Enhanced angiogenesis by the hyaluronic acid hydrogels immobilized with a VEGF mimetic peptide in a traumatic brain injury model in rats

Angiogenesis plays an important role in brain injury repair,which contributes to the reconstruction of regenerative neurovascular niche for promoting axonal regeneration in the lesion area.As a major component of developing brain extracellular matrix,hyaluronic acid(HA)has attracted more attention as a supporting matrix for brain repair.In the present study,HA-KLT hydrogel was developed via modifying HA with a VEGF mimetic peptide of KLT(KLTWQELYQLKYKGI).The characterization of the hydrogel shows that it could provide a porous,three-dimensional scaffold structure,which has a large specific surface area available for cell adhesion and interaction.Compared with the unmodified HA hydrogel,the HA-KLT hydrogel could effectively promote the attachment,spreading and proliferation of endothelial cells in vitro.Furthermore,the pro-angiogenic ability of hydrogels in vivo was evaluated by implanting them into the lesion cavities in the injured rat brain.Our results showed that the hydrogels could form a permissive interface with the host tissues at 4 weeks after implantation.Moreover,they could efficiently inhibit the formation of glial scars at the injured sites.The HA-KLT hydrogel could significantly increase the expression of endoglin/CD105 and promote the formation of blood vessels,suggesting that HA-KLT hydrogel promoted angiogenesis in vivo.Collectively,the HA-KLT hydrogel has the potential to repair brain defects by promoting angiogenesis and inhibiting the formation of glial-derived scar tissue.

Effect of hydrophilic or hydrophobic interactions on the self-assembly behavior and micro-morphology of a collagen mimetic peptide

Peptide self-assembles with bionic properties have been widely utilized for bioactive drugs and biomedical materials.Collagen mimetic peptide(CMP)gains more attention due to its unique advantages in biosecurity and function.Unfortunately,the self-assembly mechanism of CMP,particularly the effect of intermolecular forces on its self-assembly behavior and morphology,is still unrecognized.Herein,the hydrophilic glycidol(GCD)and hydrophobic Y-glycidyl ether oxypropyl trimethoxysilane(GLH)were grafted onto the side chains of CMP through the ring-opening reaction(GCD/CMP,GLH/CMP).Subsequently,the effects of hydrophilic and hydrophobic interactions on the self-assembly behavior and morphology of CMP were further studied.The results substantiated that the GCD/CMP and GLH/CMP self-assembly followed“nucleation-growth”mechanism,and the supererogatory hydrophilic and hydrophobic groups prolonged the nucleation and growth time of CMP self-assembly.Noted that the hydrophilic interaction had stronger driving effects than hydrophobic interaction on the self-assembly of CMP.The GCD/CMP and GLH/CMP self-assembles exhibited fibrous 3D network and microsphere morphology,respectively.Furthermore,the GLH/CMP self-assembles had better resistance to degradation.Consequently,the microtopography and degradation properties of CMP self-assembles could be controlled by the hydrophilic and hydrophobic interactions between CMP,which would further provide a way for subsequent purposeful design of biomedical materials.

Binding Mode of Insulin Receptor and Agonist Peptide

Insulin is a protein hormone secreted by pancreatic β cells. One of its main functions is to keep the balance of glucose inside the body by regulating the absorption and metabolism of glucose in the periphery tissue, as well as the production and storage of hepatic glycogen. The insulin receptor is a transmembrane glycoprotein in which two a subunits with a molecular weight of 135 kD and two,8 subunits with a molecular weight of 95 kD are joined by a disulfide bond to form a β-α-α-β structure. The extracellular a subunit, especially, its three domains near the N-terminal are partially responsible for signal transduction or ligand-binding, as indicated by the experiments. The extracellular α subunits are involved in binding the ligands. The experimental results indicate that the three domains of the N-terminal of the a subunits are the main determinative parts of the insulin receptor to bind the insulin or mimetic peptide. We employed the extracellular domain（ PDBID： 1IGR） of the insulin-like growth factor-1 receptor （IGF-1R） as the template to simulate and optimize the spatial structures of the three domains in the extracellular domain of the insulin receptor, which includes 468 residues. The work was accomplished by making use of the homology program in the Insight Ⅱ package on an Origin3800 server. The docking calculations of the insulin receptor obtained by homology with hexapeptides were carried out by means of the program Affinity. The analysis indicated that there were hydrogen bonding, and electrostatic and hydrophobic effects in the docking complex of the insulin receptor with hexapeptides. Moreover, we described the spatial orientation of a mimetic peptide with agonist activity in the docking complex. We obtained a rough model of binding of DLAPSQ or STIVYS with the insulin receptor, which provides the powerful theoretical support for designing the minimal insulin mimetic peptide with agonist activity, making it possible to develop oral small molecular hypoglycemic drugs.

Visible light cross-linking and bioactive peptides loaded integrated hydrogel with sequential release to accelerate wound healing complicated by bacterial infection

The effective management of bacterial infections that are resistant to multiple drugs remains a substantial clinical challenge.The eradication of drug-resistant bacteria and subsequent promotion of angiogenesis are imperative for the regeneration of the infected wounds.Here,a novel and facile peptide containing injectable hydrogel with sustained antibacterial and angiogenic capabilities is developed.The antibacterial peptide that consists of 11 residues(CM11,WKLFKKILKVL)is loaded onto acrylate-modified gelatin through charge interactions.A vascular endothelial growth factor mimetic peptide KLT(KLTWQELYQLKYKGI)with a GCG(Gly-Cys-Gly)modification at the N-terminal is covalently coupled through a visible light-induced thiol-ene reaction.In this reaction,the acrylate gelatin undergoes cross-linkage within seconds.Based on the physical/chemical double crosslinking strategy,the bioactive peptides achieve sustained and sequential release.The results show that the hydrogel significantly inhibits methicillin-resistant Staphylococcus aureus(MRSA)growth through the rapid release of CM11 peptides at early stage;it forms obvious growth inhibition zones against pathogenic bacterial strains.Moreover,cell counting kit-8 assay and scratch test confirm that the CM11/KLT-functionalized hydrogels promote cell proliferation and migration through the later release of KLT peptides.In a mouse skin wound infected with self-luminous MRSA,the CM11/KLT-functionalized hydrogels enhance wound healing,with rapidly bacterial infection reduction,lower expression of inflammatory factors,and neovascularization promotion.These results suggest that the rationally designed,sustained and sequential release CM11/KLT-functionalized hydrogels have huge potential in promoting the healing of multi-drug resistant bacterial infected wounds.

Connexins in neurons and glia: targets for intervention in disease and injury

Both neurons and glia throughout the central nervous system are organized into networks by gap junctions. Among glia, gap junctions facilitate metabolic homeostasis and intercellular communication. Among neurons, gap junctions form electrical synapses that function primarily for communication. However, in neurodegenerative states due to disease or injury gap junctions may be detrimental to survival. Electrical synapses may facilitate hyperactivity and bystander killing among neurons, while gap junction hemichannels in glia may facilitate inflammatory signaling and scar formation. Advances in understanding mechanisms of plasticity of electrical synapses and development of molecular therapeutics to target glial gap junctions and hemichannels offer new hope to pharmacologically limit neuronal degeneration and enhance recovery.

Surface decoration of development-inspired synthetic N-cadherin motif via Ac-BP promotes osseointegration of metal implants

Research works on the synergistic effect of surface modified bioactive molecules and bone metal implants have been highlighted.N-cadherin is regarded as a key factor in directing cell-cell interactions during the mesenchymal condensation preceding the osteogenesis in the musculoskeletal system.In this study,the N-cadherin mimetic peptide(Cad)was biofunctionalized on the titanium metal surface via the acryloyl bisphosphonate(Ac-BP).To learn the synergistic effect of N-cadherin mimetic peptide,when tethered with titanium substrates,on promoting osteogenic differentiation of the seeded human mesenchymal stem cells(hMSCs)and the osseointegration at the bone-implant interfaces.Results show that the conjugation of N-cadherin mimetic peptide with Ac-BP promoted the osteogenic gene markers expression in the hMSCs.The biofunctionalized biomaterial surfaces promote the expression of the Wnt/β-catenin downstream axis in the attached hMSCs,and then enhance the in-situ bone formation and osseointegration at the bone-implant interfaces.We conclude that this N-cadherin mimetic peptide tethered on Ti surface promote osteogenic differentiation of hMSCs and osseointegration of biomaterial implants in vitro and in vivo.These findings demonstrate the importance of the development-inspired surface bioactivation of metal implants and shed light on the possible cellular mechanisms of the enhanced osseointegration.