Guibo Liu

Adipose-derived stem cells promote peripheral nerve repair.

Introduction Recent evidence suggests that the implantation of bone marrow-derived mesenchymal stem cells improves peripheral nerve regeneration. In this study we aimed to investigate whether adipose-derived stem cells (ADSCs) can be used for peripheral nerve repair. Material and methods In a rat model, nerve regeneration was evaluated across a 15 mm lesion in the sciatic nerve by using an acellular nerve injected with allogenic ADSCs. The walking behaviour of rats was measured by footprint analysis, and electrophysiological analysis and histological examination were performed to evaluate the efficacy of nerve regeneration. Results Cultured ADSCs became morphologically homogeneous with a bipolar, spindle-like shape after ex vivo expansion. Implantation of ADSCs into the rat models led to (i) improved walking behaviour as measured by footprint analysis, (ii) increased conservation of muscle-mass ratio of gastrocnemius and soleus muscles, (iii) increased nerve conduction velocity, and (iv) increased number of myelinated fibres within the graft. Conclusions Adipose-derived stem cells could promote peripheral nerve repair in a rat model. Although the detailed mechanism by which ADSCs promote peripheral nerve regeneration is being investigated in our lab, our results suggest that ADSCs transplantation represents a powerful therapeutic approach for peripheral nerve injury.

Transplantation of adipose-derived stem cells for peripheral nerve repair

Mesenchymal stem cells have become a very attractive source of cell implantation for neural tissue engineering. The ideal stem cells for transplantation should be easily obtained, and should rapidly proliferate in vitro and have low immunogenicity. The purpose of this study was to investigate the regenerative potential of adipose-derived stem cells (ADSC) on peripheral nerve repair. ADSCs were isolated from rat adipose tissue and cultured until adherent cells became morphologically homogeneous with a fibroblast-like shape, and transplanted with acellular nerve allografts (ANAs) into rat models with a 10 mm gap of transected sciatic nerve defect. After cell transplantation, we found that ADSC implantation improved functional recovery of exercise behavior and increased wet weight ratio of the anterior tibial muscle. In the electrophysiological testing, we found that the percentage of activated fibers was higher in the ADSC-implanted animals as evidenced by the increase of nerve conduction velocity and amplitude. Histological examination revealed that the number of nerve fibers, axonal diameter and myelin thickness were significantly higher in the ADSC-implanted animals compared to the control. In addition, we demonstrated that the progression of the regenerative process after ADSC implantation was accompanied by elevated expression of neurotrophic factors at both the early and later phase. Taken together, these results suggest that ADSCs can promote the repair of peripheral nerve injury, and the combination of ADSC and ANA transplantation is a new therapeutic method for long distant peripheral nerve defects. Our data also provide evidence indicating the strong association of neurotrophic factor production to the regenerative potential of implanted ADSCs.

Sciatic nerve repair by acellular nerve xenografts implanted with BMSCs in rats xenograft combined with BMSCs.

Acellular nerves possess the structural and biochemical features similar to those of naive endoneurial tubes, and have been proved bioactive for allogeneil graft in nerve tissue engineering. However, the source of allogenic donators is restricted in clinical treatment. To explore sufficient substitutes for acellular nerve allografts (ANA), we investigated the effectiveness of acellular nerve xenografts (ANX) combined with bone marrow stromal cells (BMSCs) on repairing peripheral nerve injuries. The acellular nerves derived from Sprague‐Dawley rats and New Zealand rabbits were prepared, respectively, and BMSCs were implanted into the nerve scaffolds and cultured in vitro. All the grafts were employed to bridge 1 cm rat sciatic nerve gaps. Fifty Wistar rats were randomly divided into five groups (n = 10 per group): ANA group, ANX group, BMSCs‐laden ANA group, BMSCs‐laden ANX group, and autologous nerve graft group. At 8 weeks post‐transplantation, electrophysiological study was performed and the regenerated nerves were assayed morphologically. Besides, growth‐promoting factors in the regenerated tissues following the BMSCs integration were detected. The results indicated that compared with the acellular nerve control groups, nerve regeneration and functional rehabilitation for the xenogenic nervetransplantation integrated with BMSCs were advanced significantly, and the rehabilitation efficacy was comparable with that of the autografting. The expression of neurotrophic factors in the regenerated nerves, together with that of brain‐derived neurotrophic factor (BDNF) in the spinal cord and muscles were elevated largely. In conclusion, ANX implanted with BMSCs could replace allografts to promote nerve regeneration effectively, which offers a reliable approach for repairing peripheral nerve defects. Synapse, 2012.

Synergistic Effects of Bone Mesenchymal Stem Cells and Chondroitinase ABC on Nerve Regeneration After Acellular Nerve Allograft in Rats

This study aimed to evaluate whether combination therapy of bone marrow stromal cells (BMSCs) transplantation and chondroitinase ABC (ChABC) treatment further enhances axonal regeneration and functional recovery after acellular nerve allograft repair of the sciatic nerve gap in rats. Eight Sprague–Dawley rats were used as nerve donors, and 32 Wistar rats were randomly divided into four groups: Group I: acellular rat sciatic nerve (ARSN) group; Group II: ChABC treatment; Group III: BMSCs transplantation; and Group IV: ChABC treatment and BMSCs transplantation. The results showed that compared with ARSN control group, BMSC transplantation promoted axonal regeneration, the secretion of neural trophic factors NGF, BDNF and axon angiogenesis in nerve graft. ChABC treatment degraded chondroitin sulfate proteoglycans in ARSN in vitro and in vivo and improved BMSCs survival in ARSN. The combination therapy caused much better beneficial effects evidenced by increasing sciatic function index, nerve conduction velocity, restoration rate of tibialis anterior wet muscle weight, and myelinated nerve number, but did not further boost the therapeutic effects on neurotrophic factor production, axon angiogenesis, and sensory functional recovery by BMSC transplantation. Taken together, for the first time, we demonstrate the synergistic effects of BMSC transplantation and BMSCs treatment on peripheral nerve regeneration, and our findings may help establish novel strategies for cell transplantation therapy for peripheral nerve injury.

Transplantation of bone marrow-derived endothelial progenitor cells attenuates myocardial interstitial fibrosis and cardiac dysfunction in streptozotocin-induced diabetic rats

Diabetic cardiomyopathy (DCM) is a progressive disease of the heart muscle and the third most common cause of heart failure. In the present study, we evaluated the effects of bone marrow‑derived endothelial progenitor cell (EPC) transplantation on the development of DCM in a streptozotocin (STZ)-induced diabetic rat model. Ex vivo generated, characterized and cultivated rat EPCs were identified by flow cytometry of their surface markers. EPCs were transplanted intravenously into rats through the tail vein 6 weeks after they were challenged with STZ and the rats were sacrificed 4 weeks later. Before sacrifice, left ventricular (LV) catheterization was performed to evaluate the cardiac function. Myocardium sections were stained with Massons trichrome staining to investigate myocardial collagen contents. Fibrosis-, apoptosis- and oxidative stress-related gene expressions were analyzed by western blot analysis. Transplantation of EPCs alleviated the impaired cardiac function associated with diabetes and decreased the collagen volume in diabetic myocardium resulting in improved cardiac function. Furthermore, EPC transplantation decreased the expression of type I collagen, Bax, caspase-3 and p67phox, while increasing the expression of Bcl-2 and manganese superoxide dismutase (MnSOD). Taken together, our results suggest that transplantation of EPCs improved cardiac function in the rat DCM model, likely through inhibition of cardiomyocyte apoptosis and attenuating myocardial fibrosis.

Elevated expression of liver X receptor alpha (LXRα) in myocardium of streptozotocin-induced diabetic rats.

The present study was designed to investigate the myocardial expression of liver X receptor alpha (LXRα) in a streptozotocin (STZ)-induced diabetic rat model. Immunohistochemical staining, quantitative real-time RT-PCR, and Western blot analysis were used to determine the expression of LXRα in the myocardium of STZ-induced diabetic rats. The myocardial expression of LXRα target genes, long-chain acyl-CoA synthetase 3 (ACSL3), fatty acid transporter protein (FAT/CD36), ATP-binding cassette transporter A1 (ABCA1), and ABCG1 were also detected. Bisulfite sequencing analysis was employed to examine the methylation status of the CpG island at the LXRα promoter region in the myocardium of STZ-induced diabetic rats. We found that LXRα mRNA and protein expression in the left ventricles, right ventricles, and atria of diabetic rats were gradually increased during the progression of diabetic cardiomyopathy (DCM). The mRNA expression levels of ACSL3 and FAT/CD36 and the protein expression levels of ABCA1 and ABCG1 were also markedly increased in different heart chambers of diabetic rats. Moreover, there was a significant difference in the methylation status of LXRα gene between the ventricles of control and diabetic rats (P < 0.05). Our findings suggest that elevated expression of LXRα may be involved in the progression of DCM, and demethylation of LXRα is likely to be responsible for its increased expression in myocardial tissues.

Synthetic liver X receptor agonist T0901317 attenuates high glucose-induced oxidative stress, mitochondrial damage and apoptosis in cardiomyocytes.

The aim of the present study was to investigate the protective effects of T0901317 (T0), a potent agonist of liver X receptors (LXRs), on high glucose-induced oxidative stress and apoptosis in H9c2 cardiac cells. Exposure of H9c2 cells to high glucose alone, not only caused a significant increase in apoptosis and reactive oxygen species (ROS) generation, but also led to a decrease in mitochondrial membrane potential (ΔΨm), release of cytochrome c, decrease in Bcl-2, increase in Bax expression and the activation of caspase-3, caspase-9, poly (ADP-ribose) polymerase (PARP) and nuclear factor (NF)-κB. However, pretreatment with T0 effectively decreased apoptosis, reduced the levels of ROS, abrogated ΔΨm, inhibited cytochrome c release and NF-κB activation, increased Bcl-2 and decreased Bax expression. In conclusion, our data suggest that T0 exerts protective effects against high glucose-induced apoptosis in H9C2 cardiac muscle cells via inhibition of ROS production, mitochondrial death and NF-κB activation.

Biocompatibility of acellular nerves of different mammalian species for nerve tissue engineering.

Abstract: To explore the biocompatibility of acellular nerves of different mammalian species, for the acellular nerves derived from rats and rabbits, the morphology, immunocompatibility, and cytocompatibility with bone marrow stromal cells (BMSCs) were evaluated. The results indicated that the tridimensional architecture and main proteins of endoneurial tubes in both biomaterials were well retained. The nerve scaffolds did not show immunogenicity or cytotoxicity, but facilitated growth of BMSCs and secretion of neurotrophic factors in vitro. In conclusion, acellular nerves of different species possess favorable biocompatibility, and xenogenic acellular nerves combined with BMSCs have potential to replace allografts for peripheral nerve reconstruction.

Liver X receptor α is targeted by microRNA-1 to inhibit cardiomyocyte apoptosis through a ROS-mediated mitochondrial pathway

Diabetic cardiomyopathy (DCM) is defined as ventricular dysfunction occurring independently of a recognized cause such as hypertension or coronary artery disease. Liver X receptor α (LXRα), a subtype of ligand-activated transcription factors LXRs, has been considered as a potential pharmacological target in the pathogenesis of cardiovascular and metabolic diseases. However, the potential mechanism of how LXRα is regulated in cardiomyocytes is still unclear. This study investigated the effect of activating LXRα with GW3965 on cardiomyocyte apoptosis and its upstream regulator in glucose-induced H9C2 cells. Our data indicated that GW3965 up-regulated the expression of LXRα, inhibited cardiomyocyte apoptosis, and altered the apoptosis-related proteins in glucose-induced H9C2 cells. In addition, GW3965 restored the mitochondrial membrane potential level and decreased the ROS production induced by glucose. Moreover, LXRα was confirmed as a direct target of microRNA-1 (miR-1) that was involved in cardiomyocyte apoptosis of DCM, and overexpression of miR-1 abrogated the inhibiting effect of GW3965 on glucose-induced apoptosis in H9C2 cells. This study highlights an important role of LXRα in the development of DCM and brings new insights into the complex mechanisms involved in the pathogenesis of DCM.

Investigating multiple dysregulated pathways in rheumatoid arthritis based on pathway interaction network

The traditional methods of identifying biomarkers in rheumatoid arthritis (RA) have focussed on the differentially expressed pathways or individual pathways, which however, neglect the interactions between pathways. To better understand the pathogenesis of RA, we aimed to identify dysregulated pathway sets using a pathway interaction network (PIN), which considered interactions among pathways. Firstly, RA-related gene expression profile data, protein–protein interactions (PPI) data and pathway data were taken up from the corresponding databases. Secondly, principal component analysis method was used to calculate the pathway activity of each of the pathway, and then a seed pathway was identified using data gleaned from the pathway activity. A PIN was then constructed based on the gene expression profile, pathway data, and PPI information. Finally, the dysregulated pathways were extracted from the PIN based on the seed pathway using the method of support vector machines and an area under the curve (AUC) index. The PIN comprised of a total of 854 pathways and 1064 pathway interactions. The greatest change in the activity score between RA and control samples was observed in the pathway of epigenetic regulation of gene expression, which was extracted and regarded as the seed pathway. Starting with this seed pathway, one maximum pathway set containing 10 dysregulated pathways was extracted from the PIN, having an AUC of 0.8249, and the result indicated that this pathway set could distinguish RA from the controls. These 10 dysregulated pathways might be potential biomarkers for RA diagnosis and treatment in the future.