Xiaozhong Qiu

Engineering the heart: Evaluation of conductive nanomaterials for improving implant integration and cardiac function

Recently, carbon nanotubes together with other types of conductive materials have been used to enhance the viability and function of cardiomyocytes in vitro. Here we demonstrated a paradigm to construct ECTs for cardiac repair using conductive nanomaterials. Single walled carbon nanotubes (SWNTs) were incorporated into gelatin hydrogel scaffolds to construct three-dimensional ECTs. We found that SWNTs could provide cellular microenvironment in vitro favorable for cardiac contraction and the expression of electrochemical associated proteins. Upon implantation into the infarct hearts in rats, ECTs structurally integrated with the host myocardium, with different types of cells observed to mutually invade into implants and host tissues. The functional measurements showed that SWNTs were essential to improve the performance of ECTs in inhibiting pathological deterioration of myocardium. This work suggested that conductive nanomaterials hold therapeutic potential in engineering cardiac tissues to repair myocardial infarction.

Schiff based injectable hydrogel for in situ pH-triggered delivery of doxorubicin for breast tumor treatment

In this study, we report a facile approach to develop an injectable hydrogel with an in situ and pH sensitive drug delivery system for cancer treatment. The hydrogel was based on modified chitosan and alginate. We conjugated doxorubicin (DOX) to succinated chitosan (S-chi) via a Schiff base between a ketone group in the DOX and an amine group in the S-chi, which led to a pH sensitive release of DOX upon the stimulus of an acidic tumor microenvironment. Hydrogel formed in minutes while DOX conjugated S-chi was mixed with oxidized alginate. The hydrogel structure was characterized by cryo-imaging, FTIR and a rheology test. The DOX release profiles were tested in response to different pH values. The MTT assay showed a low toxicity of the hydrogel. The gel in turn inhibited the growth of tumor cells MCF-7 effectively when loaded with DOX. Finally, the DOX laden hydrogel was injected into the xenograft breast tumor model and significantly inhibited tumor growth.

Oxidative Modification of Cysteine 111 Promotes Disulfide Bond-Independent Aggregation of SOD1

Converging evidence indicates that SOD1 aggregation is a common feature of mutant SOD1-linked fALS, and seems to be directly related to the gain-of-function toxic property. However, the mechanism inducing the aggregation is not understood. To study the contribution of oxidative modification of cysteine residues in SOD1 aggregation, we systematically examined the redox state of SOD1 cysteine residues in the G37R transgenic mouse model at different stages of the disease and under oxidative stress induced by H2O2. Our data suggest that under normal circumstance, cysteine 111 residue in SOD1 is free; however, under oxidative stress, it is prone to oxidative modification by providing the thiolate anion (S−). With the progression of the disease, increased levels of oxidative insults facilitated the oxidation of thiol groups of cysteine residues; human mutant SOD1 could generate an upper shift band in reducing SDS-PAGE, which turned out to be a Cys111-peroxidized SOD1 species. We also detected the formation of SOD1 multimers at different stages of the disease, and found that accumulated oxidative stress facilitated the formation of aggregates, which were not mediated by disulfide bond. This oxidative modification of cysteine 111 therefore promotes the formation of disulfide bond-independent aggregation of SOD1.

Low concentration of lipopolysaccharide acts on MC3T3‐E1 osteoblasts and induces proliferation via the COX‐2‐independent NFκB pathway

The translocations of lipopolysaccharide (LPS) from the gut and its effects on bone healing are usually of clinical interest during bone fracture. As already widely stuided, Cyclooxygenase‐2 (COX‐2) is a key enzyme for prostaglandin E2 (PGE2) production, which induces the nuclear factor kappa B (NFκB) activation and is beneficial to fracture healing. In order to know their roles in skeletal regeneration, mouse MC3T3‐E1 osteoblasts were treated with NFκB inhibitor BAY 11‐7082 and sc791 (a selective COX‐2 inhibitor), in the presence of LPS. Interestingly, LPS could induce osteoblasts proliferation through increasing NFκB activation and translocation. This induction was not related to COX‐2 expression, suggesting that LPS‐induced NFκB activiation is independent of COX‐2. It is possible that low concentration of LPS can act as a stimulating factor of the NFκB pathway in nonstimulated cells such as osteoblasts. COX‐2 is not necessary for the NFκB pathway during LPS‐induced proliferation of osteoblasts since sc791 had no effects on this induction. These studies provide insight into a potential mechanism by which LPS can affect bone tissue repair in the initial phase of inflammation. Copyright

A 3-D multicellular tumor spheroid on ultrathin matrix coated single cancer cells provides a tumor microenvironment model to study epithelial-to-mesenchymal transitions

We report a 3D tumor spheroid model to study epithelial-to-mesenchymal transition (EMT) using ultra-thin matrix coated single cancer cells. The spheroid was characterized by light microscopy, fluorescence imaging, SEM, TEM and zeta potential. We then studied EMT related cellular CD47, mTOR, ERK, and HIF signaling. We compared (1) cells inside a multicellular tumor spheroid (3Dis), (2) cells migrated from the multicellular tumor spheroid (3Dms), and (3) 2D monolayer-cultured cells (2Ds) in EMT. 3Dis exhibited an abnormal nucleus with the occurrence of cell damage and accumulation of lipid droplets, and higher expression of the integrin-associated protein and dissociation of the mTOR complex than those of 2Ds and 3Dms. We examined the expressions of E- and N-cadherin, two EMT related factors, and found over-expression of E-cadherin in 2Ds, high N-cadherin in 3Dis, and high E- and weak N-cadherin in 3Dms. This implied that our model could trigger EMT. By injecting cells into a xenograft model, we found transitions of 2Ds from N-cadherin negative to positive and transitions of 3Dis from positive to negative, but not in 3Dms. 2D cells exhibited higher progression than other cells. This suggests that the in vivo 3D tumorigenesis environment could limit the capacity of cancer metastases for 3Dis but trigger the EMT process quickly for 2Ds and 3Dms.

Mitochondrial AIF protein involved in skeletal muscle regeneration

The mitochondrial flavoprotein apoptosis‐inducing factor (AIF) has proved to be either the main mediator of apoptosis or an anti‐apoptotic factor via its putative oxidoreductase and peroxide scavenging activities. We report here that 100 µM hydrogen peroxide (H2O2) induced the proliferation of C2C12 myoblasts and over‐expression of AIF simultaneously in vitro. Immunofluorescence showed that the over‐expression of AIF was located in the cytoplasm. The immunopositive AIF was detected in nuclei 27 days after denervation of skeletal muscle, but in the cytoplasm it was detected 27 days after fiber‐damaged skeletal muscle. AIF may be a factor involved in skeletal muscle regeneration. Copyright

Mechanical stretch regulates microRNA expression profile via NF-κB activation in C2C12 myoblasts

MicroRNAs (miRNAs/miRs) and nuclear factor (NF)-κB activation are involved in mechanical stretch-induced skeletal muscle regeneration. However, there are a small number of miRNAs that have been reported to be associated with NF-κB activation during mechanical stretch-induced myogenesis. In the present study, C2C12 myoblasts underwent cyclic mechanical stretch in vitro, to explore the relationship between miRNA expression and NF-κB activation during stretch-mediated myoblast proliferation. The results revealed that 10% deformation, 0.125 Hz cyclic mechanical stretch could promote myoblast proliferation. The miRNA expression profile was subsequently altered; miR-500, −1934, −31, −378, −331 and −5097 were downregulated, whereas miR-1941 was upregulated. These miRNAs were all involved in stretch-mediated myoblast proliferation. Notably, the expression of these miRNAs was reversed following treatment of 0.125 Hz mechanically stretched C2C12 cells with NF-κB inhibitors, which was accompanied by C2C12 cell growth suppression. Therefore, the present study is the first, to the best of our knowledge, to demonstrate that the NF-κB-dependent miRNA profile is associated with mechanical stretch-induced myoblast proliferation.

Nix Protein Positively Regulates NF-κB Activation in Gliomas

Previous reports indicate that the NIX/BNIP3L gene acts as a pro-apoptotic factor by interacting with BCL2 and BCL-XL, playing an important role in hypoxia-dependent cell death and acting as a tumor suppressor. However, many studies also showed that NIX is linked to a protective role and cell survival in cancer cells. Nuclear factor-κB (NF-κB) can attenuate apoptosis in human cancers in response to chemotherapeutic agents and ionizing radiation. We observed an absence of i-κBα (NF-κB activation inhibitor) expression, but a greater expression of Nix and p-NF-κB proteins in the Nix-wt U251 cells, which was not observed in the Nix-kn cells under hypoxic conditions. Using electrophoretic mobility shift assay (EMSA) and luciferase detection, the activation of NF-κB was detected only in the Nix-wt U251 cells with hypoxia. These data imply that Nix protein might play a role in the positive regulation of the NF-κB pathway. Moreover, 46 cases of glioma also showed high levels of Nix protein expression, which was always accompanied by high p-NF-κB expression. Patients with Nix (+) showed less tissue apoptosis behavior in glioblastoma (GBM), unlike that observed in the Nix-negative patients (−). The same apoptotic tendency was also identified in anaplastic astrocytoma (AA) groups, but not in astrocytoma (AS). On analyzing the Kaplan-Meier curve, better tumor-free survival was observed only in cases of astrocytoma, and not in AA and GBM. Thus, our study indicates that Nix protein might have multiple functions in regulating glioma behaviors. In the low-grade gliomas (astrocytoma) with low expression of NF-κB, the cell death-inducing function that occurs through a Bax mechanism might predominate and act as a tumor suppressor. While in the malignant gliomas (AA and GBM), with higher expression of the NIX gene and with activity of the NF-κB pathway, the oncogene function of Nix was predominant.

Long-term intraperitoneal injection of lipopolysaccharide induces high expression of Id2 in the brain of mice

Lipopolysaccharide (LPS) from gram negative bacteria plays an important role in the pathophysiology of neurodegenerative diseases. Many evidences showed that LPS-induced neuroinflammation is related to upregulation of NF-kappaB. Here, we report that long-term treatment of lower dosage LPS mainly causes upregulation of Id2 protein. As an inhibitor of cell differentiation, Id2 plays an import role in adult olfactory neurogenesis. However, Id2 protein in brain acts as two edges in a sword, persist over-expression of Id2 in brain can induce neurodamages and may be related to neurodegeneration.

Thermally sensitive conductive hydrogel using amphiphilic crosslinker self-assembled carbon nanotube to enhance neurite outgrowth and promote spinal cord regeneration

Spinal cord injury leads to severe sensory or motor damage in the human body. Efforts have been made to activate the nerve function by trying physical and biochemical strategies. Carbon nanotubes as conductive materials have been used to transmit electrical signals to improve cell–cell communication and cross-talk, besides providing an extracellular scaffold for neurons. We reported a thermally sensitive hydrogel using copolymerization of n-isopropylacrylamide, the oligomeric amphiphilic crosslinker of polyethylene glycol diacrylate–dodecylamine–1-(2-aminoethyl)piperazine (PEGDA–DD–AEP), and single-walled carbon nanotubes. We hypothesized that carbon nanotubes in the gel could improve neurite outgrowth and nerve regeneration. In order to overcome the aggregation issue of carbon nanotubes, the hydrophobic chains of the amphiphilic crosslinker were used to stabilize the nanotubes. The carbon nanotube–poly(n-isopropylacrylamide) (PNIPAAM) hydrogel was injectable and improved the electrical conductivity. We found that the hydrogel may have potential to promote the growth of SH-SY5Y cells, with significant neurite outgrowth while electrical stimulation was given. In a spinal cord injury model, creating a 1 mm × 1 mm × 1 mm cavity at C7, we found that the hydrogel promoted nerve tissue regeneration and reduced the formation of scar tissue. Therefore, the hydrogel may be a potential repairing biomaterial for neuron network reconstruction and spinal cord regeneration.