Multiomic analysis reveals conservation of cancer-associated fibroblast phenotypes across species and tissue of origin.

Cancer-associated fibroblasts (CAFs) are integral to the solid tumor microenvironment. CAFs were once thought to be a relatively uniform population of matrix-producing cells, but single-cell RNA sequencing has revealed diverse CAF phenotypes. Here, we further probed CAF heterogeneity with a comprehensive multiomics approach. Using paired, same-cell chromatin accessibility and transcriptome analysis, we provided an integrated analysis of CAF subpopulations over a complex spatial transcriptomic and proteomic landscape to identify three superclusters: steady state-like (SSL), mechanoresponsive (MR), and immunomodulatory (IM) CAFs. These superclusters are recapitulated across multiple tissue types and species. Selective disruption of underlying mechanical force or immune checkpoint inhibition therapy results in shifts in CAF subpopulation distributions and affected tumor growth. As such, the balance among CAF superclusters may have considerable translational implications. Collectively, this research expands our understanding of CAF biology, identifying regulatory pathways in CAF differentiation and elucidating therapeutic targets in a species- and tumor-agnostic manner.

Partial Tendon Injury at the Tendon-to-Bone Enthesis Activates Skeletal Stem Cells.

The tendon enthesis plays a critical role in facilitating movement and reducing stress within joints. Partial enthesis injuries heal in a mechanically inferior manner and never achieve healthy tissue function. The cells responsible for tendon-to-bone healing remain incompletely characterized and their origin is unknown. Here, we evaluated the putative role of mouse skeletal stem cells (mSSCs) in the enthesis after partial-injury. We found that mSSCs were present at elevated levels within the enthesis following injury and that these cells downregulated TGFß signaling pathway elements at both the RNA and protein levels. Exogenous application of TGFß post-injury led to a reduced mSSC response and impaired healing, whereas treatment with a TGFß inhibitor (SB43154) resulted in a more robust mSSC response. Collectively, these data suggest that mSSCs may augment tendon-to-bone healing by dampening the effects of TGFß signaling within the mSSC niche.

Ten-year experience with laparoscopic pedicled omental flap for cerebral revascularization in patients with Moyamoya disease.

BACKGROUND: The omental flap has numerous extraperitoneal applications in reconstruction and revascularization given its favorable immunologic and angiogenic properties. In patients with Moyamoya disease, cerebral revascularization using a pedicled omental flap has proven to be a viable option following direct revascularization procedures. Historically, harvesting omentum involved laparotomy with the associated risk of complications; herein we describe outcomes from a 10-year experience of laparoscopic harvesting of pedicled omental flap for cerebral revascularization in Moyamoya patients. METHODS: A retrospective chart review was performed of all patients with Moyamoya disease who underwent laparoscopic omental cerebral transposition between 2011 and 2021. Intraoperative and postoperative complications, length of stay (LOS), and outcomes at follow-up were analyzed. RESULTS: Twenty-one patients underwent the procedure during the study period. Three intraoperative complications occurred (one segmental transverse colectomy for mesenteric injury, one converted to omental free flap, and one requiring micro anastomosis). Average overall LOS was 6 ± 6 days, with 3 ± 3.5 days in the ICU (mean±SD). Following discharge, complications included epigastric incisional hernia at the graft fascial exit site, recurrent neck pain at subcutaneous tunneling site, and partial scalp necrosis. One patient required subsequent direct bypass seven months after the initial procedure owing to the progression of the disease. All other patients had partial or complete resolution of symptoms. CONCLUSION: Our retrospective observational study indicates that laparoscopic pedicled omental flap mobilization and transposition is a safe and effective method of indirect cerebral revascularization in patients with Moyamoya disease. LEVEL OF EVIDENCE: N/A.

Integrated spatial multiomics reveals fibroblast fate during tissue repair.

In the skin, tissue injury results in fibrosis in the form of scars composed of dense extracellular matrix deposited by fibroblasts. The therapeutic goal of regenerative wound healing has remained elusive, in part because principles of fibroblast programming and adaptive response to injury remain incompletely understood. Here, we present a multimodal -omics platform for the comprehensive study of cell populations in complex tissue, which has allowed us to characterize the cells involved in wound healing across both time and space. We employ a stented wound model that recapitulates human tissue repair kinetics and multiple Rainbow transgenic lines to precisely track fibroblast fate during the physiologic response to skin injury. Through integrated analysis of single cell chromatin landscapes and gene expression states, coupled with spatial transcriptomic profiling, we are able to impute fibroblast epigenomes with temporospatial resolution. This has allowed us to reveal potential mechanisms controlling fibroblast fate during migration, proliferation, and differentiation following skin injury, and thereby reexamine the canonical phases of wound healing. These findings have broad implications for the study of tissue repair in complex organ systems.

A narrative review of the modern surgical management of pediatric choledochal cysts.

Choledochal cysts (CC) ae rare congenital dilations of the biliary tract that harbor lifelong malignancy risk. CC are treated with surgical excision and bilioenteric reconstruction. In the modern era, the surgical approach to pediatric patients has enjoyed significant innovation with regards to minimally invasive techniques. In this review, we discuss these advances, including laparoscopic, single-incision laparoscopic, and robotic strategies, with a focus on the clinical outcomes of patients undergoing these procedures. By presenting an overview of the technical pearls emphasized by pioneers of these procedures, we examine the benefits and limitations of various minimally invasive techniques and analyze the utility and effectiveness of laparoscopy and robotics in comparison to each other and open techniques. Additionally, we highlight the importance of surgeon experience and skill in the management of this rare pediatric disease and explore the significance of the surgical learning curve in minimally invasive approaches in the excision of CC. We discuss the challenge of achieving surgical competency along this learning curve, and present proposed strategies to improve skill sets in the face of low case volumes. Finally, the relative dearth of data discussing long-term follow-up in these patients is discussed, and additional research regarding outcomes, malignancy risk and surveillance, and quality of life is necessary to better understand this disease and the implications of its surgical management.

A retrospective analysis of pancreas operations in children.

BACKGROUND: Operative intervention for pediatric pancreas diseases is rare. Our goal is to gain a better understanding of the indications and outcomes relating to pancreas surgery in children. We hypothesized that these operations are safe and effective in this population. METHODS: With IRB approval, we performed a retrospective review of data of pediatric patients (<18 years) who underwent pancreas operations at Children's Medical Center in Dallas, Texas from January 2005 to December 2018. These procedures included distal, central and total pancreatectomy, pancreaticoduodenectomy, and lateral pancreatojejunostomy. Demographics, surgical indication, and operative and postoperative outcomes were examined. RESULTS: Forty-six children underwent 47 pancreas operations. Pancreatic mass was the most common indication for resection (n=28, 60%), followed by traumatic injury (n=10, 21%) and chronic pancreatitis (n=8, 17%). The overall complication rate was 0.55 (range, 0-3) complications per procedure, including 4 pancreatic leaks. The overall unexpected hospital visit rate (emergency department and readmissions) was 0.76 (range, 0-6) visits per patient. There were no mortalities. CONCLUSIONS: While pancreas operations are rare procedures in children, our data demonstrate clear indications in this population with an associated low complication rate. This retrospective series highlights the role of pancreas resection in children.

Trainee Reliance on Public Service Loan Forgiveness.

OBJECTIVE: The Public Service Loan Forgiveness (PSLF) program is an option to trainees to help alleviate federal education debt. The prevalence of PSLF utilization and how this may impact career decisions of trainees is unknown. The purpose of this study was to understand the prevalence, impact, and understanding of PSLF participation on trainees. DESIGN: IRB-approved anonymous survey asking study subjects to report demographics, financial status, and reliance on PSLF. In addition, study subjects were asked to report their participation in PSLF, the possible impact of PSLF participation on career decisions, and to identify the qualifications needed to complete PSLF. SETTING: Online anonymous survey. PARTICIPANTS: The survey was offered to all physician trainees in all specialties at the University of Texas, Southwestern, University of Wisconsin, Madison, and University of Michigan, Ann Arbor. RESULTS: There were 934 respondents, yielding a 37.6% response rate. A total of 416/934 (44.5%) respondents were actively or planning on participating in the PSLF program with 175/934 (18.7%) belonging to a surgical specialty. Those belonging to a surgical specialty were more likely to be PSLF participants compared to medical specialties (53.1% versus 42.6%, p = 0.01). For those participating in PSLF, 82/416 (19.7%) stated this participation impacted career decisions. A total of 275/934 (29.4%) respondents obtained and 437/934 (46.8%) wanted to receive formal training/lectures in regards to the PSLF program. Of those actively or planning on participating in the PSLF program, only 58/416 (13.9%) were able to correctly identify all of the qualifications/criteria to complete the program. CONCLUSIONS: A large proportion of trainees rely on the PSLF program for education loan forgiveness with approximately 20% reporting participation impacted career decisions. Additionally, the majority may not fully understand PSLF criteria. Programs should strongly consider providing a formal education regarding PSLF to their trainees.

Disrupting the Fellowship Match: COVID-19 and the Applicant Arms Race.

Resident and fellow selection carried out via "the Match" has historically relied upon in-person interviews to evaluate and rank candidates. However, the COVID-19 pandemic has required fellowship matches and the upcoming Main Residency Match® to become wholly virtual. The 2020 pediatric surgery match offers a unique case study in the benefits and shortcomings of a virtual process and begins a much-needed conversation regarding opportunities for innovation in candidate selection. For many candidates, the application cycle imposes considerable costs - financial, professional, and personal - which have only escalated over time. We draw on our experience from the most recent match cycle to discuss limitations of the traditional Match® and suggest potential solutions to improve the subspecialty interview process moving forward.

Elucidating the fundamental fibrotic processes driving abdominal adhesion formation.

Adhesions are fibrotic scars that form between abdominal organs following surgery or infection, and may cause bowel obstruction, chronic pain, or infertility. Our understanding of adhesion biology is limited, which explains the paucity of anti-adhesion treatments. Here we present a systematic analysis of mouse and human adhesion tissues. First, we show that adhesions derive primarily from the visceral peritoneum, consistent with our clinical experience that adhesions form primarily following laparotomy rather than laparoscopy. Second, adhesions are formed by poly-clonal proliferating tissue-resident fibroblasts. Third, using single cell RNA-sequencing, we identify heterogeneity among adhesion fibroblasts, which is more pronounced at early timepoints. Fourth, JUN promotes adhesion formation and results in upregulation of PDGFRA expression. With JUN suppression, adhesion formation is diminished. Our findings support JUN as a therapeutic target to prevent adhesions. An anti-JUN therapy that could be applied intra-operatively to prevent adhesion formation could dramatically improve the lives of surgical patients.

No pain is gain: A prospective evaluation of strict non-opioid pain control after pediatric appendectomy.

INTRODUCTION: Opiates are often prescribed after pediatric operations despite safety concerns and lack of evidence confirming superiority compared to other pain control modalities. In this study, we use daily parental surveys to prospectively evaluate a strict non-opioid pain control strategy after laparoscopic appendectomy. METHODS: After IRB approval, children who underwent laparoscopic appendectomy for nonperforated acute appendicitis were recruited to the study. For these patients, our standard practice is to provide instructions to administer alternating acetaminophen and ibuprofen over-the-counter (OTC) postoperatively, and no opiate prescriptions are written. Parents of enrolled children received a daily RedCap survey via text message or e-mail on postoperative days (POD) 1 through 5 to prospectively assess pain control and medication usage. Trends were compared across postoperative days. RESULTS: One hundred twenty patients were enrolled in the study, and none received opiate prescriptions. Postoperative pain survey response rates were 54% on POD1, 47% on POD2, 35% on POD3, 34% on POD4, and 29% on POD5. Pain level was 4.7 ±â€¯2.3 (out of 10) on POD1, and down-trended significantly each postoperative day to reach 0.7 ±â€¯1.2 by POD5. On POD1, 85% of parents administered OTC medications, which reduced significantly to 14% by POD5. Parent-reported success rates to manage pain by OTC regimen were 85% on POD1, 94% on POD2, 91% on POD3, and 100% on POD4 and POD5. CONCLUSION: Strict non-opioid pain control after appendectomy exhibits high performance based upon prospective parental surveys. This strategy should be implemented as standard of care and tested for application to other surgical conditions. LEVEL OF EVIDENCE: Level II.

Intraoperative Liver Biopsy During Adolescent Bariatric Surgery: Is It Really Necessary?

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is prevalent in children with obesity and is definitively diagnosed with liver biopsy. However, the utility of routine biopsy during adolescent bariatric surgery remains unknown. We describe the usefulness of routine versus selective intraoperative liver biopsy in adolescents undergoing bariatric surgery. METHODS: A retrospective review of adolescents who received bariatric surgery at our institution between 2007 and 2018 was performed. Prior to 2014, all patients routinely received intraoperative liver biopsy. After 2014, biopsy was performed selectively on an individual basis for transaminitis or clinical concern. Demographic, biochemical, and histopathologic data were compared between patients who underwent routine, selective, or no biopsy. RESULTS: There were 77 patients who received bariatric surgery during the study period: 32 underwent routine biopsy, 13 selective biopsy, and 32 no biopsy. Selective liver biopsy was more likely to show pathologic evidence of fibrosis (84.6% versus 31.2%, p = 0.000) and steatosis (100.0% versus 59.4%, p = 0.003), and higher mean NAFLD activity score compared with routine biopsies (4.4 versus 2.1, p = 0.001). Patients with steatosis had significantly higher preoperative fasting insulin (41.4 versus 21.1 mIU/L, p = 0.000), and patients with fibrosis had significantly higher glycated hemoglobin (6.1% versus 5.5%, p = 0.033) and alanine aminotransferase (81.5 versus 52.7 mg/dL, p = 0.043). There were no biopsy complications or changes in management due to biopsy results. CONCLUSIONS: Routine intraoperative liver biopsy during adolescent bariatric surgery possesses questionable benefit, as it does not appear to impact short-term postoperative management. Prospective, longitudinal studies are needed to better understand the meaningfulness of liver histopathology in this population.

A Clearing Technique to Enhance Endogenous Fluorophores in Skin and Soft Tissue.

Fluorescent proteins are used extensively in transgenic animal models to label and study specific cell and tissue types. Expression of these proteins can be imaged and analyzed using fluorescent and confocal microscopy. Conventional confocal microscopes cannot penetrate through tissue more than 4-6 µm thick. Tissue clearing procedures overcome this challenge by rendering thick specimens into translucent tissue. However, most tissue clearing techniques do not satisfactorily preserve expression of endogenous fluorophores. Using simple adjustments to the BABB (Benzoic Acid Benzyl Benzoate) clearing methodology, preservation of fluorophore expression can be maintained. Modified BABB tissue clearing is a reliable technique to clear skin and soft tissue specimens for the study of dermal biology, wound healing and fibrotic pathologies.

Skeletal Stem Cell-Schwann Cell Circuitry in Mandibular Repair.

Regenerative paradigms exhibit nerve dependency, including regeneration of the mouse digit tip and salamander limb. Denervation impairs regeneration and produces morphological aberrancy in these contexts, but the direct effect of innervation on the stem and progenitor cells enacting these processes is unknown. We devised a model to examine nerve dependency of the mouse skeletal stem cell (mSSC), the progenitor responsible for skeletal development and repair. We show that after inferior alveolar denervation, mandibular bone repair is compromised because of functional defects in mSSCs. We present mSSC reliance on paracrine factors secreted by Schwann cells as the underlying mechanism, with partial rescue of the denervated phenotype by Schwann cell transplantation and by Schwann-derived growth factors. This work sheds light on the nerve dependency of mSSCs and has implications for clinical treatment of mandibular defects.

Does Microscopic Hematuria After Pediatric Blunt Trauma Indicate Clinically Significant Injury?

BACKGROUND: Children are more likely to have urinary system injury after blunt abdominal trauma (BAT) because of anatomical vulnerabilities. Urinalysis (UA) is often performed during initial evaluation to screen for injury. The purpose of this study was to determine how often finding microscopic hematuria after BAT leads to further testing and whether this indicates a significant injury. METHODS: A retrospective review of children evaluated for BAT at Children's Health from 2013 to 2017 was performed. Patients included had microscopic hematuria on initial UA. Data collected included demographics, injury data, laboratory and imaging data, and outcomes. Analysis was performed using descriptive statistics, Fisher's exact, and independent t-test. RESULTS: Of 1059 patients treated for BAT during the study period, 203 (19%) exhibited microscopic hematuria on UA during the initial workup. Most UAs resulted after imaging was completed and did not impact management (158, 78%); twenty-two (14%) of these patients had urinary injury, which were diagnosed by imaging regardless of UA results. Forty-five (22%) patients were found to have microscopic hematuria that independently led to workup for urinary injury. Of these, nine patients had a urinary system injury: 6 low-grade renal and three bladder wall injuries, none of which required surgery. Those with and without urinary injury in this group underwent similar numbers of radiographic studies. CONCLUSIONS: Microscopic hematuria on screening UA after BAT may lead to extensive workup, regardless of the presence of symptoms. In patients who receive cross-sectional abdominal imaging, preceding UA adds little to the clinical workup of children with BAT.

The evolving relationship of wound healing and tumor stroma.

The stroma in solid tumors contains a variety of cellular phenotypes and signaling pathways associated with wound healing, leading to the concept that a tumor behaves as a wound that does not heal. Similarities between tumors and healing wounds include fibroblast recruitment and activation, extracellular matrix (ECM) component deposition, infiltration of immune cells, neovascularization, and cellular lineage plasticity. However, unlike a wound that heals, the edges of a tumor are constantly expanding. Cell migration occurs both inward and outward as the tumor proliferates and invades adjacent tissues, often disregarding organ boundaries. The focus of our review is cancer associated fibroblast (CAF) cellular heterogeneity and plasticity and the acellular matrix components that accompany these cells. We explore how similarities and differences between healing wounds and tumor stroma continue to evolve as research progresses, shedding light on possible therapeutic targets that can result in innovative stromal-based treatments for cancer.