Identifying heterogeneous micromechanical properties of biological tissues via physics-informed neural networks.

The heterogeneous micromechanical properties of biological tissues have profound implications across diverse medical and engineering domains. However, identifying the full-field heterogeneous elastic properties of soft materials using traditional computational and engineering approaches is fundamentally challenging due to difficulties in estimating local stress fields. Recently, there has been a growing interest in using data-driven models to learn full-field mechanical responses such as displacement and strain from experimental or synthetic data. However, research studies on inferring the full-field elastic properties of materials, a more challenging problem, are scarce, particularly for large deformation, hyperelastic materials. Here, we propose a physics-informed machine learning approach to identify the elastic modulus distribution in nonlinear, large deformation hyperelastic materials. We evaluate the prediction accuracies and computational efficiency of physics-informed neural networks (PINNs) on inferring the heterogeneous material parameter maps across three nonlinear materials with structural complexity that closely resemble real tissue patterns, such as brain tissue and tricuspid valve tissue. Our improved PINN architecture accurately estimates the full-field elastic properties of three hyperelastic constitutive models, with relative errors of less than 5% across all examples. This research has significant potential for advancing our understanding of micromechanical behaviors in biological materials, impacting future innovations in engineering and medicine.

Hospital and departmental level strategies for managing the impact of adverse events on surgeons.

Adverse events have a profound impact on surgeons. This impact extends to physical and mental health, psychological wellbeing, and professional performance. Surgeons are ill prepared for these consequences of adverse events and are under-supported when they inevitably occur. Here we review the data on how adverse events affect surgeons. We explore the efforts made to date to both prepare surgeons before and support them after such events and we make recommendations regarding how this should and could be done better.

Contemporary Outcomes of Grade-C Postoperative Pancreatic Fistula in a Nationwide Database.

INTRODUCTION: Grade-C postoperative pancreatic fistulas (POPFs) are dreaded complications following pancreaticoduodenectomy. The aim of this study was to quantify the incidence and risk factors associated with grade C POPF in a national database. METHODS: The National Surgical Quality Improvement Program targeted user files were queried for patients who underwent elective pancreaticoduodenectomy (2014-2020). Outcomes were compared between clinically relevant (CR) grade B POPF and grade C POPF. RESULTS: Twenty-six thousand five hundred fifty-two patients were included, of which 90.1% (n = 23,714) had No CR POPF, 8.7% (n = 2287) suffered grade B POPF, and 1.2% (n = 327) suffered grade C POPF. There was no change in the rate Grade-C fistula overtime (m = 0.06, P = 0.63), while the rate of Grade-B fistula significantly increased (m = +1.40, P < 0.01). Fistula Risk Scores were similar between grade B and C POPFs (high risk: 34.9% versus 31.2%, P = 0.21). Associated morbidity was increased with grade C POPF, including delayed gastric emptying, organ space infections, wound dehiscence, respiratory complications, renal complications, myocardial infarction, and bleeding. On multivariate logistic regression, diabetes mellitus (odds ratio: 1.41 95% confidence interval: 1.06-1.87, P = 0.02) was associated with grade C POPF. CONCLUSIONS: This study represents the largest contemporary series evaluating grade C POPFs. Of those suffering CR POPF, the presence of diabetes mellitus was associated with grade C POPF. While modern management has led to grade C POPF in 1% of cases, they remain associated with alarmingly high morbidity and mortality, requiring further mitigation strategies to improve outcomes.

Esophageal Lichen Planus: A Descriptive Multicenter Report.

GOALS: To better understand the characteristics, treatment approaches, and outcomes of patients with esophageal lichen planus (ELP). BACKGROUND: ELP is a rare, often unrecognized and misdiagnosed disorder. Data on this unique patient population are currently limited to small, single-center series. STUDY: A multicenter, retrospective descriptive study was conducted of adults diagnosed with ELP over a 5-year period, between January 1, 2015, and October 10, 2020, from 7 centers across the United States. RESULTS: Seventy-eight patients (average age 65 y, 86% female, 90% Caucasian) were included. Over half had at least 1 extraesophageal manifestation. Esophageal strictures (54%) and abnormal mucosa (50%) were frequent endoscopic findings, with the proximal esophagus the most common site of stricture. Approximately 20% had normal endoscopic findings. Topical steroids (64%) and/or proton pump inhibitors (74%) dominated management; endoscopic response favored steroids (43% vs. 29% respectively). Almost half of the patients required switching treatment modalities during the study period. Adjunctive therapies varied significantly between centers. CONCLUSIONS: Given its at times subtle clinical and endoscopic signs, a high index of suspicion and biopsy will improve ELP diagnosis, especially in those with extraesophageal manifestations. Effective therapies are lacking and vary significantly. Prospective investigations into optimal treatment regimens are necessary.

Quantification of Mucosal Mast Cells in the Gastrointestinal Tract: A Primer for Practicing Pathologists.

CONTEXT.­: Mast cells are essential components of the immune system and play crucial pathogenetic roles in several digestive diseases, including mastocytic enterocolitis and eosinophilic gastrointestinal disorders. Pathologists have rarely been asked to evaluate the distribution and density of mast cells in gastrointestinal (GI) biopsy specimens. However, such requests are becoming more common because of an increasing awareness of the role of mast cells in functional GI disease and in both esophageal and nonesophageal eosinophilic gastrointestinal disorders. OBJECTIVE.­: To provide pathologists with tools to incorporate the assessment of mast cells in the evaluation of esophageal, gastric, and intestinal specimens by developing a systematic approach to their evaluation, counting, and reporting. DESIGN.­: This study consisted of a review of the literature followed by multiple consensus sessions to decide where to count mast cells and what a countable mast cell is. RESULTS.­: We reviewed 135 papers addressing the content of mast cells in the digestive tract, selected 21 that detailed how cells were counted (microscope lens, area of high-power fields, locations evaluated, type of cells considered as countable), and summarized their data in a table. Then, drawing from both the acceptable literature and our own extensive experience, we reached a tentative consensus on: (1) the normal numbers in the different segments of the GI tract; (2) the morphology of countable mast cells; and (3) the locations and strategies for counting them. CONCLUSIONS.­: The result is a set of suggestions for reporting mast cell counts, their distribution, and their location in a way clinicians can understand and use for management decisions.

ASO Practice Guidelines Series: Management of Resectable, Borderline Resectable, and Locally Advanced Pancreas Cancer.

Pancreatic adenocarcinoma is an aggressive disease marked by high rates of both local and distant failure. In the minority of patients with potentially resectable disease, multimodal treatment paradigms have allowed for prolonged survival in an increasingly larger pool of well-selected patients. Therefore, it is critical for surgical oncologists to be abreast of current guideline recommendations for both surgical management and multimodal therapy for pancreas cancer. We discuss these guidelines, as well as the underlying data supporting these positions, to offer surgical oncologists a framework for managing patients with pancreatic adenocarcinoma.

Defining the operative time threshold for safety in patients undergoing robotic pancreaticoduodenectomy.

BACKGROUND: Robotic pancreaticoduodenectomy (RPD) is a safe and efficacious procedure in appropriately selected patients, though frequently with increased operative times compared to open pancreaticoduodenectomy (OPD). METHODS: From 2014 to 2019, patients who underwent elective, low-risk, RPDs and OPDs in the NSQIP database were isolated. The operative time threshold (OTT) for safety in RPD patients was estimated by identifying the operative time at which complication rates for RPD patients exceeded the complication rate of the benchmark OPD control. RESULTS: Of 6270 patients identified, 939 (15%) underwent RPD and 5331 (85%) underwent OPD. The incidence of major morbidity or mortality for the OPD cohort was 35.1%. The OTT was identified as 7.7 h. Patients whose RPDs were above the OTT experienced a higher incidence of major morbidity (42.5% vs. 35.0%, p < 0.01) and 30-day mortality (2.7% vs. 1.2%, p = 0.03) than the OPD cohort. Preoperative obstructive jaundice (OR: 1.47, [95% CI: 1.08-2.01]) and pancreatic duct size <3 mm (OR: 2.44, [95% CI: 1.47-4.06]) and 3-6 mm (OR: 2.15, [95% CI: 1.31-3.52]) were risk factors for prolonged RPDs on multivariable regression. CONCLUSION: The operative time threshold for safety, identified at 7.7 h, should be used to improve patient selection for RPDs and as a competency-based quality benchmark.

Determination of Optimal Eosinophil Thresholds for Diagnosis of Eosinophilic Gastritis and Duodenitis: A Pooled Analysis of 4 Prospective Studies.

INTRODUCTION: Consensus is lacking regarding the number of eosinophils (eos) required for the diagnosis of eosinophilic gastritis (EoG) and eosinophilic duodenitis (EoD). In addition, thresholds that require multiple high-power fields (HPFs) may not be practical for clinical use, resulting in delayed or missed diagnoses. This pooled analysis of 4 prospective studies assessed thresholds for multiple and single HPFs used to diagnose EoG and EoD. METHODS: Studies included the phase 2 ENIGMA1, the phase 3 ENIGMA2, an EoG/EoD prevalence study and a healthy volunteer study. Eos were quantified in the epithelium and lamina propria for controls and symptomatic participants. Symptomatic participants were further divided by histologic diagnosis of EoG/EoD. Peak eos counts were assessed, and the area under the receiver operating characteristic curve was analyzed to identify eos cutoffs for detection of EoG/EoD using the Youden index and sensitivity and specificity equality approaches. RESULTS: Based on the highest specificity analysis in 740 patients, the optimal eos threshold was determined to be 20 eos/HPF in 5 gastric HPFs for EoG (71% sensitivity and 94% specificity) and 33 eos/HPF in 3 duodenal HPFs for EoD (49% sensitivity and 100% specificity). For single-field analysis, the optimal eos thresholds were 33 eos/HPF (EoG) and 37 eos/HPF (EoD), both corresponding to 93% sensitivity and 93% specificity. DISCUSSION: Highly specific single gastric and duodenal HPF thresholds may have more clinical applicability than thresholds requiring multiple HPFs and could better facilitate development of practical histopathologic guidelines to aid pathologists and clinicians in the detection and diagnosis of EoG and/or EoD.

Proximity to Swine Farming Operations as a Risk Factor for Eosinophilic Esophagitis.

We aimed to determine whether residential proximity to permitted swine facilities was associated with an increased risk of eosinophilic esophagitis (EoE) by conducting a case-control study using 2 complementary data sources: 1 from a tertiary care center (n = 401 cases and 1805 controls) and 1 from a large pathology group (n = 904 cases and 4074 controls). Addresses of the subjects and swine facilities were geocoded, and adjusted odds of EoE relative to proximity to and density of swine facilities were calculated. We observed a positive association between proximity to a permitted swine facility (<1 mile) and odds of EoE (adjusted odds ratio R, 2.56; 95% CI, 1.33-4.95) in the tertiary center data; density of farms (>10 farms/census tract) was also positively associated (adjusted odds ratio, 2.76; 95% CI, 1.30-5.84). However, this association was not observed in the pathology database. Though proximity to and density of swine operations were associated with EoE, associations were sensitive to the database used.

Feeding Jejunostomy Tube in Patients Undergoing Esophagectomy: Utilization and Outcomes in a Nationwide Cohort.

BACKGROUND: Feeding jejunostomy (JT) tubes are often utilized as an adjunct to optimize nutrition for successful esophagectomy; however, their utility has come into question. The aim of this study was to evaluate utilization and outcomes associated with JTs in a nationwide cohort of patients undergoing esophagectomy. METHODS: The NSQIP database was queried for patients who underwent elective esophagectomy. JT utilization was assessed between 2010 and 2019. Post-operative outcomes were compared between those with and without a JT on patients with esophagectomy-specific outcomes (2016-2019), with results validated using a propensity score-matched (PSM) analysis based on key clinicopathologic factors, including tumor stage. RESULTS: Of the 10,117 patients who underwent elective esophagectomy over the past decade, 53.0% had a JT placed concurrently and 47.0% did not. Utilization of JTs decreased over time, accounting for 60.0% of cases in 2010 compared to 41.7% in 2019 (m = - 2.14 95%CI: [- 1.49]-[- 2.80], p < 0.01). Patients who underwent JT had more composite wound complications (17.0% vs. 14.1%, p = 0.02) and a higher rate of all-cause morbidity (40.4% vs. 35.5%, p = 0.01). Following PSM, 1007 pairs were identified. Analysis of perioperative outcomes demonstrated a higher rate of superficial skin infections (6.1% vs. 3.5%, p = 0.01) in the JT group. However, length of stay, reoperation, readmission, anastomotic leak, composite wound complications, all-cause morbidity, and mortality rates were similar between groups. CONCLUSIONS: Among patients undergoing elective esophagectomy, feeding jejunostomy tubes were utilized less frequently over the past decade. Similar perioperative outcomes among matched patients support the safety of esophagectomy without an adjunct feeding jejunostomy tube.

Significant Differences in Capsid Properties and Potency Between Adeno-Associated Virus Vectors Produced in Sf9 and HEK293 Cells.

For successful vector-based gene therapy manufacturing, the selected adeno-associated virus (AAV) vector production system must produce vector at sufficient scale. However, concerns have arisen regarding the quality of vector produced using different systems. In this study, we compared AAV serotypes 1, 8, and 9 produced by two different systems (Sf9/baculovirus and HEK293/transfection) and purified by two separate processes. We evaluated capsid properties, including protein composition, post-translational modification, particle content profiles, and in vitro and in vivo vector potency. Vectors produced in the Sf9/baculovirus system displayed reduced incorporation of viral protein 1 and 2 into the capsid, increased capsid protein deamidation, increased empty and partially packaged particles in vector preparations, and an overall reduced potency. The differences observed were largely independent of the harvest method and purification process. These findings illustrate the need for careful consideration when choosing an AAV vector production system for clinical production.

Arousal state transitions occlude sensory-evoked neurovascular coupling in neonatal mice.

In the adult sensory cortex, increases in neural activity elicited by sensory stimulation usually drive vasodilation mediated by neurovascular coupling. However, whether neurovascular coupling is the same in neonatal animals as adults is controversial, as both canonical and inverted responses have been observed. We investigated the nature of neurovascular coupling in unanesthetized neonatal mice using optical imaging, electrophysiology, and BOLD fMRI. We find in neonatal (postnatal day 15, P15) mice, sensory stimulation induces a small increase in blood volume/BOLD signal, often followed by a large decrease in blood volume. An examination of arousal state of the mice revealed that neonatal mice were asleep a substantial fraction of the time, and that stimulation caused the animal to awaken. As cortical blood volume is much higher during REM and NREM sleep than the awake state, awakening occludes any sensory-evoked neurovascular coupling. When neonatal mice are stimulated during an awake period, they showed relatively normal (but slowed) neurovascular coupling, showing that that the typically observed constriction is due to arousal state changes. These result show that sleep-related vascular changes dominate over any sensory-evoked changes, and hemodynamic measures need to be considered in the context of arousal state changes.

Ecosystem responses of shallow thermokarst lakes to climate-driven hydrological change: Insights from long-term monitoring of periphytic diatom community composition at Old Crow Flats (Yukon, Canada).

Shallow waterbodies are abundant in Arctic and subarctic landscapes where they provide productive wildlife habitat and hold cultural and socioeconomic importance for Indigenous communities. Their vulnerability to climate-driven hydrological and limnological changes enhances a need for long-term monitoring data capable of tracking aquatic ecosystem responses. Here, we evaluate biological and inferred physicochemical responses associated with a rise in rainfall-generated runoff and increasingly positive lake water balances in Old Crow Flats (OCF), a 5600 km2 thermokarst landscape in northern Yukon. This is achieved by analyzing periphytic diatom community composition in biofilms accrued on artificial-substrate samplers at 14 lakes collected mostly annually during 2008-2019 CE. Results reveal that diatom communities at 10 of the 14 lakes converged toward a composition typical of lakes with rainfall-dominated input waters. These include six of nine lakes that were not initially dominated by rainfall input. The shifts in diatom community composition infer rise of lake-water pH and ionic content, and they reveal that northern shallow lake ecosystems are responsive to climate-driven increases in rainfall. Based on data generated during the 12 -year-long monitoring period, we conclude that lakes located centrally within OCF are most vulnerable to rapid climate-driven hydroecological change due to flat terrain, larger lake surface area, and sparse terrestrial vegetation, which provide less resistance to lake expansion, shoreline erosion, and sudden drainage. This information assists the local Indigenous community and natural resource stewardship agencies to anticipate changes to traditional food sources and inform adaptation options.

Acid sphingomyelinase expression is associated with survival in resectable pancreatic ductal adenocarcinoma.

Pancreatic adenocarcinoma (PDAC) is one of the most common cancers worldwide. Unfortunately, the prognosis of PDAC is rather poor, and for instance, in the USA, over 47,000 people die because of pancreatic cancer annually. Here, we demonstrate that high expression of acid sphingomyelinase in PDAC strongly correlates with long-term survival of patients, as revealed by the analysis of two independent data sources. The positive effects of acid sphingomyelinase expression on long-term survival of PDAC patients were independent of patient demographics as well as tumor grade, lymph node involvement, perineural invasion, tumor stage, lymphovascular invasion, and adjuvant therapy. We also demonstrate that genetic deficiency or pharmacological inhibition of the acid sphingomyelinase promotes tumor growth in an orthotopic mouse model of PDAC. This is mirrored by a poorer pathologic response, as defined by the College of American Pathologists (CAP) score for pancreatic cancer, to neoadjuvant therapy of patients co-treated with functional inhibitors of the acid sphingomyelinase, in particular tricyclic antidepressants and selective serotonin reuptake inhibitors, in a retrospective analysis. Our data indicate expression of the acid sphingomyelinase in PDAC as a prognostic marker for tumor progression. They further suggest that the use of functional inhibitors of the acid sphingomyelinase, at least of tricyclic antidepressants and selective serotonin reuptake inhibitors in patients with PDAC, is contra-indicated. Finally, our data also suggest a potential novel treatment of PDAC patients with recombinant acid sphingomyelinase. KEY MESSAGES: Pancreatic ductal adenocarcinoma (PDAC) is a common tumor with poor prognosis. Expression of acid sphingomyelinase (ASM) determines outcome of PDAC. Genetic deficiency or pharmacologic inhibition of ASM promotes tumor growth in a mouse model. Inhibition of ASM during neoadjuvant treatment for PDAC correlates with worse pathology. ASM expression is a prognostic marker and potential target in PDAC.

Biomechanical Impact of Pathogenic MYBPC3 Truncation Variant Revealed by Dynamically Tuning In Vitro Afterload.

Engineered cardiac microtissues were fabricated using pluripotent stem cells with a hypertrophic cardiomyopathy associated c. 2827 C>T; p.R943x truncation variant in myosin binding protein C (MYBPC3+/-). Microtissues were mounted on iron-incorporated cantilevers, allowing manipulations of cantilever stiffness using magnets, enabling examination of how in vitro afterload affects contractility. MYPBC3+/- microtissues developed augmented force, work, and power when cultured with increased in vitro afterload when compared with isogenic controls in which the MYBPC3 mutation had been corrected (MYPBC3+/+(ed)), but weaker contractility when cultured with lower in vitro afterload. After initial tissue maturation, MYPBC3+/- CMTs exhibited increased force, work, and power in response to both acute and sustained increases of in vitro afterload. Together, these studies demonstrate that extrinsic biomechanical challenges potentiate genetically-driven intrinsic increases in contractility that may contribute to clinical disease progression in patients with HCM due to hypercontractile MYBPC3 variants.

Evaluation of BASE eConsult Manitoba: patient perspectives on the use of electronic consultation to improve access to specialty advice in Manitoba.

BACKGROUND: The burden of waiting to access specialist expertise may contribute to poorer health outcomes and causes distress for patients and providers. One solution to improve access to specialist care is to use innovative tools such as remote asynchronous electronic consultation (eConsult). Modeled after the Champlain BASE™ (Building Access to Specialist Advice) eConsult service, BASE™ eConsult Manitoba was launched in 2017 to help address long waits for patients to access specialist advice. OBJECTIVE: We aimed to evaluate patients' experiences after obtaining a BASE™ eConsult Manitoba service in their primary care setting. METHODS: Patients whose Primary Care Providers (PCPs) used BASE™ eConsult as part of their care were asked to participate and complete a telephone-based or online 29-question survey between January 2021 and October 2021. The survey questions were created in consultation with patient partners and based on questions asked in studies done in other jurisdictions. RESULTS: Of the 36 patients who chose to participate, 29 completed the entire survey (80%). Two-thirds (n = 22) agreed that eConsult has been helpful in their situation, and over 80% (n = 24) of participants agreed that eConsult was an acceptable way to access specialist care. During the visit when their PCP sent the eConsult, 7 patients were expecting to be referred to a specialist for a face-to-face consultation. Over half of all respondents (n = 15) reported that before the eConsult occurred, their PCP asked them what questions they wanted to be answered by the specialist. Almost all of these respondents' questions were fully answered by the eConsult. All of the respondents were satisfied with the experience of receiving an eConsult. CONCLUSION: Using eConsult is an acceptable way to improve access to specialist advice from patients' perspectives. Consideration should be given to expanding the use of eConsult services to improve access to specialist expertise for PCPs and their patients.

Incomplete Intestinal Metaplasia Is Rare in Autoimmune Gastritis.

BACKGROUND: Incomplete intestinal metaplasia (IM) is reportedly associated with higher gastric cancer (GC) risk than its complete variant. AGA Guidelines recommend including IM subtyping in routine pathology reports. This study assesses the prevalence of complete versus incomplete IM in gastric conditions with different GC risks. METHODS: IM subtyping (complete vs. incomplete) and grading (IM extension: G1: ≤30%; G2: >30%) were assessed in 386 patients with IM + ve gastric biopsy sets that included both antral and oxyntic samples. Cases were categorized as: (a) IM foci in otherwise normal mucosa (n = 59); (b) Helicobacter pylori gastritis (n = 138); (c) reactive gastropathy (141); and (d) autoimmune atrophic gastritis (AIG, n = 48). Odds ratios (OR) and their 95% CI were used in comparing the prevalence of incomplete IM and the correlation between subtype and IM extension. RESULTS: Incomplete IM was present in 37.7% of patients with H. pylori gastritis, 8.3% of those with AIG 5.0% of those with reactive gastropathy, and none of those with otherwise normal mucosa. Incomplete IM was strongly associated with more extensive (G2-IM) mucosal intestinalization (OR = 6.69; 95% CI = 2.77-9.40). CONCLUSION: Incomplete IM is significantly more prevalent in conditions (H. pylori gastritis) known to carry a higher risk of GC and is strongly associated with its extension. The low prevalence of incomplete IM in AIG (8.3%) and reactive gastropathy (5.2%) is in keeping with the low GC risk associated with these conditions.