Influence of aorta extracellular matrix in electrospun polycaprolactone scaffolds

Combining human liver ECM with topographically featured electrospun scaffolds for engineering hepatic microenvironment

Liver disease cases are rapidly expanding worldwide, and transplantation remains the only effective cure for end-stage disease. There is an increasing demand for developing potential drug treatments, and regenerative therapies using in-vitro culture platforms. Human decellularized extracellular matrix (dECM) is an appealing alternative to conventional animal tissues as it contains human-specific proteins and can serve as scaffolding materials. Herein we exploit this with human donor tissue from discarded liver which was not suitable for transplant using a synergistic approach to combining biological and topographical cues in electrospun materials as an in-vitro culture platform. To realise this, we developed a methodology for incorporating human liver dECM into electrospun polycaprolactone (PCL) fibres with surface nanotopographies (230-580 nm). The hybrid scaffolds were fabricated using varying concentrations of dECM; their morphology, mechanical properties, hydrophilicity and stability were analysed. The scaffolds were validated using HepG2 and primary mouse hepatocytes, with subsequent results indicating that the modified scaffolds-maintained cell growth and influenced cell attachment, proliferation and hepatic-related gene expression. This work demonstrates a novel approach to harvesting the potential from decellularized human tissues in the form of innovative in-vitro culture platforms for liver.

Effects of electrospun fibers containing ascorbic acid on oxidative stress reduction for cardiac tissue engineering

Tissue engineering provides promise for regeneration of cardiac tissue following myocardial infarction. However, the harsh microenvironment of the infarct hampers the efficacy of regenerative therapies. Ischemia-reperfusion injury dramatically increases the levels of reactive oxygen species (ROS) within the infarcted area, causing a cascade of further cellular injury. Implantable tissue engineered grafts can target this oxidative stress by delivering pharmaceutical compounds directly into the diseased tissue. Herein, we successfully fabricated electrospun polycaprolactone (PCL) fibers containing varying concentrations of ascorbic acid, a potent antioxidant well known for its ROS-scavenging capabilities. The antioxidant scaffolds displayed significantly improved scavenging of DPPH radicals, superoxide anions and hydroxyl radicals, in a dose dependent manner. Mechanical properties testing indicated that incorporation of ascorbic acid enhanced the strength and Young's modulus of the material, correlating with a moderate but non-significant increase in the crystallinity. Moreover, the scaffolds supported adhesion and maintained survival of human umbilical vein endothelial cells in vitro, indicating good cytocompatibility. These results provide motivation for the use of ascorbic acid-containing fibrous scaffolds to regulate the highly oxidative microenvironment following myocardial infarction.

Fabrication of polycaprolactone electrospun fibres with retinyl acetate for antioxidant delivery in a ROS-mimicking environment

Background: Increased cancer rates denote that one in two people will be diagnosed with cancer in their lifetime. Over 60% of cancer patients receive radiotherapy, either as a stand-alone treatment or in combination with other treatments such as chemotherapy and surgery. Whilst radiotherapy is effective in destroying cancer cells, it also causes subsequent damage to healthy cells and surrounding tissue due to alterations in the tumor microenvironment and an increase in reactive oxygen species (ROS). This can cause extensive damage that impairs tissue function, and the likelihood of tissue regeneration and restoration of function is significantly reduced as new healthy cells cannot survive in the damaged environment. In the treatment of head and neck cancers, radiotherapy can cause salivary gland dysfunction. This significantly impairs the patient's quality of life and there is currently no cure, only palliative treatment options. Tissue engineering approaches are used to mimic the microenvironment of the tissue and can mediate the damaged microenvironment via bioactive compounds, to support the delivery, survival, and proliferation of new, healthy cells into the damaged environment. Methods: In this study, retinyl acetate, a derivative of vitamin A, was successfully incorporated into electrospun polycaprolactone fibres. Results: SEM images and characterization analyses showed that all scaffolds produced had similar characteristics, including fiber morphology and scaffold wettability. The vitamin scaffolds were shown to exert an antioxidant effect through scavenging activity of both DPPH and hydroxyl radicals in vitro. Critically, the antioxidant scaffolds supported the growth of human submandibular gland cells and significantly upregulated the expression of GPx1, an antioxidant enzyme, when cultured under both normal conditions and under a simulated oxidative stress environment. Discussion: These results suggest that incorporation of retinyl acetate into electrospun fibres has may mediate the damaged microenvironment post cancer radiation therapy.

From hormone replacement therapy to regenerative scaffolds: A review of current and novel primary hypothyroidism therapeutics

Primary hypothyroidism severely impacts the quality of life of patients through a decrease in the production of the thyroid hormones T3 and T4, leading to symptoms affecting cardiovascular, neurological, cognitive, and metabolic function. The incidence rate of primary hypothyroidism is expected to increase in the near future, partially due to increasing survival of patients that have undergone radiotherapy for head and neck cancer, which induces this disease in over half of those treated. The current standard of care encompasses thyroid hormone replacement therapy, traditionally in the form of synthetic T4. However, there is mounting evidence that this is unable to restore thyroid hormone signaling in all tissues due to often persistent symptoms. Additional complications are also present in the form of dosage difficulties, extensive drug interactions and poor patience compliance. The alternative therapeutic approach employed in the past is combination therapy, which consists of administration of both T3 and T4, either synthetic or in the form of desiccated thyroid extract. Here, issues are present regarding the lack of regulation concerning formulation and lack of data regarding safety and efficacy of these treatment methods. Tissue engineering and regenerative medicine have been applied in conjunction with each other to restore function of various tissues. Recently, these techniques have been adapted for thyroid tissue, primarily through the fabrication of regenerative scaffolds. Those currently under investigation are composed of either biopolymers or native decellularized extracellular matrix (dECM) in conjunction with either primary thyrocytes or stem cells which have undergone directed thyroid differentiation. Multiple of these scaffolds have successfully restored an athyroid phenotype in vivo. However, further work is needed until clinical translation can be achieved. This is proposed in the form of exploration and combination of materials used to fabricate these scaffolds, the addition of peptides which can aid restoration of tissue homeostasis and additional in vivo experimentation providing data on safety and efficacy of these implants.

Electrospinning Fabrication Methods to Incorporate Laminin in Polycaprolactone for Kidney Tissue Engineering

BACKGROUND

Today's treatment options for renal diseases fall behind the need, as the number of patients has increased considerably over the last few decades. Tissue engineering (TE) is one avenue which may provide a new approach for renal disease treatment. This involves creating a niche where seeded cells can function in an intended way. One approach to TE is combining natural extracellular matrix proteins with synthetic polymers, which has been shown to have many positives, yet a little is understood in kidney. Herein, we investigate the incorporation of laminin into polycaprolactone electrospun scaffolds.

METHOD

The scaffolds were enriched with laminin via either direct blending with polymer solution or in a form of emulsion with a surfactant. Renal epithelial cells (RC-124) were cultured on scaffolds up to 21 days.

RESULTS

Mechanical characterization demonstrated that the addition of the protein changed Young's modulus of polymeric fibres. Cell viability and DNA quantification tests revealed the capability of the scaffolds to maintain cell survival up to 3 weeks in culture. Gene expression analysis indicated healthy cells via three key markers.

CONCLUSION

Our results show the importance of hybrid scaffolds for kidney tissue engineering.

Expanding the Repertoire of Electrospinning: New and Emerging Biopolymers, Techniques, and Applications

Electrospinning has emerged as a versatile and accessible technology for fabricating polymer fibers, particularly for biological applications. Natural polymers or biopolymers (including synthetically derivatized natural polymers) represent a promising alternative to synthetic polymers, as materials for electrospinning. Many biopolymers are obtained from abundant renewable sources, are biodegradable, and possess inherent biological functions. This review surveys recent literature reporting new fibers produced from emerging biopolymers, highlighting recent developments in the use of sulfated polymers (including carrageenans and glycosaminoglycans), tannin derivatives (condensed and hydrolyzed tannins, tannic acid), modified collagen, and extracellular matrix extracts. The proposed advantages of these biopolymer-based fibers, focusing on their biomedical applications, are also discussed to highlight the use of new and emerging biopolymers (or new modifications to well-established ones) to enhance or achieve new properties for electrospun fiber materials.

Electrospun fibre diameter and its effects on vascular smooth muscle cells

Bypass grafting is a technique used in the treatment of vascular disease, which is currently the leading cause of mortality worldwide. While technology has moved forward over the years, synthetic grafts still show significantly lower rates of patency in small diameter bypass operations compared to the gold standard (autologous vessel grafts). Scaffold morphology plays an important role in vascular smooth muscle cell (VSMC) performance, with studies showing how fibre alignment and surface roughness can modulate phenotypic and genotypic changes. Herein, this study has looked at how the fibre diameter of electrospun polymer scaffolds can affect the performance of seeded VSMCs. Four different scaffolds were electrospun with increasing fibre sizes ranging from 0.75 to 6 µm. Culturing VSMCs on the smallest fibre diameter (0.75 µm) lead to a significant increase in cell viability after 12 days of culture. Furthermore, interesting trends were noted in the expression of two key phenotypic genes associated with mature smooth muscle cell contractility (myocardin and smooth muscle alpha-actin 1), whereby reducing the fibre diameter lead to relative upregulations compared to the larger fibre diameters. These results showed that the smallest (0.75 µm) fibre diameter may be best suited for the culture of VSMCs with the aim of increasing cell proliferation and aiding cell maturity.

Architected fibrous scaffolds for engineering anisotropic tissues

Mimicking the native three-dimensional microenvironment is of crucial importance when biofabricating a new healthcare material. One aspect of the native tissue that is often omitted when designing a suitable scaffold is its anisotropy. Not only is matching native mechanical properties important when designing implantable scaffolds or healthcare materials, but matching physiological structure is also important as many cell populations respond differently to fiber orientation. Therefore, novel aligned electrospun scaffolds with varying fiber angles and spacing of bundles were created and mechanically characterized. Through controlling the angle between the fibers in each layer of the scaffold, a range of different physiological anisotropic mechanical properties were achieved that encompasses values found in native tissues. Extrapolation of this mechanical data allowed for any native tissue's anisotropic Young's modulus to be mimicked by electrospinning fibers at a particular angle. These electrospun scaffolds were then incorporated with cell-laden hydrogels to create hybrid structures that contain the benefits of both scaffolding techniques with the ability to encapsulate cells in the hydrogel. To conclude, this study develops a novel bundled fiber scaffold that was architected to yield anisotropic properties matching native tissues.

From cells-on-a-chip to organs-on-a-chip: scaffolding materials for 3D cell culture in microfluidics

It is an emerging research area to integrate scaffolding materials in microfluidic devices for 3D cell culture (organs-on-a-chip). The technology of organs-on-a-chip holds the potential to obviate the gaps between pre-clinical and clinical studies. As accumulating evidence shows the importance of extracellular matrix in in vitro cell culture, significant efforts have been made to integrate 3D ECM/scaffolding materials in microfluidics. There are two families of materials that are commonly used for this purpose: hydrogels and electrospun fibers. In this review, we briefly discuss the properties of the materials, and focus on the various technologies to obtain the materials (e.g. extraction of collagen from animal tissues) and to include the materials in microfluidic devices. Challenges and potential solutions of the current materials and technologies were also thoroughly discussed. At the end, we provide a perspective on future efforts to make these technologies more translational to broadly benefit pharmaceutical and pathophysiological research.

Material Characterisation and Stratification of Conjunctival Epithelial Cells on Electrospun Poly(ε-Caprolactone) Fibres Loaded with Decellularised Tissue Matrices

The conjunctiva, an under-researched yet incredibly important tissue, plays key roles in providing protection to the eye and maintaining homeostasis of its ocular surface. Multiple diseases can impair conjunctival function leading to severe consequences that require surgical intervention. Small conjunctival defects can be repaired relatively easily, but larger defects rely on tissue grafts which generally do not provide adequate healing. A tissue engineering approach involving a biomaterial substrate capable of supporting a stratified epithelium with embedded, mucin-secreting goblet cells offers a potential solution. As a first step, this study aimed to induce stratification of human conjunctival epithelial cells cultured on electrospun scaffolds composed from poly(ε-caprolactone) (PCL) and decellularised tissue matrix (small intestinal submucosa (SIS) or urinary bladder matrix (UBM)) and held at the air/liquid interface. Stratification, up to 5 cell layers, occurred more frequently on scaffolds containing PCL + UBM. Incorporation of these decellularised tissue matrices also impacted material properties, with significant changes occurring to their fibre diameter, tensile properties, and chemical composition throughout the scaffold structure compared to PCL alone. These matrix containing scaffolds warrant further long-term investigation as a potential advanced therapy medicinal product for conjunctiva repair and regeneration.

Response differences of HepG2 and Primary Mouse Hepatocytes to morphological changes in electrospun PCL scaffolds

Liver disease cases are rapidly expanding across the globe and the only effective cure for end-stage disease is a transplant. Transplant procedures are costly and current supply of donor livers does not satisfy demand. Potential drug treatments and regenerative therapies that are being developed to tackle these pressing issues require effective in-vitro culture platforms. Electrospun scaffolds provide bio-mimetic structures upon which cells are cultured to regulate function in-vitro. This study aims to shed light on the effects of electrospun PCL morphology on the culture of an immortalised hepatic cell line and mouse primary hepatocytes. Each cell type was cultured on large 4-5 µm fibres and small 1-2 µm fibres with random, aligned and highly porous cryogenically spun configurations. Cell attachment, proliferation, morphology and functional protein and gene expression was analysed. Results show that fibre morphology has a measurable influence on cellular morphology and function, with the alteration of key functional markers such as CYP1A2 expression.

Modulating electrospun polycaprolactone scaffold morphology and composition to alter endothelial cell proliferation and angiogenic gene response

The aim of this study was to look at how the composition and morphology of polymer scaffolds could be altered to create an optimized environment for endothelial cells. Four polycaprolactone (PCL) scaffolds were electrospun with increasing fibre diameters ranging from 1.64 μm to 4.83 μm. The scaffolds were seeded with human umbilical vein endothelial cells (HUVEC) and cultured for 12 days. PCL scaffolds were then electrospun incorporating decellularized bovine aorta ECM and cultured in a hypoxic environment. We noted deeper cell infiltration on the largest fibre diameter compared to the other three scaffolds which resulted in an increase in the gene expression of CD31; a key angiogenic marker. Increased cell viability and cell proliferation were also noted on the largest fibre. Furthermore, we noted that the incorporation of extracellular matrix (ECM) had minimal effect on cell viability, both in normoxic and hypoxic culture conditions. Our results showed that these environments had limited influences on hypoxic gene expression. Interestingly, the major findings from this study was the production of excretory ECM components as shown in the scanning electron microscopy (SEM) images. The results from this study suggest that fibre diameter had a bigger impact on the seeded HUVECs than the incorporation of ECM or the culture conditions. The largest fibre dimeter (4.83 μm) is more suitable for seeding of HUVECs.

Poly(ε-caprolactone) Titanium Dioxide and Cefuroxime Antimicrobial Scaffolds for Cultivation of Human Limbal Stem Cells

Limbal Stem Cell Deficiency (LSCD) is a very serious and painful disease that often results in impaired vision. Cultivation of limbal stem cells for clinical application is usually performed on carriers such as amniotic membrane or surgical fibrin gel. Transplantation of these grafts is associated with the risk of local postoperative infection that can destroy the graft and devoid therapeutic benefit. For this reason, electrospun scaffolds are good alternatives, as proven to mimic the natural cells surroundings, while their fabrication technique is versatile with regard to polymer functionalization and scaffolds architecture. This study considers the development of poly(ε-caprolactone) (PCL) immune-compatible and biodegradable electrospun scaffolds, comprising cefuroxime (CF) or titanium dioxide (TiO₂) active components, that provide both bactericidal activity against eye infections and support of limbal stem cells growth in vitro. The PCL/CF scaffolds were prepared by blend electrospinning, while functionalization with the TiO₂ particles was performed by ultrasonic post-processing treatment. The fabricated scaffolds were evaluated in regard to their physical structure, wetting ability, static and dynamic mechanical behaviour, antimicrobial efficiency and drug release, through scanning electron microscopy, water contact angle measurement, tensile testing and dynamic mechanical analysis, antimicrobial tests and UV-Vis spectroscopy, respectively. Human limbal stem cells, isolated from surgical remains of human cadaveric cornea, were cultured on the PCL/CF and PCL/TiO₂ scaffolds and further identified through immunocytochemistry in terms of cell type thus were stained against p63 marker for limbal stem cells, a nuclear transcription factor and cytokeratin 3 (CK3), a corneal epithelial differentiation marker. The electrospun PCL/CF and PCL/TiO₂ successfully supported the adhesion, proliferation and differentiation of the cultivated limbal cells and provided the antimicrobial effect against Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans.

Integrational Technologies for the Development of Three-Dimensional Scaffolds as Platforms in Cartilage Tissue Engineering

The prevalence of osteoarthritis is on the rise, and an effective treatment for cartilage defects is still being sought. Cartilage tissue in vivo encompasses complex structures and composition, both of which influence cells and many properties of the native cartilage. The extracellular matrix structure and components provides both morphological cues and the necessary signals to promote cell functions including metabolism, proliferation, and differentiation. In the present study, cryo-printing and electrospinning were combined to produce multizone scaffolds that consist of three distinctive zones. These scaffolds successfully mimic the collagen fiber orientation of the native cartilage. Moreover, in vitro analysis of chondrocyte-seeded scaffolds demonstrated the ability of multizone scaffolds to support long-term chondrocyte attachment and survival over a 5 week culture period. Moreover, multizone scaffolds were found to regulate the expression of key genes in comparison to the controls and allowed the detection of sulfated glycosaminoglycan. Evaluation of the compressive properties revealed that the multizone scaffolds possess more suitable mechanical properties, for the native cartilage, in comparison to the electrospun and phase-separated controls. Multizone scaffolds provide viable initial platforms that capture the complex structure and compressive properties of the native cartilage. They also maintain chondrocyte phenotype and function, highlighting their potential in cartilage tissue engineering applications.

Hybrid cardiovascular sourced extracellular matrix scaffolds as possible platforms for vascular tissue engineering

The aim when designing a scaffold is to provide a supportive microenvironment for the native cells, which is generally achieved by structurally and biochemically imitating the native tissue. Decellularized extracellular matrix (ECM) possesses the mechanical and biochemical cues designed to promote native cell survival. However, when decellularized and reprocessed, the ECM loses its cell supporting mechanical integrity and architecture. Herein, we propose dissolving the ECM into a polymer/solvent solution and electrospinning it into a fibrous sheet, thus harnessing the biochemical cues from the ECM and the mechanical integrity of the polymer. Bovine aorta and myocardium were selected as ECM sources. Decellularization was achieved using sodium dodecyl sulfate (SDS), and the ECM was combined with polycaprolactone and hexafluoro-2-propanol for electrospinning. The scaffolds were seeded with human umbilical vein endothelial cells (HUVECs). The study found that the inclusion of aorta ECM increased the scaffold's wettability and subsequently lead to increased HUVEC adherence and proliferation. Interestingly, the inclusion of myocardium ECM had no effect on wettability or cell viability. Furthermore, gene expression and mechanical changes were noted with the addition of ECM. The results from this study show the vast potential of electrospun ECM/polymer bioscaffolds and their use in tissue engineering.