The role of peptides in bone healing and regeneration: A systematic review

Background: Bone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration. Methods: A systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study. Results: Based on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited. Conclusion: Further research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge

Effects of temperature in juvenile seabass (Dicentrarchus labrax L.) biomarker responses and behaviour: implications for environmental monitoring

The effects of temperature on European seabass (Dicentrarchus labrax L.) juveniles were investigated using a 30-day bioassay carried out at 18 and 25 °C in laboratory conditions. A multiparameter approach was applied including fish swimming velocity and several biochemical parameters involved in important physiological functions. Fish exposed for four weeks to 25 °C showed a decreased swimming capacity, concomitant with increased oxidative stress (increased catalase and glutathione peroxidase activities) and damage (increased lipid peroxidation levels), increased activity of an enzyme involved in energy production through the aerobic pathway (isocitrate dehydrogenase) and increased activities of brain and muscle cholinesterases (neurotransmission) compared to fish kept at 18 °C. Globally, these findings indicate that basic functions, essential for juvenile seabass surviving and well performing in the wild, such as predation, predator avoidance, neurofunction and ability to face chemical stress may be compromised with increasing water temperature. This may be of particular concern if D. labrax recruitment phase in northwest European estuaries and coastal areas happens gradually inmore warm environments as a consequence of global warming. Considering that the selected endpoints are generally applied in monitoring studies with different species, these findings also highlight the need of more research, including interdisciplinary and multiparameter approaches, on the impacts of temperature on marine species, and stress the importance of considering scenarios of temperature increase in environmental monitoring and in marine ecological risk assessment

Peptide immobilization on polyethylene terephthalate surfaces to study specific endothelial cell adhesion, spreading and migration.

To control specific endothelial cell (EC) functions, cell adhesive RGDS, EC specific REDV and YIGSR peptides, and angiogenic SVVYGLR sequences were covalently immobilized onto polyethylene terephthalate (PET) surfaces for the purpose of cell culture. X-ray photoelectron spectroscopy, atomic force microscopy, fluorescence microscopy and contact angle measurement were employed for characterization of surface modifications. The peptide density on PET surfaces was evaluated by fluorescence microscopy. The surfaces immobilized with peptides were exposed to human umbilical vein endothelial cells to study their specific effects onto EC functions. The results showed that the surface functionalized by these peptides enhanced the EC adhesion, spreading and migration as compared with native PET surfaces. Specifically, the RGDS peptides induced more cell adhesion than other peptides. The YIGSR and SVVYGLR sequences induced more cell spreading and cell migration, represented by intense focal adhesion at the leading edges of cell spreading and migration. The bi-functionalization of RGDS and SVVYGLR peptides (MIX) combined the advantages of both peptides and induced significant EC adhesion, spreading and migration. Our study indicates that the surface functionalization by peptides specific for ECs, especially the combination of RGDS with SVVYGLR or YIGSR peptides, has potential applications in promoting endothelialization of vascular prostheses and for construction of vascularized tissues in tissue engineering

A novel cyclic RGD-containing peptide polymer improves serum-free adhesion of adipose tissue-derived mesenchymal stem cells to bone implant surfaces

Seeding of bone implants with mesenchymal stem cells (MSCs) may promote osseointegration and bone regeneration. However, implant material surfaces, such as titanium or bovine bone mineral, fail to support rapid and efficient attachment of MSCs, especially under serum-free conditions that may be desirable when human applications or tightly controlled experiments are envisioned. Here we demonstrate that a branched poly[Lys(Ser i -DL-Ala m ) polymer functionalized with cyclic arginyl-glycyl-aspar- tate, when immobilized by simple adsorption to tissue culture plastic, surgical titanium alloy (Ti6Al4V), or Bio- Oss bovine bone substitute, significantly accelerates serum-free adhesion and enhances seeding efficiency of human adipose tissue-derived MSCs. Moreover, when exposed to serum-containing osteogenic medium, MSCs survived and differentiated on the peptide-coated scaffolds. In summary, the presented novel polypeptide conjugate can be conveniently used for coating various surfaces, and may find applications whenever quick and efficient seeding of MSCs is required to various scaffolds in the absence of serum

Letter to Nature. High mixing rates in the abyssal Southern Ocean

Mixing of water masses from the deep ocean to the layers above can be estimated from considerations of continuity in the global ocean overturning circulation. But averaged over ocean basins, diffusivity has been observed to be too small to account for the global upward flux of water, and high mixing intensities have only been found in the restricted areas close to sills and narrow gaps. Here we present observations from the Scotia Sea, a deep ocean basin between the Antarctic peninsula and the tip of South America, showing a high intensity of mixing that is unprecedented over such a large area. Using a budget calculation over the whole basin, we find a diffusivity of (39 +- 10) x 10^-4 m^2 s^-1, averaged over an area of 7 x 10^5 km^2. The Scotia Sea is a basin with a rough topography16, situated just east of the Drake passage where the strong flow of the Antarctic Circumpolar Current is constricted in width. The high basin-wide mixing intensity in this area of the Southern Ocean may help resolve the question of where the abyssal water masses are mixed towards the surface