STING-Activating Polymer-Drug Conjugates for Cancer Immunotherapy

The stimulator of interferon genes (STING) pathway links innate and adaptive antitumor immunity and therefore plays an important role in cancer immune surveillance. This has prompted widespread development of STING agonists for cancer immunotherapy, but pharmacological barriers continue to limit the clinical impact of STING agonists and motivate the development of drug delivery systems to improve their efficacy and/or safety. To address this challenge, we developed SAPCon, a STING-activating polymer-drug conjugate platform based on strain-promoted azide-alkyne cycloaddition of dimeric-amidobenzimidazole (diABZI) STING agonists to hydrophilic polymer chains through an enzyme-responsive chemical linker. To synthesize a first-generation SAPCon, we designed a diABZI prodrug modified with a DBCO reactive handle a cathepsin B-cleavable spacer for intracellular drug release and conjugated this to pendant azide groups on a 100 kDa poly(dimethyla acrylamide-co-azide methacrylate) copolymer backbone to increase circulation time and enable passive tumor accumulation. We found that intravenously administered SAPCon accumulated at tumor sites where they it was endocytosed by tumor-associated myeloid cells, resulting in increased STING activation in tumor tissue compared to a free diABZI STING agonist. Consequently, SAPCon promoted an immunogenic tumor microenvironment, characterized by increased frequency of activated macrophages and dendritic cells and improved infiltration of CD8+ T cells, resulting in inhibition of tumor growth, prolonged survival, and increased response to anti-PD-1 immune checkpoint blockade in orthotopic models of breast cancer. Collectively, these studies position SAPCon as a modular and programmable platform for improving the efficacy of systemically administered STING agonists for cancer immunotherapy.

Development and biological characterization of a clinical gene transfer vector for the treatment of MAK-associated retinitis pigmentosa

By combining next generation whole exome sequencing and induced pluripotent stem cell (iPSC) technology we found that an Alu repeat inserted in exon 9 of the MAK gene results in a loss of normal MAK transcript and development of human autosomal recessive retinitis pigmentosa (RP). Although a relatively rare cause of disease in the general population, the MAK variant is enriched in individuals of Jewish ancestry. In this population, 1 in 55 individuals are carriers and one third of all cases of recessive RP is caused by this gene. The purpose of this study was to determine if a viral gene augmentation strategy could be used to safely restore functional MAK protein as a step toward a treatment for early stage MAK-associated RP. Patient iPSC-derived photoreceptor precursor cells were generated and transduced with viral vectors containing the MAK transcript. One week after transduction, transcript and protein could be detected via rt-PCR and western blotting respectively. Using patient-derived fibroblast cells and mak knockdown zebra fish we demonstrate that over-expression of the retinal MAK transgene restored the cells ability to regulate primary cilia length. In addition, the visual defect in mak knockdown zebrafish was mitigated via treatment with the retinal MAK transgene. There was no evidence of local or systemic toxicity at 1-month or 3-months following subretinal delivery of clinical grade vector into wild type rats. The findings reported here will help pave the way for initiation of a phase 1 clinical trial for the treatment of patients with MAK-associated RP.

Interleukin-17A deficient mice microbiota induced regulatory T cells and suppressed experimental autoimmune encephalomyelitis (EAE) in WT HLA-DR3 transgenic mice

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system, and among all the genes associated with MS, HLA class II genes have the highest relative risk. Although IL-17A is thought to be a major cytokine in the pathogenesis of MS, the exact role of IL-17A in the MS is still poorly understood. Specifically, it is unclear whether IL-17A is required for disease initiation or disease severity or in both. Therefore, in the present study, utilizing HLA-DR3 transgenic mice lacking IL-17A (HLA-DR3.IL-17A−/−), we investigated the importance of IL-17A in disease development and progression in experimental autoimmune encephalomnyelitis (EAE) an animal model of MS. We observed that HLA-DR3.IL-17A−/− mice had a higher frequency of CD4+CD25+FoxP3+ regulatory T cells (Treg)s and developed milder EAE compared to IL-17 sufficient HLA-DR3 mice. Further characterization of mechanism identified a novel role of IL-17A in regulating the disease progression through modulation of immunoregulatory responses. We also identified an important role of gut microbiota in IL-17A dependent disease regulation specifically depletion of gut bacteria with ability to promote Treg population in IL-17A sufficient HLA-DR3 mice. Fecal transplantation of HLA.DR3 mice with HLA-DR3. IL17A−/− showed milder EAE and an increase in Treg cells in HLA-DR3 mice confirming a role of gut microbiota in shaping Treg repertoire and function. Additionally, we observed higher frequency of metabolic pathway involved with Treg promoting short chain fatty acid (SCFA) metabolism in HLA-DR3.IL17A−/− mice. Thus our study shows a novel role of IL-17A in immune homeostasis and inflammation by regulating levels of Tregs through modulation of gut microbiota.

Abstract 3150: Impact of interleukin-1 alpha and EGFR expression on recurrence and survival outcomes in head and neck squamous cell carcinomas

Interleukin-1 alpha (IL-1α) is a pleiotropic cytokine involved in inflammation and immune response and is upregulated in many solid tumors including head and neck squamous cell carcinomas (HNSCCs). Although IL-1α expression is generally associated with poor prognosis, the implications of the subcellular localization of IL-1α expression in patient outcomes are poorly understood. This study is aimed at investigating the clinical relevance of immunohistochemical IL-1α expression in HNSCCs. Tissue microarrays (TMAs) containing human papillomavirus (HPV)-positive and HPV-negative HNSCCs were analyzed for IL-1α and epidermal growth factor receptor (EGFR) expression by immunohistochemistry. Nuclear and cytoplasmic IL-1α and EGFR expression scores were correlated with clinicopathological parameters and patient outcomes. IL-1α expression was observed in the nuclear and/or cytoplasm compartments in 98% of evaluable tumors and 78% of tumors expressed IL-1α in both compartments. A higher percentage of tumors with combined high nuclear and moderate cytoplasmic IL-1α expression were observed in HPV-negative tumors compared to HPV-positive tumors. In HPV-negative tumors a combined EGFR-negative and high nuclear IL-1α expression profile was associated with a low risk of tumor recurrence and favorable overall survival compared to all other EGFR/IL-1α expression profiles. Lastly, a higher frequency of tumors with combined high nuclear and moderate cytoplasmic IL-1α expression was observed in cetuximab monotherapy responders compared to non-responders. Altogether, IL-1α in combination with EGFR expression may be a strong indicator of risk of recurrence in HPV-negative HNSCCs and warrants further study as a tissue biomarker for predicting HNSCC patient outcomes.

Citation Format: Andrean L. Simons, Anand Rajan, Katherine Gibson-Corley, Georgina Ofori-Amanfo, Patrick Ten Eyck, Madelyn Espinosa-Cotton, Sandra Schmitz, Joseph Coppock, Steven Sperry. Impact of interleukin-1 alpha and EGFR expression on recurrence and survival outcomes in head and neck squamous cell carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3150.

Pharmacologic Ascorbate Reduces Radiation-Induced Normal Tissue Toxicity and Enhances Tumor Radiosensitization in Pancreatic Cancer

: Chemoradiation therapy is the mainstay for treatment of locally advanced, borderline resectable pancreatic cancer. Pharmacologic ascorbate (P-AscH^-, i.e., intravenous infusions of ascorbic acid, vitamin C), but not oral ascorbate, produces high plasma concentrations capable of selective cytotoxicity to tumor cells. In doses achievable in humans, P-AscH^- decreases the viability and proliferative capacity of pancreatic cancer via a hydrogen peroxide (H₂O₂)-mediated mechanism. In this study, we demonstrate that P-AscH^- radiosensitizes pancreatic cancer cells but inhibits radiation-induced damage to normal cells. Specifically, radiation-induced decreases in clonogenic survival and double-stranded DNA breaks in tumor cells, but not in normal cells, were enhanced by P-AscH^-, while radiation-induced intestinal damage, collagen deposition, and oxidative stress were also reduced with P-AscH^- in normal tissue. We also report on our first-in-human phase I trial that infused P-AscH^- during the radiotherapy "beam on." Specifically, treatment with P-AscH^- increased median overall survival compared with our institutional average (21.7 vs. 12.7 months, P = 0.08) and the E4201 trial (21.7 vs. 11.1 months). Progression-free survival in P-AscH^--treated subjects was also greater than our institutional average (13.7 vs. 4.6 months, P < 0.05) and the E4201 trial (6.0 months). Results indicated that P-AscH^- in combination with gemcitabine and radiotherapy for locally advanced pancreatic adenocarcinoma is safe and well tolerated with suggestions of efficacy. Because of the potential effect size and minimal toxicity, our findings suggest that investigation of P-AscH^- efficacy is warranted in a phase II clinical trial. SIGNIFICANCE: These findings demonstrate that pharmacologic ascorbate enhances pancreatic tumor cell radiation cytotoxicity in addition to offering potential protection from radiation damage in normal surrounding tissue, making it an optimal agent for improving treatment of locally advanced pancreatic adenocarcinoma.

Nlrp12 mediates adverse neutrophil recruitment during influenza virus infection

Exaggerated inflammatory responses during influenza A virus (IAV) infection are typically associated with severe disease. Neutrophils are among the immune cells that can drive this excessive and detrimental inflammation. In moderation, however, neutrophils are necessary for optimal viral control. In this study, we explore the role of the nucleotide-binding domain leucinerich repeat containing receptor (NLR) family member Nlrp12 in modulating neutrophilic responses during lethal IAV infection. Nlrp12−/− mice are protected from lethality during IAV infection and show decreased vascular permeability, fewer pulmonary neutrophils, and a reduction in levels of neutrophil chemoattractant CXCL1 in their lungs compared to wild-type (WT) mice. Nlrp12−/− neutrophils and dendritic cells (DCs) within the IAV-infected lungs produce less CXCL1 than their WT counterparts. Decreased CXCL1 production by Nlrp12−/− cells was not due to a difference in CXCL1 protein stability, but instead to a decrease in Cxcl1 mRNA stability. Together, these data demonstrate a previously unappreciated role for Nlrp12 in exacerbating the pathogenesis of IAV infection through the regulation of CXCL1 mediated neutrophilic responses.

Human gut commensal Prevotella histicola ameliorates disease as efficiently as Copaxone and Interferon-β in a preclinical animal model of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system. We and others have shown that gut microbiota play an important role in disease pathogenesis of MS as there is an enrichment or depletion of specific gut bacteria compared to healthy controls (HC). Thus the specific human gut bacteria found depleted or showing lower abundance in MS patients can be used as potential drug to treat MS. Further, we and others have shown that patients with MS have either lower abundance of Prevotella compared to HC or an increased level of Prevotella in patients receiving disease modifying therapies such as Copaxone and/or Interferon beta (IFN-β). We have previously identified a specific strain Prevotella histicola within Prevotella genus which can suppress disease in experimental autoimmune encephalomyelitis (EAE) animal model of MS. In this present study we compared disease suppressing ability of P. histicola to Copaxone or IFN-β in HLA-DR3.DQ8 transgenic mouse model of MS. We observed that P. histicola suppresses EAE as efficiently as Copaxone and IFN-β. P. histicola treated mice showed higher level of CD4+FoxP3+ regulatory T cell frequencies and decreased levels of pro-inflammatory cytokines IFNγ and IL17 suggesting that P. histicola suppresses disease through immunomodulation. Fecal microbiota analysis of different groups showed that group receiving Prevotella histicola had a distinct gut microbiota than the control group suggesting that P. histicola as might suppresses disease through modulation of gut microbiota. In conclusion, our study suggests that human gut commensal Prevotella histicola can provide an alternate treatment option for MS patients.

Phase1 clinical trial of high doses of Seleno-L-methionine (SLM), in sequential combination with axitinib in previously treated and relapsed clear cell renal cell carcinoma (ccRCC) patients

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Background: The overexpression of hypoxia induced factor (HIF) 1a/2a in ccRCC leads to up-regulation of vascular endothelial growth factor (VEGF) that results in increased angiogenesis, tumor metastasis, and treatment resistance. Using several preclinical xenograft models, it has been demonstrated that therapeutic doses and schedules of the selenium-containing molecules, seleno-L-methionine (SLM) and methylselenocysteine (MSC) caused enhanced degradation of HIF1α/2α, down-regulation of oncogenic miRNA-210 and 155, up-regulation tumor suppressor miRNA-664 and LET-7b, and stabilization of tumor vasculature, yielding higher tumor drug uptake and protection from toxic side effects when combined with chemotherapeutic and VEGF-targeted agents. Methods: This is a phase I (3+3 design) dose finding trial of SLM (2500, 3000 or 4000 µg) given orally twice daily for 14 days, followed by once a day in combination with the standard dose of axitinib to patients with metastatic RCC. Primary endpoint is safety, secondary endpoint is efficacy including overall response rate (ORR), progression free survival (PFS) and overall survival (OS). Results: To date, 9 patients with metastatic RCC; who failed one or more prior lines of treatment; are enrolled. The first 3 patients were treated at 4000 µg, the second and third 3 patients were treated at 2500 and 3000 µg respectively. No dose limiting toxicity (DLT) is encountered. Six patients are evaluable to date. Of the 4000 µg cohort, 2 patients achieved complete remission (CR) at 18 and 20 months, 1 patient with partial response (PR) at 19 month. Of the 2500 µg cohort, one patient achieved PR at 9 months, 1 patient had stable disease for 9 months before progression, and 1 patient had disease progression at 4 months. The 3000 µg cohort is too early to evaluate for efficacy. Of interest the 4000μg SLM dose yielded a plasma selenium concentration of 40-50μM which is comparable with SLM dose determined synergistic with anti-cancer drugs in preclinical models. Conclusions: High dose SLM is safe in combination with axitinib, with promising efficacy, further data to be presented at the meeting. Clinical trial information: NCT02535533.

Abstract 48: Targeting IL-1 signaling to improve tumor response to erlotinib in HNSCC

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) including erlotinib have demonstrated poor clinical response rates for head and neck squamous cell carcinoma (HNSCC) to date compared to the EGFR monoclonal antibody cetuximab. Therefore we seek to identify molecular mechanisms involved in tumor response to erlotinib and ultimately improve the anti-tumor efficacy of erlotinib for HNSCC patients. We have shown that erlotinib-treated HNSCC cell lines induced the expression and secretion of a wide variety of genes involved in inflammation and immune response including interleukin-1 (IL-1) and interleukin-6 (IL-6) compared to control-treated cells. The secretion of IL-6 from HNSCC cells in response to erlotinib was found to be triggered by MyD88-dependent IL-1 signaling and suppression of IL-1 signaling (using a neutralizing IL-1α antibody) significantly enhanced the anti-tumor efficacy of erlotinib in vivo. In erlotinib-resistant HNSCC cell lines, IL-1 signaling was significantly upregulated compared to their respective parental cell lines. Blockade of IL-1 signaling using a neutralizing IL-1α antibody or an IL-1 receptor (IL-1R) antagonist was able to significantly suppress the growth of erlotinib-resistant HNSCC xenografts as a single agent and in combination with erlotinib which was associated with reduced immune cell recruitment and angiogenesis. Altogether, blockade of the IL-1 pathway may represent a novel strategy to improve tumor response to erlotinib and other EGFR TKIs in HNSCC patients.

Citation Format: Andrean Simons, Aditya Stanam, Adam Koch, Madelyn Espinosa-Cotton, Katherine Gibson-Corley. Targeting IL-1 signaling to improve tumor response to erlotinib in HNSCC [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr 48.

Human gut-derived commensal Prevotella histicola suppress experimental autoimmune encephalomyelitis in humanized mice

Our recent multiple sclerosis (MS) microbiome study indicates an important role of gut microbiota in pathogenesis of MS, an autoimmune disease of central nervous system. Gut microbiota help in maintaining immune-homeostasis by regulating balance between CD4+CD25+FoxP3+ regulatory T cells (Tregs) and pro-inflammatory Th1/Th17 cells. A shift of balance towards Th1/Th17 cells leading to inflammation and demyelination in central nervous system (CNS), is suggested to be responsible of disease initiation and/or relapses in MS. Therefore, gut commensals capable of restoring the microbiome to a healthy state could provide novel therapeutic options for treating autoimmune diseases including MS. Here, we report identification of human gut-derived commensal bacteria, Prevotella histicola (P. histicola), which can suppress an autoimmune disease in HLA class-II transgenic model of experimental autoimmune encephalomyelitis (EAE), an experimental model of MS. P. histicola suppresses disease through modulation of systemic immune response. P. histicola challenge led to a decrease in pro-inflammatory Th1 (IFNγ) and Th17 (IL17) cytokines, and increase in the frequencies of CD4+FoxP3+ Tregs, tolerogenic dendritic cells and suppressive macrophages. We also observed that mice with EAE had a altered gut microbiota compared to naïve mice and treatment with P. histicola restored gut flora to a normal state which further support an important role of gut microbiota in EAE/MS. Our study provides compelling evidence that administration of gut commensals may regulate a systemic immune response and have a possible role in the treatment of autoimmune diseases.

Constitutive Activation of NIK Impairs the Self-Renewal of Hematopoietic Stem/Progenitor Cells and Induces Bone Marrow Failure

Previously we have shown that loss of non-canonical NF-κB signaling impairs self-renewal of hematopoietic stem/progenitor cells (HSPCs). This prompted us to investigate whether persistent activation of the non-canonical NF-κB signaling will have supportive effects on HSPC self-renewal. NF-κB-inducing kinase (NIK) is an important kinase that mainly activates the non-canonical pathway through directly phosphorylating IKKα. In contrast to our expectations, constitutive activation of NIK in the hematopoietic system leads to bone marrow (BM) failure and postnatal lethality due to intrinsic impairment of HSPC self-renewal and extrinsic disruption of BM microenvironment through enhancing osteoclastogenesis. The impaired HSPC function is associated with reduced cell proliferation and increased apoptosis and inflammatory cytokine responses. RNAseq analysis of control and NIK-activated HSPCs reveals that these effects are through non-canonical NF-κB signaling without significant changes in the canonical pathway. Gene set expression analysis of RNAseq data reveals globally decreased stem cell signature, increased maturation signature, and increased inflammatory responses. Many genes (Mpl, Tifab, Emcn, Flt3, Bcl2, and others) that regulate HSPC self-renewal, lineage commitment, and apoptosis are significantly downregulated-and those genes that regulate inflammatory responses and cell cycle inhibition (Cdkn2a and Cdkn2b) are significantly upregulated-by activation of NIK. Importantly, our data demonstrate that activation of NIK-non-canonical signaling has distinct phenotypes-smaller spleen size, decreased white blood cell counts, and reduced HSPC proliferation-compared to activation of canonical signaling. Collectively, these data indicate that the balanced non-canonical NF-κB signaling is essential for maintaining normal hematopoiesis and NIK-non-canonical signaling contributes to the development of BM failure. Stem Cells 2017;35:777-786.

α3β1 Integrin Suppresses Prostate Cancer Metastasis via Regulation of the Hippo Pathway

Existing anticancer strategies focused on disrupting integrin functions in tumor cells or tumor-involved endothelial cells have met limited success. An alternative strategy is to augment integrin-mediated pathways that suppress tumor progression, but how integrins can signal to restrain malignant behavior remains unclear. To address this issue, we generated an in vivo model of prostate cancer metastasis via depletion of α3β1 integrin, a correlation observed in a significant proportion of prostate cancers. Our data describe a mechanism whereby α3β1 signals through Abl family kinases to restrain Rho GTPase activity, support Hippo pathway suppressor functions, and restrain prostate cancer migration, invasion, and anchorage-independent growth. This α3β1-Abl kinase-Hippo suppressor pathway identified α3 integrin-deficient prostate cancers as potential candidates for Hippo-targeted therapies currently under development, suggesting new strategies for targeting metastatic prostate cancer based on integrin expression. Our data also revealed paradoxical tumor suppressor functions for Abl kinases in prostate cancer that may help to explain the failure of Abl kinase inhibitor imatinib in prostate cancer clinical trials. Cancer Res; 76(22); 6577-87. ©2016 AACR.

Immunomodulation by Leishmania-derived surface oligosaccharides promotes pro-inflammatory cytokine secretion and reduces L. major parasite load

Lipophosphoglycans (LPG) of Leishmania spp. are known to alter innate immune responses and be critical for parasite binding to the vector gut wall. LPG displays various oligosaccharides capping the terminal and branch apexes. However, it is unknown how these capping oligosaccharides serve as immunomodulators in the absence of a conjugated protein. Several oligosaccharides including dimannose and trimannose, were synthesized and covalently linked to latex beads to study their effect in a Leishmania infection model. In vitro incubation of activated J774 or bone marrow derived macrophages with di- and tri-mannose resulted in differential modulation of IL-12p40, a key cytokine to control intracellular pathogens by driving a Th1 response. Co-inoculation of trimannose and L. major into the footpad of C57BL/6 mice increased IL-12p40 and IFN-γ production 48 hours post-infection, a significantly Th1 skewed response. Noticeably at 14 days post-infection, L. major infected, trimannose treated mice had significantly decreased lesion size and decreased parasite load compared to infected untreated, controls. Cytokines from draining lymph node supernatants measured via Luminex at 14 days post infection showed decreased IL-12p40 and IL-10 secretion and increased IFN-γ in the co-inoculated mice. In vitro, the effects of trimannose were mediated by macrophage TLR and mannose receptors as well as T cell proliferation. Leishmania-derived trimannose represents a novel immunomodulator that provides early Th1 skewed cytokine production to control parasite load and alter the course of infection.

A Transient Metabolic Recovery from Early Life Glucose Intolerance in Cystic Fibrosis Ferrets Occurs During Pancreatic Remodeling

Cystic fibrosis (CF)-related diabetes in humans is intimately related to exocrine pancreatic insufficiency, yet little is known about how these 2 disease processes simultaneously evolve in CF. In this context, we examined CF ferrets during the evolution of exocrine pancreatic disease. At 1 month of age, CF ferrets experienced a glycemic crisis with spontaneous diabetic-level hyperglycemia. This occurred during a spike in pancreatic inflammation that was preceded by pancreatic fibrosis and loss of β-cell mass. Surprisingly, there was spontaneous normalization of glucose levels at 2-3 months, with intermediate hyperglycemia thereafter. Mixed meal tolerance was impaired at all ages, but glucose intolerance was not detected until 4 months. Insulin secretion in response to hyperglycemic clamp and to arginine was impaired. Insulin sensitivity, measured by euglycemic hyperinsulinemic clamp, was normal. Pancreatic inflammation rapidly diminished after 2 months of age during a period where β-cell mass rose and gene expression of islet hormones, peroxisome proliferator-activated receptor-γ, and adiponectin increased. We conclude that active CF exocrine pancreatic inflammation adversely affects β-cells but is followed by islet resurgence. We predict that very young humans with CF may experience a transient glycemic crisis and postulate that pancreatic inflammatory to adipogenic remodeling may facilitate islet adaptation in CF.

Comparison of Two Synthetic Bone Graft Products in a Rabbit Posterolateral Fusion Model

BACKGROUND

The drawbacks of iliac crest autograft as graft material for spine fusion are well reported. Despite continued modifications to improve bone healing capacity, the efficacy of synthetic graft materials as stand-alone replacements remains uncertain. The rabbit posterolateral fusion model is an established environment for testing of fusion concepts. It offers the opportunity to obtain radiographic, biomechanical and histological data on novel fusion materials. The objective of this study was to compare the spine fusion capability of two synthetic bone graft products in an established rabbit posterolateral spine fusion (PLF) model: Signafuse® Bioactive Bone Graft Putty and Actifuse® ABX.

METHODS

Bilateral intertransverse spine fusion was performed at the L5-L6 transverse processes (TPs) of New Zealand White rabbits using either Signafuse or Actifuse ABX as the bone graft material. Bone remodeling and spine fusion were assessed at 6 and 12 weeks using radiographic, biomechanical and histological endpoints.

RESULTS

Fusion rate by manual palpation at 6 weeks was greater for Signafuse (33%) compared to Actifuse ABX (0%), and equivalent in both groups at 12 weeks (50%). Biomechanical fusion rate based on flexion-extension data was 80% in Signafuse group and 44% for Actifuse ABX. Histology revealed a normal healing response in both groups. MicroCT and histomorphometric data at 6 weeks showed greater new bone formation in the Signafuse group compared to Actifuse ABX (p <0.05), with no differences detected at 12 weeks. Histological fusion scores were greater in the Signafuse group at 6 and 12 weeks, indicated by higher degree structural remodeling and tendency towards complete bridging of the fusion bed compared to the Actifuse ABX group.

CONCLUSION

Confirmed by several metrics, Signafuse outperformed Actifuse ABX as a standalone synthetic bone graft in an established PLF model, demonstrating greater rates of bone remodeling and spine fusion. The combination of 45S5 bioactive glass and biphasic HA/βTCP granules of Signafuse appear to provide greater bone healing capability in comparison to the 0.8% silicate-substituted hydroxyapatite material of Actifuse ABX.

Finite-Element Study of the Performance Characteristics of an Intradural Spinal Cord Stimulator

We have used finite-element (FE) modeling to investigate the mechanical compliance, positional stability and contact pressures associated with a novel type of spinal cord stimulator that is placed directly on the pial surface of the spinal cord in order to more selectively activate neural structures for relief of intractable pain. The properties used in the model are those of the actual prototype devices employed in recent in vitro and chronic in vivo tests. The agreement between predictions and experimental observations serves to validate our FE approach, which can now be used to further optimize the device's design and performance.

Abstract 091: Chronic Vasopressin Infusion: A Novel, Clinically Significant, and Pregnancy-Specific Mouse Model of Preeclampsia

Recently we demonstrated that the late-pregnancy cardiovascular disorder, preeclampsia, is characterized by robust, early and sustained vasopressin (AVP) hypersecretion in all three trimesters of pregnancy in humans. We hypothesize a causative role for elevated AVP in the pathogenesis of preeclampsia. This concept was tested by chronically infusing AVP (0.24 - 240 ng/hr, s.c., or saline vehicle) in wildtype C57BL/6J female mice throughout pregnancy. In pregnant mice, AVP infusion caused pregnancy-specific increases in systolic blood pressure by tail-cuff plethysmography with significant increases in the pregnant cohort (saline n=16: 110±3, vs 24 ng/hr AVP n=11: 120±3 mmHg on GD15/16, P<0.05), but no significant difference in the nonpregnant cohort (saline n=14: 108±3, vs 24 ng/hr AVP n=5: 108±5 mmHg, P>0.05). In addition, the AVP infused mice exhibited increased proteinuria (0.24 ng/hr n=2: 66±73, 2.4 ng/hr n=5: 348±56, 24 ng/hr n=2: 799±297 mg/d, P<0.05), intrauterine growth restriction (saline n=25: 0.78±0.06, vs 24 ng/hr n=65: 0.55±0.03 g/fetus, P<0.05), spontaneous feto-placental unit resorption (saline: 0/65=0%, 0.24 ng/hr: 0/16=0%, 2.4 ng/hr: 2/45=4%, 24 ng/hr 8/73=11%, P<0.05), and maternal renal glomerular endotheliosis by electron microscopy. High doses of AVP reduced rates of successful pregnancy with single-night breeding (saline 8/18=44% vs 240 ng/hr 1/20=5%, P<0.05). These data demonstrate that AVP infusion - which simulates the large sustained increases in AVP secretion during human preeclampsia - is sufficient to induce all the cardinal phenotypes of preeclampsia in pregnant C57BL/6J mice. This identifies AVP infusion as a novel, clinically significant, and pregnancy-specific physiological model of preeclampsia in mice. These data support our hypothesis that AVP hypersecretion during pregnancy may be causative for the development of preeclampsia. Ongoing experiments are aimed at identifying the causes of AVP hypersecretion in human preeclampsia, the target tissues and receptors involved, and the utility of targeting AVP signaling as a novel therapeutic for preeclampsia.