Biomedical subjects

Larry J Suva

Publications and source records attributed to Larry J Suva.

30 records · Page 2Linked to original sources

PubMed2005

Ethanol-induced inhibition of bone formation in a rat model of distraction osteogenesis: a role for the tumor necrosis factor signaling axis.

BACKGROUND: Chronic ethanol exposure inhibits the rapid bone formation demonstrated during limb lengthening by distraction osteogenesis (DO). This inhibition is attenuated by simultaneous administration of antagonists to the cytokines interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. The individual effects on inhibition of osteogenesis by these cytokines were tested. We hypothesized that administration of individual antagonists to these cytokines [IL-1 receptor antagonist (IL-1ra) or polyethylene glycol-conjugated soluble TNF receptor type 1 (sTNFR1)] would enhance DO and that the individual administration of each cytokine [recombinant rat (rr) IL-1 or recombinant rat (rr) TNF] would inhibit DO. METHODS: Rats were either infused with a liquid diet with or without ethanol (antagonist studies) or given rat chow (recombinant studies) and underwent tibial fractures stabilized with external fixators for DO. The bioactive substances were administered by systemic (antagonist studies) or local (recombinant) diffusion. RESULTS: A comparison of histologic sections from these distracted tibias demonstrated a protective effect on bone formation by sTNFR1 (p<0.05), unexpectedly, an IL-1ra-related decrease in bone formation (p<0.02), significant decreases in bone formation with rrTNF compared with the vehicle controls (p<0.02), and no significant changes in bone formation with rrIL-1. The cellular responses (fibroblastic and inflammatory cells) were unique for each recombinant cytokine administered. CONCLUSIONS: These results suggest that the osteoinhibitory effects of chronic ethanol exposure are mediated in part by the TNF signaling axis.

Alcoholism↗

PubMed2004

Heparanase promotes the spontaneous metastasis of myeloma cells to bone.

Although widespread skeletal dissemination is a critical step in the progression of myeloma, little is known regarding mechanisms that control metastasis of this cancer. Heparanase-1 (heparanase), an enzyme that cleaves heparan sulfate chains, is expressed at high levels in some patients with myeloma and promotes metastasis of some tumor types (eg, breast, lymphoma). Using a severe combined immunodeficient (SCID) mouse model, we demonstrate that enhanced expression of heparanase by myeloma cells dramatically up-regulates their spontaneous metastasis to bone. This occurs from primary tumors growing subcutaneously and also from primary tumors established in bone. Interestingly, tumors formed by subcutaneous injection of cells metastasize not only to bone, but also to other sites including spleen, liver, and lung. In contrast, tumors formed by injection of cells directly into bone exhibit a restricted pattern of metastasis that includes dissemination of tumor to other bones but not to extramedullary sites. In addition, expression of heparanase by myeloma cells (1) accelerates the initial growth of the primary tumor, (2) increases whole-body tumor burden as compared with controls, and (3) enhances both the number and size of microvessels within the primary tumor. These studies describe a novel experimental animal model for examining the spontaneous metastasis of bone-homing tumors and indicate that heparanase is a critical determinant of myeloma dissemination and growth in vivo.

Bone and Bones↗

PubMed2004

Modeling the interactions between osteoblast and osteoclast activities in bone remodeling.

We propose a mathematical model explaining the interactions between osteoblasts and osteoclasts, two cell types specialized in the maintenance of the bone integrity. Bone is a dynamic, living tissue whose structure and shape continuously evolves during life. It has the ability to change architecture by removal of old bone and replacement with newly formed bone in a localized process called remodeling. The model described here is based on the idea that the relative proportions of immature and mature osteoblasts control the degree of osteoclastic activity. In addition, osteoclasts control osteoblasts differentially depending on their stage of differentiation. Despite the tremendous complexity of the bone regulatory system and its fragmentary understanding, we obtain surprisingly good correlations between the model simulations and the experimental observations extracted from the literature. The model results corroborate all behaviors of the bone remodeling system that we have simulated, including the tight coupling between osteoblasts and osteoclasts, the catabolic effect induced by continuous administration of PTH, the catabolic action of RANKL, as well as its reversal by soluble antagonist OPG. The model is also able to simulate metabolic bone diseases such as estrogen deficiency, vitamin D deficiency, senescence and glucocorticoid excess. Conversely, possible routes for therapeutic interventions are tested and evaluated. Our model confirms that anti-resorptive therapies are unable to partially restore bone loss, whereas bone formation therapies yield better results. The model enables us to determine and evaluate potential therapies based on their efficacy. In particular, the model predicts that combinations of anti-resorptive and anabolic therapies provide significant benefits compared with monotherapy, especially for certain type of skeletal disease. Finally, the model clearly indicates that increasing the size of the pool of preosteoblasts is an essential ingredient for the therapeutic manipulation of bone formation. This model was conceived as the first step in a bone turnover modeling platform. These initial modeling results are extremely encouraging and lead us to proceed with additional explorations into bone turnover and skeletal remodeling.

Bone Diseases, Metabolic↗

PubMed2004

Heparan sulfate proteoglycans and heparanase--partners in osteolytic tumor growth and metastasis.

This review summarizes a series of studies demonstrating that heparan sulfate proteoglycans act to promote the growth and metastasis of myeloma and breast tumors, two tumors that home to, and grow within, bone. Much of the growth-promoting effect of proteoglycans in these tumors may reside in the shed form of syndecan-1 that acts to favorably condition the tumor microenvironment. Moreover, the interplay between heparan sulfate and the extracellular enzyme heparanase-1 also has important regulatory implications. Recent studies indicate that the activity of heparanase, which likely releases heparin sulfate-bound growth factors and generates highly active heparan sulfate fragments, also promotes growth and metastasis of myeloma and breast tumors. Understanding the role of heparan sulfate and heparanase in the regulation of tumor behavior may lead to new therapeutic approaches for treating cancer.

Animals↗

PubMed2003

Investigation of the regulation of bone mass by mechanical loading: from quantitative cytochemistry to gene array.

From the 1860s to the early 1980s, the process that fitted bone architecture and mass to function had been investigated and characterized. It was known that increases in exercise were associated with increased bone mass, and that disuse caused osteopaenia, but the mechanisms by which those processes were regulated was not understood. The idea that osteocytes, the cells embedded in bone, were sensitive to the effects of mechanical loading was attractive, yet there was almost no experimental support for it, at least in part because the cells were considered inaccessible for study. In 1984, the techniques devised by Chayen and his co-workers were focused on this area. By analysis of the activity of the enzyme glucose 6-phosphate dehydrogenase in osteocytes in sections of avian bone that had been subjected to brief periods of applied mechanical loading, we showed for the first time that osteocytes could respond within a few minutes to mechanical stimulation. The lack of elevation of activity of other glycolytic enzymes led to the conclusion that this elevation was due to increased activity of the pentose shunt pathway, which was likely to be associated with increased production of reducing equivalents for biosynthesis, and ribose sugars for RNA synthesis. This was the first demonstration of an ability of osteocytes to respond to an external mechanical event and in effect provided a mechanistic link for the fundamental principle of what is known as Wolff's law of bone remodelling. These studies were dependent on several technical advances brought together in the Chayen Cellular Biology Laboratory at the Kennedy Institute. The ability to make cryosections of undecalcified bone, to perform cytochemical analysis of (soluble) enzyme activities by use of colloid stabilizers in the reaction medium, and finally to measure accurately the coloured reaction products by microdensitometry (which avoided optical heterogeneity errors) combined to provide a powerful way to explore bone cell function in situ. In the intervening years since then, similar studies have become routine, and the impact of molecular biological advances in hard tissues have remained dependent on techniques pioneered in the Chayen laboratory. During such studies, other advances have spun off, so that osteocyte gene expression has been analysed in samples taken from sections where the precise tissue characteristics were known, leading to advances in understanding of intercellular signalling mechanisms in bone by differential display, and the role of apoptosis in osteocytes in regulation of osteoclastic resorption. Still more recently, materials extracted from undecalcified sections have been used in gene array studies to discover new candidate genes with a role in the adaptive mechanism. Without Joe Chayen's involvement in this area, which now impacts on almost all bone biological science either directly or indirectly, our understanding of the pathophysiology of osteoporosis would have been very different.

Bone Density↗

PubMed2003

Interleukin-8 stimulation of osteoclastogenesis and bone resorption is a mechanism for the increased osteolysis of metastatic bone disease.

Interleukin 8 (IL-8) is a member of the alpha chemokine family of cytokines originally identified as a neutrophil chemoattractant. Recently, we reported that elevated levels of IL-8, but not parathyroid hormone-related protein (PTHrP), correlated with increased bone metastasis in a population of human breast cancer cells. We hypothesized that IL-8 expression by breast cancer cells would either indirectly influence osteoclastogenesis via nearby stromal cells or directly influence osteoclast differentiation and activity. In the present study, we investigated the role of IL-8 in the process of osteoclast formation and bone resorption, which is associated with metastatic breast cancer. The addition of recombinant human (rh) IL-8 (10 ng/ml) to cultures of stromal osteoblastic cells stimulated both RANKL mRNA expression and protein production, with no effect on the expression of osteoprotegerin. In addition, rhIL-8 also directly stimulated the differentiation of human peripheral blood mononuclear cells into bone-resorbing osteoclasts. In these cultures, IL-8 was able to stimulate human osteoclast formation even in the presence of excess (200 ng/ml) RANK-Fc. The effect of IL-8 on osteoclasts and their progenitors was associated with the cell surface expression of the IL-8-specific receptor (CXCR1) on the cells. These results demonstrate a direct effect of IL-8 on osteoclast differentiation and activity. Together, these data implicate IL-8 in the osteolysis associated with metastatic breast cancer.

Animals↗

PubMed2003

Breast cancer metastasis to bone: it is not all about PTHrP.

Breast cancer shows a predilection for metastasis to bone. Interestingly, approximately 80% of patients with breast cancer also have bone metastases develop at some point during the course of their disease. Osteolytic breast cancer induces bonedestruction via the stimulation of osteoclasts. Breast cancer cells produce many known stimulators of bone resorption with significant research effort focused on the role of parathyroid hormone-related protein (PTHrP). However, a recent prospective clinical trial has questioned the primary role of PTHrP in this process. The overexpression of interleukin-8 (IL-8) in metastatic breast cancer cells prompted additional investigation of the role of IL-8 in osteolysis. Recombinant IL-8 induces the expression of RANKL mRNA and protein in osteoblastic cells and stimulates formation of bone resorbing osteoclasts, even in the absence of RANKL. The ability of IL-8 to directly stimulate osteoclastogenesis via RANKL dependent and independent mechanisms suggests it may play an important role in the process of osteoclast formation and function. Therefore, we propose that cytokines such as IL-8 are involved in the early stages of breast cancer metastasis and initiate the process of osteoclastic bone resorption. In this modified model of breast cancer metastasis to bone, PTHrP expression is induced later to stimulate the vicious cycle of bone destruction.

Bone Neoplasms↗

PubMed2002

Expression of interleukin 8 and not parathyroid hormone-related protein by human breast cancer cells correlates with bone metastasis in vivo.

Metastasis is the process by which tumor cells spread from their site of origin to distant sites after gaining access to the circulatory system. An understanding of the factors contributing to the metastatic potential of breast cancer cells to bone will enhance the prospect of developing new therapies that impede metastasis. In this study, we have used an in vivo selection scheme involving left cardiac ventricle injection into nude mice to identify a highly metastatic human breast cancer cell line (MDA-MET) from a less metastatic (MDA-231) parental cell line. In this model, tumor-bearing mice exhibit features similar to those associated with human metastatic bone disease such as osteolytic bone destruction. After inoculation, MDA-MET cells form devastating lesions within 4 weeks, whereas the parental cells do not, even after 10 weeks. In vitro, the MDA-MET cells have a similar growth rate to the parental MDA-231 cells yet demonstrate distinct adhesive and invasive phenotypes. MDA-MET cells show increased early adhesion to type IV collagen and are significantly more invasive through Matrigel than MDA-231 cells. Analysis of the gene expression profile in the metastatic MDA-MET versus poorly metastatic MDA-231 cells identified relatively few genes whose expression was altered >2-fold. Of particular interest was the lack of parathyroid hormone-related protein (PTHrP) mRNA expression, which was supported at the protein level by immunoradiometric assay. These data support the idea that PTHrP is not predictive of the metastasis of human breast cancer to bone. Another important difference between the two cell lines was the elevated expression by MDA-MET cells of the cytokine IL-8. Reverse transcriptase-PCR and ELISA confirmed the increased expression of IL-8 in MDA-MET cells. In addition, IL-8 mRNA expression is also elevated in a variety of human cancer cell lines with different metastatic potential in vivo. These experiments suggest that the elevated expression of IL-8 (and not PTHrP) by MDA-MET cells is a phenotypic change that may be related to their enhanced ability to metastasize to the skeleton.

Bone Neoplasms↗

PubMed2002

Four distinct chondrocyte populations in the fetal bovine growth plate: highest expression levels of PTH/PTHrP receptor, Indian hedgehog, and MMP-13 in hypertrophic chondrocytes and their suppression by PTH (1-34) and PTHrP (1-40).

Differentiation and growth of chondrocytes in fetal growth plates of vertebrate long bones and ribs appear to occur in a gradual, continuous manner between the resting zone through the proliferation zone, maturation zone, and upper and lower hypertrophic zones, with a continuous increase in cell size up to 10-fold of the volume of a resting chondrocyte. Here we provide evidence, however, that after centrifugation through a continuous Percoll gradient growth plate chondrocytes separate into four distinct cell populations (B1 to B4) which differ markedly in density, size, and gene expression. These populations collect in the absence of any phase borders in the gradient which might serve as concentration barriers. Fractions B1 and B2 contained the largest cells with the lowest buoyant density and showed the highest expression levels for type X collagen (Col X), but only the B1 population expressed high levels of matrix metalloproteinase-13 (collagenase 3). Cells in fraction B3 were significantly smaller and expressed little Col X, while cells in fraction B4 were of similar size to cells in the resting zone without significant Col X expression. The highest levels of parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PTHR-1), and Indian hedgehog (Ihh) expression were also found in the hypertrophic fractions B1 and B2 and not in the prehypertrophic fraction B3, as expected from in situ hybridization data on PTHR-1 expression in fetal rodent or chicken growth plates. Incubation of fractions B1 to B3 with the amino-terminal fragments PTH (1-34) or PTHrP (1-40) suppressed the expression of Col X and PTHR-1 by more than 50% and the expression of Ihh nearly completely. In contrast, the mid-regional PTH fragment PTH (28-48) and PTH (52-84) consistently stimulated the expression of PTHR-1 by 10-20% in fractions B1 to B3. These findings confirm the existence of distinct differentiation stages within chondrocytes of the growth plate and support the hypothesis proposed by Vortkamp et al. (Science 273(1996)613) of a regulatory feedback loop of Ihh and PTH/PTHrP fragments controlling the differentiation of proliferating to prehypertrophic chondrocytes, but extend the ability to respond to PTH/PTHrP hypertrophic chondrocytes.

Animals↗

PubMed2002

Interleukin-1 and tumor necrosis factor antagonists attenuate ethanol-induced inhibition of bone formation in a rat model of distraction osteogenesis.

Chronic ethanol exposure inhibits rapid bone formation during distraction osteogenesis (DO; fracture and limb lengthening) and decreases volumetric bone mineral density (BMD) in a model of intragastric dietary infusion [total enteral nutrition (TEN)] in the rat. The hypothesis tested herein was that overexpression of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha mediates these deleterious effects of ethanol on the rat skeleton. Two studies (study 1, female rats; study 2, male rats) were performed to test the potential protective effects of the IL-1 and TNF antagonists: IL-1 receptor antagonist (IL-1ra) and 30-kDa polyethylene glycol-conjugated soluble TNF receptor type 1 (sTNFR1). All rats were infused with a liquid diet +/- ethanol (EtOH) and underwent tibial fractures and DO. During distraction, the animals received a combination of IL-1ra (1.8-2.0 mg/kg/day) and sTNFR1 (2.0 mg/kg/2 days) or vehicle. A comparison of distracted tibial histological sections demonstrated 1) significant antagonist-related increases in bone column formation over the EtOH controls (studies 1 and 2), and 2) restoration of new bone equivalent to that of the TEN controls (study 2). In contrast, examination of intact proximal tibial metaphyses by peripheral quantitative computerized tomography revealed decreases in volumetric BMD of both EtOH control and EtOH antagonist groups (study 2). These results demonstrate that short-term systemic administration of IL-1 and TNF antagonists together protect rapid bone formation during DO from the deleterious effects of chronic ethanol but are ineffective in regard to intact bone homeostasis.

Animals↗

PubMed2002

Skeletal toxicity associated with chronic ethanol exposure in a rat model using total enteral nutrition.

Chronic alcohol abuse decreases bone mass, inhibits osteoblast differentiation and function, increases fracture incidence, and delays fracture healing. Four studies were designed to use intragastric ethanol delivery as part of a total enteral nutrition (TEN) system to determine the negative systemic effects of chronic ethanol on 1) the rat skeleton and 2) local rapid bone formation during limb lengthening (distraction osteogenesis, DO). In study 1, three-point bending tests demonstrated that after 75 days of ethanol exposure, the tibiae had significantly lower load to failure versus control diet (p = 0.0006) or ad libitum chow-fed rats (p = 0.0029). Study 2 examined alcohol's effects on the density and cross-sectional area of the proximal tibial metaphysis using peripheral quantitative computed tomography and found that after 25 days of ethanol exposure the trabecular volumetric bone mineral density (p = 0.011) and cortical cross-sectional area (p = 0.011) were lower compared with controls. In study 3, a comparison of distracted tibial radiographs and histological sections demonstrated ethanol-related decreases in both gap mineralization (p = 0.03) and bone column formation (p = 0.01). Histological comparisons in study 4 reproduced the ethanol-related deficits in new bone formation during DO (p = 0.001). These results indicate that the TEN system is a viable model to study ethanol's effects on the skeleton and that chronic ethanol delivery via TEN decreases trabecular bone density, cortical area, and mature bone strength. Also, the DO studies demonstrate, for the first time, that chronic ethanol inhibits rapid bone formation during limb lengthening.

Alcoholism↗

PubMedDate not supplied

Diagnosis of pancreatic cancer using serum proteomic profiling.

In the United States, mortality rates from pancreatic cancer (PCa) have not changed significantly over the past 50 years. This is due, in part, to the lack of early detection methods for this particularly aggressive form of cancer. The objective of this study was to use high-throughput protein profiling technology to identify biomarkers in the serum proteome for the early detection of resectable PCa. Using surface-enhanced laser desorption/ionization mass spectrometry, protein profiles were generated from sera of 49 PCa patients and 54 unaffected individuals after fractionation on an anion exchange resin. The samples were randomly divided into a training set (69 samples) and test set (34 samples), and two multivariate analysis procedures, classification and regression tree and logistic regression, were used to develop classification models from these spectral data that could distinguish PCa from control serum samples. In the test set, both models correctly classified all of the PCa patient serum samples (100% sensitivity). Using the decision tree algorithm, a specificity of 93.5% was obtained, whereas the logistic regression model produced a specificity of 100%. These results suggest that high-throughput proteomics profiling has the capacity to provide new biomarkers for the early detection and diagnosis of PCa.

Biomarkers, Tumor↗