James P. Abulencia

Comparative Antiplatelet Efficacy of a Novel, Nonpeptide GPIIb/IIIa Antagonist (XV454) and Abciximab (c7E3) in Flow Models of Thrombosis

Abstract—Glycoprotein (GP) IIb/IIIa is pivotal in homotypic platelet aggregation and may also be involved in the heterotypic adhesion of leukocytes and tumor cells to platelets. This study was primarily undertaken to compare the antiplatelet efficacy of a novel, nonpeptide GPIIb/IIIa antagonist, XV454, to that of abciximab in 2 flow models of platelet thrombus formation: (1) direct shear-induced platelet aggregation imposed by a cone-and-plate rheometer and (2) platelet adhesion onto von Willebrand factor (vWF)/collagen I followed by aggregation in a perfusion system. XV454 inhibited platelet aggregation in a concentration-dependent manner in both experimental models. Maximal inhibition of aggregation was achieved by XV454 at ≈70% receptor occupancy, which is lower than the ≥85% previously reported for abciximab. At similar levels of receptor blockade (≈45%), XV454 appeared to be relatively more effective than abciximab in suppressing platelet aggregation. Neither XV454 nor abciximab inhibited platelet adhesion to collagen. Pretreatment of surface-adherent platelets with either XV454 or abciximab inhibited the attachment of monocytic THP-1 cells under flow. In contrast, the rapidly reversible GPIIb/IIIa inhibitor orbofiban failed to suppress these heterotypic interactions. These findings demonstrate that XV454 is a potent GPIIb/IIIa antagonist with a long receptor-bound lifetime like abciximab and may be beneficial for the treatment/prevention of thrombotic complications.

A comparative study of seeding techniques and three-dimensional matrices for mesenchymal cell attachment.

Mesenchymal stem cells (MSCs) offer significant potential as a cell source in tissue‐engineering applications because of their multipotent ability. The objective of this study was to evaluate the behaviour of MSCs during the seeding phase, using four different seeding techniques (spinner flask, custom vacuum system combined with a perfused bioreactor or with an orbital shaker, and orbital shaker) with four different scaffold materials [polyglycolic acid, poly(lactic acid), calcium phosphate and chitosan–hyaluronic acid]. Scaffolds were selected for their structural and/or chemical similarity with bone or cartilage, and characterized via scanning electron microscopy (SEM) and measurement of fluid retention. Cell attachment was compared between seeding techniques and scaffolds via cell‐binding kinetics, cell viability and DNA quantification. SEM was used to evaluate cell distribution throughout the constructs. We discovered from cell suspension kinetics and DNA data that the type of loading (i.e. direct or indirect) mainly influences the delivery of cells to their respective scaffolds, and that dynamic seeding in a spinner flask tended to improve the cellularity of polymer constructs, especially mesh. Regardless of the seeding method, bone marrow‐derived MSCs displayed a superior affinity for calcium phosphate scaffolds, which may be related to their hydrophobicity. MSCs tended to aggregate into flat sheets, occluding the external pores of matrices and affecting cell distribution, regardless of seeding technique or scaffold. Taken together, these results provide insight into the design of future experiments using MSCs to engineer functional tissue. Copyright

Sustainability of Water Resources for the Poor

The availability of clean drinking water is a significant concern in many rural communities around the world. The contamination of resources directly affects locals by causing adverse health effects like diarrhea and other gastrointestinal diseases. Potential solutions such as sand filtration, chlorination, and solar disinfection are effective water purification technologies. Another method includes reverse osmosis, which is the main method for water filtration in the Philippines. However, mostly due to energy and cost concerns, these technologies are not feasible applications for poor communities. To address this need for sustainable water resources, our team proposed a personal growth and service-learning program in the Philippine town of Nagcarlan. Our goals were to employ the knowledge of engineering students to use their technical skills in order to serve society. Students involved in this program have developed a personal water filter to remove contaminants, such as heavy metals, using activated carbon derived from natural resources that are biodegradable and the product of recycling waste products. Sustainability of water resources is further achieved through a community outreach program with the poor communities. Successful personal water purification at one location has the potential to motivate the replication of the proposed solution to other impoverished towns within the

Microarray analysis of the chondrocytic cell line T/C-28a2 under dynamic fluid shear

The behavior of the chondrocytic cell line T/C-28a2 under shear flow was examined using a 32,448 element microarray. A parallel plate flow chamber was used to generate a shear stress level of 20 dyn/cm/sup 2/ for 1.5 or 24 hours (h), after which gene regulation was measured. Microarray analysis revealed differentially regulated genes affecting proliferation/differentiation, extracellular matrix/cytoskeleton, and inflammation at both time points. A ribonuclease protection assay was performed on a subset of genes to confirm the data obtained from the microarray. However, the cyclooxygenase-2 (COX-2) gene, which plays a role in the prostaglandin production in inflamed tissues and the synovium of rheumatoid arthritis (RA) patients, was studied further. Western hybridization revealed that COX-2 protein is present at 24 h, but not at 6 or 12 h. Also, immunofluorescence microscopy shows that COX-2 protein localizes in the cytosol after 24 h of shear, and is not present after 1.5 h. By examining the overall gene expression profiles of chondrocytes under different conditions of dynamic fluid shear, new insights on the pathogenesis of cartilage related diseases such as rheumatoid arthritis might be generated.