Generation of a novel human dermal substitute functionalized with antibiotic-loaded nanostructured lipid carriers (NLCs) with antimicrobial properties for tissue engineering

The effect of intraoperative immersion solutions on acellular dermal matrix: Biofilm formation and mechanical property

BACKGROUND

Acellular dermal matrix (ADM) is generally used on implant-based breast operations; However, it can increase surgical site infection. Many immersion solutions are applied to ADM, however, the most effective solution is unknown. The purpose of this study is to determine the effect of different solutions on the biofilm formation and mechanical properties of ADM.

METHODS

Aseptic porcine-derived ADMs were immersed in 5 different solutions for 30 min; sterile normal saline, 10% povidone-iodine, 0.5% chlorhexidine, antibiotics (cefazolin, gentamicin, and vancomycin), and taurolidine. They are transferred to 10 ml suspension of methicillin-sensitive/resistant Staphylococcus aureus (MSSA/MRSA) or Staphylococcus epidermidis and an overnight culture was performed. After rinsing and sonication to obtain the biofilm on ADM, colony forming unit (CFU) was measured. In addition, the maximum load before ADM deformation and the elongation length of ADM at the start of the maximum load was determined.

RESULTS

Regardless of strains, povidone-iodine, chlorhexidine, and taurolidine group had lower CFUs than the saline group with statistical significance. Meanwhile, the antibiotics group did not show statistical difference from the saline group. Moreover, only taurolidine group showed higher tensile strength (MRSA, p = 0.0003; S. epidermidis, p = 0.0023) and elongation length (MSSA, p = 0.0015) than the saline group. The antibiotics and chlorhexidine group yielded lower tensile strength and elongation length than the povidone-iodine and taurolidine groups.

CONCLUSIONS

It was suggested that the 10% povidone-iodine or taurolidine solution is effective. In contrast, the antibiotics solution could be considered as an effective intraoperative solution.

Fibrin and Marine-Derived Agaroses for the Generation of Human Bioartificial Tissues: An Ex Vivo and In Vivo Study

Development of an ideal biomaterial for clinical use is one of the main objectives of current research in tissue engineering. Marine-origin polysaccharides, in particular agaroses, have been widely explored as scaffolds for tissue engineering. We previously developed a biomaterial based on a combination of agarose with fibrin, that was successfully translated to clinical practice. However, in search of novel biomaterials with improved physical and biological properties, we have now generated new fibrin-agarose (FA) biomaterials using 5 different types of agaroses at 4 different concentrations. First, we evaluated the cytotoxic effects and the biomechanical properties of these biomaterials. Then, each bioartificial tissue was grafted in vivo and histological, histochemical and immunohistochemical analyses were performed after 30 days. Ex vivo evaluation showed high biocompatibility and differences in their biomechanical properties. In vivo, FA tissues were biocompatible at the systemic and local levels, and histological analyses showed that biointegration was associated to a pro-regenerative process with M2-type CD206-positive macrophages. These results confirm the biocompatibility of FA biomaterials and support their clinical use for the generation of human tissues by tissue engineering, with the possibility of selecting specific agarose types and concentrations for applications requiring precise biomechanical properties and in vivo reabsorption times.

The origin of human epithelial tissue

The histological structure of human epithelial tissue is complex, but all epithelia share three major features: cohesion, polarity and attachment. These functions are mainly achieved by the presence of specialized structures such as intercellular junctions, polarity protein complexes and basement membranes. In the present review, we have analyzed the presence of each of these structures in several groups of animals that are considered to be at the base of the animal evolution tree. Interestingly, these characters seem to have evolved independently, and a careful histological and structural analysis of the phylogenetic tree shows different groups of animals in which epithelia are absent and groups in which cells show only some of the specialized structures found in differentiated epithelia. These findings could contribute to understand how epithelial tissues evolved and determine their current protective functions.

Optical Behavior of Human Skin Substitutes: Absorbance in the 200-400 nm UV Range

The most recent generation of bioengineered human skin allows for the efficient treatment of patients with severe skin defects. Despite UV sunlight can seriously affect human skin, the optical behavior in the UV range of skin models is still unexplored. In the present study, absorbance and transmittance of the UGRSKIN bioartificial skin substitute generated with human skin cells combined with fibrin-agarose biomaterials were evaluated for: UV-C (200−280 nm), -B (280−315 nm), and -A (315−400 nm) spectral range after 7, 14, 21 and 28 days of ex vivo development. The epidermis of the bioartificial skin substitute was able to mature and differentiate in a time-dependent manner, expressing relevant molecules able to absorb most of the incoming UV radiation. Absorbance spectral behavior of the skin substitutes showed similar patterns to control native skin (VAF > 99.4%), with values 0.85−0.90 times lower than control values at 7 and 14- days and 1.05−1.10 times the control values at 21- and 28-days. UV absorbance increased, and UV transmission decreased with culture time, and comparable results to the control were found at 21 and 28 days. These findings support the use of samples corresponding to 21 or 28 days of development for clinical purposes due to their higher histological similarities with native skin, but also because of their absorbance of UV radiation.

Development of secretome-based strategies to improve cell culture protocols in tissue engineering

Advances in skin tissue engineering have promoted the development of artificial skin substitutes to treat large burns and other major skin loss conditions. However, one of the main drawbacks to bioengineered skin is the need to obtain a large amount of viable epithelial cells in short periods of time, making the skin biofabrication process challenging and slow. Enhancing skin epithelial cell cultures by using mesenchymal stem cells secretome can favor the scalability of manufacturing processes for bioengineered skin. The effects of three different types of secretome derived from human mesenchymal stem cells, e.g. hADSC-s (adipose cells), hDPSC-s (dental pulp) and hWJSC-s (umbilical cord), were evaluated on cultured skin epithelial cells during 24, 48, 72 and 120 h to determine the potential of this product to enhance cell proliferation and improve biofabrication strategies for tissue engineering. Then, secretomes were applied in vivo in preliminary analyses carried out on Wistar rats. Results showed that the use of secretomes derived from mesenchymal stem cells enhanced currently available cell culture protocols. Secretome was associated with increased viability, proliferation and migration of human skin epithelial cells, with hDPSC-s and hWJSC-s yielding greater inductive effects than hADSC-s. Animals treated with hWJSC-s and especially, hDPSC-s tended to show enhanced wound healing in vivo with no detectable side effects. Mesenchymal stem cells derived secretomes could be considered as a promising approach to cell-free therapy able to improve skin wound healing and regeneration.

α-Linolenic acid and linoleic acid modulate the lipidome and the skin barrier of a tissue-engineered skin model

Polyunsaturated fatty acids (PUFAs) play an important role in the establishment and the maintenance of the skin barrier function. However, the impact of their derived lipid mediators remains unclear. Skin substitutes were engineered according to the self-assembly method with a culture medium supplemented with 10 μM of both α-linolenic acid (ALA) and linoleic acid (LA). The supplementation with ALA and LA decreased testosterone absorption through a tissue-engineered reconstructed skin model, thus indicating an improved skin barrier function following supplementation. The exogenously provided fatty acids were incorporated into the phospholipid and triglyceride fractions of the skin substitutes. Indeed, the dual supplementation increased the levels of eicosapentaenoic acid (EPA) (15-fold), docosapentaenoic acid (DPA) (3-fold), and LA (1.5-fold) in the epidermal phospholipids while it increased the levels of ALA (>20-fold), DPA (3-fold) and LA (1.5-fold) in the epidermal triglycerides. The bioactive lipid mediator profile of the skin substitutes, including prostaglandins, hydroxy-fatty acids, N-acylethanolamines and monoacylglycerols, was next analyzed using liquid chromatography-tandem mass spectrometry. The lipid supplementation further modulated bioactive lipid mediator levels of the reconstructed skin substitutes, leading to a lipid mediator profile more representative of the one found in normal human skin. These findings show that an optimized supply of PUFAs via culture media is essential for the establishment of improved barrier function in vitro. STATEMENT OF SIGNIFICANCE: Supplementation of the culture medium with 10 μM of both α-linolenic acid (ALA) and linoleic acid (LA) improved the skin barrier function of a tissue-engineered skin model. The exogenously provided fatty acids were incorporated into the phospholipid and triglyceride fractions of the skin substitutes and further modulated bioactive lipid mediator levels, including prostaglandins, hydroxy-fatty acids, N-acylethanolamines and monoacylglycerols. These findings highlight the important role of ALA and LA in skin homeostasis and show that an optimized supply of polyunsaturated fatty acids via culture media is essential for the establishment of improved barrier function in vitro.

Usefulness of a Nanostructured Fibrin-Agarose Bone Substitute in a Model of Severely Critical Mandible Bone Defect

Critical defects of the mandibular bone are very difficult to manage with currently available materials and technology. In the present work, we generated acellular and cellular substitutes for human bone by tissue engineering using nanostructured fibrin-agarose biomaterials, with and without adipose-tissue-derived mesenchymal stem cells differentiated to the osteogenic lineage using inductive media. Then, these substitutes were evaluated in an immunodeficient animal model of severely critical mandibular bone damage in order to assess the potential of the bioartificial tissues to enable bone regeneration. The results showed that the use of a cellular bone substitute was associated with a morpho-functional improvement of maxillofacial structures as compared to negative controls. Analysis of the defect site showed that none of the study groups fully succeeded in generating dense bone tissue at the regeneration area. However, the use of a cellular substitute was able to improve the density of the regenerated tissue (as determined via CT radiodensity) and form isolated islands of bone and cartilage. Histologically, the regenerated bone islands were comparable to control bone for alizarin red and versican staining, and superior to control bone for toluidine blue and osteocalcin in animals grafted with the cellular substitute. Although these results are preliminary, cellular fibrin-agarose bone substitutes show preliminary signs of usefulness in this animal model of severely critical mandibular bone defect.

Improvement of Cell Culture Methods for the Successful Generation of Human Keratinocyte Primary Cell Cultures Using EGF-Loaded Nanostructured Lipid Carriers

Human skin keratinocyte primary cultures can be established from skin biopsies with culture media containing epithelial growth factor (EGF). Although current methods are efficient, optimization is required to accelerate the procedure and obtain these cultures in less time. In the present study, we evaluated the effect of novel formulations based on EGF-loaded nanostructured lipid carriers (NLC). First, biosafety of NLC containing recombinant human EGF (NLC-rhEGF) was verified in immortalized skin keratinocytes and cornea epithelial cells, and in two epithelial cancer cell lines, by quantifying free DNA released to the culture medium. Then we established primary cell cultures of human skin keratinocytes with basal culture media (BM) and BM supplemented with NLC-rhEGF, liquid EGF (L-rhEGF), or NLC alone (NLC-blank). The results showed that cells isolated by enzymatic digestion and cultured with or without a feeder layer had a similar growth rate regardless of the medium used. However, the explant technique showed higher efficiency when NLC-rhEGF culture medium was used, compared to BM, L-rhEGF, or NLC-blank. Gene expression analysis showed that NLC-rhEGF was able to increase EGFR gene expression, along with that of other genes related to cytokeratins, cell–cell junctions, and keratinocyte maturation and differentiation. In summary, these results support the use of NLC-rhEGF to improve the efficiency of explant-based methods in the efficient generation of human keratinocyte primary cell cultures for tissue engineering use.

Antimicrobial Peptide Dendrimers and Quorum-Sensing Inhibitors in Formulating Next-Generation Anti-Infection Cell Therapy Dressings for Burns

Multidrug resistance infections are the main cause of failure in the pro-regenerative cell-mediated therapy of burn wounds. The collagen-based matrices for delivery of cells could be potential substrates to support bacterial growth and subsequent lysis of the collagen leading to a cell therapy loss. In this article, we report the development of a new generation of cell therapy formulations with the capacity to resist infections through the bactericidal effect of antimicrobial peptide dendrimers and the anti-virulence effect of anti-quorum sensing MvfR (PqsR) system compounds, which are incorporated into their formulation. Anti-quorum sensing compounds limit the pathogenicity and antibiotic tolerance of pathogenic bacteria involved in the burn wound infections, by inhibiting their virulence pathways. For the first time, we report a biological cell therapy dressing incorporating live progenitor cells, antimicrobial peptide dendrimers, and anti-MvfR compounds, which exhibit bactericidal and anti-virulence properties without compromising the viability of the progenitor cells.

Applications of Nanosized-Lipid-Based Drug Delivery Systems in Wound Care

Impaired wound healing is an encumbering public health issue that increases the demand for developing new therapies in order to minimize health costs and enhance treatment efficacy. Available conventional therapies are still unable to maximize their potential in penetrating the skin at the target site and accelerating the healing process. Nanotechnology exhibits an excellent opportunity to enrich currently available medical treatments, enhance standard care and manage wounds. It is a promising approach, able to address issues such as the permeability and bioavailability of drugs with reduced stability or low water solubility. This paper focuses on nanosized-lipid-based drug delivery systems, describing their numerous applications in managing skin wounds. We also highlight the relationship between the physicochemical characteristics of nanosized, lipid-based drug delivery systems and their impact on the wound-healing process. Different types of nanosized-lipid-based drug delivery systems, such as vesicular systems and lipid nanoparticles, demonstrated better applicability and enhanced skin penetration in wound healing therapy compared with conventional treatments. Moreover, an improved chemically and physically stable drug delivery system, with increased drug loading capacity and enhanced bioavailability, has been shown in drugs encapsulated in lipid nanoparticles. Their applications in wound care show potential for overcoming impediments, such as the inadequate bioavailability of active agents with low solubility. Future research in nanosized-lipid-based drug delivery systems will allow the achievement of increased bioavailability and better control of drug release, providing the clinician with more effective therapies for wound care.