Lin28 enhances tissue repair by reprogramming cellular metabolism.

Regeneration capacity declines with age, but why juvenile organisms show enhanced tissue repair remains unexplained. Lin28a, a highly conserved RNA-binding protein expressed during embryogenesis, plays roles in development, pluripotency, and metabolism. To determine whether Lin28a might influence tissue repair in adults, we engineered the reactivation of Lin28a expression in several models of tissue injury. Lin28a reactivation improved hair regrowth by promoting anagen in hair follicles and accelerated regrowth of cartilage, bone, and mesenchyme after ear and digit injuries. Lin28a inhibits let-7 microRNA biogenesis; however, let-7 repression was necessary but insufficient to enhance repair. Lin28a bound to and enhanced the translation of mRNAs for several metabolic enzymes, thereby increasing glycolysis and oxidative phosphorylation (OxPhos). Lin28a-mediated enhancement of tissue repair was negated by OxPhos inhibition, whereas a pharmacologically induced increase in OxPhos enhanced repair. Thus, Lin28a enhances tissue repair in some adult tissues by reprogramming cellular bioenergetics. PAPERCLIP:

Improving clinical documentation of evaluation and management care and patient acuity improves reimbursement as well as quality metrics.

OBJECTIVE: Accurate documentation of patient care and acuity is essential to determine appropriate reimbursement as well as accuracy of key publicly reported quality metrics. We sought to investigate the impact of standardized note templates by inpatient advanced practice providers (APPs) on evaluation and management (E/M) charge capture, including outside of the global surgical package (GSP), and quality metrics including case mix index (CMI) and mortality index (MI). We hypothesized this clinical documentation initiative as well as improved coding of E/M services would result in increased reimbursement and quality metrics. METHODS: A documentation and coding initiative on the heart and vascular service line was initiated in 2016 with focus on improving inpatient E/M capture by APPs outside the GSP. Comprehensive training sessions and standardized documentation templates were created and implemented in the electronic medical record. Subsequent hospital care E/M (current procedural terminology codes 99231, 99232, 99233) from the years 2015 to 2017 were audited and analyzed for charge capture rates, collections, work relative value units (wRVUs), and billing complexity. Data were compared over time by standardizing CMS values and reimbursement rates. In addition, overall CMI and MI were calculated each year. RESULTS: One year following the documentation initiative, E/M charges on the vascular surgery service line increased by 78.5% with a corresponding increase in APP charges from 0.4% of billable E/M services to 70.4% when compared with pre-initiative data. The charge capture of E/M services among all inpatients rose from 21.4% to 37.9%. Additionally, reimbursement from CMS increased by 65% as total work relative value units generated from E/M services rose by 78.4% (797 to 1422). The MI decreased over the study period by 25.4%. Additionally, there was a corresponding 5.6% increase in the cohort CMI. Distribution of E/M encounter charges did not vary significantly. Meanwhile, the prevalence of 14 clinical comorbidities in our cohort as well as length of stay (P = .88) remained non-statistically different throughout the study period. CONCLUSIONS: Accurate clinical documentation of E/M care and ultimately inpatient acuity is critical in determining quality metrics that serve as important measures of overall hospital quality for CMS value-based payments and rankings. A system-based documentation initiative and expanded role of inpatient APPs on vascular surgery teams significantly improved charge capture and reimbursement outside the GSP as well as CMI and MI in a consistently complex patient population.

Frailty and Biomarkers of Frailty Predict Outcome in Veterans After Open and Endovascular Revascularization.

BACKGROUND: Frailty predicts poor outcome after vascular surgery. We determined the predictive utility of the modified frailty index (mFI) after first-time revascularization and identified biomarkers of frailty predictive of outcome in veterans with peripheral arterial disease. METHODS: A retrospective study was performed of first-time revascularizations (open surgery [OS] and endovascular surgery [ES]) in male veterans (2003-2016). Preoperative mFI scores were calculated, and serum and nonserum biomarkers of frailty were recorded. The primary endpoint was 2-y incidence of reintervention, amputation, and mortality. Secondary endpoints included 30-day morbidity and readmissions. RESULTS: Four hundred and thirty one patients (OS, n = 188; ES, n = 243), mean age of 66 ± 9 y, and 16 mo of median follow-up were studied. Mean mFI was 0.39 ± 0.16 for OS and 0.38 ± 0.15 for ES (P = 0.43). 30-day complications (adjusted odds ratio, 4.89; 95% confidence interval [CI]: 1.67-14.33) and readmissions (adjusted hazard ratio [aHR] 3.32; 95% CI: 1.16-9.55) were increased in the OS versus ES group when stratified by mFI. Survival analysis showed a correlation between risk of amputation, death, and composite outcome with increasing mFI (P < 0.005) in both groups. Frailty independently predicted major amputation (aHR 2.16; 1.06-4.39), mortality (aHR 2.62; 95% CI: 1.17-5.88), and composite outcome (aHR 1.97; 95% CI: 1.06-3.68) when the groups are combined. Except for absolute neutrophil count, all preoperative lab values correlated with mFI (P < 0.5). Higher albumin was independently associated with lower risk of amputation (aHR: 0.58 [0.36-0.94]) and mortality (aHR: 0.45 [0.25-0.83]); higher hemoglobin predicted limb salvage (aHR 0.7 [0.62-0.84]). CONCLUSIONS: Frailty predicts short- and long-term outcomes after first-time revascularization in veterans. Hypoalbuminemia and anemia are associated with higher mFI and independently predict poor outcome, suggesting albumin and hemoglobin are viable biomarkers of frailty in veterans.

Lin28a regulates germ cell pool size and fertility.

Overexpression of LIN28A is associated with human germ cell tumors and promotes primordial germ cell (PGC) development from embryonic stem cells in vitro and in chimeric mice. Knockdown of Lin28a inhibits PGC development in vitro, but how constitutional Lin28a deficiency affects the mammalian reproductive system in vivo remains unknown. Here, we generated Lin28a knockout (KO) mice and found that Lin28a deficiency compromises the size of the germ cell pool in both males and females by affecting PGC proliferation during embryogenesis. Interestingly however, in Lin28a KO males, the germ cell pool partially recovers during postnatal expansion, while fertility remains impaired in both males and females mated to wild-type mice. Embryonic overexpression of let-7, a microRNA negatively regulated by Lin28a, reduces the germ cell pool, corroborating the role of the Lin28a/let-7 axis in regulating the germ lineage.

Fetal deficiency of lin28 programs life-long aberrations in growth and glucose metabolism.

LIN28A/B are RNA binding proteins implicated by genetic association studies in human growth and glucose metabolism. Mice with ectopic over-expression of Lin28a have shown related phenotypes. Here, we describe the first comprehensive analysis of the physiologic consequences of Lin28a and Lin28b deficiency in knockout (KO) mice. Lin28a/b-deficiency led to dwarfism starting at different ages, and compound gene deletions showed a cumulative dosage effect on organismal growth. Conditional gene deletion at specific developmental stages revealed that fetal but neither neonatal nor adult deficiency resulted in growth defects and aberrations in glucose metabolism. Tissue-specific KO mice implicated skeletal muscle-deficiency in the abnormal programming of adult growth and metabolism. The effects of Lin28b KO could be rescued by Tsc1 haplo-insufficiency in skeletal muscles. Our data implicate fetal expression of Lin28a/b in the regulation of life-long effects on metabolism and growth, and demonstrate that fetal Lin28b acts at least in part via mTORC1 signaling.

A Hybrid Internal Iliac Artery Reconstruction for Open Common Iliac Artery Aneurysm Repair.

Common iliac artery (CIA) aneurysms present across a spectrum of anatomic variants that can pose unique operative challenges. A wide variety of procedural approaches have been described in the literature with current therapeutic options including both open and endovascular repair. These techniques may involve either ligation or embolization of the internal iliac artery (IIA) with reliance on collateralized blood flow to the pelvis to mitigate postoperative complications. However, preservation of the IIA is often preferred. This case report describes a hybrid surgical approach for treating CIA aneurysms while preserving IIA perfusion. Our technique mitigates the risks of hypogastric artery dissection (including hypogastric vein injury) in the presence of a large CIA aneurysm.

LIN28 phosphorylation by MAPK/ERK couples signalling to the post-transcriptional control of pluripotency.

Signalling and post-transcriptional gene control are both critical for the regulation of pluripotency, yet how they are integrated to influence cell identity remains poorly understood. LIN28 (also known as LIN28A), a highly conserved RNA-binding protein, has emerged as a central post-transcriptional regulator of cell fate through blockade of let-7 microRNA biogenesis and direct modulation of mRNA translation. Here we show that LIN28 is phosphorylated by MAPK/ERK in pluripotent stem cells, which increases its levels via post-translational stabilization. LIN28 phosphorylation had little impact on let-7 but enhanced the effect of LIN28 on its direct mRNA targets, revealing a mechanism that uncouples LIN28's let-7-dependent and -independent activities. We have linked this mechanism to the induction of pluripotency by somatic cell reprogramming and the transition from naive to primed pluripotency. Collectively, our findings indicate that MAPK/ERK directly impacts LIN28, defining an axis that connects signalling, post-transcriptional gene control, and cell fate regulation.

Precise let-7 expression levels balance organ regeneration against tumor suppression.

The in vivo roles for even the most intensely studied microRNAs remain poorly defined. Here, analysis of mouse models revealed that let-7, a large and ancient microRNA family, performs tumor suppressive roles at the expense of regeneration. Too little or too much let-7 resulted in compromised protection against cancer or tissue damage, respectively. Modest let-7 overexpression abrogated MYC-driven liver cancer by antagonizing multiple let-7 sensitive oncogenes. However, the same level of overexpression blocked liver regeneration, while let-7 deletion enhanced it, demonstrating that distinct let-7 levels can mediate desirable phenotypes. let-7 dependent regeneration phenotypes resulted from influences on the insulin-PI3K-mTOR pathway. We found that chronic high-dose let-7 overexpression caused liver damage and degeneration, paradoxically leading to tumorigenesis. These dose-dependent roles for let-7 in tissue repair and tumorigenesis rationalize the tight regulation of this microRNA in development, and have important implications for let-7 based therapeutics.

Lin28b is sufficient to drive liver cancer and necessary for its maintenance in murine models.

Lin28a/b are RNA-binding proteins that influence stem cell maintenance, metabolism, and oncogenesis. Poorly differentiated, aggressive cancers often overexpress Lin28, but its role in tumor initiation or maintenance has not been definitively addressed. We report that LIN28B overexpression is sufficient to initiate hepatoblastoma and hepatocellular carcinoma in murine models. We also detected Lin28b overexpression in MYC-driven hepatoblastomas, and liver-specific deletion of Lin28a/b reduced tumor burden, extended latency, and prolonged survival. Both intravenous siRNA against Lin28b and conditional Lin28b deletion reduced tumor burden and prolonged survival. Igf2bp proteins are upregulated, and Igf2bp3 is required in the context of LIN28B overexpression to promote growth. Therefore, multiple murine models demonstrate that Lin28b is both sufficient to initiate liver cancer and necessary for its maintenance.