Stem cells introduced to site of injury primarily act via indirect paracrine effects rather than direct cell replacement of damaged cells. This gives rise to understanding the stem cell secretome. In this study, in vitro studies demonstrate that the secretome activates the PI3K/Akt or FAK/ERK1/2 signaling cascades and subsequently enhances the proliferative and migratory abilities of various types of skin cells, such as fibroblasts, keratinocytes, and vascular epithelial cells, ultimately accelerating wound contraction. Indeed, inhibition of these signaling pathways with synthetic inhibitors resulted in the disruption of secretome-induced beneficial effects on various skin cells. In addition, major components of the stem cell secretome (EGF, basic FGF, and HGF) may be responsible for the acceleration of wound contraction. Stimulatory effects of these three prominent factors on wound contraction are achieved through the upregulation of PI3K/Akt or FAK/ERK1/2 activity. Overall, we lay the rationale for using the stem cell secretome in promoting wound contraction. In vivo wound healing studies are warranted to test the significance of our in vitro findings.

Hypoxia, a feature common to most solid tumors, is known to regulate many aspects of tumorigenesis. Recently, it was suggested that hypoxia increased the size of the cancer stem-cell (CSC) subpopulations and promoted the acquisition of a CSC-like phenotype. However, candidate hypoxia-regulated mediators specifically relevant to the stemness-related functions of colorectal CSCs have not been examined in detail. In the present study, we showed that hypoxia specifically promoted the self-renewal potential of CSCs. Through various in vitro studies, we found that hypoxia-induced Wnt/β-catenin signaling increased the occurrence of CSC-like phenotypes and the level of Id2 expression in colorectal-cancer cells. Importantly, the levels of hypoxia-induced CSC-sphere formation and Id2 expression were successfully attenuated by treatment with a Wnt/β-catenin-signaling inhibitor. We further demonstrated, for the first time, that the degree of hypoxia-induced CSC-sphere formation (CD44+ subpopulation) in vitro and of tumor metastasis/dissemination in vivo were markedly suppressed by knocking down Id2 expression. Taken together, these data suggested that Wnt/β-catenin signaling mediated the hypoxia-induced self-renewal potential of colorectal-cancer CSCs through reactivating Id2 expression.

Nod-like receptors (NLRs) are cytosolic sensors for microbial molecules. Nucleotide-binding oligomerization domain (NOD)1 and NOD2 recognize the peptidoglycan derivatives, meso-diaminopimelic acid (meso-DAP) and muramyl dipeptide (MDP), respectively, and trigger host innate immune responses. In the present study, we examined the function of NOD1 and NOD2 on innate immune responses in human periodontal ligament (PDL) cells. The gene expression of NOD1 and NOD2 was examined by RT-PCR. IL-6 and IL-8 production in culture supernatants was measured by ELISA. Western blot analysis was performed to determine the activation of NF-κB and MAPK in response to Tri-DAP and MDP. The genes of NOD1 and NOD2 appeared to be expressed in PDL cells. Although the levels of NOD2 expression were weak in intact cells, MDP stimulation increased the gene expression of NOD2 in PDL cells. Tri-DAP and MDP led to the production of IL-6 and IL-8 and the activation of NF-κB and MAPK in PDL cells. Toll-like receptor (TLR) stimulation led to increased gene expression of NOD1 and NOD2 in PDL cells. Pam3CSK4 (a TLR2 agonist) and IFN-γ synergized with Tri-DAP and MDP to produce IL-8 and IL-6 in PDL cells. Our results indicate that NOD1 and NOD2 are functionally expressed in human PDL cells and can trigger innate immune responses.

A protein purification procedure is required to obtain high-value recombinant injectable vaccine proteins produced in plants as a bioreactor. However, existing purification procedures for plant-derived recombinant proteins are often not optimized and are inefficient, with low recovery rates. In our previous study, we used 25–30% ammonium sulfate to precipitate total soluble proteins (TSPs) in purification process for recombinant proteins from plant leaf biomass which has not been optimized. Thus, the objective in this study is to optimize the conditions for plant-derived protein purification procedures. Various ammonium sulfate concentrations (15–80%) were compared to determine their effects on TSPs yield. With 50% ammonium sulfate, the yield of precipitated TSP was the highest, and that of the plant-derived colorectal cancer-specific surface glycoprotein GA733 fused to the Fc fragment of human IgG tagged with endoplasmic reticulum retention signal KDEL (GA733P-FcK) protein significantly increased 1.8-fold. SDS-PAGE analysis showed that the purity of GA733P-FcK protein band appeared to be similar to that of an equal dose of mammalian-derived GA733-Fc (GA733M-Fc). The binding activity of purified GA733P-FcK to anti-GA733 mAb was as efficient as the native GA733M-Fc. Thus, the purification process was effectively optimized for obtaining a high yield of plant-derived antigenic protein with good quality. In conclusion, the purification recovery rate of large quantities of recombinant protein from plant expression systems can be enhanced via optimization of ammonium sulfate concentration during downstream processes, thereby offering a promising solution for production of recombinant GA733-Fc protein in plants.

No abstract