Limb Vasculature Research Articles

Vasculature of older females show heterogeneity in the association between cardiovascular risk and vascular function

Although affecting both sexes, loss of sex hormones and consequently increased risk for cardiovascular disease (CVD) render particular features to vascular aging in females. More importantly, while the female’s vasculature is more sensitive to CVD risk factors, CVD is often underdiagnosed in women. In the present study, we investigated vascular function in the arm and leg skeletal muscle microvasculature and conduit artery in young and older females. We also applied a mixed-effect regression analysis to examine the relationship between vascular function and CVD risk factors in women. We showed that the detrimental effects of age in conduit artery vascular function, as assessed by flow-mediated dilation (%FMD), was more evident in the lower limb (Older, 2.6 ± 0.5 vs. Young, 7.2 ± 0.9%, p=0.0116). compared to the upper limb (Older, 5.3 ± 0.5 vs. Young, 7.3 ± 0.4%, p=0.175) In addition, we demonstrate that CVD risk factors, mainly plasma lipid levels (VLDL-c: r2=0.415, p=0.007; HDL-c: r2=0.313, p=0.024; triglycerides: r2=0.422, p=0.006) and insulin sensitivity index (HOMA-IR: r2=0.635, p<0.001; QUICKI: r2=0.792, p<0.001), were exclusively associated with upper limb skeletal muscle microvascular function in older females. In aggregate, our findings provide novel evidence that impairments in conduit artery function in older females are more pronounced in the lower limb vasculature compared to the upper limb. Also, we demonstrate that older women’s upper limb microvasculature function may be more susceptible to the impact of CVD risk factors than lower limb microvasculature function and both limb’s conduit arteries.

Drug-eluting devices for lower limb peripheral arterial disease.

Peripheral arterial disease is the third leading cause of cardiovascular morbidity after coronary artery disease and stroke. Lower limb peripheral arterial disease commonly involves infrainguinal arteries, may impair walking ability (intermittent claudication) and may confer a significant risk of limb loss (chronic limb-threatening ischaemia), depending on the severity of ischaemia. Endovascular treatment has become the mainstay revascularisation option in both the femoropopliteal and the below-the-knee arterial segments. After crossing and preparing the lesion, treatment results in these arterial segments can be enhanced by using drug-coated devices (drug-eluting stents and drug-coated balloons) that mitigate the occurrence of restenosis. As for other medical devices, the use of drug-eluting devices is based on their demonstrated safety and efficacy profiles when applied in the distinct segments of the lower limb vasculature. In this state-of-the-art narrative review we provide an overview of the safety and efficacy of drug-coated devices when used in the femoropopliteal and below-the-knee arterial segments.

Simulation-Based Medical Education: 3D Printing and the Seldinger Technique

Three-dimensional (3D)-printed models with high anatomic fidelity are an increasingly viable tool in simulation-based medical education. One advantage of 3D models is they provide enhanced tactile and spatial understanding of complex anatomy to develop technical skills used in minimally invasive procedures. We propose that 3D anatomical models can improve the development of interventional radiology vascular access skills—first described in the 1950s as the Seldinger technique—for pre-clerkship medical students. The early adoption of 3D-printed technology in pre-clinical medical education can lead to improved student engagement and satisfaction when learning procedural techniques. This study involved creating a 3D model of the upper limb vasculature from an anonymized Computed tomography (CT) angiogram, using it as a medical education tool for 31 pre-clinical medical students practicing the Seldinger Technique on a prefabricated venipuncture upper limb, and assessing student satisfaction with this form of learning. Overall, attendees responded positively to the incorporation of the 3D model in medical education to improve their anatomic understanding and application of the Seldinger technique. These results indicate that the use of 3D models in simulation-based medical education can provide benefits in acquiring technical skills and the potential to decrease training costs without harming a patient.

Recent developments in targets for ischemic foot disease.

Diabetes is a key risk factor for ischaemic foot disease, which causes pain, tissue loss, hospital admission, and major amputation. Currently, treatment focuses on revascularisation, but many patients are unsuitable for surgery and revascularisation is frequently unsuccessful. The authors describe recent research in animal models and clinical trials investigating novel medical targets for ischaemia, including theories about impaired wound healing, animal models for limb ischaemia and recent randomised controlled trials testing novel medical therapies. Novel targets identified in animal models included stimulating mobilisation of CD34+ progenitor cells through upregulating oncostatin M or microRNA-181, downregulating tumour necrosis factor superfamily member 14, or activating the Wingless pathway. Within the ischaemic limb vasculature, upregulation of apolipoprotein L domain containing 1, microRNA-130b or long noncoding RNA that enhances endothelial nitric oxide synthase expression promoted limb blood supply recovery, angiogenesis, and arteriogenesis. Similarly, administration of soluble guanylate cyclase stimulators riociguat or praliciguat or 3-ketoacyl-CoA thiolase inhibitor trimetazidine promoted blood flow recovery. Translating pre-clinical findings to patients has been challenging, mainly due to limitations in clinically translatable animal models of human disease. Promising results have been reported for administering plasmids encoding hepatocyte growth factor or intra-arterial injection of bone marrow derived cells in small clinical trials. It remains to be seen whether these high resource therapies can be developed to be widely applicable. In conclusion, an ever-expanding list of potential targets for medical revascularisation is being identified. It is hoped that through ongoing research and further larger clinical trials, these will translate into new broadly applicable therapies to improve outcomes.

3D-printed model of simulation for acute thrombus removal in peripheral arteries.

Surgical training and evaluation of medical devices require simulation models. The aim of this study was to assess a 3D-printed model as a training model for peripheral endovascular procedures, including thromboaspiration in acute limb ischemia (ALI). The 3D-simulation model was modeled from an aorta and lower limbs CT scan by segmentation of the arterial light. The 3D simulator was printed in multimaterial with photo-polymerizable resins (Polyjet). The simulator consisted of interchangeable cartridges intended to reproduce the lower limb vasculature. The simulator was connected to a pump to obtain a pulsative flow. A gelled product was positioned in a cartridge just above a stenosis in order to simulate an ALI by in-situ thrombosis. Vascular interventionalists should perform a thrombo-aspiration (Indigo®, Penumbra Inc., Alameda, CA, USA) by crossover in an experimental hybrid room (Discovery®, General Electric, Boston, MA, USA). The analysis of the results was based on the feedback of vascular interventionalists using a Likert Psychometric Scale. A total of 6 vascular surgeons performed two training sessions in real-life conditions. Access to the target lesion was achieved by cross-over or antegrade approach with an 8 F - 45 cm introducer. An angiogram was used to localize the thrombus. Due to the flow, a part of the thrombus was migrating from femoropopliteal segment to below the knee level. Thromboaspiration was realized by Indigo (Penumbra Inc.) CAT-8 and -6 with separators. The average score out of 5 was 4.5 (±0.55) regarding anatomical reproducibility, 4.3 (±0.82) for navigation, and 4.5 (±0.84) for aspiration. The didactical evaluation showed a score of 4.3 (±0.52) for improving technical skills. The improvement of the confidence score in the simulator was +1.2 (±1.72). The 3D-simulation model for peripheral endovascular procedures provides a realistic training for thromboaspiration. This model could mimic different types of peripheral arterial pathologies and participate to the vascular interventionalists training.

Single-cell transcriptomics of popliteal lymphatic vessels and peripheral veins reveals altered lymphatic muscle and immune cell populations in the TNF-Tg arthritis model

BackgroundLymphatic dysfunction exists in tumor necrosis factor transgenic (TNF-Tg) mice and rheumatoid arthritis (RA) patients. While joint-draining TNF-Tg popliteal lymphatic vessels (PLVs) have deficits in contractility during end-stage arthritis, the nature of lymphatic muscle cells (LMCs) and their TNF-altered transcriptome remain unknown. Thus, we performed single-cell RNA-sequencing (scRNAseq) on TNF-Tg LMCs in PLVs efferent to inflamed joints versus wild-type (WT) controls.MethodsSingle-cell suspensions of PLVs were sorted for smooth muscle cells (SMCs), which was validated by Cspg4-Cre;tdTomato reporter gene expression. Single-cell RNA-seq was performed on a 10x Genomics platform and analyzed using the Seurat R package. Uniform Manifold Approximation and Projections (UMAPs) and Ingenuity Pathway Analysis software were used to assess cell clusters and functional genomics in WT vs. TNF-Tg populations.ResultsFluorescent imaging of Cspg4-Cre;tdTomato vessels demonstrated dim PLVs and strong reporter gene expression in the adjacent superficial saphenous vein, which was corroborated by flow cytometry of LMCs and vascular smooth muscle cells (VSMCs) from these vessels. Due to their unique morphology, these populations could also be readily detected by scatter analysis of cells from non-fluorescent mice. Bioinformatics analysis of flow sorted WT and TNF-Tg cells identified 20 unique cell clusters that together were 22.4% LMCs, 15.0% VSMCs, and 62.6% non-muscle cells of 8879 total cells. LMCs and M2-macrophages were decreased, while inflammatory monocytes were increased in TNF-Tg lower limb vasculature. SMC populations were defined by Cald1, Tpm1, and Pdgfrb expression and were enriched in myofibroblast-like gene expression. TNF-Tg LMCs exhibited enhanced functional genomics associated with cell death, phagocyte recruitment, and joint inflammation. Among the most prominent TNF-induced genes in SMCs were Mmp3, Cxcl12, and Ccl19, and the most downregulated genes were Zbtb16, Galnt15, and Apod.ConclusionsSingle-cell RNA-seq can be used to investigate functional genomics of lower limb vasculature in mice. Our findings confirm the inflammatory transcriptome of TNF-Tg vessels and altered gene expression in SMC populations. This study further supports a potential role of mesenchymal stromal cells in inflammatory-erosive arthritis pathogenesis, and warrants future studies to define the effects of this TNF-altered transcriptome on PLV function and joint homeostasis.

Distal venous arterialisation for ‘no-option’ chronic limb-threatening ischaemia

Chronic limb-threatening ischaemia (CLTI), defined as significant peripheral arterial disease causing ischaemic rest pain and/or tissue loss, is associated with a high amputation and mortality rate. Avoiding amputation in CLTI is crucial and restoration of blood flow is usually achieved using endovascular or open surgical revascularisation. However, significant occlusion of the distal limb vasculature may result in ‘no option’ CLTI, where there are no available target vessels for angioplasty or bypass. An emerging procedure to treat patients with ‘no option’ CLTI is distal venous arterialisation (DVA). This involves using the distal venous system as a conduit for arterial blood to revascularise the lower limb. This report describes a patient presenting with ‘no option’ CLTI who underwent limb-saving treatment with DVA. The case highlights how worsening clinical outcomes may occur despite technical success of DVA. It also emphasises complications of the procedure. Finally, the evidence base surrounding DVA for CLTI is examined.

Dorsalis pedis artery pseudoaneurysm: A rare entity in the field of vascular surgery.

IntroductionDorsalis pedis artery aneurysms (PDAA) and pseudoaneurysms are rare conditions of lower limb vasculature. The rarity of the disease increases in the pediatric age group where only 4 cases of pediatric patients with PDAA.Presentation of the caseWe present A case of a 2-year-old baby girl who was diagnosed with dorsalis pedis pseudoaneurysm, which was treated successfully with pseudoaneurysm dissection and anastomosis.Clinical discussionThe dorsalis pedis pseudoaneurysm in this case has a rare anatomical location in addition to the unusual onset at this age group. Due to the rarity of this condition among all age groups, there is not a well-structured approach.ConclusionDPAA/pseudoaneurysm is a rare entity in the field of vascular surgery. Medical treatment is not suitable for DPAA/pseudoaneurysm to avoid the future risk of thrombosis or ischemia. The surgical approach is the Mainstay of treatment.

Regional thermal hyperemia in the human leg: Evidence of the importance of thermosensitive mechanisms in the control of the peripheral circulation.

Hyperthermia is thought to increase limb blood flow through the activation of thermosensitive mechanisms within the limb vasculature, but the precise vascular locus in which hyperthermia modulates perfusion remains elusive. We tested the hypothesis that local temperature‐sensitive mechanisms alter limb hemodynamics by regulating microvascular blood flow. Temperature and oxygenation profiles and leg hemodynamics of the common (CFA), superficial (SFA) and profunda (PFA) femoral arteries, and popliteal artery (POA) of the experimental and control legs were measured in healthy participants during: (1) 3 h of whole leg heating (WLH) followed by 3 h of recovery (n = 9); (2) 1 h of upper leg heating (ULH) followed by 30 min of cooling and 1 h ULH bout (n = 8); and (3) 1 h of lower leg heating (LLH) (n = 8). WLH increased experimental leg temperature by 4.2 ± 1.2ºC and blood flow in CFA, SFA, PFA, and POA by ≥3‐fold, while the core temperature essentially remained stable. Upper and lower leg blood flow increased exponentially in response to leg temperature and then declined during recovery. ULH and LLH similarly increased the corresponding segmental leg temperature, blood flow, and tissue oxygenation without affecting these responses in the non‐heated leg segment, or perfusion pressure and conduit artery diameter across all vessels. Findings demonstrate that whole leg hyperthermia induces profound and sustained elevations in upper and lower limb blood flow and that segmental hyperthermia matches the regional thermal hyperemia without causing thermal or hemodynamic alterations in the non‐heated limb segment. These observations support the notion that heat‐activated thermosensitive mechanisms in microcirculation regulate limb tissue perfusion during hyperthermia.

Myocardial Infarction and Three-Vessel Coronary Artery Disease as Presenting Features of Granulomatosis with Polyangiitis: A Case Report with Review of Literature

Granulomatosis with Polyangiitis (GPA) is a systemic, autoimmune disorder characterized by inflammatory insult and granulomatous processes in small and medium-sized vessels leading to various clinical presentations from underlying vasculitis. Underlying such inflammatory cascade is the overactivity of Antineutrophil Cytoplasmic Antibodies (c-ANCA) targeting serum Proteinase 3 (PR3), whose aberrant targeting classically modulates molecular signaling pathways leading to clinical manifestations of the Ear, Nose and Throat (ENT), in addition to renal impairment. Peripheral vessel involvement (i.e. limb vasculature) is not generally associated with GPA. With the exception of seldom reports in the literature, it is rare for GPA to present with coronary artery involvement. Moreover, reports of multi-vessel disease (e.g. triple-vessel disease) with GPA warranting Coronary Artery Bypass Graft (CABG) are lacking in such accounts. The latter with preceding iliac artery claudication makes such a presentation of GPA exceptionally novel and warrants contextual commentary regarding inflammation and Coronary Artery Disease (CAD). We report the case of a 55-year-old Caucasian male presenting with a 2 years history of right-sided groin cramping and an acute one-week history of claudication in the same area. After advised to follow up as an outpatient, this patient returned shortly thereafter to an acute care setting with hemoptysis and myocardial infarction worked up for GPA and triple-vessel disease. The patient was subsequently treated with immunosuppressive pharmacotherapy prior to CABG. We conducted a review of the literature underpinned in clinical and translational biology with a focus on the salient inflammatory pathways featured in both coronary artery disease and GPA.

The vascular origins of antero-medial tibial bowing in congenital fibular deficiency.

Anteromedial bowing and shortening of the tibia are intrinsic features of limbs with congenital fibular deficiency (CFD). Tibial bowing occurs more frequently when the fibula is radiographically absent rather than deficient. The bowing has been attributed to rapid longitudinal growth of the tibial anlage coupled with anteromedial tibial bending moments of the posterior crural and lateral peroneal musculature unopposed in the absence of a fibular strut. Eccentric mechanical loading results in asymmetric mineral deposition and thickening of the diaphyseal cortex. Skeletogenesis depends upon an intimate interplay between the normally prefigured tibial cartilage anlage and beginning muscular contractile actions during initial vascularization of the anlage, while the embryonic limb vasculature is undergoing a series of transitions. A diaphyseal periosteal collar normally forms at the site of nutrient artery invasion and stabilizes the growing anlage. In CFD however, arteriography consistently reveals anomalous tibial nutrient arterial branches, which originate from a primitive axial artery rather than from the usual posterior tibial artery. These anomalous nutrient arteries enter the tibial shaft at the posterior aspect of the proximal metaphysis, establishing an eccentric bone collar. The developing vasculature of the embryonic limb is responsive to the then most metabolically active tissues. Disruption of the reciprocal relationship between the transitioning vasculature and the developing long bones is pivotal in producing the diverse skeletal malformations of the congenital short limb (CSL). Embryonic vascular dysgenesis contributes not only to the well-recognized congenital tibial and fibular shortenings but also predisposes to congenital anteromedial bowing of the tibia.

Outcome after Hybrid Outflow Interventions for Chronic Limb-threatening Ischemia.

Because chronic limb-threatening ischemia (CLTI) is often associated with multilevel arterial disease, it usually requires revascularization at different sites of the limb vasculature. We aim to assess the outcome of the hybrid interventions including open surgical revascularization together with outflow segment percutaneous transluminal angioplasty (PTA) in patients with chronic limb-threatening ischemia. This study included all hybrid outflow-PTA interventions (n = 80) on patients suffering from CLTI performed in Helsinki University Hospital between 2003 and 2015. Follow-up ended on 31 December 2019. Patient data were prospectively collected into our vascular registry and scrutinized retrospectively. Thirty-one patients (39%) suffered from rest pain (Rutherford category IV) and 49 patients (61%) had ischemic ulcers (Rutherford category V-VI). The most common open surgical procedure was femoral endarterectomy (n = 63, 79%) and the most common endovascular procedure was superficial femoral artery percutaneous transluminal angioplasty (n = 65, 81%). Mean follow-up time was 56 months (range: 4 days-183 months). Limb salvage was at 30 days-92%, at 1 year-91%, and at 5 and 10 years-86%. Survival and amputation-free survival were at 30 days-93% and 86%, at 1 year-80% and 76%, at 5 years-51% and 48%, and at 10 years-21% and 21%. Wound healing at 3, 6, and 12 months was 48%, 71%, and 87%. Freedom from target lesion revascularization was at 30 days-97%, at 1 year-88%, at 5 years-72%, and at 10 years-66%. Hybrid outflow revascularization is an important tool in the vascular surgeon's armamentarium for treatment of patients with multilevel arterial disease causing chronic limb-threatening ischemia.

Analysis of Variation in Anatomy of Lower Limb Vasculature and Implications for Free Fibula Flap by Color Doppler Imaging.

The free fibula flap (FFF) has proved to be an adequate adjunct tool in the reconstruction of defects following cancer ablation. Although various investigation tools in the past have been proved to be adequate to study the blood supply of the various trunks of arteries, for the survival of graft, the color Doppler flow study (CDF) can be done for the accurate examination of various perforators for the same in the lower limbs prior to its harvest. 40 patients were included in the study and were examined for free fibula flap tissue transfer via color Doppler study for the lower limb perforators. In the study, the perforators that are musculocutaneous, septocutaneous and septomusculocutaneous were detected in 80 legs that were examined and all of them had adequate diameter to justify the fact that the graft can be taken for harvesting, except for only two cases where it was found that they were hypoplastic. CDF can be a reliable and informative tool in patients planned for free fibula tissue transfer. Also, the skin perforators can be mapped, so as to determine skin paddle inclusion.

Revealing Unseen Detailed Human Vascular Anatomy of the Thumb using a Novel Contrast Agent and technique with 4D Helical Micro CT Scanner

INTRODUCTIONCross‐sectional imaging of human vasculature (hospital CT and MRI scans) is often enhanced by injecting contrast mediums, which classically is either iodine or gadolinium. Unfortunately, these agents exit medium sized vessels and occasionally medium to small sized vessels. Vascular pathologies can be identified from hospital CT and MRI scan widths of large to medium sized vessels especially when enhanced by 3‐D software imaging. The objective of this study was to investigate if an alternative contrast agent perfused into a donor cadaver using 1 of only 2, 4D Helical Micro CT scanners worldwide could demonstrate previously unseen detailed human vascular anatomy of the thumb.METHODSLiterature search revealed a source developed by the authors using a novel barium sulfate contrast agent which does not exit vessels and reveals medium sized (2–5 mm), small (1–2 mm), very small (less then 1mm) and micro (less then 100 microns) vessels. Human donor cadavers greater then 75 years old (N=4 donors:3M‐1F:8‐Thumbs) were chosen to assess whether the contrast agent could negotiate through elderly vessels and be imaged with the 4D helical micro CT scanner. Cadavers were initially embalmed with Freedom Art solution, then scanned with Sonosite ultrasound finger probe to assess vessel patency. Perfusing the contrast agent was conducted at the common carotid site within the neck and rescanned to assess patency of vessels in upper limb. 4D Helical Micro CT scanning was conducted post contrast perfusion and viewed with high end desktop computer software (Avizo) for 3D rendering for virtual dissection by the Sectra visualization table (VT).RESULTSThe embalming and contrast was successfully perfused into human donor cadavers. Sonosite ultrasound finger probe revealed patent medium and small vessel ultrasound images day 1, day 3, and day 7 post contrast perfusion. The perfusion technique was also deemed successful as the 4D helical micro CT scanning of the human cadaver thumbs revealed detailed thumb vascular anatomy images (micro, 8–40 microns). Each thumb was subsequently dissected wearing surgical loops which revealed patent vessels filled with contrast. DICOM files were successfully rendered into 3D images using Sectra visualization table revealing micro vasculature of the human thumb.DISCUSSIONThis study successfully conducted a unique perfusion technique to donor cadavers with a novel contrast agent illuminating previously unseen micro vasculature imaging of the human thumb region from a 4D Helical Micro CT scanner. Sonosite ultrasound finger probe was a successful tool to assess vessel patency suggesting contrast remains within the upper limb vasculature for at least 7 days.CONCLUSIONThe positive outcome from this pilot study warrants further studies which will improve our understanding of detailed vascular anatomy enabling accurate future medical simulation, artificial intelligence and developing innovative medical technology.

Anatomical Variation of High Bilateral Brachial Artery Bifurcation: A Case Report

The brachial artery is a continuation of the axillary artery below the inferior border of the teres major muscle. It commonly bifurcates into the radial and ulnar artery low to the neck of the radius. Previous studies have documented variability for upper limb vasculature (9%–18.5%) and variability of brachial bifurcation in the middle of the arm (3–15%). However, there are a lack of cadaver studies that have discussed the effects of a brachial bifurcation in the proximal third of the arm, close to the teres major muscle. During routine anatomical dissections of 24 donors (11 males and 13 females) at Oakland University William Beaumont School of Medicine, it was found that only one donor (female) had a bilateral brachial artery bifurcation in the proximal third of the arm (4.17%). Both right and left arms were measured to be 21cm long, along with brachial artery bifurcation occurring 3cm from the teres major muscle. The bilateral bifurcation may be explained in terms of embryogenesis where there may be a persistence, unusual path, or obliteration of primitive vessels. The variance in the brachial artery bifurcation, especially in the proximal third of the arm, presents heavy clinical considerations. There is a potential that such bifurcations may affect the course of the median, radial, and ulnar nerves. Such variances may complicate surgeries in the brachial region, percutaneous brachial catheterization, and increase the likelihood of inaccurate readings of angiograms and other relevant radiological techniques. Brachial artery proximal bifurcation may also cause individuals to be vulnerable to laceration, which may result in hematomas. A proximal bifurcation of the brachial artery may affect the anastomosis of the ulnar artery with the superior and inferior ulnar collateral arteries and contribute to the excessive hematoma that was observed on the variant donor. The awareness of this clinically significant variation implicates the need for pre‐operative vessel mapping in order to decrease the possibility of iatrogenic injuriesBifurcation of brachial artery on the left arm.Figure 1Bifurcation of brachial artery on the right hand. The blood was determined to be pre‐mortem, leading to a conclusion of a hematoma.Figure 2

Attenuation of Mineralocorticoid Receptor Signaling Promotes Vascular Recovery from Hind Limb Ischemia in a Sex Specific Manner

Peripheral arterial disease (PAD) is a growing concern affecting 8.5 million Americans annually and contributing to both fatal and non‐fatal cardiovascular ischemic events. Importantly, available evidence indicates that women experience higher rates of occlusion, reintervention, and mortality than males, however, mechanisms underlying these sex differences remain unclear. Recent evidence has revealed sex‐specific deleterious effects of mineralocorticoid receptor (MR) signaling in a variety of cardiovascular conditions including vascular inflammation and endothelial dysfunction, which have been implicated in PAD. Whether MR signaling differentially impairs microvascular adaptations in males and females following an ischemic insult, however, has not been examined. Accordingly, we evaluated the hypothesis that attenuation of MR signaling promotes microvascular compensation and perfusion recovery following hind limb ischemia (HLI) to a greater extent in females than in males involving enhanced capillary neovascularization and augmented outward remodeling of existing collaterals. Male and female C57BL/6J mice (10–12 weeks old) underwent unilateral femoral artery ligation and excision to induce HLI after implantation of pellets containing either placebo or the MR antagonist spironolactone (20mg/kg/day, sc). The contralateral leg underwent sham surgery with no ligation or excision. Hind limb perfusion was serially assessed for 28 days with laser Doppler imaging. At 28 days post occlusion, the hind limb vasculature was perfusion fixed following maximal dilation and perfused with bismuth for assessment of collateral morphology by micro‐CT imaging. These studies were complemented with immunohistochemistry and angiogenic assay experiments. Additional preliminary HLI experiments were conducted in male mice with endothelial cell‐specific MR (EC MR) deletion. Systemic inhibition of MR signaling enhanced recovery of hind limb perfusion in female, not male, mice. This effect of MR blockade was associated with greater outward collateral remodeling in females compared to males. Interestingly, spironolactone similarly increased skeletal muscle capillary density in both hind limbs of males and females consistent with impairment of VEGF‐stimulated capillary sprouting by the MR agonist aldosterone in an aortic angiogenesis assay. Finally, preliminary studies revealed enhanced recovery of hind limb perfusion in male mice with EC MR deletion and that EC MR deletion enhanced aortic capillary sprouting in vitro. Taken together, these data suggest that MR signaling limits the microvascular response to ischemia and that enhanced perfusion recovery following MR blockade in females involves greater collateral expansion compared to males. Significant vascular cell‐specificity of MR signaling underlying these responses may contribute to these sex differences and warrant further investigation.Support or Funding InformationFunded by HL136386, HL095590, and HL088105.

Tuning molecular aggregation to achieve highly bright AIE dots for NIR-II fluorescence imaging and NIR-I photoacoustic imaging.

Currently, bright aggregation-induced emission luminogens (AIEgens) with high photoluminescence quantum yields (PLQYs) in the NIR-II region are still limited, and thus an efficient strategy to enhance NIR-II fluorescence performance through tuning molecular aggregation is proposed here. The synthesized donor–acceptor tailored AIEgen (DTPA-TBZ) not only exhibits an excellent absorptivity in the NIR-I region, but also good fluorescence signals in the NIR-II region with an emission extending to 1200 nm. Benefiting from such improved intramolecular restriction and aggregation, a significant absolute PLQY value of 8.98% was obtained in solid DTPA-TBZ. Encouragingly, the resulting AIE dots also exhibit a high relative PLQY of up to 11.1% with IR 26 as the reference (PLQY = 0.5%). Finally, the AIE dots were applied in high performance NIR-II fluorescence imaging and NIR-I photoacoustic (PA) imaging: visualization of abdominal vessels, hind limb vasculature, and cerebral vessels with high signal to background ratios was performed via NIR-II imaging; Moreover, PA imaging has also been performed to clearly observe tumors in vivo. These results demonstrate that by finely tuning molecular aggregation in DTPA-TBZ, a good NIR-I absorptivity and a highly emissive fluorescence in the NIR-II region can be achieved simultaneously, finally resulting in a promising dual-modal imaging platform for real-world applications to achieve precise cancer diagnostics.

Quaternary Ammonium Salt Based NIR-II Probes for in vivo Imaging.

Traditional luminescent materials including fluorescent probes suffer from notorious aggregation-caused quenching (ACQ) in aqueous solutions. Although several approaches such as the aggregation-induced emission (AIE) effect have been developed, it remains a significant challenge to identify an effective and efficient strategy to resolve this issue. Herein, quaternary ammonium salts Q8PBn and Q8PNap as a novel class of bright near infrared window II (NIR-II, 1,000 - 1,700 nm) probes were designed and synthesized, and the twisted intramolecular charge transfer (TICT) formation at the excited state can be effectively suppressed for the newly designed probes. Furthermore, Q8PNap complexation with fetal bovine serum (Q8PNap/FBS) significantly increased the quantum yield by ~ 32-fold compared with PEGylated tertiary amine Q8P, and Q8PNap/FBS was successfully used to achieve high spatial and temporal resolution imaging of hind limb vasculature, lymphatic system, and small tumor metastasis, as well as precise NIR-II imaging-guided tumor and lymph node surgery in small animal models for the first time.

Enhancing Photoacoustic Intensity of Upconversion Nanoparticles by Photoswitchable Azobenzene‐Containing Polymers for Dual NIR‐II and Photoacoustic Imaging In Vivo

AbstractNear‐infrared photoacoustic (PA) imaging is developing rapidly as an alternative to optical imaging and promises benefits in terms of deeper tissue penetration and higher spatial resolution. This paper proposes a strategy to enhance the PA intensity of upconverted nanoparticles (UCNPs) by functionalized photoswitchable azobenzene‐containing poly (acrylic acid) (UCNPs@PAA‐Azo) to yield a PA signal that is up to six times higher than that of UCNPs without a decay in NIR‐II emission. The mechanism of enhanced photoacoustic activity of the UCNPs@PAA‐Azo can be attributed to the decay of UV and blue light as well as vibrations of the azobenzene group. This technology delivers high resolution of the hind limb vasculature using dual NIR‐II and PA imaging. Using this nanoprobe, NIR‐II imaging provides real‐time means for the precise resection of the lymph node (LN) during surgery, where PA imaging allows for quicker (up to 30 min) detection of LNs than that through NIR‐II imaging. Combining the advantages of dual NIR‐II and PA modalities allows us to achieve complementary information and improve the accuracy of disease diagnosis. This work is critical to the synthesis of dual NIR‐II and PA modal probes and is utilized in small animals imaging with high resolution and a high signal‐to‐noise ratio.

The Foot Angiosomes as Integrated Level ofLower Limb Arterial Perfusion: Amendmentsfor Chronic Limb Threatening IschemiaPresentations

Introduction: The angiosome concept was initially pioneered by Taylor and Palmer in the plastic reconstructive surgery field. The authors described a reproducible model of arterial and venous distribution in humans that follows specific three-dimensional (3D) networks of tissue. The angiosome model yet represents a specific level among other staged and graduated levels of harmonious arterial irrigation in the lower extremity. Specific CLTI pathologies enhance characteristic arterial branches affectation, including the angiosomal source arteries. Evaluating main atherosclerotic lesions at peculiar Levels of arterial division may afford useful clinical information. Method: The present study proposes a description of six levels of degressive arterial division and collateral distribution in the inferior limb, including the angiosomal stage. Following succeeding perioperative 2D angiographic observations over an eight-year period, these levels (I to VI) were analyzed (including the angiosomal Level III) and summarized in attached tables. The medical files of 323 limb-threatening ischemic foot wounds (Rutherford 4-6) in 295 patients (71% men) were retrospectively reviewed. All arterial patterns were defined by preoperative Angio-CT, or Angio-MRI, associating in each case perioperative angiography. For each anatomical Level the worse atherosclerotic lesions (TASC II) were located, then compared with adjacent levels in same individual CLTI patterns. For each ramification stage the heaviest occlusive angiographic lesions (TASC “C-D”) were selected and defined as “dominant”, in comparison with parallel “associate” atherosclerotic locations. A comparison between 196 diabetic, against 127 non-diabetic CLTI patterns of atherosclerotic occlusive disease was performed. Results: Notable differences in the distribution of the dominant occlusive lesions were observed among the two Groups. Specific “Level I” iliac and common femoral lesions (10%), adding “Level II” superficial femoral (17%) also “Level II” femoro-popliteal (32%) dominant occlusive lesions in non-diabetics prevailed against correspondent iliac (3%), superficial femoral (7%), and femoro-popliteal (21%) occlusive lesions in diabetic CLTI subjects. Conversely, “Level II” distal popliteal and tibial occlusions (33%), “Level III” pedal and angiosomal branches (34%) adding “Level III” dominant foot arches occlusions (5%) in diabetic patients, overruled correspondent popliteo-tibial (30%), pedal-angiosomal (5%), and isolated foot arches (0%) lesions in non-diabetics. Conclusion: Inferior limb vasculature affords a harmonious 3D distribution of “tissueoriented” arterial axes including the angiosomal source arteries. These branches are coupled to a vast collateral compensatory system (choke-vessels, cutaneous perforators, and arterial-arterial interconnections) in a degressive array. Six Levels of arterial ramification (I-VI) can be described on angiographic analysis. To specific Levels I-II bear atherosclerotic occlusive disease location, characteristic Levels III-IV topographic occlusive disease is opposed in diabetic CLTI patients.