRT) infection. After C. muridarum intravaginal infection, IFN-γ-deficient and T cell-deficient mice exhibited opposite phenotypes for survival and bacterial shedding at the FRT mucosa, demonstrating the distinct requirements for IFN-γ and CD4 T cells in host defense against Chlamydia In Rag1-deficient mice, IFN-γ produced by innate lymphocytes (ILCs) accounted for early bacterial control and prolonged survival in the absence of adaptive immunity. Although type I ILCs are potent IFN-γ producers, we found that mature NK cells and ILC1s were not the sole sources of innate IFN-γ in response to Chlamydia By conducting T cell adoptive transfer, we showed definitively that IFN-γ-deficient CD4 T cells were sufficient for effective bacterial killing in the FRT during the first 21 days of infection and reduced bacterial burden more than 1,000-fold, although mice receiving IFN-γ-deficient CD4 T cells failed to completely eradicate the bacteria from the FRT like their counterparts receiving wild-type (WT) CD4 T cells. Together, our results revealed that innate IFN-γ is essential for preventing systemic Chlamydia dissemination, whereas IFN-γ produced by CD4 T cells is largely redundant at the FRT mucosa.

Antibody, but not B-cell-dependent antigen presentation, plays an essential role in preventing Chlamydia systemic dissemination in mice.

The obligate intracellular bacterium Chlamydia trachomatis causes the most prevalent bacterial sexually transmitted infection worldwide. CD4 T cells play a central role in the protective immunity against Chlamydia female reproductive tract (FRT) infection, while B cells are thought to be dispensable for resolution of primary Chlamydia infection in mouse models. We recently reported an unexpected requirement of B cells in local Chlamydia-specific CD4 T-cell priming and bacterial containment within the FRT. Here, we sought to tackle the precise effector function of B cells during Chlamydia primary infection. Using mixed bone marrow chimeras that lack B-cell-dependent Ag presentation (MHCIIB-/- ) or devoid of circulating antibodies (AID-/- × µS-/- ), we show that Chlamydia-specific CD4 T-cell expansion does not rely on Ag presentation by B cells. Importantly, we demonstrate that antibody, but not B-cell-dependent Ag presentation, is required for preventing systemic bacterial dissemination following Chlamydia FRT infection.

THE FUTURE OF TECHNOLOGY AND ROBOTICS IN SURGERY.

In the past three decades, several technologies designed for other purposes, have been applied in surgery to provide more precision to the surgical procedures and better outcomes. In surgery, innovation requires evidence before widespread implementation of novelties and a continuous quality improvement process to assess benefits and risks. Robotics in surgery has been widely implemented, but in some cases, there are many doubts regarding its clinical benefit and cost utility. The future of surgery lies in the fulfillment of four main conditions: safety, access, efficiency, and efficacy. Innovation and technology should help to accomplish these conditions, but it must not be the center of surgical practice. We present here our perspective on the main issues related to technology and robotics focusing on evidence-based surgery.

Disparities in bile duct injury care.

BACKGROUND: An international group proposed a standardized terminology to report outcomes after bile duct repair. Data on this surgical complication vary depending on the center and country where patients are treated. The aim of this work is to show disparities in the care process of bile duct injury between patients from two different income-level countries, using a standard terminology of outcomes and clinical reporting. METHODS: A retrospective review comparing primary repair and re-repaired cases performed in an upper middle-income country (UMIC) versus primary repair cases treated in a high-income country (HIC) was performed. All pertinent data included in the tabular reporting system and outcomes classification were collected. Patients' characteristics were reported by calculating descriptive statistics. RESULTS: A total of 261 patients from UMIC (148 (56%) primary repair and 113 (44%) re-repair) were compared with 122 primary repair from HIC. Open cholecystectomy (55.4% vs 3.3%) and more E4 injuries (37.8% vs 19.7%) were found in the UMIC group. More Accordion 3 and higher complications were present in the UMIC primary and repair groups, as well as more episodes of postoperative acute cholangitis. Eleven patients were listed for liver transplant in the UMIC re-repair group. Primary patency by the end of the index treatment period was present in 217 (83%) of the full UMIC cohort. Median time to loss of primary patency was not reached in the primary repair, and was 3.8 years in the re-repair group. Patency was below HIC primary repaired cases. CONCLUSIONS: Standardized reporting outcomes after primary repair are applicable to re-repaired patients and are helpful to compare different populations, showing better outcomes in HIC. Measures of surgical access disparities exist among the process of bile duct injury care.

Timing of Surgical Repair After Bile Duct Injury Impacts Postoperative Complications but Not Anastomotic Patency.

OBJECTIVE: Our goal was to determine the optimal timing for repair of bile duct injuries sustained during cholecystectomy. BACKGROUND: Bile duct injury during cholecystectomy is a serious complication that often requires surgical repair. There is heterogeneity in the literature regarding the optimal timing of surgical repair, and it remains unclear to what extent timing determines postoperative morbidity and long-term anastomotic function. METHODS: A single institution prospective database was queried for all E1 to E4 injuries from 1989 to 2014 using a standardized tabular reporting format. Timing was stratified into 3 groups [early (<7 days), intermediate (8 days until 6 weeks), and late (>6 weeks) after injury]. Analysis was stratified between those who had a previous bile duct repair or not, including postoperative complications and anastomotic failure as outcome variables in 2 separate multivariate logistic regression models. RESULTS: There were 614 patients included in the study. The mean age was 41 years (range, 15-85 yrs), and the majority were female (80%). The mean follow-up time was 40.5 months. Side-to-side hepaticojejunostomy was performed in 94% of repairs. Intermediate repair was associated with a higher risk of postoperative complications [odd ratio = 3.7, 95% confidence interval (1.3-10.2), P = 0.01] when compared with early and late in those with a previous repair attempt. Sepsis control and avoidance of biliary stents were protective factors against anastomotic failure. CONCLUSIONS: Adequate sepsis control and delayed repair of biliary injuries should be considered for patients presenting between 8 days and 6 weeks after injury to prevent complications, if a previous bile duct repair was attempted.

Performance of robotic simulated skills tasks is positively associated with clinical robotic surgical performance.

OBJECTIVE: To compare user performance of four fundamental inanimate robotic skills tasks (FIRST) as well as eight da Vinci Skills Simulator (dVSS) virtual reality tasks with intra-operative performance (concurrent validity) during robot-assisted radical prostatectomy (RARP) and to show that a positive correlation exists between simulation and intra-operative performance. MATERIALS AND METHODS: A total of 21 urological surgeons with varying robotic experience were enrolled. Demographics were captured using a standardized questionnaire. User performance was assessed concurrently in simulated (FIRST exercises and dVSS tasks) and clinical environments (endopelvic dissection during RARP). Intra-operative robotic clinical performance was scored using the previously validated six-metric Global Evaluative Assessment of Robotic Skills (GEARS) tool. The relationship between simulator and clinical performance was evaluated using Spearman's rank correlation. RESULTS: Performance was assessed in 17 trainees and four expert robotic surgeons with a median (range) number of previous robotic cases (as primary surgeon) of 0 (0-55) and 117 (58-600), respectively (P = 0.001). Collectively, the overall FIRST (ρ = 0.833, P < 0.001) and dVSS (ρ = 0.805, P < 0.001) simulation scores correlated highly with GEARS performance score. Each individual FIRST and dVSS task score also demonstrated a significant correlation with intra-operative performance, with the exception of Energy Switcher 1 exercise (P = 0.063). CONCLUSIONS: This is the first study to show a significant relationship between simulated robotic performance and robotic clinical performance. Findings support implementation of these robotic training tools in a standardized robotic training curriculum.

Multi-Institutional Validation of Fundamental Inanimate Robotic Skills Tasks.

PURPOSE: Our group has previously reported the development and validation of FIRST (Fundamental Inanimate Robotic Skills Tasks), a series of 4 inanimate robotic skills tasks. Expanding on the initial validation, we now report face, content and construct validity of FIRST in a large multi-institutional cohort of experts and trainees. MATERIALS AND METHODS: A total of 96 residents, fellows and attending surgeons completed the FIRST exercises at participating institutions. Participants were classified based on previous robotic experience and task performance was compared across groups to establish construct validity. Face and content validity was assessed from participant ratings of the tasks on a 5-point Likert scale. RESULTS: A total of 51 novice, 22 intermediate and 23 expert participants with a median previous robotic experience of 0 (range 0 to 3), 10 (range 5 to 30) and 200 cases (range 55 to 2,000), respectively (p<0.001), were assessed across all 4 inanimate robotic skills tasks. Expert and intermediate groups reliably outperformed novices (p<0.01). Experts also performed better than intermediates on all exercises (p<0.01). A survey of participants on their perceptions of the tasks yielded excellent face and content validity. CONCLUSIONS: We confirm robust face, content and construct validity of 4 inanimate robotic training tasks in a large multi-institutional cohort. FIRST tasks are reliably able to discern among expert, intermediate and novice robotic surgeons. Validation data from this large multi-institutional cohort is useful as we incorporate these tasks into a comprehensive robotic training curriculum.

Incidence, significance and natural history of persistent retrograde venous flow after varicocelectomy in children and adolescents: correlation with catch-up growth.

PURPOSE: Varying incidences and levels of persistent retrograde venous flow have been reported following adult and adolescent varicocelectomy but the significance remains unclear. We sought to determine the incidence and natural history of persistent flow and whether it had any effect on postoperative testicular catch-up growth. MATERIALS AND METHODS: We retrospectively analyzed pre-varicocelectomy and post-varicocelectomy Doppler duplex ultrasound findings. Peak retrograde venous flow, maximum vein diameter, flow quality and varicocele grade were recorded at each visit. Catch-up growth was defined as less than 15% testicular asymmetry at final visit. RESULTS: Of 330 patients (median age 15.4 years) undergoing varicocelectomy (laparoscopic in 247, open in 83) 145 had residual retrograde venous flow after Valsalva maneuver with a mean peak of 13.3 cm per second. Of 290 patients with repeat Doppler duplex ultrasound (median followup 2.6 years) 124 had initial peak retrograde venous flow less than 20 cm per second (43%) and only 17 (6%) had flow 20 cm per second or greater. Incidence of post-varicocelectomy retrograde venous flow at last visit (48%) was similar to that at initial postoperative visit (49%). Of 330 boys 20 had recurrence of palpable varicocele (grade 2 or 3), of whom 18 (90%) had initial retrograde venous flow. Catch-up growth was more likely in patients with no retrograde venous flow, and rates of catch-up growth decreased as peak retrograde venous flow increased. All 5 patients with initial testicular asymmetry and persistent retrograde venous flow at levels greater than 30 cm per second had continued testicular asymmetry (ie none had catch-up growth). CONCLUSIONS: Retrograde venous flow is frequently present after varicocelectomy and is almost always associated with peak retrograde venous flow rates significantly lower than those seen in patients who are recommended for initial varicocelectomy. Retrograde venous flow tends to persist during followup at stable peak retrograde venous flow rates. Palpable recurrence and persistent testicular asymmetry are most often associated with postoperative peak retrograde venous flow rates 20 cm per second or greater.

Comparison of laparoendoscopic single site (LESS) and conventional laparoscopic donor nephrectomy at a single institution.

UNLABELLED: WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Most transplant centres harvest living donor kidneys via a conventional laparoscopic surgical approach. Laparoendoscopic single-site donor nephrectomy (LESS-DN) is a relatively novel minimally invasive approach that allows the surgery to be performed via a single incision. This technique may be advantageous in decreasing surgical morbidity and improving cosmetic outcomes, thus plausibly reducing the barriers to kidney donation. The study demonstrates the safety and feasibility of LESS-DN in a large consecutive series of kidney donors. Comparative analysis between LDN and LESS-DN showed that there was a significant decrease in intra-operative blood loss and allograft warm ischaemia time in the LESS-DN group, but also a significant increase in operating time. Other peri-operative outcomes were similar between the two approaches. Evaluation of the LESS-DN cases alone revealed that, the operating times did not significantly change through the course of the series. Using this outcome as a surrogate for technical difficulty suggests a relatively shallow learning curve for LESS-DN. OBJECTIVE: To present a comparative analysis of peri-operative outcomes for >200 cases of conventional laparoscopic donor nephrectomy (LDN) and laparoendoscopic single site donor nephrectomy (LESS-DN). PATIENTS AND METHODS: From 2006 to 2011, 213 donor nephrectomies were performed by two surgeons (R.E.L and W.A.M.) at a tertiary transplant centre. The approach changed from conventional LDN to LESS-DN over the course of the series. The two approaches were compared retrospectively and evaluated for differences in peri-operative outcomes. Statistical significance was assessed using Student's t-test and chi-squared analysis. RESULTS: A total of 111 patients underwent LDN and 102 patients underwent LESS-DN. Total operating time was significantly longer in the LESS-DN group (206.1 vs 181.9 min, P < 0.001), but LESS-DN resulted in less intra-operative blood loss (61.5 mL vs 85.9 mL, P < 0.001) and shorter warm ischaemia times (4.4 vs 5.0 min, P = 0.01). There were no significant differences in analgesic requirements, subjective pain scores, length of hospital stay, postoperative graft function, or donor's postoperative glomerular filtration rate between the two approaches. Complication rates were low regardless of the approach, and there were no major complications (>grade II) in the LESS-DN group. CONCLUSIONS: In experienced hands, LESS-DN results in peri-operative outcomes similar to those of conventional LDN without compromising donor safety, while providing a desirable cosmetic result. For surgeons familiar with LDN, transitioning to the LESS approach using this technique appears to have a relatively short learning curve.

BHLHE40 drives protective polyfunctional CD4 T cell differentiation in the female reproductive tract against Chlamydia.

The protein basic helix-loop-helix family member e40 (BHLHE40) is a transcription factor recently emerged as a key regulator of host immunity to infections, autoimmune diseases and cancer. In this study, we investigated the role of Bhlhe40 in protective T cell responses to the intracellular bacterium Chlamydia in the female reproductive tract (FRT). Mice deficient in Bhlhe40 exhibited severe defects in their ability to control Chlamydia muridarum shedding from the FRT. The heightened bacterial burdens in Bhlhe40-/- mice correlated with a marked increase in IL-10-producing T regulatory type 1 (Tr1) cells and decreased polyfunctional CD4 T cells co-producing IFN-γ, IL-17A and GM-CSF. Genetic ablation of IL-10 or functional blockade of IL-10R increased CD4 T cell polyfunctionality and partially rescued the defects in bacterial control in Bhlhe40-/- mice. Using single-cell RNA sequencing coupled with TCR profiling, we detected a significant enrichment of stem-like T cell signatures in Bhlhe40-deficient CD4 T cells, whereas WT CD4 T cells were further down on the differentiation trajectory with distinct effector functions beyond IFN-γ production by Th1 cells. Altogether, we identified Bhlhe40 as a key molecular driver of CD4 T cell differentiation and polyfunctional responses in the FRT against Chlamydia.

Strasberg's Critical View: Strategy for a Safe Laparoscopic Cholecystectomy.

Background: Every year, worldwide, the celebration for patient safety is carried out; since about 2.6 million people are documented who die each year from events that can potentially be avoided during their medical care, it is even estimated that around 15% of hospital costs can be attributed to treatment resulting in patient safety. As an important part of its dissemination in the medical-surgical community, we present the following article in relation to the critical vision of safety in the bile duct, promoted and published initially by Dr Steven Strasberg, which aims to reduce the number of complications during laparoscopic cholecystectomies. Materials and methods: A bibliographic search was carried out in PubMed, Medline, Clinical Key, and Index Medicus. From May 2020 to July 2021 in Spanish and English with the following. Conclusions: Strasberg's critical view is a proposed strategy to minimize the risk to zero during laparoscopic gallbladder surgery. It consists of obtaining a plane in which the surgeon can visualize the anatomical structures that make up the bile duct, as well as its irrigation and drainage. Being able to clearly observe these structures allows the surgeon to cut freely and safely to avoid bile duct injuries which are not so uncommon during this procedure. How to cite this article: Montalvo-Javé EE, Contreras-Flores EH, Ayala-Moreno EA, et al. Strasberg's Critical View: Strategy for a Safe Laparoscopic Cholecystectomy. Euroasian J Hepato-Gastroenterol 2022;12(1):40-44.

Arcuate ligament compression as a cause of early-onset thrombosis of the hepatic artery after liver transplantation.

BACKGROUND: Early hepatic artery thrombosis (HAT) is a potentially lethal complication after orthotopic liver transplantation (OLT) requiring immediate intervention. AIM: To report an infrequent cause of HAT after OLT and by itself a controversial clinical entity, the median arcuate ligament celiac artery compression. CASE REPORT: A 59-year-old female with hepatitis C virus-induced cirrhosis, Child B, MELD 15, underwent cadaveric-donor OLT with complete vena cava exclusion. Type 1 hepatic artery anatomy was found both in the donor and the recipient, the gastroduodenal artery was ligated. During the first eight postoperative days, clinical and analytical evolution was satisfactory and Doppler ultrasound showed no abnormalities. On the ninth postoperative day, the patient developed hypovolemic shock due to bleeding at the hepatic artery anastomosis, surgical reconstruction was performed. Postoperative color Doppler showed absent hepatic artery flow and an angiography suggested celiac artery compression. The patient was explored again the same day, liberating the celiac artery from the median arcuate ligament and performing thrombectomy and reconstruction of the hepatic artery anastomosis. The patient made a satisfactory recovery and color Doppler showed adequate flow in the hepatic artery. She is alive, free of biliary complications and enjoying a good quality of life 12 months after transplantation. CONCLUSION: Median arcuate ligament celiac artery compression is an infrequent anatomical variant that should be intentionally evaluated in the recipient at the time of arterial reconstruction in OLT and specifically be considered in early HAT to allow recognition and effective correction.

Testicular asymmetry and adolescent varicoceles managed expectantly.

PURPOSE: Adolescent varicocele is often associated with testicular asymmetry. Depending on the degree of asymmetry, some physicians will recommend surgery. However, given the possibility that asynchronous growth may be transient, others advocate for a period of observation. We reviewed our outcomes in such patients who were initially treated expectantly. MATERIALS AND METHODS: We retrospectively reviewed our pediatric varicocele database. We analyzed the outcomes of patients presenting for evaluation of varicocele who were followed with serial testicular volume measurements using scrotal ultrasound or ring orchidometry and who had at least a 6-month interval between measurements. Fisher's exact test was used to compare groups based on initial and final testicular asymmetry. RESULTS: We identified 181 patients (median age 13.8 years) who were followed expectantly. Serial volume measurements had been obtained at a median interval of 12 months (interquartile range 8 to 21) between first and most recent visits. Mean percent asymmetry for the group did not change with time. Among patients who initially had less than 20% asymmetry 35% had 20% or greater asymmetry on followup, and among those with 20% or greater asymmetry initially 53% remained in that range (p = 0.007). CONCLUSIONS: Asymmetry can be a transient phenomenon. Patients with initial asymmetry can end up with significant asymmetry, and many with significant asymmetry can have catch-up growth. However, when patients have a peak retrograde flow of 38 cm per second or greater on duplex Doppler ultrasound in association with 20% or greater asymmetry spontaneous catch-up growth is unlikely to occur.

Twist1 homodimers enhance FGF responsiveness of the cranial sutures and promote suture closure.

Haploinsufficiency of the transcription factor TWIST1 is associated with Saethre-Chotzen Syndrome and is manifested by craniosynostosis, which is the premature closure of the calvaria sutures. Previously, we found that Twist1 forms functional homodimers and heterodimers that have opposing activities. Our data supported a model that within the calvaria sutures Twist1 homodimers (T/T) reside in the osteogenic fronts while Twist1/E protein heterodimers (T/E) are in the mid-sutures. Twist1 haploinsufficiency alters the balance between these dimers, favoring an increase in homodimer formation throughout the sutures. The data we present here further supports this model and extends it to integrate the Twist1 dimers with the pathways that are known to regulate cranial suture patency. This data provides the first evidence of a functional link between Twist1 and the FGF pathway, and indicates that differential regulation of FGF signaling by T/T and T/E dimers plays a central role in governing cranial suture patency. Furthermore, we show that inhibition of FGF signaling prevents craniosynostosis in Twist1(+/-) mice, demonstrating that inhibition of a signaling pathway that is not part of the initiating mutation can prevent suture fusion in a relevant genetic model of craniosynostosis.