Biomarkers from subcutaneous engineered tissues predict acute rejection of organ allografts

Invasive graft biopsies assess the efficacy of immunosuppression through lagging indicators of transplant rejection. We report on a microporous scaffold implant as a minimally invasive immunological niche to assay rejection before graft injury. Adoptive transfer of T cells into Rag2-/- mice with mismatched allografts induced acute cellular allograft rejection (ACAR), with subsequent validation in wild-type animals. Following murine heart or skin transplantation, scaffold implants accumulate predominantly innate immune cells. The scaffold enables frequent biopsy, and gene expression analyses identified biomarkers of ACAR before clinical signs of graft injury. This gene signature distinguishes ACAR and immunodeficient respiratory infection before injury onset, indicating the specificity of the biomarkers to differentiate ACAR from other inflammatory insult. Overall, this implantable scaffold enables remote evaluation of the early risk of rejection, which could potentially be used to reduce the frequency of routine graft biopsy, reduce toxicities by personalizing immunosuppression, and prolong transplant life.

Age-associated adipose tissue inflammation promotes monocyte chemotaxis and enhances atherosclerosis

Although aging enhances atherosclerosis, we do not know if this occurs via alterations in circulating immune cells, lipid metabolism, vasculature, or adipose tissue. Here, we examined whether aging exerts a direct pro-atherogenic effect on adipose tissue in mice. After demonstrating that aging augmented the inflammatory profile of visceral but not subcutaneous adipose tissue, we transplanted visceral fat from young or aged mice onto the right carotid artery of Ldlr-/- recipients. Aged fat transplants not only increased atherosclerotic plaque size with increased macrophage numbers in the adjacent carotid artery, but also in distal vascular territories, indicating that aging of the adipose tissue enhances atherosclerosis via secreted factors. By depleting macrophages from the visceral fat, we identified that adipose tissue macrophages are major contributors of the secreted factors. To identify these inflammatory factors, we found that aged fat transplants secreted increased levels of the inflammatory mediators TNFα, CXCL2, and CCL2, which synergized to promote monocyte chemotaxis. Importantly, the combined blockade of these inflammatory mediators impeded the ability of aged fat transplants to enhance atherosclerosis. In conclusion, our study reveals that aging enhances atherosclerosis via increased inflammation of visceral fat. Our study suggests that future therapies targeting the visceral fat may reduce atherosclerosis disease burden in the expanding older population.

Continuous glucose monitoring reveals glycemic variability and hypoglycemia after vertical sleeve gastrectomy in rats

Objective

Post–bariatric surgery hypoglycemia (PBH) is defined as the presence of neuroglycopenic symptoms accompanied by postprandial hypoglycemia in bariatric surgery patients. Recent clinical studies using continuous glucose monitoring (CGM) technology revealed that PBH is more frequently observed in vertical sleeve gastrectomy (VSG) patients than previously recognized. PBH cannot be alleviated by current medication. Therefore, a model system to investigate the mechanism and treatment is required.

Methods

We used CGM in a rat model of VSG and monitored the occurrence of glycemic variability and hypoglycemia in various meal conditions for 4 weeks after surgery. Another cohort of VSG rats with CGM was used to investigate whether the blockade of glucagon-like peptide-1 receptor (GLP-1R) signaling alleviates these symptoms. A mouse VSG model was used to investigate whether the impaired glucose counterregulatory system causes postprandial hypoglycemia.

Results

Like in humans, rats have increased glycemic variability and hypoglycemia after VSG. Postprandial hypoglycemia was specifically detected after liquid versus solid meals. Further, the blockade of GLP-1R signaling raises the glucose nadir but does not affect glycemic variability.

Conclusions

Rat bariatric surgery duplicates many features of human post–bariatric surgery hypoglycemia including postprandial hypoglycemia and glycemic variability, while blockade of GLP-1R signaling prevents hypoglycemia but not the variability.

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VSG causes glycemic variability during ad lib feeding condition.

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Single liquid meal ingestion causes post-VSG hypoglycemia.

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Blockade of GLP-1 receptor prevents post-VSG hypoglycemia.

Resolution of venous thrombosis using a novel oral small-molecule inhibitor of P-selectin (PSI-697) without anticoagulation

P-selectin inhibition has been shown to decrease thrombogenesis in multiple animal species. In this study, we show that a novel oral small-molecule inhibitor of P-selectin, PSI-697, promotes thrombus resolution and decreases inflammation in a baboon model of venous thrombosis. Experimental groups consisted of the following: 1) primates receiving a single oral dose of PSI-697 (30 mg/kg) daily starting three days pre-iliac vein balloon occlusion, and continued for six days; 2) primates receiving a single treatment dose of a low-molecular-weight-heparin (LMVVH) (1.5 mg/kg) daily starting one day pre-iliac balloon occlusion, and continued for six days; and 3) primates receiving a single oral dose of a vehicle control daily starting three days pre-iliac vein balloon occlusion, and continued for six days. Animals receiving PSI-697, although thrombosed after balloon deflation, demonstrated greater than 80% vein lumen opening over time, with no opening (0%) for vehicle control (p<0.01). LMVVH opening evident after balloon deflation slightly deteriorated overtime compared to PSI-697. PSI-697 therapy also significantly decreased vein wall inflammation determined by magnetic resonance venography (MRV). Importantly, this beneficial opening occurred without measured anticoagulation. Animals receiving PSI-697 demonstrated significantly increased plasma D-dimer levels versus LMVVH and control animals six hours post thrombus induction (p<0.01). This study is the first to demonstrate the effectiveness of oral P-selectin inhibition to modify venous thrombogenesis, increase vein lumen opening, and decrease inflammation in a large animal model.

Dose-dependent thrombus resolution due to oral plasminogen activator inhibitor (PAI)-1 inhibition with tiplaxtinin in a rat stenosis model of venous thrombosis

This study aimed to evaluate a small-molecule PAI-1 inhibitor (PAI-039; tiplaxtinin) in a rodent stenosis model of venous thrombosis in a two-phase experiment. Phase 1 determined the efficacy of tiplaxtinin against Lovenox (LOV), while phase 2 determined the dose-dependent efficacy. For both phases, drug treatment began 24 hours after surgically induced venous thrombosis and continued for four days. Phase 1 animals (n = 24) receiving low-dose (LD; 1 mg/kg oral gavage) PAI-1 inhibitor demonstrated a 52% decrease in thrombus weight (TW) versus controls (p < 0.05) with significant reductions in active plasma PAI-1, while the high-dose (HD; 10 mg/kg oral gavage) group demonstrated a 23% reduction in TW versus controls. Animals treated subcutaneously with LOV (3 mg/kg) showed a 39% decrease in TW versus controls (p < 0.05). Coagulation tests (aPTT and TCT) were significantly different in LOV compared to PAI-1 inhibitor groups. PAI-039 treatment was also associated with significantly increased return of inferior vena cava blood flow four days post-thrombosis versus controls (p < 0.05). In phase 2 (n = 30), TW was reduced from the 0.5 mg/kg to 5 mg/ kg experimental groups, with the 10 mg/kg group demonstrating a paradoxical increase. The 5 mg/kg group showed statistically significant decreases in TW versus controls after four treatment days (p < 0.05). This is the first study to demonstrate dose related effects of PAI-039 on increasing thrombus resolution and inferior vena cava blood flow without adverse effects on anti-coagulation in a rat stenosis model of venous thrombosis.

Leukocyte- and platelet-derived microparticles correlate with thrombus weight and tissue factor activity in an experimental mouse model of venous thrombosis

Microparticles (MP) are lipid vesicles from platelets, leukocytes and endothelial cells that are involved in early thrombogenesis. We evaluated a detailed time-course analysis of MPs on thrombogenesis and the associated tissue factor (TF) activity in wild-type, in gene-deleted for E- and P-selectins and with high levels of P-selectin expression after the initiation of venous thrombosis in mice.Inferior vena cava (IVC) ligation was performed on C57BL/6 mice (n =191, 59 = wild-type [WT], 55 = gene-deleted for E- and P – selectins [knock-outs, EPKO] and 77 = elevated levels of soluble P-selectin, named Delta Cytoplasmic Tail (ΔCT). Animals were euthanised at various time points to assess MP production, origin and thrombus weight. MPs were re-injected into separate mice at concentrations of 80,000 and 160,000 units, as well as from different ages. In addition, MPs from thrombosed animals were pooled and TF activity quantitated using a chromogenic assay. Thrombus weight correlated negatively with MPs derived from leukocytes, and positively with MPs derived from platelets for WT animals (p<0.05), while MPs from platelets presented a positive correlation to thrombus weight in the WT and EPKO groups (p<0.01). Total MPs correlated negatively with thrombus weight in the ΔCT group (p<0.05). MP re-injections led to greater thrombus weight, while older MP reinjections tended to form larger thrombus than younger. Finally, TF bearing MPs showed a significant correlation to MP concentrations (R=0.99). In conclusion, MPs appear to be an important element in venous thrombogenesis.

Tissue inhibitor of metalloproteinase-1 is an early marker of acute endothelial dysfunction in a rodent model of venous oxidative injury

Although there are extensive research data regarding arterial endothelial dysfunction, the effects of venous endothelial dysfunction are not well characterized. Matrix metalloproteinases (MMPs) have a defined role in vascular remodeling. MMPs are endopeptidases that are capable of degrading extracellular matrix proteins. We hypothesize that tissue inhibitor of metalloproteinase-1 (TIMP-1) can serve as an indicator of acute venous endothelial dysfunction in a rat model of oxidative injury. The experimental groups evaluated were as follows: rats not undergoing oxidative injury (controls), rats that received rose bengal but no laser (shams), and rats that received both rose bengal and laser illumination, resulting in an oxidative injury. Animals were evaluated at baseline (control, shams) and at 1 hr and 1 day post-oxidative injury. mRNA expression was determined by gene array technology and real-time polymerase chain reaction, plasma and vein wall TIMP-1 protein concentrations were determined by enzyme-linked immunosorbent assay, and vein wall morphometrics (cells/five high-power fields) were performed. B-cell lymphoma 2-like gene expression was upregulated at both 1 hr and 1 day post-injury. TIMP-1 protein and mRNA expression were significantly increased post-oxidative injury. One hour postinjury, vein wall polymorphonuclear leukocytes were present in significant numbers. Our results support the hypothesis that increased expression of TIMP-1 in venous endothelium and plasma may serve as an early indicator of endothelial dysfunction.

Selectins influence thrombosis in a mouse model of experimental deep venous thrombosis

BACKGROUND

This study characterizes venous thrombosis in the mouse and examines the important role that the adhesion molecules P-selectin and E-selectin and the anti-inflammatory cytokine interleukin-10 (IL-10) play in the thrombotic process.

MATERIALS AND METHODS

C57BL/6 (wild-type) mice in a natural history protocol (Phase I) and gene-targeted (KO) mice for P-selectin, E-selectin, P/E-selectin, and IL-10 in a follow-up protocol (Phase II) were studied. Inferior vena caval thrombosis was produced by ligation just below the renal veins, and mice were sacrificed and evaluated at various time points up to 12 days later.

RESULTS

Phase I: A significant increase in neutrophils on day 2 and in monocytes on day 6 postthrombosis was found in ligated vs sham animals. An associated significant increase in vein wall P-selectin mRNA (6 h, day 2) and an increase in protein (6 h through day 6) were found, while E-selectin mRNA was significantly increased (day 2 through day 6), with a smaller increase in E-selectin protein. IL-10 mRNA increased significantly later (day 2 through day 9), with the values increasing progressively. A positive correlation existed (r = 0.77) between neutrophils and thrombosis at day 2.

PHASE II

The E-selectin and P/E-selectin double-KO mice showed the least thrombus at day 2 vs wild-type clotted mice, P < 0.01. Additionally, P/E-KO mice demonstrated the lowest inflammatory cell extravasation into the vein wall at day 2.

CONCLUSIONS

This study demonstrates an acute to chronic inflammatory response in the vein wall associated with venous thrombosis. Inhibition of selectins decreased thrombus formation.

Effects of ovariectomy in beagle dogs

Beagle dogs 3-7 years old were ovariectomized (n = 9) or sham operated (n = 6) and followed for 48 weeks with measurements of body weight, tibial shaft bone mineral content (BMC), and serum biochemistry. Following killing, measurements were made of bone strength and histomorphometry. Ovariectomy (OX) significantly reduced serum estrone and estradiol concentrations and their variability from month to month. There was a transient decrease in cortical BMC of the OX dogs during the first 12 postoperative weeks but no difference between the groups after 48 weeks. Serum osteocalcin was elevated, but there was little effect on serum alkaline phosphatase, Ca, P, or calcitonin. OX increased the number of tetracycline-labeled osteons in cortical bone but reduced the percent trabecular surface labeled with tetracycline. OX produced no significant changes in the composition of the bones or loss of cortical area, but a statistically significant 15% trabecular bone loss occurred in the spine. However, bone strength had not been significantly affected at the time of sacrifice.

Subclavian steal syndrome

Subclavian steal syndrome is caused by proximal subclavian occlusion with retrograde filling of the subclavian artery via the vertebral artery. This syndrome is characterized by symptoms due to decreased cerebral blood flow and decreased blood flow to the arm and hand. It is twice as common in men as in women. Diagnosis is confirmed with angiography. Medical management is of limited value. Surgery is the treatment of choice for the symptomatic patient.

Further investigation of hydrogel lens power changes due to flexure

Measured values for ametropia-correcting powers and front surface radii of lenses on the eye are compared to values which would be expected, using the Equal Change Hypothesis and the Invariant Normals-Constant Arc Hypothesis. Photographs of various lenses on the eye, with large molecule fluorescein instilled, are presented and show no noticeable tear lens of a finite power. These photographs and our data indicate that the Equal Change Hypothesis is not valid for predicting lens power changes due to flexure. In contrast, the Invariant Normals-Constant Arc Hypothesis appears to closely predict lens flexure effects. A clinical application of this study would be to note that thin minus hydrogels correct slightly more ametropia in their flexed state than in their unflexed state. Thin plus hydrogels correct slightly less ametropia in the flexed state than in the unflexed state.