Daniel Schimel

Anti-vascular endothelial growth factor treatment normalizes tuberculosis granuloma vasculature and improves small molecule delivery

Significance Tuberculosis (TB) is the second most lethal pathogen worldwide. Pulmonary granulomas are a hallmark of this disease. By discovering similarities between granulomas and solid cancerous tumors, we identified a novel therapeutic target for TB, the abnormal granuloma-associated vasculature that contributes to the abnormal granuloma microenvironment. We then asked if we could “normalize” granuloma vasculature by blocking VEGF signaling, an approach originally shown to enhance cancer treatment. Our results demonstrate that bevacizumab, a widely prescribed anti-VEGF antibody for cancer and eye diseases, is able to create more structurally and functionally normal granuloma vasculature and improve the delivery of a low-molecular-weight tracer. This effect suggests that vascular normalization in combination with anti-TB drugs has the potential to enhance treatment in patients with TB. Tuberculosis (TB) causes almost 2 million deaths annually, and an increasing number of patients are resistant to existing therapies. Patients who have TB require lengthy chemotherapy, possibly because of poor penetration of antibiotics into granulomas where the bacilli reside. Granulomas are morphologically similar to solid cancerous tumors in that they contain hypoxic microenvironments and can be highly fibrotic. Here, we show that TB-infected rabbits have impaired small molecule distribution into these disease sites due to a functionally abnormal vasculature, with a low-molecular-weight tracer accumulating only in peripheral regions of granulomatous lesions. Granuloma-associated vessels are morphologically and spatially heterogeneous, with poor vessel pericyte coverage in both human and experimental rabbit TB granulomas. Moreover, we found enhanced VEGF expression in both species. In tumors, antiangiogenic, specifically anti-VEGF, treatments can “normalize” their vasculature, reducing hypoxia and creating a window of opportunity for concurrent chemotherapy; thus, we investigated vessel normalization in rabbit TB granulomas. Treatment of TB-infected rabbits with the anti-VEGF antibody bevacizumab significantly decreased the total number of vessels while normalizing those vessels that remained. As a result, hypoxic fractions of these granulomas were reduced and small molecule tracer delivery was increased. These findings demonstrate that bevacizumab treatment promotes vascular normalization, improves small molecule delivery, and decreases hypoxia in TB granulomas, thereby providing a potential avenue to improve delivery and efficacy of current treatment regimens.

Differential Virulence and Disease Progression following Mycobacterium tuberculosis Complex Infection of the Common Marmoset (Callithrix jacchus)

ABSTRACT Existing small-animal models of tuberculosis (TB) rarely develop cavitary disease, limiting their value for assessing the biology and dynamics of this highly important feature of human disease. To develop a smaller primate model with pathology similar to that seen in humans, we experimentally infected the common marmoset (Callithrix jacchus) with diverse strains of Mycobacterium tuberculosis of various pathogenic potentials. These included recent isolates of the modern Beijing lineage, the Euro-American X lineage, and M. africanum. All three strains produced fulminant disease in this animal with a spectrum of progression rates and clinical sequelae that could be monitored in real time using 2-deoxy-2-[18F]fluoro-d-glucose (FDG) positron emission tomography (PET)/computed tomography (CT). Lesion pathology at sacrifice revealed the entire spectrum of lesions observed in human TB patients. The three strains produced different rates of progression to disease, various extents of extrapulmonary dissemination, and various degrees of cavitation. The majority of live births in this species are twins, and comparison of results from siblings with different infecting strains allowed us to establish that the infection was highly reproducible and that the differential virulence of strains was not simply host variation. Quantitative assessment of disease burden by FDG-PET/CT provided an accurate reflection of the pathology findings at necropsy. These results suggest that the marmoset offers an attractive small-animal model of human disease that recapitulates both the complex pathology and spectrum of disease observed in humans infected with various M. tuberculosis strain clades.

Meropenem-Clavulanic Acid Shows Activity against Mycobacterium tuberculosis In Vivo

ABSTRACT The carbapenems imipenem and meropenem in combination with clavulanic acid reduced the bacterial burden in Mycobacterium tuberculosis-infected macrophages by 2 logs over 6 days. Despite poor stability in solution and a short half-life in rodents, treatment of chronically infected mice revealed significant reductions of bacterial burden in the lungs and spleens. Our results show that meropenem has activity in two in vivo systems, but stability and pharmacokinetics of long-term administration will offer significant challenges to clinical evaluation.

Disrupted erythropoietin signalling promotes obesity and alters hypothalamus proopiomelanocortin production

While erythropoietin is the cytokine known that regulates erythropoiesis, erythropoietin receptor (EpoR) expression and associated activity beyond hematopoietic tissue remain uncertain. Here we show that mice with EpoR expression restricted to hematopoietic tissues (Tg) develop obesity and insulin resistance. Tg-mice exhibit a decrease in energy expenditure and an increase in white fat mass and adipocyte number. Conversely, erythropoietin treatment of wild-type mice increases energy expenditure and reduces food intake and fat mass accumulation but showed no effect in body weight of Tg-mice. EpoR is expressed at a high level in white adipose tissue and in the proopiomelanocortin neurons of the hypothalamus. While Epo treatment in wild-type mice induces the expression of the polypeptide hormone precursor gene, proopiomelanocortin, mice lacking EpoR show reduced levels of proopiomelanocortin in the hypothalamus. This study provides the first evidence that mice lacking EpoR in nonhematopoietic tissue become obese and insulin resistant with loss of erythropoietin regulation of energy homeostasis.

A Sterilizing Tuberculosis Treatment Regimen Is Associated with Faster Clearance of Bacteria in Cavitary Lesions in Marmosets

ABSTRACT Shortening the lengthy treatment duration for tuberculosis patients is a major goal of current drug development efforts. The common marmoset develops human-like disease pathology and offers an attractive model to better understand the basis for relapse and test regimens for effective shorter duration therapy. We treated Mycobacterium tuberculosis-infected marmosets with two drug regimens known to differ in their relapse rates in human clinical trials: the standard four-drug combination of isoniazid, rifampin, pyrazinamide, and ethambutol (HRZE) that has very low relapse rates and the combination of isoniazid and streptomycin that is associated with higher relapse rates. As early as 2 weeks, the more sterilizing regimen significantly reduced the volume of lung disease by computed tomography (P = 0.035) and also significantly reduced uptake of [18F]-2-fluoro-2-deoxyglucose by positron emission tomography (P = 0.049). After 6 weeks of therapy, both treatments caused similar reductions in granuloma bacterial load, but the more sterilizing, four-drug regimen caused greater reduction in bacterial load in cavitary lesions (P = 0.009). These findings, combined with the association in humans between cavitary disease and relapse, suggest that the basis for improved sterilizing activity of the four-drug combination is both its faster disease volume resolution and its stronger sterilizing effect on cavitary lesions. Definitive data from relapse experiments are needed to support this observation.

Skeletal abnormalities and extra-skeletal ossification in mice with restricted Gsα deletion caused by a renin promoter-Cre transgene

We have recently generated a transgenic mouse line (termed hRen-Cre) that expresses Cre-recombinase under the control of a 12.2-kb fragment of the human renin promoter. In the present study, we have crossed hRen-Cre mice with a mouse strain in which exon 1 of the Gnas gene is flanked by loxP sites. Gnas encodes the α-subunit of the stimulatory G protein (Gsα). Our aim has been to generate a mouse model with locally restricted inactivation of Gsα to extend studies of the role of Gsα function in vivo. Mice with local Cre-mediated inactivation of Gsα (rCre-Gsα) are viable and fertile. Their most obvious phenotype consists of marked skeletal malformations of the forelimbs in which computer-tomography scans reveal shortened and fused extremity bones. Extraskeletal ossifications occur in the subcutis and in skeletal muscles associated with the affected long bones. Plasma calcium, phosphate and parathyroid hormone are normal. Skin histology has demonstrated diffuse mineralization and ossification associated with the basal cells of hair follicles. This phenotype in part resembles syndromes in humans associated with loss-of-function of Gsα, such as Albright hereditary osteodystrophy and progressive osseous heteroplasia. The renal phenotype of rCre-Gsα mice is inconspicuous. Plasma renin concentration, ambient urine osmolarity, and the glomerular filtration rate of rCre-Gsα mice do not differ from controls. The absence of measurable functional changes in the renin-angiotensin system indicates insufficient Cre expression in juxtaglomerular granular cells in this strain of mice. Nevertheless, the present report reaffirms the importance of Gsα signaling for bone development and the suppression of ectopic ossification.

Computed tomography imaging of lungs in mouse models of human disease : advancing the computing interfaces with physiology

New research applications for imaging can come from combining advances in anesthetic management and respiratory synchronization with computed tomography (CT) algorithms. CT imaging has the potential to provide lung pathologic details non-invasively, and to facilitate the structural and functional studies in mouse models of human diseases. Examples include atelectasis in lungs of transgenic mice expressing sickle hemoglobin, and bacterial pneumonia. However, human high-resolution CT is typically obtained during a breath-hold, asking the patient to voluntarily hold her breath for several seconds and hold still for a crisp image. Mice cannot cooperate in this manner, so inhalational general anesthesia keeps the animal in position but breathing spontaneously during the 20 to 40 minutes of scans. Mice with pleural effusion and with severe pulmonary fibrosis survived micro CT under anesthesia. Imaging can be gated to obtain one set of images in the expiratory phase of the respiratory cycle, and another in the inspiratory phase. Respiratory gating provides superior image quality, and comparing inspiratory vs. expiratory lung volume provides an estimate of tidal volume. Correlating human conditions with pathophysiology in mouse models will permit more translational research.

Abstract B19: Anti-VEGF treatment normalizes tuberculosis granuloma vasculature and improves small molecule delivery

Tuberculosis (TB) causes almost 2 million deaths annually, and an increasing number of patients are resistant to existing therapies. TB patients require lengthy chemotherapy, possibly because of poor penetration of antibiotics into granulomas where the bacilli reside. Granulomas are morphologically similar to solid cancerous tumors in that they contain hypoxic microenvironments and can be highly fibrotic. Here we show that TB-infected rabbits have impaired small molecule distribution into these disease sites due to a functionally abnormal vasculature, with a low molecular weight tracer accumulating only in peripheral regions of granulomatous lesions. Granuloma-associated vessels are morphologically and spatially heterogeneous, with poor vessel pericyte coverage in both human and experimental rabbit TB granulomas. Moreover, we found enhanced vascular endothelial growth factor (VEGF) expression in both species. In tumors, anti-angiogenic, specifically anti-VEGF, treatments can “normalize” their vasculature, reducing hypoxia and creating a window-of-opportunity for conjunctive chemotherapy; thus, we investigated vessel normalization in rabbit TB granulomas. Treatment of TB-infected rabbits with the anti-VEGF antibody bevacizumab significantly decreased the total number of vessels while normalizing those that remained. As a result, hypoxic fractions of these granulomas were reduced and small molecule tracer delivery increased. These findings demonstrate that bevacizumab treatment promotes vascular normalization, improves small molecule delivery, and decreases hypoxia in TB granulomas, thereby providing a potential new avenue to improve delivery and efficacy of current treatment regimens. Citation Format: Meenal Datta, Laura E. Via, Walid S. Kamoun, Chong Liu, Wei Chen, Giorgio Seano, Danielle M. Weiner, Daniel Schimel, Kathleen England, John D. Martin, Xing Gao, Lei Xu, Clifton E. Barry, III, Rakesh K. Jain. Anti-VEGF treatment normalizes tuberculosis granuloma vasculature and improves small molecule delivery. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B19.