The intervertebral disc nucleus pulposus (NP) has two phenotypically distinct cell types-notochordal cells (NCs) and nonnotochordal chondrocyte-like cells. In human discs, NCs are lost during adolescence, which is also when discs begin to show degenerative signs. However, little evidence exists regarding the link between NC disappearance and the pathogenesis of disc degeneration. To clarify this, a rat tail disc degeneration model induced by static compression at 1.3 MPa for 0, 1, or 7 days was designed and assessed for up to 56 postoperative days. Radiography, MRI, and histomorphology showed degenerative disc findings in response to the compression period. Immunofluorescence displayed that the number of DAPI-positive NP cells decreased with compression; particularly, the decrease was notable in larger, vacuolated, cytokeratin-8-and galectin-3-co-positive cells, identified as NCs. The proportion of TUNEL-positive cells, which predominantly comprised non-NCs, increased with compression. Quantitative PCR demonstrated isolated mRNA up-regulation of ADAMTS-5 in the 1-day loaded group and MMP-3 in the 7-day loaded group. Aggrecan-1 and collagen type 2a-1 mRNA levels were down-regulated in both groups. This rat tail temporary static compression model, which exhibits decreased NC phenotype, increased apoptotic cell death, and imbalanced catabolic and anabolic gene expression, reproduces different stages of intervertebral disc degeneration. ß

House-keeping genes (HKGs) are generally used as endogenous controls for molecular normalization in quantitative PCR analysis. However, whether all the so-called HKGs are useful for intervertebral disc research is controversial. Our objective was, using a prevalidated rat tail static compression loading-induced disc degeneration model, to clarify the feasibility of common HKGs for genequantification in the nucleus pulposus cells. In real-time RT-PCR for five HKGs [b-actin, b-glucuronidase, b-2 microglobulin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and lactate dehydrogenase A (LDHA)], static compression at 1.3 MPa for up to 56 days demonstrated messenger RNA (mRNA) expression levels of consistent b-2 microglobulin and GAPDH, slightly up-regulated b-glucuronidase, and fairly down-regulated b-actin and LDHA. Especially, b-actin had a drastic suppression to 0.15-fold in the loaded relative to unloaded discs at 7 days. In immunofluorescence, b-actin showed a significant down-regulation to almost undetectable levels from 28 days, while GAPDH was constantly detected throughout. b-Actin mRNA and protein-distribution are thought to be affected by the loading treatment, however, GAPDH mRNA and protein-distribution can retain relatively stable expressions. Under prolonged static compression, b-actin and probably LDHA are inappropriate, and GAPDH is a feasible HKG as internal references in the disc cells.

It is suggested that pro-inflammatory cytokines, which are produced by interaction of the intervertebral nucleus pulposus cells and macrophages, may be linked to the cause of pain of the intervertebral disc herniation. This study carries out the in vitro experiments to examine the mechanism, with the use of the co-culture of an immortalized cell line of nucleus pulposus of the human intervertebral disc and the macrophage cell line. As a result, it is found that the production of pro-inflammatory cytokines is significantly larger at the co-culture group than at the independent culture group. Also, at the co-culture group of macrophages and intervertebral nucleus pulposus cells with over-expression of fas ligand (FasL), the production of pro-inflammatory cytokines is found to be far larger. Furthermore, it is found that these pro-inflammatory cytokines are produced mainly by the intervertebral nucleus pulposus cells with over-expression of FasL, and that the expression of a disintegrin and metalloproteinase (ADAM) 10, which controls the expression of FasL and activates reverse signaling inside cells, also increases. From these findings, it is suggested that FasL and ADAM10 play an important role in the production of pro-inflammatory cytokines coming from interaction of the intervertebral nucleus pulposus cells and macrophages. ß

No abstract

While SOFCs are the most flexible fuel cells with respect to fuel selection, fuel impurities in practical SOFC fuels can cause degradation of electrodes and thus electrochemical performance. The understanding of fuel impurity poisoning and the increase in tolerance are therefore of technological relevance for SOFC commercialization. Along with thermochemical calculations on the stability of typical fuel impurities under SOFC operational conditions, fuel impurity poisoning of SOFCs is analyzed by using various impurity-containing fuel gases with respect to operational temperature, type and concentration of impurities, fuel composition, and steam-to-carbon ratio. We have revealed that poisoning depends on operational conditions and types of fuels and impurities. The poisoning effect becomes significant for internal-reforming SOFCs operated with humidified methane-based fuels. Poisoning mechanisms are discussed, based on cell voltage and durability data.