School of Medicine

Mitochondria are crucial for cellular metabolism and signalling. Mitochondrial activity is modulated by mitochondrial fission and fusion, which are required to properly balance metabolic functions, transfer material between mitochondria, and remove defective mitochondria. Mitochondrial fission occurs at mitochondria-endoplasmic reticulum (ER) contact sites, and requires the formation of actin filaments that drive mitochondrial constriction and the recruitment of the fission protein DRP1. The role of actin in mitochondrial fusion remains entirely unexplored. Here we show that preventing actin polymerisation on either mitochondria or the ER disrupts both fission and fusion. We show that fusion but not fission is dependent on Arp2/3, whereas both fission and fusion require INF2 formin-dependent actin polymerization. We also show that mitochondria-associated actin marks fusion sites prior to the fusion protein MFN2. Together, our work introduces a method for perturbing organelle-associated actin and demonstrates a previously unknown role for actin in mitochondrial fusion.

BACKGROUND: Obesity is an independent risk factor for complications after abdominal hernia repair. Glucagon-like-peptide-1 (GLP-1) receptor agonists are gaining popularity as pharmacologic weight loss adjuncts and may help patients reach weight loss goals for surgery. We examine our early experience utilizing GLP-1 agonists versus lifestyle modifications alone to achieve weight loss in patients before elective hernia repair. METHODS: This single-center, retrospective review identified obese patients who underwent elective hernia repair from 2014 to 2023. Patients were asked to achieve a BMI ≤ 33 kg/m2 before surgery. Patients who lost weight with GLP-1 therapy in addition to lifestyle changes were compared to a control cohort that achieved similar preoperative weight loss without GLP-1 therapy. Primary outcome was mean time from GLP-1 agonist initiation and initial surgery clinic visit to surgery. Secondary outcomes were 30-day morbidity, mortality, and reoperation rates, and hernia recurrence. RESULTS: Forty-six patients with ventral/incisional, flank, umbilical, parastomal, inguinal, and hiatal hernias were identified (GLP-1 N = 24, control N = 22). 81.8% (N = 18) of controls had a ventral/incisional hernia, compared to 45.8% (N = 11) of GLP-1 patients (p = 0.03). Mean BMI at GLP-1 agonist initiation was similar to mean BMI at initial clinic visit for controls (38.1 ± 4.9 vs 38.2 ± 2.7 kg/m2, p = 0.66). Preoperative mean percentage total weight loss (14.9 ± 7.5 vs 12.4 ± 6.9 kg, p = 0.39) and mean BMI reduction (6.0 ± 3.8 vs 4.9 ± 2.3 kg/m2, p = 0.43) were similar between groups. The mean time from GLP-1 agonist initiation to surgery was significantly shorter than initial clinic visit to surgery for controls (6.3 ± 4.0 vs 14.7 ± 17.6 months, p = 0.03). There was no statistically significant difference in time from initial clinic visit to surgery between groups (7.6 ± 4.4 vs 14.7 ± 17.6 months, p = 0.06). There was no significant difference in 30-day morbidity between groups (8.3 vs 27.3%, p = 0.13). CONCLUSION: GLP-1 agonists accelerate preoperative weight loss for obese hernia patients without negatively impacting postoperative outcomes.

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BACKGROUND: Traumatic rib fractures are associated with pain lasting weeks to months and a decreased ability to inspire deeply or cough to clear secretions. Ultrasound-guided percutaneous cryoneurolysis involves reversibly ablating peripheral nerve(s) using exceptionally low temperature with a transdermal probe, resulting in a prolonged nerve block with a duration measured in months. We hypothesized that cryoneurolysis would improve analgesia and inspired volume following rib fracture. METHODS: Adults with 1-6 traumatic rib fractures were randomized to either active cryoneurolysis and a sham peripheral nerve block (PNB), or sham cryoneurolysis and active PNB in a participant/observer-masked fashion. The primary endpoint was the maximum inspired volume the day after the procedure as measured with an incentive spirometer. RESULTS: The day after the procedure, the unadjusted median [IQR] maximum inspired volume for participants who received cryoneurolysis (n=11) was 2,250 mL [1,500; 2,500] versus 1,300 mL [750; 2,500] for PNB (n=9, mean difference 496; 95%CI -428 to 1420; t-test P=0.269). When adjusted for covariates (e.g., baseline lung volume), the cryoneurolysis group had an estimated 793 mL greater mean volume than PNB (95%CI 273 to 1,312; ANCOVA P=0.005). Improvement from baseline in maximum inspired volume for cryoneurolysis was 1,000 mL [1,000; 1,375] versus 300 mL [0; 1,000] for PNB (t-test P=0.002). This was equivalent to an improvement over baseline of 100% [90%, 188%] for cryoneurolysis versus 30% [0%, 50%] for PNB (t-test P=0.003). Average daily pain scores were generally lower for the cryoneurolysis group throughout the first month. Total cumulative oxycodone equivalents were 5 mg [0, 13] for cryoneurolysis vs 45 mg [43, 135] for PNB (t-test P=0.013). CONCLUSIONS: Ultrasound-guided percutaneous cryoneurolysis improves maximum inspired lung volume while concurrently decreasing pain and opioid consumption after traumatic rib fracture. These results should be considered preliminary, requiring confirmation with a trial including a larger sample size.

Amyotrophic lateral sclerosis (ALS) is linked to the reduction of certain nucleoporins in neurons. Increased nuclear localization of charged multivesicular body protein 7 (CHMP7), a protein involved in nuclear pore surveillance, has been identified as a key factor damaging nuclear pores and disrupting transport. Using CRISPR-based microRaft, followed by gRNA identification (CRaft-ID), we discovered 55 RNA-binding proteins (RBPs) that influence CHMP7 localization, including SmD1, a survival of motor neuron (SMN) complex component. Immunoprecipitation-mass spectrometry (IP-MS) and enhanced crosslinking and immunoprecipitation (CLIP) analyses revealed CHMP7's interactions with SmD1, small nuclear RNAs, and splicing factor mRNAs in motor neurons (MNs). ALS induced pluripotent stem cell (iPSC)-MNs show reduced SmD1 expression, and inhibiting SmD1/SMN complex increased CHMP7 nuclear localization. Crucially, overexpressing SmD1 in ALS iPSC-MNs restored CHMP7's cytoplasmic localization and corrected STMN2 splicing. Our findings suggest that early ALS pathogenesis is driven by SMN complex dysregulation.

PURPOSE: From 2018-2019, the height of over 400 miles of southern border wall was raised to 30 feet. Our aim was to evaluate the impact of the increase in border wall height on upper-extremity injuries sustained via barrier fall. METHODS: A retrospective review of patients admitted with upper-extremity injuries sustained via border wall fall between January 2015 and December 2022 at a Level 1 trauma center serving the United States-Mexico border. Patients admitted between 2015-2018 were included in the preincrease group, and those admitted between 2019-2022 were included in the postincrease group. Demographic data, injury severity metrics, fracture characteristics, operative treatments, hospital charges, and lengths of stay were compared. RESULTS: In total, 110 patients were identified, with 16 preincrease and 94 postincrease. Following the barrier height increase, patients had higher injury severity scores. Radial fractures were most common pre- and postincrease and accounted for nearly one-third of all fractures. Postincrease upper-extremity trauma patients required more operative events (2.15 ± 2.10 vs 1.44 ± 0.73 preincrease). The average cost for each patients hospital stay also quadrupled after the increase in wall height ($397,632 ± $1,057,574 vs $98,978 ± $84,169 preincrease). CONCLUSIONS: The increase in overall injury severity and costly inpatient treatment of upper-extremity injuries among patients who fell from the border following construction has placed additional stress on an already strained health care system. LEVEL OF EVIDENCE: Differential Diagnosis/Symptom Prevalence Study, IV.

Transfer-RNA-derived fragments (tRFs) are a novel class of small non-coding RNAs that have been implicated in oncogenesis. tRFs may act as post-transcriptional regulators by recruiting AGO proteins and binding to highly complementary regions of mRNA at seed regions, resulting in the knockdown of the transcript. Therefore, tRFs may be critical to tumorigenesis and warrant investigation as potential biomarkers. Meanwhile, the incidence of papillary thyroid carcinoma (PTC) has increased in recent decades and current diagnostic technology stands to benefit from new detection methods. Although small non-coding RNAs have been studied for their role in oncogenesis, there is currently no standard for their use as PTC biomarkers, and tRFs are especially underexplored. Accordingly, we aim to identify dysregulated tRFs in PTC that may serve as biomarker candidates. We identified dysregulated tRFs and driver genes between PTC primary tumor samples (n = 511) and adjacent normal tissue samples (n = 59). Expression data were obtained from MINTbase v2.0 and The Cancer Genome Atlas. Dysregulated tRFs and genes were analyzed in tandem to find pairs with anticorrelated expression. Significantly anticorrelated tRF-gene pairs were then tested for potential binding affinity using RNA22-if a heteroduplex can form via complementary binding, this would support the hypothesized RNA silencing mechanism. Four tRFs were significantly dysregulated in PTC tissue (p < 0.05), with only AsnGTT 3-tRF being upregulated. Binding affinity analysis revealed that tRF-30-RY73W0K5KKOV (AsnGTT 3-tRF) exhibits sufficient complementarity to potentially bind to and regulate transcripts of SLC26A4, SLC5A8, DIO2, and TPO, which were all found to be downregulated in PTC tissue. In the present study, we identified dysregulated tRFs in PTC and found that AsnGTT 3-tRF is a potential post-transcriptional regulator and biomarker.

Older adults aged 70 and older who drive have higher crash death rates per mile driven compared to middle aged (35-54 years) adults who drive in the US. Prior studies have found that depression and or antidepressant medication use in older adults are associated with an increase in the vehicular crash rate. Using data from the prospective multi-site AAA Longitudinal Research on Aging Drivers Study, this analysis examined the independent and interdependent associations of self-reported depression and antidepressant use with driving behaviors that can increase motor vehicle crash risk such as hard braking, speeding, and night-time driving in adults over age 65. Of the 2951 participants, 6.4% reported having depression and 21.9% were on an antidepressant medication. Correcting for age, race, gender, and education level, participants on an antidepressant had increased hard braking events (1.22 [1.10-1.34]) but self-reported depression alone was not associated with changes in driving behaviors.

BACKGROUND: The present study aimed to validate the accuracy of a tumor-specific antibody to target liver metastases of colorectal cancer. METHODS: A humanized anti-CEA antibody conjugated to a fluorescent dye (M5A-IR800) was tested for targeting human colorectal cancer liver metastases (CRLMs) expressing luciferase in an orthotopic mouse model. Orthotopic mouse models of CRLMs were established by implanting fragments of a luciferase-expressing human colorectal cancer cell line, LS174T, in the liver of nude mice. Mice received 50 µg M5A-IR800 72 h prior to imaging. To test co-localization, bioluminescence imaging was performed using D-luciferin, which was given via intraperitoneal injection just prior to imaging. RESULTS: Tumors were able to be visualized non-invasively through the skin with the luciferase-luciferin signal. Intra-abdominal imaging showed accurate labeling of CRLMs with M5A-IR800, which co-localized with the luciferase-luciferin signal. CONCLUSIONS: The present results validate the accuracy of a tumor-specific anti-CEA antibody in targeting liver metastases of colorectal cancer.