Biomaterial pretreatment with ECGF to augment endothelial cell proliferation

Vascular Tissue Engineering: Challenges and Requirements for an Ideal Large Scale Blood Vessel

Since the emergence of regenerative medicine and tissue engineering more than half a century ago, one obstacle has persisted: the in vitro creation of large-scale vascular tissue (>1 cm³) to meet the clinical needs of viable tissue grafts but also for biological research applications. Considerable advancements in biofabrication have been made since Weinberg and Bell, in 1986, created the first blood vessel from collagen, endothelial cells, smooth muscle cells and fibroblasts. The synergistic combination of advances in fabrication methods, availability of cell source, biomaterials formulation and vascular tissue development, promises new strategies for the creation of autologous blood vessels, recapitulating biological functions, structural functions, but also the mechanical functions of a native blood vessel. In this review, the main technological advancements in bio-fabrication are discussed with a particular highlights on 3D bioprinting technologies. The choice of the main biomaterials and cell sources, the use of dynamic maturation systems such as bioreactors and the associated clinical trials will be detailed. The remaining challenges in this complex engineering field will finally be discussed.

Fluorescence polarization assay to detect the presence of traces of ciprofloxacin

Detection of ciprofloxacin residues in milk by sensitive and rapid methods is of great interest due to its use in the treatment of dairy livestock health. Current analytical approaches to antibiotics detection, are laboratory-based methods and they are time-consuming and require trained personnel. To cope this problem, we propose an assay, based on fluorescence polarization principle, able to detect the presence of ciprofloxacin in diluted milk sample without any pre-treatment. The proposed method is based on the use of ciprofloxacin-protein conjugate labeled with near infrared fluorescence dye, which upon binding to specific antibody causes an increase of the fluorescence polarization emission signal. The developed assay allows for the detection of ciprofloxacin at a concentration of 1ppb, which represents an amount lower than the maximum residual limit (MRL) of ciprofloxacin in milk, as set by the European Union regulation (100 ppb).

Minoxidil Promotes Hair Growth through Stimulation of Growth Factor Release from Adipose-Derived Stem Cells

Minoxidil directly promotes hair growth via the stimulation of dermal papilla (DP) and epithelial cells. Alternatively, there is little evidence for indirect promotion of hair growth via stimulation of adipose-derived stem cells (ASCs). We investigated whether minoxidil stimulates ASCs and if increased growth factor secretion by ASCs facilitates minoxidil-induced hair growth. Telogen-to-anagen induction was examined in mice. Cultured DP cells and vibrissae hair follicle organ cultures were used to further examine the underlying mechanisms. Subcutaneous injection of minoxidil-treated ASCs accelerated telogen-to-anagen transition in mice, and increased hair weight at day 14 post-injection. Minoxidil did not alter ASC proliferation, but increased migration and tube formation. Minoxidil also increased the secretion of growth factors from ASCs, including chemokine (C-X-C motif) ligand 1 (CXCL1), platelet-derived endothelial cell growth factor (PD-ECGF), and platelet-derived growth factor-C (PDGF-C). Minoxidil increased extracellular signal–regulated kinases 1/2 (ERK1/2) phosphorylation, and concomitant upregulation of PD-ECGF and PDGF-C mRNA levels were attenuated by an ERK inhibitor. Subcutaneous injection of CXCL1, PD-ECGF, or PDGF-C enhanced anagen induction in mice, and both CXCL1 and PDGF-C increased hair length in ex vivo organ culture. Treatment with CXCL1, PD-ECGF, or PDGF-C also increased the proliferation index in DP cells. Finally, topical application of CXCL1, PD-ECGF, or PDGF-C with 2% minoxidil enhanced anagen induction when compared to minoxidil alone. Minoxidil stimulates ASC motility and increases paracrine growth factor signaling. Minoxidil-stimulated secretion of growth factors by ASCs may enhance hair growth by promoting DP proliferation. Therefore, minoxidil can be used as an ASC preconditioning agent for hair regeneration.

Biomaterials for vascular tissue engineering

Cardiovascular disease is the leading cause of mortality in the USA. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. While synthetic polymers have been extensively studied as substitutes in vascular engineering, they fall short of meeting the biological challenges at the blood-material interface. Various tissue engineering strategies have emerged to address these flaws and increase long-term patency of vascular grafts. Vascular cell seeding of scaffolds and the design of bioactive polymers for in situ arterial regeneration have yielded promising results. This article describes the advances made in biomaterials design to generate suitable materials that not only match the mechanical properties of native vasculature, but also promote cell growth, facilitate extracellular matrix production and inhibit thrombogenicity.

Polymeric materials for tissue engineering of arterial substitutes

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute.

Biointeractive polymers and tissue engineered blood vessels

The regulation of endothelial cell (EC) and smooth muscle cell (SMC) proliferation following vascular interventions is critical to clinical efficacy. Our laboratory has developed a method of impregnating biomaterials with suspensions containing bioactive proteins resulting in the capability of differentially modulating EC and SMC growth in vitro and in vivo following implantation. We have previously reported that 60 mu internodal distance ePTFE grafts impregnated with fibrin glue (FG) containing FGF-1 and heparin develop confluent endothelialization with transiently increased EC and SMC proliferation after 4 weeks in dogs. Thoraco-abdominal implants after 20 weeks were developed significantly thicker (139 mu) inner capsules in response to the FGF. To minimize SMC proliferation we studied the effects of FGF-1, heparin, and thrombin concentrations on SMC growth in vitro. FG caused a 182% increase (P < 0.001) in DNA synthesis. Heparin within FG diminished this effect in a dose-dependant manner, with complete inhibition of FG-induced growth at 500 U ml-1 (versus FG alone, P < 0.001). FGF-1 within FG without heparin had no effect, but together, FGF-1 caused a dose-dependant growth increase while increasing heparin concentrations initially increased and then decreased proliferation. FGF-1 and heparin in the medium of quiescent SMCs had similar effects. Only thrombin concentrations > 3.2 U ml-1 stimulated SMC growth and this stimulation was blocked by heparin. A synergism between FGF and heparin on EC proliferation was also found but without EC growth inhibition in response to higher concentrations of heparin. It is thus possible to modulate the relative proliferative activity of ECs versus SMCs by altering the FGF:heparin ratio. This same system may be useful with other proteins to induce other local affects by the applied protein or systemic affects following release of that protein.