Biomedical subjects

Benjamin Wu

Publications and source records attributed to Benjamin Wu.

11 recordsLinked to original sources

PubMed2005

Nell-1 induced bone formation within the distracted intermaxillary suture.

Maxillary bone deficiencies, such as cleft palate and underdeveloped maxilla that require bone graft or regeneration after orthopedic or surgical expansion, pose a significant biomedical burden. Nell-1 is a secreted molecule that possesses chordin-like domains and induces cranial suture bone growth and osteoblast differentiation. To accelerate bone formation in acutely distracted palatal sutures, rat organ cultures were stimulated with Nell-1 or BMP-7 for 8 days in vitro. We hypothesized that Nell-1 stimulation to the distracted palatal suture would accelerate bone formation. Distracted palates of 4-week-old male rats were maintained in an organ culture system, and tissue was either unstimulated or stimulated with Nell-1 or BMP-7 for 8 days. MicroCT was conducted to quantitate bone formation, while alcian blue staining was conducted for cartilage localization. Immunohistochemistry of Sox9 for chondrocyte proliferation, type X collagen for hypertrophic cartilage in endochondral bone formation, and bone sialoprotein for bone formation was conducted to characterize the cellular mechanism of newly developed tissues. Distracted palates cultured in the presence of Nell-1 or BMP-7 produced statistically significantly (P < 0.05) more bone and cartilage within the intermaxillary suture, relative to unstimulated control samples. While both BMP-7 and Nell-1 induced similar bone formation in the distracted suture, BMP-7 induced both chondrocyte proliferation and differentiation, while Nell-1 accelerated chondrocyte hypertrophy and endochondral bone formation. While both Nell-1 and BMP-7 are effective in forming bone in the distracted palatal suture, they are suggested to have distinctively different mechanisms. The ability of Nell-1 to accelerate bone formation within the palate suture demonstrates the versatility of Nell-1 within the craniofacial complex as well as an exciting advance in palate suture defect healing.

Animals↗

PubMed2005

Detection of picomolar levels of interleukin-8 in human saliva by SPR.

Researchers at UCLA have discovered that the levels of interleukin-8 (IL-8) protein in the saliva of healthy individuals and patients with oropharyngeal squamous cell carcinoma (OSCC) are 30 pM and 86 pM, respectively. In this study, we present the development of the first immunoassay for the quantification of picomolar IL-8 concentrations in human saliva using Biacore surface plasmon resonance (SPR) in a microfluidic channel. A sandwich assay using two monoclonal antibodies, which recognize different epitopes on the antigen (IL-8), was used. Only 13 minutes were required to determine the quantity of pure IL-8 added to just 100 microL of either buffer or saliva-based samples. The limit of detection (LOD) of this immunoassay in buffer was 2.5 pM, and the precision of the response for each concentration was <3% of the coefficient of variation. When first analyzing the saliva supernatants, non-specific binding to the surface was observed. By adding carboxymethyl dextran sodium salt (10 mg mL(-1)) to compete with the surface dextran and primary antibody for non-specific interactions, the signal to noise ratio was greatly improved. The LOD of this immunoassay in saliva was 184 pM. A minimum concentration of 250 pM of exogenous IL-8 could then be consistently detected in a salivary environment. The precision of the response for each IL-8 concentration tested was <7% of the coefficient of variation. Diagnostic sensitivity for oral cancer can be achieved by pre-concentrating the saliva samples 10 fold prior to SPR analysis, making the target levels of IL-8 300 pM for healthy individuals and 860 pM for oral cancer patients.

Animals↗

PubMed2005

Evolving concepts in bone tissue engineering.

The field of tissue engineering integrates the latest advances in molecular biology, biochemistry, engineering, material science, and medical transplantation. Researchers in the developing field of regenerative medicine have identified bone tissue engineering as an attractive translational target. Clinical problems requiring bone regeneration are diverse, and no single regeneration approach will likely resolve all defects. Recent advances in the field of tissue engineering have included the use of sophisticated biocompatible scaffolds, new postnatal multipotent cell populations, and the appropriate cellular stimulation. In particular, synthetic polymer scaffolds allow for fast and reproducible construction, while still retaining biocompatible characteristics. These criteria relate to the immediate goal of determining the ideal implant. The search is becoming a reality with widespread availability of biocompatible scaffolds; however, the desired parameters have not been clearly defined. Currently, most research focuses on the use of bone morphogenetic proteins (BMPs), specifically BMP-2 and BMP-7. These proteins induce osteogenic differentiation in vitro, as well as bone defect healing in vivo. Protein-scaffold interactions that enhance BMP binding are of the utmost importance, since prolonged BMP release creates the most osteogenic microenvironment. Transition into clinical studies has had only mild success and relies on large doses of BMPs for bone formation. Advances within the field of bone tissue engineering will likely overcome these challenges and lead to more clinically relevant therapies.

Animals↗

PubMed2004

BMP-2 exerts differential effects on differentiation of rabbit bone marrow stromal cells grown in two-dimensional and three-dimensional systems and is required for in vitro bone formation in a PLGA scaffold.

Osteogenic differentiation of bone marrow stromal cells (BMSC) in a three-dimensional (3-D) scaffold has not been well studied. In this work, we studied expression of bone-related genes during differentiation of rabbit BMSCs in response to bone morphogenetic protein (BMP)-2 in both 2-D and 3-D culture systems. When BMSCs were cultured on films (2-D) of biodegradable poly(lactide-co-glycolide) (PLGA), increases in mRNA expression of type I collagen (Col I) and vascular endothelial growth factor (VEGF) became evident after 1 week. However, expression of both genes was only mildly stimulated by BMP-2. Expression of the osteopontin gene was highly stimulated by BMP-2 treatment. Expression of chordin, a BMP antagonist, increased significantly after 7 days. The increase was abrogated by BMP-2 treatment. BMP-2 was also able to stimulate mineralization of cultured BMSCs. After cells were switched to 3-D PLGA scaffolds for 24 h, expression of osteopontin and VEGF were markedly increased while expression of type I collagen and chordin remained unchanged. Expression of Col I did not increase with time in a 3-D culture as it did when cells were cultured on a 2-D film. We further explored the possibility of engineering bone tissue in vitro by seeding BMSCs into PLGA scaffolds. Cellular differentiation and bone formation in the scaffolds were analyzed histologically at 2 weeks and 2 months. Secretion of ECM by cells was evident at both 2-week and 2-month scaffolds, and was enhanced by rhBMP-2. Striking differences in 2-month scaffolds were observed between BMP-treated and untreated cells. A woven bone-like structure appeared in the scaffolds treated with BMP-2. The structure was verified to be bone-related by: (1) the presence of organized collagen fibrils; (2) the presence of mineral; and (3) morphological features of trabecular bone. Although collagen was abundant in the untreated 2-month scaffolds, it was disorganized. The untreated scaffolds also lacked mineral deposits, which were present in 2-D cultured cells even in the absence of BMP-2. Our results indicate that the requirement of osteo-inductive agents, such as BMP-2, is essential for bone tissue engineering.

Animals↗

PubMed2004

Adipose-derived adult stromal cells heal critical-size mouse calvarial defects.

In adults and children over two years of age, large cranial defects do not reossify successfully, posing a substantial biomedical burden. The osteogenic potential of bone marrow stromal (BMS) cells has been documented. This study investigates the in vivo osteogenic capability of adipose-derived adult stromal (ADAS) cells, BMS cells, calvarial-derived osteoblasts and dura mater cells to heal critical-size mouse calvarial defects. Implanted, apatite-coated, PLGA scaffolds seeded with ADAS or BMS cells produced significant intramembranous bone formation by 2 weeks and areas of complete bony bridging by 12 weeks as shown by X-ray analysis, histology and live micromolecular imaging. The contribution of implanted cells to new bone formation was 84-99% by chromosomal detection. These data show that ADAS cells heal critical-size skeletal defects without genetic manipulation or the addition of exogenous growth factors.

Adipose Tissue↗

PubMed2004

Interleukin 6 and interleukin 8 as potential biomarkers for oral cavity and oropharyngeal squamous cell carcinoma.

BACKGROUND: Since morbidity and mortality rates due to oral cavity and oropharyngeal squamous cell carcinoma (OSCC) have improved little in the past 30 years, early detection or prevention of this disease is likely to be most effective. Using laser-capture microdissection, we have identified the expression of 2 cellular genes that are uniquely associated with OSCC: interleukin (IL) 6 and IL-8. These cytokines may contribute to the pathogenesis of this disease, and have been linked with increased tumor growth and metastasis. OBJECTIVES: To investigate whether IL-6 and/or IL-8 could serve as informative biomarkers for OSCC in saliva and/or serum and to determine if there is a role for saliva as a diagnostic medium for OSCC. PATIENTS AND METHODS: Patients with newly diagnosed T1 or T2 oral cavity or oropharyngeal histologically confirmed squamous cell carcinoma were recruited for the study. Age and sex-matched disease-free subjects were used as controls. Using quantitative real-time polymerase chain reaction analysis and enzyme-linked immunosorbent assay, we respectively assessed the expression of IL-6 and IL-8 in serum (controls, n = 32; patients with OSCC, n = 19) and saliva (controls, n = 32; patients with OSCC, n = 32) at the messenger RNA (mRNA) and protein levels. MAIN OUTCOME MEASURES: Specificity and sensitivity of these biomarkers for OSCC and their predictive value. RESULTS: Interleukin 8 was detected at higher concentrations in saliva (P<.01) and IL-6 was detected at higher concentrations in serum of patients with OSCC (P<.01). We confirmed these results at both the mRNA and the protein levels, and the results were concordant. The concentration of IL-8 in saliva and IL-6 in serum did not appear to be associated with sex, age, or alcohol or tobacco use (P>.75). Using statistical analysis, we were able to determine the threshold value, sensitivity, and specificity of each biomarker, as well as a combination of biomarkers, for detecting OSCC. CONCLUSIONS: Our findings indicate that IL-8 in saliva and IL-6 in serum hold promise as biomarkers for OSCC. A saliva-based test could be a cost-effective adjunctive tool in the diagnosis and follow-up of patients with OSCC.

Adult↗

PubMed2004

Evaluation of a surrogate antibody for preclinical safety testing of an anti-CD11a monoclonal antibody.

Surrogate antibodies are a potential solution to the limited safety testing possible with humanized monoclonal antibodies with restricted species cross-reactivity. However, there are currently no defined criteria by which a potential surrogate antibody should be judged prior to its use in determining safety issues for the clinical agent. We propose that, potential surrogates should undergo rigorous evaluation to assess pharmacological and toxicological activities in comparison to the clinical agent. The current studies evaluated a chimeric mouse/rat anti-mouse CD11a monoclonal antibody (muM17) as a potential surrogate for efalizumab, a humanized anti-CD11a antibody in development for psoriasis. CD11a is a subunit of lymphocyte function associated antigen-1, an integrin involved in cell-cell interactions important to immune responses and inflammation. In vitro pharmacology studies included binding affinity to whole mouse blood and inhibitory activity of muM17 in a mixed lymphocyte response assay. In vivo pharmacology was examined using a delayed type hypersensitivity assay in female CD-1 mice. The toxicology evaluation included a murine tissue cross-reactivity study and in vivo multiple dose studies in female CD-1 mice which were administered muM17 (0.1-30 mg/kg) via subcutaneous injections once a week for 4 weeks. Clinical observations, body weight, clinical pathology, T cell CD11a expression, immunogenicity, toxicokinetics, and lymphoid organ histopathology were evaluated. Finally, since reproductive safety testing would be an important application of the proposed surrogate antibody, a pilot study in pregnant mice was conducted that demonstrated proportional transfer of muM17 into the fetus. These studies demonstrated that muM17 has pharmacological and toxicological activities similar to efalizumab. The selection of dose and regimen for GLP (Good Laboratory Practice) toxicology studies and extrapolation to clinical dose levels was based on pharmacodynamic activity (CD11a downmodulation on T cells).

Animals↗

PubMed2003

Overexpression of Nell-1, a craniosynostosis-associated gene, induces apoptosis in osteoblasts during craniofacial development.

UNLABELLED: We studied the cellular function of Nell-1, a craniosynostosis-related gene, in craniofacial development. Nell-1 modulates calvarial osteoblast differentiation and apoptosis pathways. Nell-1 overexpression disrupts these pathways resulting in craniofacial anomalies such as premature suture closure. INTRODUCTION: Craniosynostosis (CS), one of the most common congenital craniofacial deformities, is the premature closure of cranial sutures. Previously, we reported NELL-1 as a novel molecule overexpressed during premature cranial suture closure in patients with CS. Nell-1 overexpression induced calvarial overgrowth and resulted in premature suture closure in a rodent model. On a cellular level, Nell-1 is suggested to promote osteoblast differentiation. MATERIALS AND METHODS: Different levels of Nell-1 were introduced into osteoblastic cells by viral infection and recombinant protein. Apoptosis and gene expression assays were performed. Mice overexpressing Nell-1 were examined for apoptosis. RESULTS: In this report, we further showed that overexpression of Nell-1 induced apoptosis along with modulation of apoptosis-related genes. The induction of apoptosis by Nell-1 was observed only in osteoblastic cells and not in NIH3T3 or primary fibroblasts. The CS mouse model overexpressing Nell-1 showed increased levels of apoptosis in the calvaria. CONCLUSION: We show that Nell-1 expression modulates calvarial osteoblast differentiation and apoptosis pathways. Nell-1 overexpression disrupts these pathways resulting in craniofacial anomalies such as premature suture closure.

Animals↗

PubMed2002

Development and application of an analytical method for the determination of squalene in formulations of anthrax vaccine adsorbed.

Specific lots of Anthrax Vaccine Adsorbed, administered to members of the US Armed Forces, have been described on various Internet sites and in news articles as a source of squalene, a chemical purported by these media to be associated with the Gulf War Syndrome. We have developed and validated a method using high-performance liquid chromatography with ultraviolet detection for the determination of squalene in anthrax vaccine preparations. The method has a limit of detection of 140 parts per billion and has been successfully applied to a commercial vaccine known to contain squalene. We have applied this method to 17 lots of Anthrax Vaccine Adsorbed administered to members of the US Armed Forces. No squalene has been detected in any lot. The results of these analyses provide direct evidence for the absence of squalene as an ingredient or a manufacturing contaminant in Anthrax Vaccine Adsorbed.

Anthrax Vaccines↗

PubMedDate not supplied

Pharmacokinetics of the antimalarial drug, AQ-13, in rats and cynomolgus macaques.

The purpose of this study was to evaluate the bioavailability and pharmacokinetics of a new antimalarial drug, AQ-13, a structural analog of chloroquine (CQ) that is active against CQ-resistant Plasmodium species, in rats and cynomolgus macaques. Sprague-Dawley rats (n = 4/sex) were administered a single dose of AQ-13 intravenously (i.v.) (10 mg/kg) or orally (20 or 102 mg/kg). Blood and plasma samples were collected at several timepoints. AQ-13 achieved C(max) after oral administration at approximately 3 to 4 h and could be detected in blood for 2 to 5 days after oral administration. The ratio of area under the curve (AUC) values at the high and low dose for AQ-13 deviated from an expected ratio of 5.0, indicating nonlinear kinetics. A metabolite peak was noted in the chromatograms that was identified as monodesethyl AQ-13. Oral bioavailability of AQ-13 was good, approximately 70%. The pharmacokinetics of AQ-13 was also determined in cynomolgus macaques after single (i.v., 10 mg/kg; oral, 20 or 100 mg/kg) and multiple doses (oral loading dose of 50, 100, or 200 mg/kg on first day followed by oral maintenance dose of 25, 50, or 100 mg/kg, respectively, for 6 days). The AUC and C(max) values following single oral dose administration were not dose proportional; the C(max) value for AQ-13 was 15-fold higher following an oral dose of 100 mg/kg compared to 20 mg/kg. Monodesethyl AQ-13 was a significant metabolite formed by cynomolgus macaques and the corresponding C(max) values for this metabolite increased only 3.8-fold over the dose range, suggesting that the formation of monodesethyl AQ-13 is saturable in this species. The bioavailability of AQ-13 in cynomolgus macaques following oral administration was 23.8% for the 20-mg/kg group and 47.6% for the 100-mg/kg group. Following repeat dose administration, high concentrations of monodesethyl AQ-13 were observed in the blood by day 4, exceeding the AQ-13 blood concentrations through day 22. Saturation of metabolic pathways and reduced metabolite elimination after higher doses are suggested to play a key role in AQ-13 pharmacokinetics in macaques. In summary, the pharmacokinetic profile and metabolism of AQ-13 are very similar to that reported in the literature for chloroquine, suggesting that this new agent is a promising candidate for further development for the treatment of chloroquine-resistant malaria.

Administration, Oral↗

PubMedDate not supplied

Bone morphogenetic protein 2 and retinoic acid accelerate in vivo bone formation, osteoclast recruitment, and bone turnover.

Reconstruction of craniofacial defects presents a substantial biomedical burden, and requires complex surgery. Interestingly, children after age 2 years and adults are unable to heal large skull defects. This nonhealing paradigm provides an excellent model system for craniofacial skeletal tissueengineering strategies. Previous studies have documented the in vivo osteogenic potential of adipose-derived stromal (ADS) cells and bone marrow-derived stromal (BMS) cells. This study investigates the ability to accelerate in vivo osteogenesis on ex vivo recombinant human bone morphogenetic protein 2 (BMP-2) and retinoic acid stimulation. Mouse osteoblasts, ADS cells, and BMS cells were seeded onto apatite-coated PLGA scaffolds, stimulated with rhBMP-2 and retinoic acid ex vivo for 4 weeks, and subsequently implanted into critically sized (4 mm) calvarial defects. Samples were harvested after 2, 4, 8, and 12 weeks. Areas of complete bony bridging were noted as early as 2 weeks in vivo; however, osteoclasts were attracted to the scaffold as identified by calcitonin receptor staining and tartrate-resistant acid phosphatase activity staining. Although the optimal method of in vitro osteogenic priming for mesenchymal cells remains unknown, these results provide evidence that BMP-2 and retinoic acid stimulation of multipotent cells ex vivo can subsequently induce significant quantities of bone formation within a short time period in vivo.

Animals↗