Matrimeres are systemic nanoscale mediators of tissue integrity and function.

Tissue barriers must be rapidly restored after injury to promote regeneration. However, the mechanism behind this process is unclear, particularly in cases where the underlying extracellular matrix is still compromised. Here, we report the discovery of matrimeres as constitutive nanoscale mediators of tissue integrity and function. We define matrimeres as non-vesicular nanoparticles secreted by cells, distinguished by a primary composition comprising at least one matrix protein and DNA molecules serving as scaffolds. Mesenchymal stromal cells assemble matrimeres from fibronectin and DNA within acidic intracellular compartments. Drawing inspiration from this biological process, we have achieved the successful reconstitution of matrimeres without cells. This was accomplished by using purified matrix proteins, including fibronectin and vitronectin, and DNA molecules under optimal acidic pH conditions, guided by the heparin-binding domain and phosphate backbone, respectively. Plasma fibronectin matrimeres circulate in the blood at homeostasis but exhibit a 10-fold decrease during systemic inflammatory injury in vivo . Exogenous matrimeres rapidly restore vascular integrity by actively reannealing endothelial cells post-injury and remain persistent in the host tissue matrix. The scalable production of matrimeres holds promise as a biologically inspired platform for regenerative nanomedicine.

Telestroke value through the eyes of emergency medicine providers: A counterfactual analysis.

Objectives: Emergency Medicine (EM) provider experiences consulting telestroke (TS) are poorly studied. In this qualitative study, we aimed to determine how TS changes patient management and to measure TS effects on EM provider confidence with acute ischemic stroke (AIS) treatment. Materials and methods: We designed a survey for EM providers querying perceptions of TS value, confidence with treating AIS, and counterfactuals regarding what EM providers would have done without TS. Eligible EM providers participated in an audio-visual TS consult within a 6-state TS network between 11/2016-11/2017. Results: We received 48 surveys (response rate 43%). The most common reason (71%) for using TS was tPA eligibility expert opinion. Most EM providers (94%) thought the patient/family were satisfied with TS and none felt their medical knowledge was doubted because of using TS. EM providers had high confidence in diagnosing AIS (95%) and tPA decision-making (86%), but not in determining thrombectomy eligibility (10%). Among EM providers who administered tPA, 85% said tPA would not have been given without TS consultation. TS consultation changed patient diagnosis in 60% of all patients and treatment plans in 56% of non-stroke patients. Most EM providers (86%) had increased confidence in their knowledge of future stroke patient management. Nearly all TS consults (93%) resulted in EM providers being more likely to use TS again. Conclusions: TS consult frequently results in both patient management change and increased EM knowledge of stroke management with increased likelihood of repeat usage. Discomfort in determining eligibility for thrombectomy points to educational opportunities.

Development of a programmable magnetic agitation device to maintain colloidal suspension of cells during microfluidic syringe pump perfusion.

Droplet-based microfluidic devices have been used to achieve homogeneous cell encapsulation, but cells sediment in a solution, leading to heterogeneous products. In this technical note, we describe automated and programmable agitation device to maintain colloidal suspensions of cells. We demonstrate that the agitation device can be interfaced with a syringe pump for microfluidic applications. Agitation profiles of the device were predictable and corresponded to device settings. The device maintains the concentration of cells in an alginate solution over time without implicating cell viability. This device replaces manual agitation, and hence is suitable for applications that require slow perfusion for a longer period of time in a scalable manner.

Predicting neuroimaging eligibility for extended-window endovascular thrombectomy.

OBJECTIVE: Endovascular thrombectomy (EVT) and tissue plasminogen activator (tPA) are effective ischemic stroke treatments in the initial treatment window. In the extended treatment window, these treatments may offer benefit, but CT and MR perfusion may be necessary to determine patient eligibility. Many hospitals do not have access to advanced imaging tools or EVT capability, and further patient care would require transfer to a facility with these capabilities. To assist transfer decisions, the authors developed risk indices that could identify patients eligible for extended-window EVT or tPA. METHODS: The authors retrospectively identified stroke patients who had concurrent CTA and perfusion and evaluated three potential outcomes that would suggest a benefit from patient transfer. The first outcome was large-vessel occlusion (LVO) and target mismatch (TM) in patients 5-23 hours from last known normal (LKN). The second outcome was TM in patients 5-15 hours from LKN with known LVO. The third outcome was TM in patients 4.5-12 hours from LKN. The authors created multivariable models using backward stepping with an α-error criterion of 0.05 and assessed them using C statistics. RESULTS: The final predictors included the National Institutes of Health Stroke Scale (NIHSS), the Alberta Stroke Program Early CT Score (ASPECTS), and age. The prediction of the first outcome had a C statistic of 0.71 (n = 145), the second outcome had a C statistic of 0.85 (n = 56), and the third outcome had a C statistic of 0.86 (n = 54). With 1 point given for each predictor at different cutoffs, a score of 3 points had probabilities of true positive of 80%, 90%, and 94% for the first, second, and third outcomes, respectively. CONCLUSIONS: Despite the limited sample size, compared with perfusion-based examinations, the clinical variables identified in this study accurately predicted which stroke patients would have salvageable penumbra (C statistic 71%-86%) in a range of clinical scenarios and treatment cutoffs. This prediction improved (C statistic 85%-86%) when utilized in patients with confirmed LVO or a less stringent tissue mismatch (TM < 1.2) cutoff. Larger patient registries should be used to validate and improve the predictive ability of these models.

Effect of low recumbent angle on cycling performance, fatigue, and V˙O(2) kinetics.

PURPOSE: This study aimed to examine the effect of the degree of inclination from upright to supine postures on cycling performance, fatigue, and oxygen uptake (V˙O(2)) kinetics. METHODS: In experiment 1, 10 subjects performed graded and fatigue (exhaustive constant-load heavy exercise with 10 s all-out efforts interspersed every minute) tests at four cycling postures: upright, 30° recumbent (R), 15° R, and supine. In experiment 2, nine different subjects performed two bouts of constant-load heavy exercise in the same four cycling postures. Bout 1 was brought to failure, and bout 2 was limited to 6 min, so that the breath-by-breath V˙O(2) data from the first 6 min of each bout were averaged and curve fit. RESULTS: The time sustained during the graded test was significantly shorter in the supine compared with the other three postures and also shorter in the 15° R compared with the upright. The rate of fatigue was higher in the supine compared with the other three postures, and the normalized EMG activities of three leg muscles at end exercise were larger in the supine (and in some cases 15° R) compared with upright posture. The time sustained (min) during high-intensity constant-load cycling was significantly longer during upright (12.8 ± 5.3) and 30° R (14.2 ± 6.1) compared with 15° R (8.5 ± 1.7) and supine (6.8 ± 2.0) postures, but the amplitudes of the slow component of the V˙O(2) response (L·min) were larger during 15° R (0.57 ± 0.10) and supine (0.61 ± 0.15) compared with 30° R (0.39 ± 0.12) and also larger in the supine than upright (0.43 ± 0.13) postures. Inert gas rebreathing analysis revealed similar cardiac output responses at 60 s into the exercise among postures. CONCLUSION: Lowering the recumbent angle to 15° resulted in shorter performance, larger fatigue, and altered V˙O(2) kinetics.

Process of discovery: a fourth-year translational science course.

BACKGROUND: The Liaison Committee on Medical Education notes the importance of educating medical students on clinical and translational research principles. PURPOSE: To describe a fourth-year course, "Process of discovery," which addresses teaching these principles, and to discuss students' perceptions of the course. METHODS: Core components and pedagogical methods of this course are presented. Course assessment was performed with specific pre- and post-course assessments. RESULTS: During academic years 2004 to 2009, 562 students were enrolled, with assessment response rate of 94% pre-course and 85% post-course. The students' self-assessment of their current understanding of clinical and translation research significantly increased, as well as their understanding of how clinical advances will take place over the next decade. CONCLUSIONS: A fourth-year course teaching clinical and translational research is successful, is seen as a positive experience and can meet the requirements for including clinical and translational research in the medical school curriculum.

IGF-I and microglia/macrophage proliferation in the ischemic mouse brain.

We have used a model of hypoxic-ischemic brain injury in adult male C57BL/6 mice to study insulin-like growth factor-I (IGF-I) and IGF-binding protein (IGFBP) expression in response to cerebral hypoxia-ischemia (H/I) in the adult mouse. A period of 20 min of H/I that resulted in histopathology in cortex, striatum, and thalamus was correlated with induction of mRNA for IGF-I, IGFBP-2, IGFBP-3, IGFBP-5, and glial fibrillary acidic protein (GFAP) by 4 days of recovery. Increased IGF-I mRNA was located within damaged regions and was surrounded by IGFBP-2 mRNA expression. The results of combined immunostaining/in situ hybridzation showed that the cells expressing IGFBP-2 mRNA were also GFAP-positive and comprised a subset of activated astrocytes immediately surrounding areas of damage. In contrast, staining within damaged regions showed high numbers of cells immunopositive for F4/80 and lectin B(4) indicative of microglia and macrophages but no cells immunopositive for the astrocytic proteins GFAP or S-100beta. Microglia/macrophages within the damaged areas expressed IGF-I mRNA and were also immunopositive for the proliferating cell nuclear antigen. To determine whether expression of IGF-I could contribute to proliferation of microglia, we treated purified cultures of adult brain microglia with IGF-I in the presence of (3)H-thymidine. IGF-I stimulated a twofold increase in DNA synthesis in cultures of adult brain microglia. Taken together with previous data demonstrating that IGF-I promotes proliferation of peripheral macrophages, these data support the hypothesis that IGF-I is an autocrine/paracrine mitogen for microglia/macrophages after H/I.