Stabilization of Rapidly Progressive Cardiac Allograft Vasculopathy Using mTOR Inhibition After Heart Transplantation.

BACKGROUND: Inhibition of the mammalian target of rapamycin (mTor) pathway after heart transplantation has been associated with reduced progression of coronary allograft vasculopathy (CAV). The application of low-dose mTOR inhibition in the setting of modern immunosuppression, including tacrolimus, remains an area of limited exploration. METHODS: This retrospective study included patients who received heart transplantation between January 2009 and January 2019 and had baseline, 1-year and 2-3-year coronary angiography with intravascular ultrasound (IVUS). Intimal thickness in 5 segments along the left anterior descending artery was compared across imaging time points in patients who were transitioned to low-dose mTOR inhibitor (sirolimus) vs standard treatment with mycophenolate on a background of tacrolimus. Long-term adverse cardiovascular outcomes (revascularization, severe CAV, retransplant, and cardiovascular death) were also assessed. RESULTS: Among 216 patients (mean age 51.5 ± 11.9 years, 77.8% men, 80.1% white), 81 individuals (37.5%) were switched to mTOR inhibition. mTOR inhibition was associated with a reduction in intimal thickness by 0.05 mm (95% CI 0.02-0.07; P < 0.001). This reduction was driven by patients who met the criteria for rapidly progressive CAV 1-year post-transplant (0.12 mm; P = 0.016 for interaction). After a median follow-up of 8.6 (IQR 6.6-11) years, 40 patients had major adverse cardiovascular outcomes. The use of mTOR inhibitors was not significantly associated with cardiovascular outcomes (P = 0.669). CONCLUSION: Transitioning patients after heart transplantation to an immunosuppression regimen composed of low-dose mTOR inhibition and tacrolimus was associated with a lack of progression of CAV, particularly in those with rapidly progressive CAV at 1 year, but not with long-term cardiovascular outcomes.

Progression from normal vessel wall to atherosclerotic plaque: lessons from an optical coherence tomography study with follow-up of over 5 years.

The initial process of atherosclerotic development has not been systematically evaluated. This study aimed to observe atherosclerotic progression from normal vessel wall (NVW) to atherosclerotic plaque and examine local factors associated with such progression using > 5-year long-term follow-up data obtained by serial optical coherence tomography (OCT). A total of 49 patients who underwent serial OCT for lesions with NVW over 5 years (average: 6.9 years) were enrolled. NVW was defined as a vessel wall with an OCT-detectable three-layer structure and intimal thickness ≤ 300 µm. Baseline and follow-up OCT images were matched, and OCT cross sections with NVW > 30° were enrolled. Cross sections were diagnosed as "progression" when the NVW in these cross sections was reduced by > 30° at > 5-year follow-up. Atherogenic progression from NVW to atherosclerotic plaque was observed in 40.8% of enrolled cross sections. The incidence of microchannels in an adjacent atherosclerotic plaque within the same cross section (6.7 vs. 3.3%; p = 0.046) and eccentric distribution of atherosclerotic plaque (25.0 vs. 12.6%; p < 0.001) at baseline was significantly higher in cross sections with progression than in those without. Cross sections with progression exhibited significantly higher NVW intimal thickness at baseline than cross sections without progression (200.1 ± 53.7 vs. 180.2 ± 59.6 µm; p < 0.001). Multivariate analysis revealed that the presence of microchannels in an adjacent atherosclerotic plaque, eccentric distribution of atherosclerotic plaque, and greater NVW intimal thickness at baseline were independently associated with progression at follow-up. The presence of microchannels in an adjacent atherosclerotic plaque, eccentric distribution of atherosclerotic plaque, and greater NVW intimal thickness were potentially associated with initial atherosclerotic development from NVW to atherosclerotic plaque.

The more critical murderer of atherosclerosis than lipid metabolism: chronic stress.

BACKGROUND: The mortality of atherosclerotic cerebrovascular disease is on the rise, and changes in intimal and media thickness are a leading cause of cerebral ischemia-related death. Levels of low density lipoprotein cholesterol (LDLC), total cholesterol (TC), and chronic stress (CS) are all recognized risk factors for atherosclerosis (AS). However, the leading independent risk factor is indistinct. This study explored the effects of chronic stress, LDLC, and TC on AS and intimal and media thickness, preliminarily explored the main risk factor of AS, and analyzed the related histocyte mechanisms for macrophages and endothelial cells. METHODS: Conditions include normal, high-fat diet (HF), and HF plus CS. The correlations between intimal and media thickness and general risk factors were analyzed using χ2, Spearman's rho test, and multiple linear regression. Univariate Cox regression was used to identify potential factors that affect the non-depression time (NDT). We performed a ROC curve to determine the ability of this condition to predict the thickness. Immunohistochemistry was implemented to detect macrophagocytes and endotheliocytes. RESULTS: Based on χ2 and Spearman's rho test, LDLC, TC, and CS are all related with intimal and media thickness (P < 0.05). However, in multiple linear regression, CS is still a risk factor of thickness (P < 0.05) but LDLC and TC are not. High levels of LDLC, TC, and CS were correlated with poor NDT (P < 0.05). This condition can predict the thickness sensitively. The endarterium is richest in macrophagocytes, and the arrangement of endotheliocytes is disordered and cracked under CS. CONCLUSION: CS is the main independent risk factor for AS and intimal (and media) thickness, rather than LDLC or TC.

Pre-existing and Postoperative Intimal Hyperplasia and Arteriovenous Fistula Outcomes.

BACKGROUND: The contribution of intimal hyperplasia (IH) to arteriovenous fistula (AVF) failure is uncertain. This observational study assessed the relationship between pre-existing, postoperative, and change in IH over time and AVF outcomes. STUDY DESIGN: Prospective cohort study with longitudinal assessment of IH at the time of AVF creation (pre-existing) and transposition (postoperative). Patients were followed up for up to 3.3 years. SETTING & PARTICIPANTS: 96 patients from a single center who underwent AVF surgery initially planned as a 2-stage procedure. Veins and AVF samples were collected from 66 and 86 patients, respectively. Matched-pair tissues were available from 56 of these patients. PREDICTORS: Pre-existing, postoperative, and change in IH over time. OUTCOMES: Anatomic maturation failure was defined as an AVF that never reached a diameter > 6mm. Primary unassisted patency was defined as the time elapsed from the second-stage surgery to the first intervention. MEASUREMENTS: Maximal intimal thickness in veins and AVFs and change in intimal thickness over time. RESULTS: Pre-existing IH (>0.05mm) was present in 98% of patients. In this group, the median intimal thickness increased 4.40-fold (IQR, 2.17- to 4.94-fold) between AVF creation and transposition. However, this change was not associated with pre-existing thickness (r(2)=0.002; P=0.7). Ten of 96 (10%) AVFs never achieved maturation, whereas 70% of vascular accesses remained patent at the end of the observational period. Postoperative IH was not associated with anatomic maturation failure using univariate logistic regression. Pre-existing, postoperative, and change in IH over time had no effects on primary unassisted patency. LIMITATIONS: The small number of patients from whom longitudinal tissue samples were available and low incidence of anatomic maturation failure, which decreased the statistical power to find associations between end points and IH. CONCLUSIONS: Pre-existing, postoperative, and change in IH over time were not associated with 2-stage AVF outcomes.

A predictive model for patent ductus arteriosus seven days postpartum in preterm infants: an ultrasound-based assessment of ductus arteriosus intimal thickness within 24†h after birth.

Objectives: To develop a predictive model for patent ductus arteriosus (PDA) in preterm infants at seven days postpartum. The model employs ultrasound measurements of the ductus arteriosus (DA) intimal thickness (IT) obtained within 24 h after birth. Methods: One hundred and five preterm infants with gestational ages ranging from 27.0 to 36.7 weeks admitted within 24 h following birth were prospectively enrolled. Echocardiographic assessments were performed to measure DA IT within 24 h after birth, and DA status was evaluated through echocardiography on the seventh day postpartum. Potential predictors were considered, including traditional clinical risk factors, M-mode ultrasound parameters, lumen diameter of the DA (LD), and DA flow metrics. A final prediction model was formulated through bidirectional stepwise regression analysis and subsequently subjected to internal validation. The model's discriminative ability, calibration, and clinical applicability were also assessed. Results: The final predictive model included birth weight, application of mechanical ventilation, left ventricular end-diastolic diameter (LVEDd), LD, and the logarithm of IT (logIT). The receiver operating characteristic (ROC) curve for the model, predicated on logIT, exhibited excellent discriminative power with an area under the curve (AUC) of 0.985 (95% CI: 0.966-1.000), sensitivity of 1.000, and specificity of 0.909. Moreover, the model demonstrated robust calibration and goodness-of-fit (χ2 value = 0.560, p > 0.05), as well as strong reproducibility (accuracy: 0.935, Kappa: 0.773), as evidenced by 10-fold cross-validation. A decision curve analysis confirmed the model's broad clinical utility. Conclusions: Our study successfully establishes a predictive model for PDA in preterm infants at seven days postpartum, leveraging the measurement of DA IT. This model enables identifying, within the first 24 h of life, infants who are likely to benefit from timely DA closure, thereby informing treatment decisions.

Differential culprit plaque morphology in acute coronary syndrome: a comparison between very young patients (≤35 years) and older counterparts using optical coherence tomography.

Aims: Underlying mechanisms responsible for acute coronary syndrome (ACS) in young patients compared with older counterparts are yet to be explored with optical coherence tomography (OCT). This study aims to explore underlying mechanisms of ACS in ≤35- (very young) and >35-year-old (older counterparts) ACS patients using OCT. Methods and results: This was a prospective, single-centre, investigational study. Patients were divided into groups according to age (≤35 and >35 years) and further subdivided according to the underlying mechanism i.e. plaque rupture (PR) and plaque erosion (PE). A total of 93 patients were analysed. Thin-cap fibroatheroma (TCFA) was significantly higher among older counterparts than very young patients for both PR (80.0% vs. 31.8%, P = 0.002) and PE (66.7% vs. 6.3%, P < 0.001) groups. Microchannels were also significantly more prevalent among older than very young patients for both PR (65.0% vs. 18.2%, P = 0.004) and PE groups (55.6% vs.12.5%, P = 0.013). Macrophages were significantly higher in older than very young patients for both PR (25.0% vs. 0%, P = 0.018) and PE (44.4% vs. 0%, P = 0.003) groups. In contrast, fibrous cap thickness was greater in very young than older patients for both PR (105.71 ± 48.02 vs. 58.00 ± 15.76 µm, P < 0.001) and PE (126.67 ± 48.22 vs. 54.38 ± 24.21 µm, P < 0.001) groups. Intimal thickness was greater in older than very young patients for both PR (728.00 ± 313.92 vs. 342.27 ± 142.02 µm, P < 0.001) and PE (672.78 ± 334.57 vs. 295.00 ± 99.60 µm, P < 0.001) groups. Conclusion: Frequency of TCFA, microchannels, macrophages, and intimal thickness was significantly higher in older ACS patients compared with very young patients. However, fibrous cap thickness was significantly greater in very young ACS patients compared with older patients.

Echocardiographic assessment of intimal thickness growth of patent ductus arteriosus in neonates and analysis of influencing factors.

The spontaneous closure rate of patent ductus arteriosus (PDA) is high, and the necessity of early intervention is debated. Quantitative echocardiographic assessment of the intima in PDA has not been reported. This study evaluated intimal thickness growth in neonatal cases of PDA via echocardiography and investigated its correlation with clinical factors. Seventy-three neonates were enrolled, and echocardiography was performed three times: within 24 h post-birth (first echo), 48 h after the first echo (second echo), and before discharge (third echo). According to PDA outcome, the neonates were divided into the PDA-open group (n = 18 cases), PDA-closure at second echo group (n = 32 cases), and non-PDA at first echo group (n = 23 cases). We measured the intimal thickness (IT1 and IT2 at first and second echo, respectively), lumen diameter of ductus arteriosus (D1 and D2 at first and second echo, respectively), IT1/D1 ratio, and intimal thickness growth rate (V). Correlations between echocardiographic indicators, perinatal factors, and clinical treatment were analyzed. On first echo, the PDA-open group showed a significantly lower IT1/D1 than the combined PDA-closure group (P < 0.05). On second echo, the PDA-open group showed a significantly lower IT2 and V than the PDA-closure group as well as a significantly higher D2 (P < 0.05). Smaller gestational age correlated with a larger D2 but smaller IT2 and V (P < 0.05) and a higher level of respiratory support within 72 h post-birth correlated with a larger D2 and smaller IT 2 (P < 0.05). Increasing oxygen demand within 72 h of birth correlated with a larger D1 and D2 (P < 0.05). Echocardiographic assessment of intimal thickness growth in PDA may provide an approach for predicting spontaneous PDA closure, thereby guiding decision-making regarding early intervention.

Donor specific anti-HLA antibodies and cardiac allograft vasculopathy: A prospective study using highly automated 3-D optical coherence tomography analysis.

INTRODUCTION: Recent studies suggested potential positive correlations between HLA-specific antibodies and development of cardiac allograft vasculopathy (CAV). METHODS: This prospective two-center study investigated early progression of CAV by coronary optical coherence tomography in 1 month and 12 months after heart transplantation (HTx) in 104 patients. Detection and characterization of donor specific (DSA) and MHC class-I polypeptide-related sequence A (MICA) antibodies were performed before, 1, 6 and 12 months after transplantation. RESULTS: During the first post-HTx year, we observed a significant reduction in the mean coronary luminal area (P < .001), and progression in mean intimal thickness (IT) (P < .001). DSA and anti-MICA occurred in 17% of all patients, but no significant relationship was observed between presence of DSA/anti-MICA and IT progression within 12 months after HTx. In contrast, we observed significant association between presence of DSA (p=0.031), de-novo DSA (p=0.031), HLA Class II DSA (p=0.017) and media thickness (MT) progression. CONCLUSION: Results of our study did not identify a direct association between presence of DSA/anti-MICA and intimal thickness progression in an early period after HTx. However, we found significant relationships between DSA and media thickness progression that may identify a newly recognized immune-pathological aspect of CAV.

Helical Radiotherapy in Early Laryngeal Cancers Could Lead to Excess Local Recurrence: Lessons From a Phase II Prospective Study.

AIMS: A prospective study was conducted to investigate the feasibility and efficacy of carotid-sparing intensity-modulated radiotherapy (CSIMRT) in early glottic cancers (EGC). MATERIALS AND METHODS: Eighteen patients underwent CSIMRT using helical tomotherapy to a dose of 55 Gy/20 fractions/4 weeks. Carotid intimal thickness (CIT) at prespecified carotid levels was measured using B-mode ultrasound at 6, 18 and 36 months. Serial changes in CIT were also measured in a control prospective cohort of 18 patients with head and neck cancers receiving bilateral neck nodal radiation over the same time period (54-60 Gy/30 fraction/6 weeks). The outcomes of 18 patients undergoing CSIMRT were compared against a retrospective consecutive cohort of 41 patients with EGC to confirm comparable local control. RESULTS: No significant CIT differences were identified between patients undergoing CSIMRT versus the control group. However, four patients in the CSIMRT group had a local recurrence between 8 and 39 months. In all patients the epicentre of the recurrence was noted at the anterior part of the larynx. The 5-year local recurrence-free survival was 75.1% (95% confidence interval 56.6-99.7%). By contrast, in the group of EGC patients treated without carotid sparing, local recurrence was noted only in a single patient (patient treated with helical tomotherapy) and the 5-year local recurrence-free survival was 97.1% (95% confidence interval 91.8-100%) (Log-rank P = 0.01). CONCLUSION: We failed to show the safety of CSIMRT using helical tomotherapy in this population of EGC patients. Use of CSIMRT also did not translate into a substantial reduction in CIT until 36 months. Use of CSIMRT using rotational arc techniques such as helical tomotherapy may be associated with a greater risk of local recurrence due to intrafractional motion interplay effects.

Early detection of cardiac allograft vasculopathy using highly automated 3-dimensional optical coherence tomography analysis.

BACKGROUND: Optical coherence tomography (OCT)-based studies of cardiac allograft vasculopathy (CAV) published thus far have focused mainly on frame-based qualitative analysis of the vascular wall. Full capabilities of this inherently 3-dimensional (3D) imaging modality to quantify CAV have not been fully exploited. METHODS: Coronary OCT imaging was performed at 1 month and 12 months after heart transplant (HTx) during routine surveillance cardiac catheterization. Both baseline and follow-up OCT examinations were analyzed using proprietary, highly automated 3D graph-based optimal segmentation software. Automatically identified borders were efficiently adjudicated using our "just-enough-interaction" graph-based segmentation approach that allows to efficiently correct local and regional segmentation errors without slice-by-slice retracing of borders. RESULTS: A total of 50 patients with paired baseline and follow-up OCT studies were included. After registration of baseline and follow-up pullbacks, a total of 356 ± 89 frames were analyzed per patient. During the first post-transplant year, significant reduction in the mean luminal area (p = 0.028) and progression in mean intimal thickness (p = 0.001) were observed. Proximal parts of imaged coronary arteries were affected more than distal parts (p < 0.001). High levels of LDL cholesterol (p = 0.02) and total cholesterol (p = 0.031) in the first month after HTx were the main factors associated with early CAV development. CONCLUSIONS: Our novel, highly automated 3D OCT image analysis method for analyzing intimal and medial thickness in HTx recipients provides fast, accurate, and highly detailed quantitative data on early CAV changes, which are characterized by significant luminal reduction and intimal thickness progression as early as within the first 12 months after HTx.

Comparison of ultrasound-measured properties of the common carotid artery to tobacco smoke exposure in a cohort of Indonesian patients.

BACKGROUND: The purpose of this study was to use point-of-care ultrasound (POCUS) to investigate the relationship between tobacco smoke exposure and the characteristics of the common carotid artery (CCA). The effect of both primary and secondary smoking on CCA properties was evaluated. METHODS: We performed a prospective cross-sectional study across 20 primary care clinics in Bandung, West Java, Indonesia in July 2016. Point of care ultrasound was performed on a convenience sample of Indonesian patients presenting to clinic. The CCA wall stiffness and carotid intima-media thickness (CIMT) were measured during diastole and systole. These measurements were correlated with smoke exposure and cardiovascular disease. RESULTS: We enrolled 663 patients in the study, with 426 patients enrolled in the smoking category and 237 patients enrolled in the second-hand smoke category. There was an overall positive correlation with the measured lifestyle factors and the ultrasound-measured variables in the group of individuals who smoked. For all variables, age seemed to contribute the most out of all of the lifestyle factors for the positive changes in CIMT and CCA wall stiffness. CONCLUSION: Our data yielded correlations between CCA properties and cardiovascular risk, as well as between CIMT and arterial stiffness. We were also able to demonstrate an increase in thickness of the CIMT in patients who have been exposed by tobacco through the use of ultrasound. Further large scale studies comparing patients with multiple cardiac risk factors need to be performed to confirm the utility of ultrasound findings of cardiovascular disease and stroke.

Calcification of Human Saphenous Vein Associated with Endothelial Dysfunction: A Pilot Histopathophysiological and Demographical Study.

While the pathophysiology and clinical significance of arterial calcifications have been studied extensively, minimal focus has been placed on venous calcification deposition. In this study, we evaluated the association between calcium deposition in human saphenous vein (HSV), endothelial function, and patient demographic risk factors. Fifty-four HSV segments were collected at the time of coronary artery bypass graft (CABG) surgery. The presence or absence of calcium deposits was visualized using the Von Kossa staining method. Endothelial function was determined by measuring muscle tissue contraction with phenylephrine and relaxation with carbachol in a muscle bath. Additional segments of vein underwent histologic evaluation for preexisting intimal thickness and extracellular matrix (ECM) deposition. Patient demographics data were obtained through our institution's electronic medical record, with patient consent. Calcium was present in 16 of 54 samples (29.6%). Veins with calcium deposits had significantly greater intimal-to-medial thickness ratios (p = 0.0058) and increased extracellular collagen deposition (p = 0.0077). Endothelial relaxation was significantly compromised in calcified veins vs. those without calcium (p = 0.0011). Significant patient risk factors included age (p = 0.001) and preoperative serum creatinine (p = 0.017). Calcified veins can be characterized as having endothelial dysfunction with increased basal intimal thickness and increased ECM deposition. Patient risk factors for calcium deposits in veins were similar to those for arteries, namely, advanced age and kidney disease. Further studies are needed to determine the effect of preexisting vein calcification on short- and long-term graft patency.

Topologic distributions of vasa vasorum and lymphatic vasa vasorum in the aortic adventitia--Implications for the prevalence of aortic diseases.

BACKGROUND AND AIMS: Vasa vasorum (VV) and lymphatic vasa vasorum (LVV) form their own networks in the adventitia. VV supply the aorta with nutrition and oxygen; however, the distribution and role of LVV remains to be determined. The purpose of this study was to investigate differences in the distribution of VV and LVV along the aorta. METHODS: Aortic samples were obtained from 22 autopsy cases without medical history of aortic diseases. Aortic segments were classified as arch (Ar), descending thoracic (De), suprarenal abdominal (S-Ab), and infrarenal abdominal (I-Ab). Adventitial VV and LVV were identified immunohistochemically. RESULTS: VV were most dense in the arch aorta, becoming less dense along the aorta in more distal segments, with the lowest density occurring in the infrarenal abdominal aorta. There was a significant correlation between the numbers of VV and medial thickness in the total aortic segments (r = 0.518, p < 0.01). In contrast, there was no significant correlation between the number of LVV and medial thickness in any aortic segments. However, there was a significant correlation between the number of LVV and intimal thickness in I-Ab (r = 0.425, p < 0.05). CONCLUSIONS: The distributions of adventitial VV and LVV were characteristic along the aortic segments. Differences in the distributions may imply the prevalence of aortic diseases such as dissection, abdominal aortic aneurysm, and atherosclerotic occlusive disease in each aortic segment.

Serial assessment of vessel interactions after drug-eluting stent implantation in unprotected distal left main coronary artery disease using frequency-domain optical coherence tomography.

OBJECTIVES: This study sought to assess stent-vessel interactions after drug-eluting stent (DES) implantation in unprotected left main coronary artery (ULM) by frequency-domain optical coherence tomography (FD-OCT). BACKGROUND: Percutaneous coronary intervention using DES in ULM has been increasingly performed in routine practice. Recently, FD-OCT assessments of DES-vessel interactions have been used as surrogates for DES safety; however, there are no FD-OCT studies in ULM. METHODS: We prospectively enrolled 33 consecutive patients with ULM disease treated with sirolimus- (n = 11) and everolimus-eluting stents (n = 22). FD-OCT assessments were performed post-percutaneous coronary intervention and at 9-month follow-up. Three different segments of ULM were compared: distal (DIS), bifurcation (BIF), and ostial-body (BODY). The primary endpoints were percentages of uncovered and malapposed struts at 9-month follow-up, and the secondary endpoint was neointimal hyperplasia area. RESULTS: We analyzed 25,873 stent struts. Significant differences were demonstrated for percentage of uncovered struts (3.4%, 11.7%, and 18.7%, respectively for DIS, BIF, and BODY; p < 0.05 for all the comparisons). Malapposition was also more common in BODY (5.3%) than in DIS (0.6%) and BIF (2.0%) segments (p < 0.05 for BODY vs. DIS, and BODY vs. BIF). Equivalent neointimal hyperplasia areas were demonstrated in all segments. Acute malapposition rates led to different patterns of DES-vessel interactions at 9-month follow-up. CONCLUSIONS: Distinct patterns of DES-vessel interactions were demonstrated in different segments of ULM. Acute stent strut malapposition affects these findings.

Remarkable similarities between the hemichordate (Saccoglossus kowalevskii) and vertebrate GPCR repertoire.

Saccoglossus kowalevskii (the acorn worm) is a hemichordate belonging to the superphylum of deuterostome bilateral animals. Hemichordates are sister group to echinoderms, and closely related to chordates. S. kowalevskii has chordate like morphological traits and serves as an important model organism, helping developmental biologists to understand the evolution of the central nervous system (CNS). Despite being such an important model organism, the signalling system repertoire of the largest family of integral transmembrane receptor proteins, G protein-coupled receptors (GPCRs) is largely unknown in S. kowalevskii. Here, we identified 260 unique GPCRs and classified as many as 257 of them into five main mammalian GPCR families; Glutamate (23), Rhodopsin (212), Adhesion (18), Frizzled (3) and Secretin (1). Despite having a diffuse nervous system, the acorn worm contains well conserved orthologues for human Adhesion and Glutamate family members, with a similar N-terminal domain architecture. This is particularly true for genes involved in CNS development and regulation in vertebrates. The average sequence identity between the GPCR orthologues in human and S. kowalevskii is around 47%, and this is same as observed in couple of the closest vertebrate relatives, Ciona intestinalis (41%) and Branchiostoma floridae (~47%). The Rhodopsin family has fewer members than vertebrates and lacks clear homologues for 6 of the 13 subgroups, including olfactory, chemokine, prostaglandin, purine, melanocyte concentrating hormone receptors and MAS-related receptors. However, the peptide and somatostatin binding receptors have expanded locally in the acorn worm. Overall, this study is the first large scale analysis of a major signalling gene superfamily in the hemichordate lineage. The establishment of orthologue relationships with genes involved in neurotransmission and development of the CNS in vertebrates provides a foundation for understanding the evolution of signal transduction and allows for further investigation of the hemichordate neurobiology.