No abstract

Post-traumatic and focal cartilage defects of the knee affect over 3 million Americans annually. Autologous cell-based cartilage repair, for example, autologous chondrocyte implantation, is limited by the need for ex vivo chondrocyte expansion and donor site morbidity. Mesenchymal stem cells (MSCs), owing to their relative ease of isolation, higher replication activity, and chondrogenic potential, represent an alternative reparative cell type. Platelet-rich plasma (PRP) is an autologous, growth factor-rich biologic preparation that has recently received increasing attention and use as a therapeutic adjunct for the treatment of degenerative joint diseases, and there is evidence suggesting that PRP acts by promoting stem cell proliferation and tissue healing. In this study, we have examined the effect of PRP treatment on chondrogenic differentiation of adult human MSCs derived from infrapatellar fat pad-adipose stem cells (IFP-ASCs) and bone marrow (BM-MSCs). Both cell types were placed in high-density pellet culture and hydrogel-encapsulated culture under chondrogenic conditions. Our results showed that PRP did not improve IFP-ASC or BM-MSC chondrogenesis. In general, chondrogenesis was inhibited with increasing PRP concentrations and duration of exposure, on the basis of histological, biochemical, and gene expression analyses. Taken together, these findings suggest that although PRP is reported to be beneficial in terms of pain relief and joint function improvement, its mechanism of action is unlikely to directly involve enhancement of MSC-mediated hyaline cartilage formation.

This work introduces a contact line pinning based microfluidic platform for the generation of interstitial and intramural flows within a three dimensional (3D) microenvironment for cellular behaviour studies. A contact line pinning method was used to confine natively derived biomatrix, collagen, in microfluidic channels without walls. By patterning collagen in designated wall-less channels, we demonstrated and validated the intramural flows through a microfluidic channel bounded by a monolayer of endothelial cells (mimic of a vascular vessel), as well as slow interstitial flows within a cell laden collagen matrix using the same microfluidic platform. The contact line pinning method ensured the generation of an engineered endothelial tube with straight walls, and spatially uniform interstitial fluid flows through the cell embedded 3D collagen matrix. Using this device, we demonstrated that the breast tumour cells’ (MDA-MB-231 cell line) morphology and motility were modulated by the interstitial flows, and the motility of a sub-population of the cells was enhanced by the presence of the flow. The presented microfluidic platform provides a basic framework for studies of cellular behaviour including cell transmigration, growth, and adhesion under well controlled interstitial and intramural flows, and within a physiologically realistic 3D co-culture setting.

Laboratory incubations of coal-tar waste-contaminated sediment microbial communities under relatively controlled physiological conditions were used to interpret results of a field-based stable isotope probing (SIP) assay. Biodegradation activity of 13C-benzene was examined by GC/MS determination of net 13CO2 production and by GC headspace analysis of benzene loss. Key experimental variables were: the site of the assays (laboratory serum-bottle incubations and in situ field sediments), benzene concentration (10, 36 or 200 p.p.m. in laboratory assays), and physiological conditions (anaerobic with or without sulfate or nitrate additions versus aerobic headspace or the uncontrolled field). In anaerobic laboratory incubations of benzene at 10 p.p.m., greater than 60% of the substrate was eliminated within 15 days. During anaerobic incubations of 200 p.p.m. benzene (70 days), 0.9% benzene mineralization occurred. When benzene (36 p.p.m.) was added to sediment with air in the serum-bottle headspace, 14% of the initial 13C was mineralized to 13CO2 in 2.5 days. In the field experiment (178 microg 13C-benzene dosed to undisturbed sediments), net 13CO2 production reached 0.3% within 8.5 h. After isopycnic separation of 13C (heavy)-labelled DNA from the above biodegradation assays, sequencing of 13C-DNA clone libraries revealed a broad diversity of taxa involved in benzene metabolism and distinctive libraries for each biodegradation treatment. Perhaps most importantly, in the field SIP experiment the clone libraries produced were dominated by Pelomonas (betaproteobacteria) sequences similar to those found in the anaerobic 10 p.p.m. benzene laboratory experiment. These data indicate that the physiological conditions that prevail and govern in situ biodegradation of pollutants in the field may be interpreted by knowing the physiological preferences of potentially active populations.

Tissue engineering has gained attention as an alternative approach for developing small diameter tissue-engineered vascular grafts intended for bypass surgery, as an option to treat coronary heart disease. To promote the formation of a healthy endothelial cell monolayer in the lumen of the graft, polycaprolactone/gelatin/fibrinogen scaffolds were developed, and the surface was modified using thermoforming and coating with collagen IV and fibronectin. Human cord blood-derived endothelial cells (hCB-ECs) were seeded onto the scaffolds and the important characteristics of a healthy endothelial cell layer were evaluated under static conditions using human umbilical vein endothelial cells as a control. We found that polycaprolactone/gelatin/fibrinogen scaffolds that were thermoformed and coated are the most suitable for endothelial cell growth. hCB-ECs can proliferate, produce endothelial nitric oxide synthase, respond to interleukin 1 beta, and reduce platelet deposition.