Correlation between µCT imaging, histology and functional capacity of the osteoarthritic knee in the rat model of osteoarthritis.

BACKGROUND: To acquire the most meaningful understanding of human arthritis, it is essential to select the disease model and methodology translatable to human conditions. The primary objective of this study was to evaluate a number of analytic techniques and biomarkers for their ability to accurately gauge bone and cartilage morphology and metabolism in the medial meniscal tear (MMT) model of osteoarthritis (OA). METHODS: MMT surgery was performed in rats to induce OA. A dynamic weight bearing system (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs in rats. At the end of a 10-week study cartilage pathology was evaluated by micro computed tomography (µCT), contrast enhanced µCT (EPIC µCT) imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization. RESULTS: The study results showed a negative impact of MMT surgery on the weight-bearing capacity of the operated limb. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by elevated CTX-II in serum, EPIC µCT and histology. Bone analysis by µCT showed thickening of the subchondral bone beneath the damaged cartilage, loss of cancellous bone at the metaphysis and active osteophyte formation. CONCLUSIONS: The study emphasizes the need for using various methodologies that complement each other to provide a comprehensive understanding of the pathophysiology of OA at the organ, tissue and cellular levels. Results from this study suggest that use of histology, µCT and EPIC µCT, and functional DWB tests provide powerful combination to fully assess the key aspects of OA and enhance data interpretation.

Oral administration of soluble guanylate cyclase agonists to rats results in osteoclastic bone resorption and remodeling with new bone formation in the appendicular and axial skeleton.

Orally administered small molecule agonists of soluble guanylate cyclase (sGC) induced increased numbers of osteoclasts, multifocal bone resorption, increased porosity, and new bone formation in the appendicular and axial skeleton of Sprague-Dawley rats. Similar histopathological bone changes were observed in both young (7- to 9-week-old) and aged (42- to 46-week-old) rats when dosed by oral gavage with 3 different heme-dependent sGC agonist (sGCa) compounds or 1 structurally distinct heme-independent sGCa compound. In a 7-day time course study in 7- to 9-week-old rats, bone changes were observed as early as 2 to 3 days following once daily compound administration. Bone changes were mostly reversed following a 14-day recovery period, with complete reversal after 35 days. The mechanism responsible for the bone changes was investigated in the thyroparathyroidectomized rat model that creates a low state of bone modeling and remodeling due to deprivation of thyroid hormone, calcitonin (CT), and parathyroid hormone (PTH). The sGCa compounds tested increased both bone resorption and formation, thereby increasing bone remodeling independent of calciotropic hormones PTH and CT. Based on these studies, we conclude that the bone changes in rats were likely caused by increased sGC activity.

Deep-breath frequency in bronchoconstricted monkeys (Macaca fascicularis).

Deep-breath frequency has been shown to increase in spontaneously obstructed asthmatic subjects. Furthermore, deep breaths are known to be regulated by lung rapidly adapting receptors, yet the mechanism by which these receptors are stimulated is unclear. This study tested the hypothesis that deep-breath frequency increases during experimentally induced bronchoconstriction, and the magnitude of the increased deep-breath frequency is dependent on the method by which bronchoconstriction is induced. Nine cynomolgus monkeys (Macaca fascicularis) were challenged with methacholine (MCh), Ascaris suum (AS), histamine, or an external mechanical resistance. Baseline (BL) and challenge deep-breath frequency were calculated from the number of deep breaths per trial period. Airway resistance (Raw) and tissue compliance (Cti), as well as tidal volume, respiratory rate, and minute ventilation, were analyzed for BL and challenged conditions. Transfer impedance measurements were fit with the DuBois model to determine the respiratory parameters (Raw and Cti). The flow at the airway opening was measured and analyzed on a breath-by-breath basis to obtain the ventilatory parameters (tidal volume, respiratory rate, and minute ventilation). Deep-breath frequency resulting from AS and histamine challenges [0.370 (SD 0.186) and 0.467 breaths/min (SD 0.216), respectively] was significantly increased compared with BL, MCh, or external resistance challenges [0.61 (SD 0.046), 0.156 (SD 0.173), and 0.117 breaths/min (SD 0.082), respectively]. MCh and external resistance challenges resulted in insignificant changes in deep-breath frequency compared with BL. All four modalities produced similar levels of bronchoconstriction, as assessed through changes in Raw and Cti, and had similar effects on the ventilatory parameters except that non-deep-breath tidal volume was decreased in AS and histamine. We propose that increased deep-breath frequency during AS and histamine challenge is the result of increased vascular permeability, which acts to increase rapidly adapting receptor activity.

Effect of antiresorptive and anabolic bone therapy on development of osteoarthritis in a posttraumatic rat model of OA.

INTRODUCTION: Osteoarthritis (OA) is a leading cause of disability, but despite the high unmet clinical need and extensive research seeking dependable therapeutic interventions, no proven disease-modifying treatment for OA is currently available. Due to the close interaction and interplay between the articular cartilage and the subchondral bone plate, it has been hypothesized that antiresorptive drugs can also reduce cartilage degradation, inhibit excessive turnover of the subchondral bone plate, prevent osteophyte formation, and/or that bone anabolic drugs might also stimulate cartilage synthesis by chondrocytes and preserve cartilage integrity. The benefit of intensive zoledronate (Zol) and parathyroid hormone (PTH) therapy for bone and cartilage metabolism was evaluated in a rat model of OA. METHODS: Medial meniscectomy (MM) was used to induce OA in male Lewis rats. Therapy with Zol and human PTH was initiated immediately after surgery. A dynamic weight-bearing (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs. At the end of the 10-week study, the rats were euthanized and the cartilage pathology was evaluated by contrast (Hexabrix)-enhanced µCT imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization. RESULTS: The results of this study highlight the complex changes in bone metabolism in different bone compartments influenced by local factors, including inflammation, pain and mechanical loads. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by contrast-enhanced µCT and histology. The study results showed the negative impact of MM surgery on the weight-bearing capacity of the operated limb, which was not corrected by treatment. Although both Zol and PTH improved subchondral bone mass and Zol reduced serum CTX-II level, both treatments failed to prevent or correct cartilage deterioration, osteophyte formation and mechanical incapacity. CONCLUSIONS: The various methods utilized in this study showed that aggressive treatment with Zol and PTH did not have the capacity to prevent or correct the deterioration of the hyaline cartilage, thickening of the subchondral bone plate, osteophyte formation or the mechanical incapacity of the osteoarthritic knee.

Patient-derived xenografts reveal limits to PI3K/mTOR- and MEK-mediated inhibition of bladder cancer.

BACKGROUND: Metastatic bladder cancer is a serious condition with a 5-year survival rate of approximately 14 %, a rate that has remained unchanged for almost three decades. Thus, there is a profound need to identify the driving mutations for these aggressive tumors to better determine appropriate treatments. Mutational analyses of clinical samples suggest that mutations in either the phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) or RAS/MEK/ERK pathways drive bladder cancer progression, although it remains to be tested whether the inhibition of either (or both) of these pathways can arrest PI3K/mTOR- or Ras-driven proliferation. METHODS: Herein, we used several bladder cancer cell lines to determine drug sensitivity according to genetic background and also studied mouse models of engrafted UM-UC-3 cells and patient-derived xenografts (PDXs) to test PI3K/mTOR and MEK inhibition in vivo. RESULTS: Inhibition of these pathways utilizing PF-04691502, a PI3K and mTOR inhibitor, and PD-0325901, a MEK inhibitor, slowed the tumor growth of PDX models of bladder cancer. The growth inhibitory effect of combination therapy was similar to that of the clinical maximum dose of cisplatin; mechanistically, this appeared to predominantly occur via drug-induced cytostatic growth inhibition as well as diminished vascular endothelial growth factor secretion in the tumor models. Kinase arrays of tumors harvested after treatment demonstrated activated p53 and Axl as well as STAT1 and STAT3. CONCLUSION: Taken together, these results indicate that clinically relevant doses of PF-04691502 and PD-0325901 can suppress bladder tumor growth in PDX models, thus offering additional potential treatment options by a precision medicine approach.

Antitumor effect of vascular endothelial growth factor inhibitor sunitinib in preclinical models of hepatocellular carcinoma.

OBJECTIVE: Tumor recurrence and metastasis is the most common cause of mortality in hepatocellular carcinoma (HCC) patients. Despite positive results with vascular endothelial growth factor (VEGF) inhibitors in preclinical studies using HCC xenograft models, the clinical outcome in HCC patients has been disappointing. So far, only the multitargeted tyrosine kinase inhibitor sorafenib has been shown to significantly improve survival in HCC patients, suggesting that this class of agents could be effective against HCC. Recently, another VEGF inhibitor, sunitinib, showed survival benefits in HCC hepatitis B-positive patients, but failed to improve survival in HCC hepatitis C-positive patients. Obviously, concomitant liver disease, liver function in general, and the local liver environment have a huge impact on treatment outcomes. In this study, we aimed to examine the antiproliferative effect of sunitinib in different HCC cell lines in vitro, and then in xenograft and orthotopic models of HCC in order to assess the effect of the local liver vasculature on drug efficacy. METHODS: Human cancer cell lines Huh7.5, Hep3B, and SK-Hep-1 were used for in-vitro studies. In in-vivo studies, each mouse carried Huh7.5 cells in both the subcutaneous and the intrahepatic compartment; therefore, drug exposure and treatment regimen were identical in both tumors. RESULTS: Sunitinib has the potential to moderately inhibit proliferation in the Huh7.5 cell line, induce p53 in the p53-wild-type cell line SK-hep-1, and to increase the S-phase and the sub-G1 component of the cell cycle in the Hep3B cell line. Diverse responses to sunitinib in HCC cell lines emphasize the heterogeneity of HCC tumors and may further explain the discrepancy between preclinical and clinical results. The in-vivo results show that sunitinib treatment was far less effective against intrahepatic tumors compared with xenografts. Histological data indicate that large solid intrahepatic tumors are severely affected by sunitinib as shown by large areas of necrosis and diminished number of viable tumor cells. CONCLUSION: The real problem when treating intrahepatic tumors with sunitanib and/or other VEGF inhibitors seems to arise from unopposed local growth of the small tumors and perhaps the development of distant micrometastases. Even though both xenograft and orthotopic models have limitations, these models add value to our understanding of tumor biology and help to better design treatment paradigms for patients with HCC. In comparison with xenograft models, the orthotopic HCC model allows for a more realistic assessment of drug efficacy in patients, in particular by enhancing our knowledge of the role that organ vasculature plays in the development of local metastasis and tumor resistance to antiangiogenic treatments.

Models of hepatocellular carcinoma and biomarker strategy.

The overwhelming need to improve preclinical models in oncology has stimulated research efforts to refine and validate robust orthotopic models that closely mimic the disease population and therefore have the potential to better predict clinical outcome with novel therapies. Sophisticated technologies including bioluminescence, contrast enhanced ultrasound imaging, positron emission tomography, computed tomography and magnetic resonance imaging have been added to existing serum- and histology-based biomarkers to assist with patient selection and the design of clinical trials. The rationale for the use of human hepatocellular carcinoma (HCC) cell lines, implementation of xenograft and orthotopic animal models and utilization of available biomarkers have been discussed, providing guidelines to facilitate preclinical research for the development of treatments for HCC patients.

Sunitinib and PF-562,271 (FAK/Pyk2 inhibitor) effectively block growth and recovery of human hepatocellular carcinoma in a rat xenograft model.

EXPERIMENTAL DESIGN: To investigate the antitumor effect of sunitinib and FAK/Pyk2 tyrosine kinase inhibitor (PF-562,271)combination therapy in vivo, utilizing human hepatocellular carcinoma (HCC) cells Huh7.5. Nude rats were inoculated subcutaneously with Huh7.5 hepatoma cells. Dosing for Phase 1 was initiated on day 5 post tumor inoculations with Vehicle(Group 1), sunitinib (25 mg/kg/day; Group 2) and sunitinib plus PF-562,271 combination (15 mg/kg/day; Group 3). Phase 2 of the study started on day 26, and each of the three original groups was divided in two subgroups; half of the rats remained on original therapy (Groups 1A and 2A) with the exception of Group 3A that was euthanized after Phase 1. The other half of the rats were switched to sunitinib and PF-562,271 combination (Group 1B) or vehicle (Groups 2B and 3B). Tumor volume and weight, serum alpha feto-protein (AFP), contrast-enhanced ultrasound imaging (CEUS) and tumor histology were used to evaluate effects of treatment on tumor growth. RESULTS: The results from this study indicate that the combination of sunitinib and PF-562,271 TKI has the potential to target different aspects of angiogenesis and tumor aggressiveness and may have significantly greater effect than relevant single agent, blocking not only tumor growth, but also impacting the ability of the tumor to recover upon withdrawal of the therapy.

Dual focal adhesion kinase/Pyk2 inhibitor has positive effects on bone tumors: implications for bone metastases.

BACKGROUND: Lytic bone metastases occur frequently in cancer patients and present major clinical issues including lack of effective therapies. The mechanism of lytic bone metastases involves interactions between tumor cells, bone matrix, and bone cells. Both focal adhesion kinase (FAK) and Pyk2 are implicated in the biology and physiology of bone and cancer. METHODS: The efficacy of PF-562,271 was evaluated using MDA-MB-231 cells implanted in the tibia of nude rats. The drug was administered orally at a dose of 5 mg/kg, 7 days per week for 28 days. Serum and urine biomarkers, imaging, and histologic techniques were deployed to monitor tumor take rate, disease progression, and response to therapy. RESULTS: The compound was well tolerated. Both compound-treated groups demonstrated significant and similar increases in osteocalcin and cancellous bone parameters. Radiographic evaluation of tumor-bearing tibiae revealed tumor expansion in nontreated rats compared with a decrease in tumor growth and signs of bone healing in rats treated with PF-562,271. Tartrate-resistant acid phosphatase and fluorescent in situ hybridization analysis revealed that the majority of bone resorption at the tumor site was performed by osteoclasts of rat origin. CONCLUSIONS: The oral administration of PF-562,271 at a dose of 5 mg/kg suppressed the growth and local spread of intratibial tumors and restored tumor-induced bone loss. The unique ability of PF-562,271 to both curb tumor growth and safely increase bone formation may be an effective therapy for many cancer patients with bone metastases and cancer-associated osteoporosis.

Age-related changes in marmoset trabecular and cortical bone and response to alendronate therapy resemble human bone physiology and architecture.

In older humans, bone elongation ceases, periosteal expansion continues, and bone remodeling remains a dominant metabolic process. An appropriate animal model of type I and type II osteoporosis would be a species with sealed growth plates and persistence of bone remodeling. The rat is commonly used as a primary model, but due to delayed epiphyseal closure with continuous modeling and lack of Haversian remodeling, Food and Drug Administration guidelines recommend assessment of bone quality in an additional, non rodent, remodeling species. This study investigated the skeletal characteristics of senescent marmosets to evaluate their suitability as an osteoporosis model. Animals were randomized across three experimental groups; controls for both sexes and marmosets receiving alendronate for either 30 or 60 days (28 microg/kg, sc, twice per week). Outcome measures included serum chemistry and bone biomarkers, DEXA, histomorphometry, micro-computed tomography, and histopathology. Results showed that the adult marmoset skeleton has similar anatomical characteristics to the adult human, including the absence of growth plates, presence of Haversian system, and true remodeling of cancellous and cortical bone. Structural analyses of senescent marmoset cancellous bone demonstrated loss of trabecular mass and architecture similar to skeletal changes described for elderly men and women. Treatment with alendronate improved trabecular volume and number by reducing bone resorption, although bone formation was also reduced through coupling of bone remodeling. The common marmoset may provide a valuable model for research paradigms targeting human bone pathology and osteoporosis due to skeletal features that are similar to age-related changes and response to bisphosphonate therapy reported for humans.