Nano-fibrous scaffolding promotes osteoblast differentiation and biomineralization.

Nano-fibrous poly(L-lactic acid) (PLLA) scaffolds with interconnected pores were developed under the hypothesis that nano-fibrous scaffolding would mimic a morphological function of collagen fibrils to create a more favorable microenvironment for cells versus solid-walled scaffolds. In this study, an in vitro system was used to examine biological properties of the nano-fibrous scaffolds compared with those of solid-walled scaffolds for their potential use in bone tissue engineering. Biomineralization was enhanced substantially on the nano-fibrous scaffolds compared to solid-walled scaffolds, and this was confirmed by von Kossa staining, measurement of calcium contents, and transmission electron microscopy. In support of this finding, osteoblasts cultured on the nano-fibrous scaffolds exhibited higher alkaline phosphatase activity and an earlier and enhanced expression of the osteoblast phenotype versus solid-walled scaffolds. Most notable were the increases in runx2 protein and in bone sialoprotein mRNA in cells cultured on nano-fibrous scaffolds versus solid-walled scaffolds. At the day 1 of culture, alpha2 and beta1 integrins as well as alphav and beta3 integrins were highly expressed on the surface of cells seeded on nano-fibrous scaffolds, and linked to this were higher levels of phospho-Paxillin and phospho-FAK in cell lysates. In contrast, cells seeded on solid-walled scaffolds expressed significantly lower levels of these integrins, phospho-Paxillin, and phospho-FAK. To further examine the role of nano-fibrous architecture, we inhibited the formation of collagen fibrils by adding 3,4-dehydroproline to cultures and then assayed cells for expression of alpha2 integrin. Cells seeded on nano-fibrous scaffolds sustained expression of alpha2 integrin in the presence of dehydroproline, while suppression of alpha2 integrin was evident in cells seeded on solid-walled scaffolds. These results provide initial evidence that synthetic nano fibers may exhibit certain properties that are comparable to natural collagen fibers, and thus, the nano-fibrous architecture may serve as a superior scaffolding versus solid-walled architecture for promoting osteoblast differentiation and biomineralization.

N-acetylcysteine prevents LPS-induced pro-inflammatory cytokines and MMP2 production in gingival fibroblasts.

Periodontitis is an inflammatory process that ultimately results in tooth loss. Although the primary etiologic agent for periodontitis is bacteria, the majority of periodontal tissue destruction is thought to be caused by an inappropriate host response. Reactive oxygen species (ROS) have been known to be involved in periodontal tissue destruction. We treated human gingival fibroblasts with lipopolysaccharide (LPS) obtained from E. coli and the periodontopathogens Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis, and examined their inflammatory responses in the presence and absence of the antioxidant N-acetylcysteine (NAC). LPS enhanced ROS production, as well as, expression of pro-inflammatory cytokines such as interleukin-1beta, interleukin-6, interleukin-8 and tumor necrosis factor-alpha, and the production and activation of MMP2. NAC suppressed all LPS-induced inflammatory responses examined, suggesting that LPS-induced ROS may play a major regulatory role in these responses in gingival fibroblasts. In addition, NAC prevented LPS-induced activation of p38 MAPK and JNK but not phosphorylation and subsequent degradation of IkB. These results indicate that NAC exerts anti-inflammatory effects in LPS-stimulated gingival fibroblasts, functioning at least in part via down-regulation of JNK and p38 MAPK activation. Furthermore, this work suggests that antioxidants may be useful in adjunctive therapies that complement conventional periodontal treatments.