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Previous studies have shown that adoptive cell transfer (ACT) of regulatory T cells (Tregs) mitigate AAA growth in mice, however these studies have used a dissection AAA model and have not thoroughly studied Treg function in mice after ACT. Treg suppression of systemic or local inflammation has not been rigorously studied in our model. We therefore sought to evaluate the effects of Treg ACT in mice with a specific focus on Treg migration, colonization, and inflammatory changes within local tissue. Methods: AAA was induced in B57Bl/6 mice expressing the Thy 1.2 allele using a topical elastase + BAPN model (E-BAPN). Heat inactivated elastase (HiE-BAPN) was used as a control. On postoperative day (POD) 2, animals were treated with PBS (E-BAPN-PBS) injection or ACT of 2 million Tregs (E-BAPN-Tregs). CD4+ CD25+ FoxP3+ Tregs used for ACT were isolated from B57Bl/6 mice expressing the Thy 1.1 allele. Mice underwent surveillance ultrasounds (US) weekly to track AAA growth for 42 days. At specific time points mice were sacrificed and aortic diameter was recorded. Aortic tissue and regional lymph nodes were harvested for analysis. Results: Maximum aortic diameter (MAD) by both US and video microscopy was significantly higher in the AAA group (E-BAPN vs. HiE-BAPN; pThy1.1+ Tregs were detected in the tissue and regional aortic lymph nodes (LN) until day 42 with only a slight declination in the percent Thy1.1 + cells over time. Thy1.1+ Tregs retained phenotypic markers over time. E-BAPN-Treg mice had significantly altered inflammatory markers compared to E-BAPN-PBS mice including local macrophage and T-cell composition as well as inflammatory cytokines. Conclusion: Treg ACT suppress AAA growth in a topical elastase + BAPN mouse model through tissue and LN colonization and alteration of the local inflammatory milieu.

Introduction: Regulatory T cells (Tregs) suppress inflammation in atherosclerosis, and therefore have the therapeutic potential to reduce the risk of MI and stroke. However, there is currently no method to generate antigen specific Tregs that target atherosclerosis. We therefore engineered Tregs that express a Chimeric Antigen Receptor (CAR) targeting malonaldehyde-modified LDL (MDA-LDL), the most common form of oxidized LDL and a key molecular component of atherosclerosis. Methods: Novel single chain variable fragments (scFv) were synthesized using sequences from antibodies targeting human MDA-LDL. Oxidized-LDL specific CARs (ox-CARs) were subsequently engineered by fusing each scFv to an IgG4 hinge, CD28 transmembrane and CD28/CD3z cytoplasmic domains. CD4 + CD25 + CD127 low/- Tregs were purified from human blood via FACS and lentivirally transduced to express the novel ox-CARs (ox-CAR-Tregs). Human atherosclerotic plaques were obtained from patients undergoing carotid endarterectomy (CEA). Autologous ox-CAR-Tregs were analyzed for activation after ex-vivo co-culture with CEA samples. Results: A rationally designed panel of 42 ox-CARs were engineered using scFv derived from 12 antibodies targeting MDA-LDL. We first assessed CAR expression and activation in Jurkat T cells to identify promising ox-CAR variants for further evaluation in human Tregs. After culture in the presence of MDA-LDL, six ox-CAR-Treg variants consistently showed significant activation, compared to controls, based on CD71 expression, cytokine expression and proliferation in the absence of CD3/28 stimulation. Human atherosclerotic samples were identified to have substantial amounts of MDA-LDL epitopes using IHC. Autologous ox-CAR-Tregs showed a dose-dependent increase in CD71 expression after ex-vivo co-culture with atherosclerotic plaque. Conclusion: An optimized CAR targeting MDA-LDL activates Tregs when cultured with human atherosclerotic plaque ex-vivo.

Background and Purpose: Homozygous mutation in arteriovenous malformation (AVM) causative genes in a fraction of endothelial cells (ECs) causes brain AVMs (bAVMs). Heterozygous mutation of endoglin, an AVM causative gene, in bone marrow (BM) caused capillary dysplasia in mouse brain. We tested if (1) homozygous mutation of activin receptor-like kinase 1 ( Alk1, another AVM causative gene) in BM derived ECs (BMDECs) can cause bAVM in brain angiogenic region, (2) Alk1 - ECs clonally expand in bAVM, and (3) the burden of Alk1 - ECs correlates with bAVM severity. Methods: The BMs of Pdgfb iCreER; Alk1 2 f/2f ;Ai14 mice with EC-specific tamoxifen-inducible Cre and Alk1 floxed alleles were transplanted into wild-type mice to analyze the role of BMDECs in bAVM development. Pdgfb iCreER; Alk1 2 f/2f ;confetti +/- mice with Cre-regulated confetti transgene were used to study EC clonal expansion. Brain AVMs were induced by intra-brain injection of an adeno-associated viral vector expressing vascular endothelial growth factor followed by intra-peritoneal injection of tamoxifen. Results: Wild-type mice transplanted with Pdgfb iCreER; Alk1 2 f/2f ;Ai14 BM developed bAVMs after bAVM induction. Recombined BMDECs were detected in bAVMs. The presence of clusters of ECs expressing same confetti color in bAVMs suggests that Alk1 - ECs had been clonally expanded. Increasing tamoxifen dose increased the number of Alk1 - ECs and abnormal vessels in bAVMs of Pdgfb iCreER; Alk1 2 f/2f mice. Conclusion: Homozygous mutation of Alk1 in BMDECs is sufficient to cause bAVM development in brain angiogenic region; clonal expansion of Alk1 - ECs provides a likely mechanism for how a fraction of mutant ECs causes bAVM; and the burden of Alk1 - ECs correlates with AVM severity.

Background and Purpose: Deletion of Endoglin (Eng), an arteriovenous malformation (AVM) causative gene causes AVM in the brain angiogenic region. Reduction of pericytes is correlate with brain AVM hemorrhage. The platelet-derived growth factor B and its receptor β (PDGF-B/PDGFRβ) play important roles in regulating pericyte recruitment during angiogenesis. We hypothesize that mutation of PDGFRβ causes cerebrovascular malformation and enhances bAVM severity in Eng mutant mice. Methods: Three mouse models were used: (1) Pdgfrβ F7 (F7) mice that have mutations disrupting Pdgfrβ signaling, (2) Pdgfb -icreER; Eng f /f mice that have Pdgfb promoter driving, tamoxifen (TM) inducible cre expression in ECs and an floxed Eng gene; and (3) Pdgfb -icreER; Eng f /f ;F7 +/- mice. Brain angiogenesis was induced by intra-brain injection of an adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF). Brain AVMs were induced in Pdgfb -icreER; Eng f /f and Pdgfb -icreER; Eng f /f ;F7 mice by TM induced EC Eng deletion and intra-brain AAV-VEGF injection. Brain AVM phenotypes were analyzed 8-weeks after model induction by latex vascular cast to detect arteriovenous shunts and macroscopic level of AVMs, immunostaining and Prussian blue staining to quantify dysplasia vessels and hemorrhage. Results: Compared to WT mice, F7 +/- and F7 +/+ mice have more dysplastic vessels and fewer vascular pericyte before and after AAV-VEGF injection. F7 +/- and F7 +/+ mice showed hemorrhage on the AAV-VEGF injection sites and AVM like vessels (a few arteriovenous shunts) in 16% F7 +/- and 66% of F7 +/+ mice. Pdgfb -icreER; Eng f /f mice showed dysplastic vessels and hemorrhage at AAV-VEGF injection sites. Compared to Pdgfb -icreER; Eng f /f mice, Pdgfb -icreER; Eng f /f ;F7 +/- had a higher penetrance of bAVM (71% vs 50%) and more dysplastic vessels. Conclusion: F7 mutation cause AVM like structure in mouse brain and exacerbates bAVM phenotype in Eng mutant mice.

Introduction: Tibia fracture (BF) enhances stroke injury and when occurring 6 hrs before stroke (BF6+Stroke) causes long-lasting cognitive dysfunction in mouse. Activation of α-7 nicotinic acetylcholine receptor (α-7 nAchR) reduced neuroinflammation, neuronal injury and sensorimotor dysfunction in mice with BF one day after stroke (Stroke+1BF). Hypothesis: Activation of α-7 nAchR improves long-term cognitive function of BF6+Stroke mice. Methods: BF6+Stroke mice were randomly assigned to saline, PHA-568487 (α-7 nAchR agonist) and MLA (α-7 nAchR antagonist) treatment groups. The sensorimotor function were tested by adhesive removal and corner tests at 3 days, the cognitive function was tested by Y-maze weekly for 8 weeks and Novel Objective Recognition (NOR) at 8 weeks post-injuries. The neuronal damage, neuroinflammaiton, neurogenesis were analyzed 3 and/or 8 weeks post-injuries. Results: Similar to Stroke+1BF mice, PHA reduced and MLA enhanced neuronal injury, neuroinflammation, and sensorimotor dysfunction of BF6+Stroke mice. Further, PHA reduced and MLA enhanced their long-term cognitive dysfunction. In Y maze test, all mice made fewer alternations 1-week post-surgeries than baseline; PHA group recovered to baseline at week 5 post-surgeries; saline and MLA groups continuously made fewer alternations throughout the 8-weeks. In NOR test, PHA group spent more time, MLA group spent less time than saline group on novel objects. Injection of BrdU in the 2 nd week post-surgeries labeled more neurons in the contralateral than in the ipsilateral dentate gyrus in all groups; PHA group had the most, MLA group had the least BrdU + neurons. Injection BrdU in the 7th week post-surgeries did not labeled any neuron. Conclusion: Activation of α-7 nAchR decreased neuronal damage and neuroinflammation, increased neurogenesis at the dentate gyrus of BF6+Stroke mice; and improved their sensorimotor and long-term cognitive function.

Background and Purpose— Brain arteriovenous malformation (bAVM) is an important risk factor for intracranial hemorrhage. Current treatments for bAVM are all associated with considerable risks. There is no safe method to prevent bAVM hemorrhage. Thalidomide reduces nose bleeding in patients with hereditary hemorrhagic telangiectasia, an inherited disorder characterized by vascular malformations. In this study, we tested whether thalidomide and its less toxic analog, lenalidomide, reduce bAVM hemorrhage using a mouse model. Methods— bAVMs were induced through induction of brain focal activin-like kinase 1 ( Alk1 , an AVM causative gene) gene deletion and angiogenesis in adult Alk1 -floxed mice. Thalidomide was injected intraperitoneally twice per week for 6 weeks, starting either 2 or 8 weeks after AVM induction. Lenalidomide was injected intraperitoneally daily starting 8 weeks after AVM induction for 6 weeks. Brain samples were collected at the end of the treatments for morphology, mRNA, and protein analyses. The influence of Alk1 downregulation on PDGFB (platelet-derived growth factor B) expression was also studied on cultured human brain microvascular endothelial cells. The effect of PDGFB in mural cell recruitment in bAVM was explored by injection of a PDGFB overexpressing lentiviral vector to the mouse brain. Results— Thalidomide or lenalidomide treatment reduced the number of dysplastic vessels and hemorrhage and increased mural cell (vascular smooth muscle cells and pericytes) coverage in the bAVM lesion. Thalidomide reduced the burden of CD68 + cells and the expression of inflammatory cytokines in the bAVM lesions. PDGFB expression was reduced in ALK1-knockdown human brain microvascular endothelial cells and in mouse bAVM lesion. Thalidomide increased Pdgfb expression in bAVM lesion. Overexpression of PDGFB mimicked the effect of thalidomide. Conclusions— Thalidomide and lenalidomide improve mural cell coverage of bAVM vessels and reduce bAVM hemorrhage, which is likely through upregulation of Pdgfb expression.

Background and purpose: High level of VEGF has been implicated in bAVM bleeding and rupture through analyzing the VEGF levels in patients’ blood and in surgically resected bAVM specimens. However, the direct evidence is missing. Using a mouse bAVM model, we tested the hypothesis that elevation of focal VEGF level exacerbates the severity of bAVM hemorrhage. Methods: Brain AVMs were induced in adult mice that have Alk1 (an AVM causal gene) exons 4-6 floxed by injection of an adenoviral vector expressing Cre-recombinase (Ad-Cre) and an adeno-associated viral vector expressing human VEGF (AAV-VEGF) into the basal ganglia. Two doses of AAV-VEGF, 5x10 9 (high) or 2x10 9 (low) viral genomes were used. In addition, the common carotid artery and jugular vein were anastomosis in a group of mice treated with low dose AAV-VEGF 6 weeks after the model induction to induce venous hypertension (VH), because VH increases VEGF level in the brain. Hemorrhages in the bAVM lesions were quantified on brain sections stained with Prussian blue, which detect iron deposition 8 or 9 weeks after model induction. VEGF levels were quantified by ELISA. Results: Compared to mice injected with low dose AAV-VEGF, mice injected with high dose of AAV-VEGF had a higher level of VEGF, larger Prussian blue positive areas in the bAVM lesion at 8 and 9-weeks after model induction (P Conclusion: Using mouse bAVM models, we demonstrated that the evaluation of VEGF level through viral vector mediated overexpression of VEGF or create VH increases bAVM hemorrhage and mouse mortality.