Cellular Physiology and Biochemistry

Background/Aims: Mesenchymal stem cells (MSCs) are multipotent progenitors that can differentiate into several lineages including bone. Successful bone formation requires osteogenesis and angiogenesis coupling of MSCs. Here, we investigate if simultaneous activation of BMP9 and Notch signaling yields effective osteogenesis-angiogenesis coupling in MSCs. Methods: Recently-characterized immortalized mouse adipose-derived progenitors (iMADs) were used as MSC source. Transgenes BMP9, NICD and dnNotch1 were expressed by adenoviral vectors. Gene expression was determined by qPCR and immunohistochem¡stry. Osteogenic activity was assessed by in vitro assays and in vivo ectopic bone formation model. Results: BMP9 upregulated expression of Notch receptors and ligands in iMADs. Constitutively-active form of Notch1 NICD1 enhanced BMP9-induced osteogenic differentiation both in vitro and in vivo, which was effectively inhibited by dominant-negative form of Notch1 dnNotch1. BMP9- and NICD1-transduced MSCs implanted with a biocompatible scaffold yielded highly mature bone with extensive vascularization. NICD1 enhanced BMP9-induced expression of key angiogenic regulators in iMADs and Vegfa in ectopic bone, which was blunted by dnNotch1. Conclusion: Notch signaling may play an important role in BMP9-induced osteogenesis and angiogenesis. It’s conceivable that simultaneous activation of the BMP9 and Notch pathways should efficiently couple osteogenesis and angiogenesis of MSCs for successful bone tissue engineering.

Reactive oxygen species (ROS) are produced by living cells as normal cellular metabolic byproduct. Under excessive stress conditions, cells will produce numerous ROS, and the living organisms eventually evolve series of response mechanisms to adapt to the ROS exposure as well as utilize it as the signaling molecules. ROS molecules would trigger oxidative stress in a feedback mechanism involving many biological processes, such as apoptosis, necrosis and autophagy. Growing evidences have suggested that ROS play a critical role as the signaling molecules throughout the entire cell death pathway. Overwhelming production of ROS can destroy organelles structure and bio-molecules, which lead to inflammatory response that is a known underpinning mechanism for the development of diabetes and cancer. Cytochrome P450 enzymes (CYP) are regarded as the markers of oxidative stress, can transform toxic metabolites into ROS, such as superoxide anion, hydrogen peroxide and hydroxyl radical which might cause injury of cells. Accordingly, cells have evolved a balanced system to neutralize the extra ROS, namely antioxidant systems that consist of enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidases (GPxs), thioredoxin (Trx) as well as the non-enzymatic antioxidants which collectively reduce oxidative state. Herein, we review the recent novel findings of cellular processes induced by ROS, and summarize the roles of cellular endogenous antioxidant systems as well as natural anti-oxidative compounds in several human diseases caused by ROS in order to illustrate the vital role of antioxidants in prevention against oxidative stress.

Background/Aims: Neurotoxic A1 astrocytes are induced by inflammation after spinal cord injury (SCI), and the inflammation-related Nuclear Factor Kappa B (NFκB) pathway may be related to A1-astrocyte activation. Mesenchymal stem cell (MSC) transplantation is a promising therapy for SCI, where transplanted MSCs exhibit anti-inflammatory effects by downregulating proinflammatory factors, such as Tumor Necrosis Factor (TNF)-α and NFκB. MSC-exosomes (MSC-exo) reportedly mimic the beneficial effects of MSCs. Therefore, in this study, we investigated whether MSCs and MSC-exo exert inhibitory effects on A1 astrocytes and are beneficial for recovery after SCI. Methods: The effects of MSC and MSC-exo on SCIinduced A1 astrocytes, and the potential mechanisms were investigated in vitro and in vivo using immunofluorescence and western blot. In addition, we assessed the histopathology, levels of proinflammatory cytokines and locomotor function to verify the effects of MSC and MSC-exo on SCI rats. Results: MSC or MSC-exo co-culture reduced the proportion of SCIinduced A1 astrocytes. Intravenously-injected MSC or MSC-exo after SCI significantly reduced the proportion of A1 astrocytes, the percentage of p65 positive nuclei in astrocytes, and the percentage of TUNEL-positive cells in the ventral horn. Additionally, we observed decreased lesion area and expression of TNFα, Interleukin (IL)-1α and IL-1β, elevated expression of Myelin Basic Protein (MBP), Synaptophysin (Syn) and Neuronal Nuclei (NeuN), and improved Basso, Beattie & Bresnahan (BBB) scores and inclined-plane-test angle. In vitro assay showed that MSC and MSC-exo reduced SCI-induced A1 astrocytes, probably via inhibiting the nuclear translocation of the NFκB p65. Conclusion: MSC and MSC-exo reduce SCI-induced A1 astrocytes, probably via inhibiting nuclear translocation of NFκB p65, and exert antiinflammatory and neuroprotective effects following SCI, with the therapeutic effect of MSCexo comparable with that of MSCs when applied intravenously.