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A highly interesting source for adult stem cells is adipose tissue, from which the stromal vascular fraction (SVF)-a heterogeneous cell population including the adipose-derived stromal/stem cells-can be obtained. To enhance the regenerative potential of freshly isolated SVF cells, low-level light therapy (LLLT) was used. The effects of pulsed blue (475 nm), green (516 nm), and red (635 nm) light from light-emitting diodes applied on freshly isolated SVF were analysed regarding cell phenotype, cell number, viability, adenosine triphosphate content, cytotoxicity, and proliferation but also osteogenic, adipogenic, and proangiogenic differentiation potential. The colony-forming unit fibroblast assay revealed a significantly increased colony size after LLLT with red light compared with untreated cells, whereas the frequency of colony-forming cells was not affected. LLLT with green and red light resulted in a stronger capacity to form vascular tubes by SVF when cultured within 3D fibrin matrices compared with untreated cells, which was corroborated by increased number and length of the single tubes and a significantly higher concentration of vascular endothelial growth factor. Our study showed beneficial effects after LLLT on the vascularization potential and proliferation capacity of SVF cells. Therefore, LLLT using pulsed light-emitting diode light might represent a new approach for activation of freshly isolated SVF cells for direct clinical application.

Treatment of peripheral nerve injuries has evolved over the past several decades to include the use of sophisticated new materials endowed with trophic and topographical cues that are essential for in vivo nerve fibre regeneration. In this research, we explored the use of an advanced design strategy for peripheral nerve repair, using biological and semi-synthetic hydrogels that enable controlled environmental stimuli to regenerate neurons and glial cells in a rat sciatic nerve resection model. The provisional nerve growth conduits were composed of either natural fibrin or adducts of synthetic polyethylene glycol and fibrinogen or gelatin. A photo-patterning technique was further applied to these 3D hydrogel biomaterials, in the form of laser-ablated microchannels, to provide contact guidance for unidirectional growth following sciatic nerve injury. We tested the regeneration capacity of subcritical nerve gap injuries in rats treated with photo-patterned materials and compared these with injuries treated with unpatterned hydrogels, either stiff or compliant. Among the factors tested were shear modulus, biological composition, and micropatterning of the materials. The microchannel guidance patterns, combined with appropriately matched degradation and stiffness properties of the material, proved most essential for the uniform tissue propagation during the nerve regeneration process.

One of the mainstays of facial rejuvenation strategies is volume restoration, which can be achieved by autologous fat grafting. In our novel approach, we treated the adipose tissue harvest site with extracorporeal shock wave therapy (ESWT) in order to improve the quality of the regenerative cells in situ. The latter was demonstrated by characterizing the cells of the stromal vascular fraction (SVF) in the harvested liposuction material regarding cell yield, adenosine triphosphate (ATP) content, proliferative capacity, surface marker profile, differentiation potential and secretory protein profile. Although the SVF cell yield was only slightly enhanced, viability and ATP concentration of freshly isolated cells as well as proliferation doublings after 3 weeks in culture were significantly increased in the ESWT compared with the untreated group. Likewise, cells expressing mesenchymal and endothelial/pericytic markers were significantly elevated concomitant with an improved differentiation capacity towards the adipogenic lineage and enhancement in specific angiogenic proteins. Hence, in situ ESWT might be applied in the future to promote cell fitness, adipogenesis and angiogenesis within the fat graft for successful facial rejuvenation strategies with potential long-term graft survival.

Skeletal ischaemia-reperfusion (I-R) injury may influence patient outcome after severe vascular trauma or clamping of major vessels. The aim of this study was to observe whether locally applied vascular endothelial growth factor (VEGF) in fibrin could induce the expression of VEGF-receptor-2 (VEGFR-2) and improve the outcome after I-R injury. Transgenic mice expressing VEGFR-2 promoter-controlled luciferase were used for the assessment of VEGFR-2 expression. Ischaemia was induced for 2 h by a tension-controlled tourniquet to the hind limb, followed by 24 h of reperfusion. The animals were locally injected subcutaneously with fibrin sealant containing 20 or 200 ng VEGF; control animals received no treatment or fibrin sealant application. In vivo VEGFR-2 expression was quantified upon administration of luciferin at several observation times. For oedema and inflammation quantification, wet:dry ratio measurements and a myeloperoxidase assay of the muscle tissue were performed. Laser Doppler imaging showed that ischaemia was present and that the blood flow had returned to baseline levels after 24 h of reperfusion. VEGFR-2 expression levels in the fibrin + 200 ng VEGF were significantly higher than in all other groups. Granulocyte infiltration was reduced in both treatment groups, as well as reduced oedema formation. These results showed that VEGF released from fibrin had a positive effect on early I-R outcome in a mouse model, possibly via VEGFR-2. Copyright © 2016 John Wiley & Sons, Ltd.

Fibrin-based sealants consist of natural coagulation factors involved in the final phase of blood coagulation, during which fibrinogen is enzymatically converted by thrombin to form a solid-phase fibrin clot. For applications in tissue regeneration, a controlled process of matrix degradation within a certain period of time is essential for optimal wound healing. Hence, it is desirable to follow the kinetics of fibrinolysis at the application site. Non-invasive molecular imaging systems enable real-time tracking of processes in the living animal. In this study, a non-invasive fluorescence based imaging system was applied to follow and quantify site-specific degradation of fibrin sealant. To enable non-invasive tracking of fibrin in vivo, fibrin-matrix was labelled by incorporation of a fluorophore-conjugated fibrinogen component. Protein degradation and release of fluorescence were, in a first step, correlated in vitro. In vivo, fluorophore-labelled fibrin was subcutaneously implanted in mice and followed throughout the experiment using a multispectral imaging system. For the fluorescent fibrin, degradation correlated with the release of fluorescence from the clots in vitro. In vivo it was possible to follow and quantify implanted fibrin clots throughout the experiment, demonstrating degradation kinetics of approximately 16 days in the subcutaneous compartment, which was further confirmed by histological evaluation of the application site.