Local Vasculature Research Articles

Comparative Study on Enhanced Skin Permeation Efficiency of Phenylephrine via Novel Lipid Vesicles: A Promising Approach in Preventing Chemotherapy-Induced Alopecia Management.

Chemotherapy-induced alopecia (CIA) significantly impacts patients' emotional and psychological well-being and treatment regimen. Phenylephrine, a topical vasoconstrictor, can potentially reduce hair loss by limiting chemotherapy drug delivery to hair follicles. However, effective delivery of Phenylephrine through the skin remains challenging. This study investigates lipid vesicles as delivery vehicles to enhance Phenylephrine's skin permeation and sustained release due to their biocompatibility and encapsulation capabilities. This study aimed to formulate and compare different lipid vesicles of Phenylephrine HCl for enhanced permeation through the skin for deep dermal delivery with sustained release of the drug so as to achieve local vasoconstriction. Phenylephrine-loaded ethosomes, invasomes, and transfersomes were prepared and characterized for particle size (PS), polydispersity index (PDI), and entrapment efficiency (EE %). These lipid vesicles were incorporated into hydrogels to facilitate sustained drug release to deep dermal layers where they could target local vasculature and cause vasoconstriction. The prepared vesicular gels were evaluated for various permeation parameters. The entrapment efficiencies of the developed vesicles ranged from 49.51 ± 3.25% to 69.09 ± 2.32%, with vesicle sizes ranging from 162.5 ± 5.21 nm to 321.32 ± 3.75 nm. Statistical analysis revealed significantly higher flux values (Jss, μg/cm2 h) of 0.6251, 0.6314, and 0.4075 for invasomal gel, ethosomal gel, and transfersomal gel, respectively, compared to plain gel (0.1254) (p < 0.005). The enhancement factors were 4.9848, 5.0350, and 3.2496 for invasomal gel, ethosomal gel, and transfersomal gel, respectively, indicating superior permeation abilities of ethosomal and invasomal formulations. The results demonstrate that ethosomal and invasomal formulations were efficient in delivering the drug to deep dermal layers of skin in a sustained manner. These findings suggest that these Lipidic vesicles would be able to target the local vasoconstrictor to vasculature, causing reduced hair loss by limiting chemotherapy drug delivery to hair follicles and managing chemotherapy-induced alopecia.

Vascular Signaling Plasticity Reprograms Blood Delivery Mechanisms to Meet Fluctuating Neuronal Energy Needs

Neuronal computation is metabolically expensive and depends on precision delivery of energy substrates—oxygen and glucose—via tightly coordinated blood flow to ensure that energy demands are continually met. This is facilitated by neurovascular coupling (NVC)—a range of mechanisms matching neural activity to local blood flow. These NVC mechanisms are typically considered invariant, and whether they are reshaped according to ever-changing neuronal metabolic needs has not been examined. We present evidence that neural activity continually reprograms the blood flow control mechanisms embedded in the local vasculature, a process we refer to as ‘vascular signaling plasticity’ (VSP). Using an established enrichment paradigm, we find that animals housed in conditions that increase input to the barrel cortex for 7 days exhibit profound neuronal plasticity in this region. This resculpts local vascular reactivity to elevate blood delivery. Indeed, VSP results in increased basal capillary blood flow and augmented activity of vasodilatory agents in vivo manifesting as increased red blood cell (RBC) flux responses to capillary stimulation and upstream diameter changes measured using 2-photon laser scanning microscopy. Moreover, the sensitivity of capillaries to stimulation is also dramatically elevated in an ex vivo isolated capillary-arteriole preparation. Using K+-mediated capillary-to-arteriole electrical signaling as a springboard to study the molecular underpinnings of VSP, we find that this process induces a ~70% increase in the density of strong inward rectifier K+ (Kir2.1) currents in capillary endothelial cells, which profoundly augments the retrograde hyperpolarization generated by these channels to control upstream diameter at the level of the penetrating arteriole. Through whole-cell patch clamp electrophysiology, we characterize the mechanism of VSP induction and recapitulate this phenomenon in vitro. We validate our findings through Crispr/Cas9-mediated endothelial cell-specific knockout of the transcription factor responsible for VSP induction. Our data thus recast the vasculature as a plastic, brain-wide activity sensing network that is continually reshaped at the molecular level by local neuronal input, leading to precisely-tuned blood delivery to meet continually fluctuating neural energy needs. VSP represents a new dimension to brain plasticity that may underpin a range of vital physiological processes and is likely disrupted in numerous brain pathologies with a blood flow component. This work was supported by the American Heart Association (23POST1023086), and NIH grants 1DP2NS121347, 1R01AG066645, and 5R01NS115401. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Autocrine VEGF drives neural stem cell proximity to the adult hippocampus vascular niche.

The vasculature is a key component of adult brain neural stem cell (NSC) niches. In the adult mammalian hippocampus, NSCs reside in close contact with a dense capillary network. How this niche is maintained is unclear. We recently found that adult hippocampal NSCs express VEGF, a soluble factor with chemoattractive properties for vascular endothelia. Here, we show that global and NSC-specific VEGF loss led to dissociation of NSCs and their intermediate progenitor daughter cells from local vasculature. Surprisingly, though, we found no changes in local vascular density. Instead, we found that NSC-derived VEGF supports maintenance of gene expression programs in NSCs and their progeny related to cell migration and adhesion. In vitro assays revealed that blockade of VEGF receptor 2 impaired NSC motility and adhesion. Our findings suggest that NSCs maintain their own proximity to vasculature via self-stimulated VEGF signaling that supports their motility towards and/or adhesion to local blood vessels.

Noninvasive in vivo microscopy of single neutrophils in the mouse brain via NIR-II fluorescent nanomaterials.

In vivo microscopy of single cells enables following pathological changes in tissues, revealing signaling networks and cell interactions critical to disease progression. However, conventional intravital microscopy at visible and near-infrared wavelengths <900 nm (NIR-I) suffers from attenuation and is typically performed following the surgical creation of an imaging window. Such surgical procedures cause the alteration of the local vasculature and induce inflammation in skin, muscle and skull, inevitably altering the microenvironment in the imaging area. Here, we detail the use of near-infrared fluorescence (NIR-II, 1,000-1,700 nm) for in vivo microscopy to circumvent attenuation in living tissues. This approach enables the noninvasive visualization of cell migration in deep tissues by labeling specific cells with NIR-II lanthanide downshifting nanoparticles exhibiting high physicochemical stability and photostability. We further developed a NIR-II fluorescence microscopy setup for in vivo imaging through the intact skull with high spatiotemporal resolution, which we use for the real-time dynamic visualization of single-neutrophil behavior in the deep brain of a mouse model of ischemic stroke. The labeled downshifting nanoparticle synthesis takes 5-6 d, the imaging system setup takes 1-2 h, the in vivo cell labeling takes 1-3 h, the in vivo NIR-II microscopic imaging takes 3-5 h and the data analysis takes 3-8 h. The procedures can be performed by users with standard laboratory training in nanomaterials research and appropriate animal handling.

Adaptive patterning of vascular network during avian skin development: Mesenchymal plasticity and dermal vasculogenesis

A vasculature network supplies blood to feather buds in the developing skin. Does the vasculature network during early skin development form by sequential sprouting from the central vasculature or does local vasculogenesis occur first that then connect with the central vascular tree? Using transgenic Japanese quail Tg(TIE1p.H2B-eYFP), we observe that vascular progenitor cells appear after feather primordia formation. The vasculature then radiates out from each bud and connects with primordial vessels from neighboring buds. Later they connect with the central vasculature. Epithelial-mesenchymal recombination shows local vasculature is patterned by the epithelium, which expresses FGF2 and VEGF. Perturbing noggin expression leads to abnormal vascularization. To study endothelial origin, we compare transcriptomes of TIE1p.H2B-eYFP+ cells collected from the skin and aorta. Endothelial cells from the skin more closely resemble skin dermal cells than those from the aorta. The results show developing chicken skin vasculature is assembled by (1) physiological vasculogenesis from the peripheral tissue, and (2) subsequently connects with the central vasculature. The work implies mesenchymal plasticity and convergent differentiation play significant roles in development, and such processes may be re-activated during adult regeneration. Summary statementWe show the vasculature network in the chicken skin is assembled using existing feather buds as the template, and endothelia are derived from local bud dermis and central vasculature.

Single-cell adhesive profiling in an optofluidic device elucidates CD8+ T lymphocyte phenotypes in inflamed vasculature-like microenvironments

Tissue infiltration by circulating leukocytes occurs via adhesive interactions with the local vasculature, but how the adhesive quality of circulating cells guides the homing of specific phenotypes to different vascular microenvironments remains undefined. We developed an optofluidic system enabling fluorescent labeling of photoactivatable cells based on their adhesive rolling velocity in an inflamed vasculature-mimicking microfluidic device under physiological fluid flow. In so doing, single-cell level multidimensional profiling of cellular characteristics could be characterized and related to the associated adhesive phenotype. When applied to CD8+ Tcells, ligand/receptor expression profiles and subtypes associated with adhesion were revealed, providing insight into inflamed tissue infiltration capabilities of specific CD8+ T lymphocyte subsets and how local vascular microenvironmental features may regulate the quality of cellular infiltration. This methodology facilitates rapid screening of cell populations for enhanced homing capabilities under defined biochemical and biophysical microenvironments, relevant to leukocyte homing modulation in multiple pathologies.

Twenty-four hour diurnal variation in retinal oxygen saturation

Retinal oxygen saturation is influenced by systemic and local vasculature, intraocular pressure (IOP), and individual cellular function. In numerous retinal pathologies, early changes take place at the level of the microvasculature, thereby affecting retinal oxygenation. The purpose of this study was to investigate diurnal variations in retinal oximetry measures and evaluate the relationship with other ocular and systemic physiological processes. Healthy adults (n = 18, mean age 27 ± 5.5 years) participated. Ocular and systemic measures were collected every four hours over 24 h and included retinal oximetry, IOP, optical coherence tomography (OCT), OCT-angiography (OCTA), biometry, blood pressure, and partial pressure of oxygen. Amplitude and acrophase for retinal oxygen saturation, axial length, retinal and choroidal thickness, OCTA parameters, and mean arterial and ocular perfusion pressure (MAP, MOPP) were determined were determined using cosine fits, and multiple regression analysis was performed to compare metrics. Retinal oxygenation saturation demonstrated a significant diurnal variation with an amplitude of 5.84 ± 3.86% and acrophase of 2.35 h. Other parameters that demonstrated significant diurnal variation included IOP, MOPP, axial length, choroidal thickness, superficial vessel density, heart rate, systolic blood pressure, and MAP. Diurnal variations in retinal oxygen saturation were in-phase with choroidal thickness, IOP, and density of the superficial vascular plexus and out-of-phase with axial length and MOPP. In conclusion, retinal oxygenation saturation undergoes diurnal variations over 24 h. These findings contribute to a better understanding of intrinsic and extrinsic factors influencing oxygenation of the area surrounding the fovea.

A new fasciocutaneous flap model identifies a critical role for endothelial Notch signaling in wound healing and flap survival

Flap surgery is a common treatment for severe wounds and a major determinant of surgical outcome. Flap survival and healing depends on adaptation of the local flap vasculature. Using a novel and defined model of fasciocutaneous flap surgery, we demonstrate that the Notch ligand Delta-like 1 (Dll1), expressed in vascular endothelial cells, regulates flap arteriogenesis, inflammation and flap survival. Utilizing the stereotyped anatomy of dorsal skin arteries, ligation of the major vascular pedicle induced strong collateral vessel development by end-to-end anastomosis in wildtype mice, which supported flap perfusion recovery over time. In mice with heterozygous deletion of Dll1, collateral vessel formation was strongly impaired, resulting in aberrant vascularization and subsequent necrosis of the tissue. Furthermore, Dll1 deficient mice showed severe inflammation in the flap dominated by monocytes and macrophages. This process is controlled by endothelial Dll1 in vivo, since the results were recapitulated in mice with endothelial-specific deletion of Dll1. Thus, our model provides a platform to study vascular adaptation to flap surgery and molecular and cellular regulators influencing flap healing and survival.

Simplified soft tissue coverage of the distal lower extremity: The reverse sural flap.

Soft tissue defects involving the distal lower extremity present challenging problems for orthopaedic surgeons to manage. Historically, wounds not amenable to primary closure have necessitated assistance from multidisciplinary teams using plastic surgeons to obtain adequate soft tissue coverage through rotational flap or free tissue transfer procedures. Techniques related to soft tissue rearrangement and local rotational flap coverage have advanced over the years with a growing knowledge of local anatomy and vasculature. The reverse sural flap may be performed to cover soft tissue defects within 10 cm of the foot or ankle region, negating the need for microvascular intervention. The simplistic nature of the reverse sural flap is appealing to orthopaedic surgeons as a means to provide timely patient care without additional support because it does not require microvasculature work or the need for intraoperative microscopes and has been popularized among orthopaedic trauma surgeons as a necessary tool to possess. Here, we discuss the reverse sural flap to include history, relevant anatomy, clinical indications, and a description of the technique for application.

MDB-42. UNCOVERING DYNAMIC CHANGES IN MEDULLOBLASTOMA ASSOCIATED VASCULATURE IN ZEBRAFISH

Abstract Medulloblastoma (MB) is an embryonal-derived lesion arising in the cerebellum, contributing to 20% of childhood brain tumours and 63% of intracranial embryonal tumours. Currently, standard of care includes surgical resection and chemotherapy, used in conjunction with radiation. While these treatments have significantly improved survival rates, the therapy side effects are detrimental to survivors’ quality of life. Furthermore, relapse occurs in 30% of patients and unfortunately these are untreatable and therefore fatal for 95% of patients. It is presumed that in patients that present with a recurrent tumour, initial treatment has been ineffective. A major cause of this can be the heterogenous vasculature in and around the tumour. Recent studies have identified that the blood brain barrier (BBB), in the context of MB, is highly heterogenous with differences in BBB cellular composition and integrity between MB sub-types and within single tumours. It remains unclear however, how these vascular differences emerge and what the primary defects are. This gap in our knowledge is mainly due to the lack of models that allow long-term live imaging. We have established a xenograft approach to examine human MB tumour cells in zebrafish embryonal brains. We have validated that human Medulloblastoma cells of the Group 3 (Gp3) MB subgroup, are viable in zebrafish brains. This work has also identified that in the presence of these human Gp3 MB tumour cells, the local vasculature becomes dysmorphic and tortuous over time. Timelapse imaging of these tumour and vasculature interactions demonstrates that there is a rapid and long ranging angiogenic response with new vessel sprouts growing towards the tumour cells. By utilising our large range of transgenic zebrafish lines, we will continue investigating how MB cells interact and alter distinctive BBB cell types and how these changes impact vessel function.

Propeller Perforator Flaps Used for Hand and Digit Reconstruction: A Systematic Review

BackgroundPropeller perforator flaps (PPFs) have increased in popularity due to the freedom in design and ability to cover a variety of defects without sacrificing the major vessels. Present reports of PPFs for upper limb reconstruction have not provided guidance for hand reconstruction, specifically. This study aims to review the current literature and evaluate techniques for use of PPFs in hand reconstruction. MethodsA comprehensive literature review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for articles published from 1991 to 2021. The database search was queried for records using appropriate Medical Subject Headings (MeSH) terms. Studies reporting PPFs were limited to English language and excluded lower extremity or upper extremity reconstruction not specific to defects in the hand or digits. Study characteristics, patient demographics, indications, preoperative testing, flap characteristics, flap survival, and complication rates were collected. ResultsOut of the initial 1,348 citations yielded, 71 underwent full-text review. Ultimately, 25 unique citations were included encompassing 12 retrospective reviews (48%), 3 prospective cohort studies (10%), and 10 case series (40%). In review, 525 patients underwent reconstruction with a total of 613 propeller flaps performed to repair defects of the hand, digits, or both with use of 18 unique flap types. Overall flap survival was 97.8%. Acute wounds accounted for 72.9% of performed reconstructions. The mean flap coverage was 14.7 cm2. Complications occurred in 19.8% of cases, with venous congestion and partial flap necrosis occurring in 5.5 and 6.5% of cases, respectively, leading to a flap failure rate of 2.1%. ConclusionPPFs are a reliable option for hand or digital reconstruction, allowing surgeons to cover a variety of defects without sacrificing local vasculature. Despite nearly a 20% reported complication rate, nearly all flaps with venous congestion and partial flap necrosis included in these articles resolved without the need for secondary intervention, retaining an excellent overall flap survival.

Pyrrolopyrrole aza-BODIPY-based NIR-II fluorophores for in vivo dynamic vascular dysfunction visualization of vascular-targeted photodynamic therapy

Real-time monitoring vascular responses is crucial for evaluating the therapeutic effects of vascular-targeted photodynamic therapy (V-PDT). Herein, we developed a highly-stable and bright aggregation induced emission (AIE) fluorophore (PTPE3 NP) for dynamic fluorescence (FL) imaging of vascular dysfunction beyond 1300 nm window during V-PDT. The superior brightness (ϵmaxΦf>1000 nm ≈ 180.05 M−1 cm−1) and high resolution of PTPE3 NP affords not only high-clarity images of whole-body and local vasculature (hindlimbs, mesentery, and tumor) but also high-speed video imaging for tracking blood circulation process. By virtue of the NPs’ prolonged blood circulation time (t1/2 ≈ 86.5 min) and excellent photo/chemical (pH, RONS) stability, mesenteric and tumor vascular dysfunction (thrombosis formation, vessel occlusion, and hemorrhage) can be successfully visualized during V-PDT by FL imaging for the first time. Furthermore, the reduction of blood flow velocity (BFV) can be monitored in real time for precisely evaluating efficacy of V-PDT. These provide a powerful approach for assessing vascular responses during V-PDT and promote the development of advanced fluorophores for biological imaging.

Abstract 4585: Tumor lymphangiogenesis sensitizes melanomas to the immunological effects of radiotherapy but also disrupts the local lymphatic vasculature

Abstract Tumor lymphangiogenesis is typically associated with cancer progression and metastasis. However, recent studies from our group have demonstrated that tumor lymphangiogenesis promotes intratumor T cell infiltration and potentiates the efficacy of a wide range of immunotherapies in melanoma-bearing mice as well as patients undergoing checkpoint blockade. Radiotherapy (RT) can also induce immunogenic tumor cell death, so we investigated whether lymphangiogenic tumors would yield more immunogenic responses to RT than non-lymphangiogenic tumors. Here, we compared effects of RT in mice bearing B16-F10 melanomas expressing either a control vector (B16-Ctrl) or overexpression the lymphangiogenic factor VEGF-C (B16-VC), where lymphatic vessels were significantly increased in number and size compared to B16-Ctrl tumors. First, we find that B16-VC regress faster than B16-CT after RT (either a single 20 Gy dose or two 15 Gy doses), and that this regression was correlated with enhanced CD8+ T cell activity. On the other hand, lymphatic endothelial cells (LECs) can be more sensitive to damage from RT if they are undergoing lymphangiogenesis. We found that irradiated B16-VC tumors showed higher levels of intra-lymphatic fibrin. Consistent with this, LECs in the irradiated B16-VC tumors expressed higher levels of tissue factor and caspase-3, which correlated with the degree of lymphatic clotting. Fibrin clotting was also observed in the subcapsular sinus of the draining lymph nodes of irradiated B16-VC tumors. These findings highlight the complex role of tumor lymphangiogenesis in radiotherapy responses, where they may potentiate acute anti-tumor immune responses but may also cause localized damage of the vasculature, potentially leading to increased metastasis. Further studies are needed to investigate therapeutic targets to inhibit lymphatic coagulation and look at its effects on cancer immunotherapy and metastasis. Citation Format: Anish Mukherjee, Nikolaos Mitrousis, Mari Stella Sasso, Margo MacDonald, Ainhoa Arina, Phillip Ang, Ariana Baginski, J. Emiliano G. Medellin, Ralph R. Weichselbaum, Melody A. Swartz. Tumor lymphangiogenesis sensitizes melanomas to the immunological effects of radiotherapy but also disrupts the local lymphatic vasculature. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4585.

Oxygen-Generating Biomaterials for Translational Bone Regenerative Engineering.

Successful regeneration of critical-size defects remains one of the significant challenges in regenerative engineering. These large-scale bone defects are difficult to regenerate and are often reconstructed with matrices that do not provide adequate oxygen levels to stem cells involved in the regeneration process. Hypoxia-induced necrosis predominantly occurs in the center of large matrices since the host tissue's local vasculature fails to provide sufficient nutrients and oxygen. Indeed, utilizing oxygen-generating materials can overcome the central hypoxic region, induce tissue in-growth, and increase the quality of life for patients with extensive tissue damage. This article reviews recent advances in oxygen-generating biomaterials for translational bone regenerative engineering. We discussed different oxygen-releasing and delivery methods, fabrication methods for oxygen-releasing matrices, biology, oxygen's role in bone regeneration, and emerging new oxygen delivery methods that could potentially be used for bone regenerative engineering.

Influence of stent-induced vessel deformation on hemodynamic feature of bloodstream inside ICA aneurysms

One of the effective treatment options for intracranial aneurysms is stent-assisted coiling. Though, previous works have demonstrated that stent usage would result in the deformation of the local vasculature. The effect of simple stent on the blood hemodynamics is still uncertain. In this work, hemodynamic features of the blood stream on four different ICA aneurysm with/without interventional are investigated. To estimate the relative impacts of vessel deformation, four distinctive ICA aneurysm is simulated by the one-way FSI technique. Four hemodynamic factors of aneurysm blood velocity, wall pressure and WSS are compared in the peak systolic stage to disclose the impact of defamation by the stent in two conditions. The stent usage would decrease almost all of the mentioned parameters, except for OSI. Stenting reduces neck inflow rate, while the effect of interventional was not consistent among the aneurysms. The deformation of an aneurysm has a strong influence on the hemodynamics of an aneurysm. This outcome is ignored by most of the preceding investigations, which focused on the pre-interventional state for studying the relationship between hemodynamics and stents. Present results show that the application of stent without coiling would improve most hemodynamic factors, especially when the deformation of the aneurysm is high enough.

A phenomenological model of proton FLASH oxygen depletion effects depending on tissue vasculature and oxygen supply.

Radiation-induced oxygen depletion in tissue is assumed as a contributor to the FLASH sparing effects. In this study, we simulated the heterogeneous oxygen depletion in the tissue surrounding the vessels and calculated the proton FLASH effective-dose-modifying factor (FEDMF), which could be used for biology-based treatment planning. The dose and dose-weighted linear energy transfer (LET) of a small animal proton irradiator was simulated with Monte Carlo simulation. We deployed a parabolic partial differential equation to account for the generalized radiation oxygen depletion, tissue oxygen diffusion, and metabolic processes to investigate oxygen distribution in 1D, 2D, and 3D solution space. Dose and dose rates, particle LET, vasculature spacing, and blood oxygen supplies were considered. Using a similar framework for the hypoxic reduction factor (HRF) developed previously, the FEDMF was derived as the ratio of the cumulative normoxic-equivalent dose (CNED) between CONV and UHDR deliveries. Dynamic equilibrium between oxygen diffusion and tissue metabolism can result in tissue hypoxia. The hypoxic region displayed enhanced radio-resistance and resulted in lower CNED under UHDR deliveries. In 1D solution, comparing 15 Gy proton dose delivered at CONV 0.5 and UHDR 125 Gy/s, 61.5% of the tissue exhibited ≥20% FEDMF at 175 μm vasculature spacing and 18.9 μM boundary condition. This percentage reduced to 34.5% and 0% for 8 and 2 Gy deliveries, respectively. Similar trends were observed in the 3D solution space. The FLASH versus CONV differential effect remained at larger vasculature spacings. A higher FLASH dose rate showed an increased region with ≥20% FEDMF. A higher LET near the proton Bragg peak region did not appear to alter the FLASH effect. We developed 1D, 2D, and 3D oxygen depletion simulation process to obtain the dynamic HRF and derive the proton FEDMF related to the dose delivery parameters and the local tissue vasculature information. The phenomenological model can be used to simulate or predict FLASH effects based on tissue vasculature and oxygen concentration data obtained from other experiments.

Uterine NK Cells Ace an "A" in Education: NKG2A Sets Up Crucial Functions at the Maternal-Fetal Interface.

I argue here that reproduction was a driving force in the evolution of NK-cell education, which is set by interactions between inhibitory receptors and self MHC. Maternal lymphocytes also interact with allogeneic MHC on fetal trophoblast cells. How the maternal immune system accommodates the semi-allogeneic fetus is a fascinating question. But it may be the wrong question. Tissue lymphocytes, like uterine NK (uNK) cells, do not attack the mismatched fetus and its placenta. Instead, they help the local vasculature to accommodate changes necessary to nourish the fetus. Education of uNK cells, driven by the ancient CD94:NKG2A inhibitory receptor and self MHC, sets them up to deliver these key functions at the maternal-fetal interface. /112

Chronic Exertional Compartment Syndrome of the Lower Extremity: Diagnosis and Surgical Treatment.

Chronic exertional compartment syndrome of the lower extremity is a condition that characteristically presents as recurrent anterior, posterior, and/or lateral lower-extremity pain on repetitive activity and physical exertion1. This condition is commonly seen in athletes, runners, and military personnel2. Open fasciotomy has been demonstrated to be a highly effective surgical treatment for patients with this condition who do not experience symptomatic relief after a thorough trial of nonoperative treatment3. Diagnostic compartment pressure management is achieved through direct insertion of a compartment-pressure-measuring device into the anterior, lateral, and posterior compartments of the lower extremity4. Surgical treatment of the anterior and lateral compartments with use of open fasciotomy employs longitudinal proximal and distal incisions that are made on the lateral surface of the leg approximately 3 finger-breadths distal and proximal to the fibular flare, respectively, and 3 finger-breadths lateral to the tibial crest. Surgical treatment of the posterior compartments with use of open fasciotomy employs a single, mid-shaft incision made approximately 2.5 cm medial to the tibial ridge. Dissection is carried down to the deep fascia at both sites, beginning at the distal operative site. Care is taken to avoid transection of the superficial peroneal nerve at the distal anterolateral incision and saphenous vein and nerve at the medial incision. Once down to the deep fascia, a scalpel is utilized to incise the fascia. Metzenbaum scissors are then employed under the incision, spreading the scissors while sliding them over the muscles proximally and distally to release the muscular attachments from the fascia as well as to release the fascia itself3. This process is repeated in the anterior, lateral, and superficial posterior compartments through the proximal and distal incisions. In the deep posterior compartment, the fascia is released from the tibial ridge with a large Cobb elevator. Closure is achieved with deep dermal and superficial sutures. Nonoperative alternatives have been reported to include nonpharmacological modalities such as walking modification and shoe inserts, pharmacological therapy with nonsteroidal anti-inflammatory drugs, and physical therapy targeted at conditioning the lower extremity5. Nonoperative intervention has been demonstrated to increase endurance in select patients; however, most patients must either stop the activity associated with the compartment syndrome altogether or proceed to surgery for complete resolution of symptoms5. There are a few surgical alternatives that differ in their utilization of minimally invasive approaches versus a direct open approach6; however, all existing surgical treatments of this condition involve physical release of the fascial compartment. Diagnostic compartment-pressure measurement is useful in confirming or ruling out the presence of this condition in patients with unclear symptoms4. Furthermore, diagnostic compartment-pressure management ensures accuracy in diagnosis and validates invasive treatment when patients desire surgical intervention. Surgical management of exertional compartment syndrome of the lower extremity is indicated in patients when nonoperative treatment has failed despite clinically notable symptoms and objectively elevated lower-extremity compartment pressures. Open fasciotomy has been postulated to prevent compression of local vasculature and effectively prevent ischemia; however, the definitive mechanism is unclear1. Surgical treatment of chronic exertional compartment syndrome with use of open fasciotomy is highly successful in the civilian population. One study showed excellent return to activity/sport in 15 of 16 patients (25 of 26 limbs; 96%), with patients often reporting no symptoms postoperatively3. Military personnel have been reported to experience satisfactory results, with another study showing positive subjective feedback in 35 (76%) of 46 patients on long-term follow-up; however, only 19 patients (41%) were able to return to full active duty postoperatively7. Balloting the fascial compartment with ∼1 cc of saline solution can be helpful in determining successful placement of the pressure-measuring device at the time of needle entry.Identifying the course of the superficial peroneal nerve via physical examination can help avoid iatrogenic injury to this important superficial structure during the dissection leading to the distal fasciotomy.Deep posterior compartment release with use of open fasciotomy may not provide symptomatic relief; patients who demonstrate elevation of pressures in this specific compartment should be counseled accordingly. ROM = range of motionSPN = superficial peroneal nerve.

A single-cell map of vascular and tissue lymphocytes identifies proliferative TCF-1+ human innate lymphoid cells.

Innate lymphoid cells (ILCs) play important roles in tissue homeostasis and host defense, but the proliferative properties and migratory behavior of especially human ILCs remain poorly understood. Here we mapped at single-cell resolution the spatial distribution of quiescent and proliferative human ILCs within the vascular versus tissue compartment. For this purpose, we employed MISTRG humanized mice as an in-vivo model to study human ILCs. We uncovered subset-specific differences in the proliferative status between vascular and tissue ILCs within lymphoid and non-lymphoid organs. We also identified CD117-CRTH2-CD45RA+ ILCs in the spleen that were highly proliferative and expressed the transcription factor TCF-1. These proliferative ILCs were present during the neonatal period in human blood and emerged early during population of the human ILC compartment in MISTRG mice transplanted with human hematopoietic stem and progenitor cells (HSPCs). Single-cell RNA-sequencing combined with intravascular cell labeling suggested that proliferative ILCs actively migrated from the local vasculature into the spleen tissue. Collectively, our comprehensive map reveals the proliferative topography of human ILCs, linking cell migration and spatial compartmentalization with cell division.

IFN-γ-dependent tumor-antigen cross-presentation by lymphatic endothelial cells promotes their killing by T cells and inhibits metastasis.

Tumor-associated lymphatic vessels promote metastasis and regulate antitumor immune responses. Here, we assessed the impact of cytotoxic T cells on the local lymphatic vasculature and concomitant tumor dissemination during an antitumor response. Interferon-γ (IFN-γ) released by effector T cells enhanced the expression of immunosuppressive markers by tumor-associated lymphatic endothelial cells (LECs). However, at higher effector T cell densities within the tumor, T cell–based immunotherapies induced LEC apoptosis and decreased tumor lymphatic vessel density. As a consequence, lymphatic flow was impaired, and lymph node metastasis was reduced. Mechanistically, T cell–mediated tumor cell death induced the release of tumor antigens and cross-presentation by tumor LECs, resulting in antigen-specific LEC killing by T cells. When LECs lacked the IFN-γ receptor expression, LEC killing was abrogated, indicating that IFN-γ is indispensable for reducing tumor-associated lymphatic vessel density and drainage. This study provides insight into how cytotoxic T cells modulate tumor lymphatic vessels and may help to improve immunotherapeutic protocols.