The healing effect of unrestricted somatic stem cells loaded in collagen-modified nanofibrous PHBV scaffold on full-thickness skin defects

Stem Cells and Nanofibers for Skin Regeneration and Wound Healing

Stem cells have been attractive targets for tissue regeneration due to their inherent ability to differentiate into various specialized cell types; however, efforts for stem cell transplantation for the treatment of degenerated tissues have been hampered by the propensity of some stem cell types to form teratomas and the lessened viability of stem cells after transplantation. These disadvantages can be prevented using tailored extracellular matrix-like materials that can be used as an aid for the transplantation of stem cells. Nanomaterials, in particular nanofibers, have great potential to be used as extracellular matrix-like materials for this purpose. In this article, we will review the use of stem cells and nanofibers for skin regeneration and wound healing.

Influence of Electrospinning Parameters on the Morphology of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fibrous Membranes and Their Application as Potential Air Filtration Materials

A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Polyhydroxyalkonates (PHAs) are receiving increasing attention because of the unique biodegradability and biocompatibility they offer. However, the applications of PHAs are still limited due to high production costs and insufficient study. This project examines the optimal electrospinning parameters for the production of PHA-based fibrous membranes for air filtration. A common biodegradable polyester, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was electrospun into a nanofibrous membrane with a well-controlled surface microstructure. In order to produce smooth, bead-free fibers with micron-scale diameters, the effect of the process parameters (applied electric field, solution flow rate, inner diameter of hollow needle, and polymer concentration) on the electrospun fiber microstructure was optimized. The well-defined fibrous structure was optimized at an applied electric field of 20 kV, flow rate of 0.5 mL/h, solution concentration of 12 wt.%, and needle inner diameter of 0.21 mm. The morphology of the electrospun PHBV fibrous membrane was observed by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) and Raman spectroscopy were used to explore the chemical signatures and phases of the electrospun PHBV nanofiber. The ball burst strength (BBS) was measured to assess the mechanical strength of the membrane. The small pore size of the nanofiber membranes ensured they had good application prospects in the field of air filtration. The particle filtration efficiency (PFE) of the optimized electrospun PHBV fibrous membrane was above 98% at standard atmospheric pressure.

Polyhydroxyalkanoates: the natural biopolyester for future medical innovations

Polyhydroxyalkanoates (PHAs) are a family of natural microbial biopolyesters with the same basic chemical structure and diverse side chain groups. Based on their excellent biodegradability, biocompatibility, thermoplastic properties and diversity, PHAs are highly promising medical biomaterials and elements of medical devices for applications in tissue engineering and drug delivery. However, due to the high cost of biotechnological production, most PHAs have yet to be applied in the clinic and have only been studied at laboratory scale. This review focuses on the biosynthesis, diversity, physical properties, biodegradability and biosafety of PHAs. We also discuss optimization strategies for improved microbial production of commercial PHAs via novel synthetic biology tools. Moreover, we also systematically summarize various medical devices based on PHAs and related design approaches for medical applications, including tissue repair and drug delivery. The main degradation product of PHAs, 3-hydroxybutyrate (3HB), is recognized as a new functional molecule for cancer therapy and immune regulation. Although PHAs still account for only a small percentage of medical polymers, up-and-coming novel medical PHA devices will enter the clinical translation stage in the next few years.

Vascularization of cutaneous wounds by stem cells

Differentiated skin cells have limited self-renewal capacity; thus, the application of stem/progenitor cells, adult or induced stem cells, has attracted much attention for wound healing applications. Upon skin injury, vascularization, known as a highly dynamic process, occurs with the contribution of cells, the extracellular matrix, and relevant growth factors. Considering the importance of this process in tissue regeneration, several strategies have been proposed to enhance angiogenesis and accelerate wound healing. Previous studies report the effectiveness of stem/progenitor cells in skin wound healing by facilitating the vascularization process. This chapter reviews and highlights some of the key and recent investigations on application of stem/progenitor cells to induce skin revascularization after trauma.

Healing effect of acellular fish skin with plasma rich in growth factor on full-thickness skin defects

Acellular skin as a scaffold has a good potential to regenerate or repair damaged tissues. Growth factors such as Plasma Rich in Growth Factor (PRGF) as a rich source of active proteins can accelerate tissue regeneration. In this study, an acellular scaffold derived from fish skin with growth factors was used to repair full-thickness skin defects in a rat model. Cellular results demonstrated that epithelial cells adhere well to acellular scaffolds. The results of animal studies showed that the groups treated with acellular scaffold and growth factor have a high ability to close and heal wounds on the 28th day after surgery. Histological and staining results showed that in the treated groups with scaffold and growth factor, an epidermal layer was formed with some skin appendages similar to normal skin. Overall, such scaffolds with biological agents can cause an acceptable synergistic effect on skin regeneration and wound healing.

Electrospun Nanofibers Revisited: An Update on the Emerging Applications in Nanomedicine

Electrospinning (ES) has become a straightforward and customizable drug delivery technique for fabricating drug-loaded nanofibers (NFs) using various biodegradable and non-biodegradable polymers. One of NF's pros is to provide a controlled drug release through managing the NF structure by changing the spinneret type and nature of the used polymer. Electrospun NFs are employed as implants in several applications including, cancer therapy, microbial infections, and regenerative medicine. These implants facilitate a unique local delivery of chemotherapy because of their high loading capability, wide surface area, and cost-effectiveness. Multi-drug combination, magnetic, thermal, and gene therapies are promising strategies for improving chemotherapeutic efficiency. In addition, implants are recognized as an effective antimicrobial drug delivery system overriding drawbacks of traditional antibiotic administration routes such as their bioavailability and dosage levels. Recently, a sophisticated strategy has emerged for wound healing by producing biomimetic nanofibrous materials with clinically relevant properties and desirable loading capability with regenerative agents. Electrospun NFs have proposed unique solutions, including pelvic organ prolapse treatment, viable alternatives to surgical operations, and dental tissue regeneration. Conventional ES setups include difficult-assembled mega-sized equipment producing bulky matrices with inadequate stability and storage. Lately, there has become an increasing need for portable ES devices using completely available off-shelf materials to yield highly-efficient NFs for dressing wounds and rapid hemostasis. This review covers recent updates on electrospun NFs in nanomedicine applications. ES of biopolymers and drugs is discussed regarding their current scope and future outlook.

Design of a decellularized fish skin as a biological scaffold for skin tissue regeneration

The use of decellularized natural skin as an extracellular matrix (ECM) may be a great candidate to regenerate damaged tissues. In this study, decellularized scaffolds from fish skin were designed by different techniques (physical, chemical, and enzymatic methods) and investigated by analyses such as Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Tensile strength, Degradability, Histological studies, Toxicity test, and Determination of DNA content. Results showed that the best sample is related to the decellularized skin by hypertonic & hypotonic technique and Triton X100 solutions. Structural and mechanical results were demonstrated that samples have similar properties to human skin to regenerate it. The cytotoxicity results showed that decellularized skin by hypertonic & hypotonic method and Triton solution is non-toxic with minimal amount of genetic materials. Cellular results with epithelial cells indicated good adhesion on decellularized matrix, so it can be a suitable candidate for skin tissue regeneration.

Prevention of excessive scar formation using nanofibrous meshes made of biodegradable elastomer poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

To reduce excessive scarring in wound healing, electrospun nanofibrous meshes, composed of haloarchaea-produced biodegradable elastomer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), are fabricated for use as a wound dressing. Three PHBV polymers with different 3HV content are used to prepare either solution-cast films or electrospun nanofibrous meshes. As 3HV content increases, the crystallinity decreases and the scaffolds become more elastic. The nanofibrous meshes exhibit greater elasticity and elongation at break than films. When used to culture human dermal fibroblasts in vitro, PHBV meshes give better cell attachment and proliferation, less differentiation to myofibroblasts, and less substrate contraction. In a full-thickness mouse wound model, treatment with films or meshes enables regeneration of pale thin tissues without scabs, dehydration, or tubercular scar formation. The epidermis of wounds treated with meshes develop small invaginations in the dermis within 2 weeks, indicating hair follicle and sweat gland regeneration. Consistent with the in vitro results, meshes reduce myofibroblast differentiation in vivo through downregulation of α-SMA and TGF-β1, and upregulation of TGF-β3. The regenerated wounds treated with meshes are softer and more elastic than those treated with films. These results demonstrate that electrospun nanofibrous PHBV meshes mitigate excessive scar formation by regulating myofibroblast formation, showing their promise for use as wound dressings.

Skin regenerative medicine advancements in the Islamic Republic of Iran: a concise review

In the last decade, the Islamic Republic of Iran has witnessed significant improvement and growth in the field of interdisciplinary medicine and in its translation to patients, including the field of cell and stem cell therapy. The main aim of this report is to highlight various advances in regenerative medicine for skin and dermatology using stem cell technology, and its translation to clinic in the past two decades, in Iranian academic centers, clinical institutes and hospitals. While there have been numerous positive advances in clinical outcomes reported in Iran, there is no comparative analytical information on these studies. Here we present a historical overview of the progress and key advancements seen in skin regeneration in this country, review the research frameworks, regulatory approach and pathways and offer perspectives for the future.

Biomimetic Properties of Force-Spun PHBV Membranes Functionalised with Collagen as Substrates for Biomedical Application

The force-spinning process parameters (i.e., spin speed, spinneret-collector distance, and polymer concentration), optimised and characterised in previous work by this group, allowed the rapid fabrication of large quantities of high surface area poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) polymeric fibre membranes. This paper examined the potential application for force-spun PHBV fibres functionalised with type I collagen for tissue regeneration applications. PHBV fibre scaffolds provide a biologically suitable substrate to guide the regeneration of dermal tissues, however, have poor cellular adhesion properties. The grafting of collagen type-I to PHBV fibres demonstrated improved cell adhesion and growth in Neo-NHDF (neonatal human dermal fibroblasts) fibroblasts. The examination of fibre morphology, thermal properties, collagen content, and degradability was used to contrast the physicochemical properties of the PHBV and PHBV-Collagen fibres. Biodegradation models using phosphate buffered saline determined there was no appreciable change in mass over the course of 6 weeks; a Sirius Red assay was performed on degraded samples, showing no change in the quantity of collagen. Cell metabolism studies showed an increase in cell metabolism on conjugated samples after three and 7 days. In addition, in vitro cytocompatibility studies demonstrated superior cell activity and adhesion on conjugated samples over 7 days.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) improved osteogenic differentiation of the human induced pluripotent stem cells while considered as an artificial extracellular matrix

Cocell polymers can be the best implants for replacing bone defects in patients. The pluripotent stem cells produced from the patient and the nanofibrous polymeric scaffold that can be completely degraded in the body and its produced monomers could be also usable are the best options for this implant. In this study, electrospun poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers were fabricated and characterized and then osteogenic differentiation of the human-induced pluripotent stem cells (iPSCs) was investigated while cultured on PHBV scaffold. MTT results showed that cultured iPSCs on PHBV proliferation were increased compared to those cultured on tissue culture polystyrene (TCPS) as the control. Alkaline phosphatase (ALP) activity and calcium content were also significantly increased in iPSCs cultured on PHBV compared to the cultured on TCPS under osteogenic medium. Gene expression evaluation demonstrated that Runx2, collagen type I, ALP, osteonectin, and osteocalcin were upregulated in iPSCs cultured on PHBV scaffold in comparison with those cultured on TCPS for 2 weeks. Western blot analysis have shown that osteocalcin and osteopontin expression as two major osteogenic markers were increased in iPSCs cultured on PHBV scaffold. According to the results, nanofiber-based PHBV has a promising potential to increase osteogenic differentiation of the stem cells and iPSCs-PHBV as a cell-co-polymer construct demonstrated that has a great efficiency for use as a bone tissue engineered bioimplant.

The effect of the carbodiimide cross-linker on the structural and biocompatibility properties of collagen-chondroitin sulfate electrospun mat

BACKGROUND

Collagen and chondroitin sulfate (CS) are an essential component of the natural extracellular matrix (ECM) of most tissues. They provide the mechanical stability to cone the compressive forces in ECM. In tissue engineering, electrospun nanofibrous scaffolds prepared by electrospinning technique have emerged as a suitable candidate to imitate natural ECM functions. Cross-linking with 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride/N-hydroxy succinimide can overcome the weak mechanical integrity of the engineered scaffolds in addition to the increased degradation stability under physiological conditions.

MATERIALS AND METHODS

This study has synthesized nanofibrous collagen-CS scaffolds by using the electrospinning method.

RESULTS

The results have shown that incorporation of CS in higher concentration, along with 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride/N-hydroxy succinimide, enhanced mechanical stability. Scaffolds showed more resistance to collagenase digestion. Fabricated scaffolds showed biocompatibility in corneal epithelial cell attachment.

CONCLUSION

These results demonstrate that cross-linked electrospun CO-CS mats exhibited a uniform nanofibrous and porous structure, especially for lower concentration of the cross-linker and may be utilized as an alternative effective substrate in tissue engineering.

3D bio-printing technology for body tissues and organs regeneration

In the last decade, the use of new technologies in the reconstruction of body tissues has greatly developed. Utilising stem cell technology, nanotechnology and scaffolding design has created new opportunities in tissue regeneration. The use of accurate engineering design in the creation of scaffolds, including 3D printers, has been widely considered. Three-dimensional printers, especially high precision bio-printers, have opened up a new way in the design of 3D tissue engineering scaffolds. In this article, a review of the latest applications of this technology in this promising area has been addressed.

Unrestricted somatic stem cells, as a novel feeder layer: Ex vivo culture of human limbal stem cells

Ex vivo culture of limbal stem cells (LSCs) is a current promising approach for reconstruction of the ocular surface. In this context, 3T3 feeder layer cells (mouse embryo fibroblast) are generally utilized to maintain and expand LSCs. The aim of this study is to develop a novel culture method (animal-derived products free) to expand LSCs, using umbilical cord derived human unrestricted somatic stem cells (hUSSCs) instead of 3T3 cell with an emphasis on maintaining of the Stemness in LSCs. Using flow-cytometer, isolated hUSSCs were characterized for CD105, CD90, CD166, CD34, CD45, CD31 cell surface markers and their differentiation capability into adipogenic as well as osteogenic lineages were evaluated. In addition to colony-forming efficiency (CFE), epithelial lineage differentiation and karyotyping, LSC properties were evaluated for ABCG2, ΔNP63-α, CK19, CK3, and CK12 mRNA and protein expressions using quantitative RT-PCR (qRT-PCR) and immunocytochemistry, when these cells were co-cultured with hUSSCs (in comparison with 3T3 feeder layer). LSCs, co-cultured with hUSSCs, showed normal karyotype (46, XX), while they could efficiently form colony (86 ± 3) and display up-regulation of the genes associated with stemness and down-regulation of corneal epithelial differentiation genes. Consistent with 3T3 feeder cells, hUSSCs with spindle-shaped morphology and quick splitting up properties had ability to preserve the stem like-cell phenotype of LSCs. These findings were confirmed by qRT-PCR and flow-cytometer. Findings of present study suggest hUSSCs as a promising alternative method for 3T3 feeder layer cells, to preserve growth and stemness of LSCs ex vivo culture.

Paediatric nanofibrous bioprosthetic heart valve

The search for an optimal aortic valve implant with durability, calcification resistance, excellent haemodynamic parameters and ability to withstand mechanical loading is yet to be met. Thus, there has been struggled to fabricate bio-prosthetics heart valve using bioengineering. The consequential product must be resilient with suitable mechanical features, biocompatible and possess the capacity to grow. Defective heart valves replacement by surgery is now common, this improves the value and survival of life for a lot of patients. The recent paediatric heart valve implant is suboptimal due to their inability of somatic growth. They usually have multiple surgeries to change outgrown valves. Short-lived valve bio-prostheses occurring in older patients and younger ones who more usually need the replacement of its damaged heart with prosthesis led to a new invasive surgical interventions with an improved quality of life. The authors propose that nanofibre scaffold for paediatric tissue-engineered heart valve will meet most of these conditions, most particularly those related to somatic growth, and, as the nanofibre scaffold is eroded, new valve is produced, the valve matures in the child until adulthood.

Recent advances on biomedical applications of scaffolds in wound healing and dermal tissue engineering

The tissue engineering field has developed in response to the shortcomings related to the replacement of the tissues lost to disease or trauma: donor tissue rejection, chronic inflammation and donor tissue shortages. The driving force behind the tissue engineering is to avoid the mentioned issues by creating the biological substitutes capable of replacing the damaged tissue. This is done by combining the scaffolds, cells and signals in order to create the living, physiological, three-dimensional tissues. A wide variety of skin substitutes are used in the treatment of full-thickness injuries. Substitutes made from skin can harbour the latent viruses, and artificial skin grafts can heal with the extensive scarring, failing to regenerate structures such as glands, nerves and hair follicles. New and practical skin scaffold materials remain to be developed. The current article describes the important information about wound healing scaffolds. The scaffold types which were used in these fields were classified according to the accepted guideline of the biological medicine. Moreover, the present article gave the brief overview on the fundamentals of the tissue engineering, biodegradable polymer properties and their application in skin wound healing. Also, the present review discusses the type of the tissue engineered skin substitutes and modern wound dressings which promote the wound healing.

Electrospun poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite scaffold with unrestricted somatic stem cells for bone regeneration

The combination of scaffolds and cells can be useful in tissue reconstruction. In this study, nanofibrous poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/nanohydroxyapatite (nano-HAp) scaffolds, filled with unrestricted somatic stem cells (USSCs), were used for healing calvarial bone in rat model. The healing effects of these scaffolds, with and without stem cells, in bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting. The results of CT analysis showed that bone regeneration on the scaffolds, and the amounts of regenerated new bone for polymer/nano-HAp scaffold with USSC, was significantly greater than the scaffold without cell and untreated control samples. Therefore, the combination of scaffold especially with USSC could be considered as a useful method for bone regeneration.

Electrospun mat with eyelid fat-derived stem cells as a scaffold for ocular epithelial regeneration

The aim of this study was to develop nanofibrous gelatin substrates for eyelid fat stem cell (EFSC) expansion that can serve as a potential alternative substrate to replace human amniotic membrane. Biocompatibility results indicated that all substrates were highly biocompatible, as EFSCs could favorably attach and proliferate on the nanofibrous surfaces. Microscopic figures showed that the EFSC were firmly anchored to the substrates and were able to retain a normal stem cell phenotype. Immunocytochemistry (ICC) and real time-PCR results revealed change in the expression profile of EFSCs grown on nanofibrous substrates when compared to those grown on control in epithelial induction condition. In addition, electrospun gelatin mats especially oriented scaffold provides not only a milieu supporting EFSCs expansion, but also serves as a useful alternative carrier for ocular surface tissue engineering and could be used as an alternative substrate to amniotic membrane.

Human unrestricted somatic stem cells loaded in nanofibrous PCL scaffold and their healing effect on skin defects

Unrestricted somatic stem cells (USSCs) loaded in nanofibrous polycaprolactone (PCL) scaffolds can be used for skin regeneration when grafted onto full-thickness skin defects of rats. Nanofibrous PCL scaffolds were designed by the electrospinning method and crosslinked with laminin protein. Afterwards, the scaffolds were evaluated by scanning electron microscopy, and physical and mechanical assays. In this study, nanofibrous PCL scaffolds loaded with USSCs were grafted onto the skin defects. The wounds were subsequently investigated 21 days after grafting. Results of mechanical and physical analyses showed good resilience and compliance to movement as a skin graft. In animal models; study samples exhibited the most pronounced effect on wound closure, with statistically significant improvement in wound healing being seen at 21 days post-operatively. Histological examinations of healed wounds from all samples showed a thin epidermis plus recovered skin appendages in the dermal layer for samples with cell. Thus, the graft of nanofibrous PCL scaffolds loaded with USSC showed better results during the healing process of skin defects in rat models.

New advances in the mesenchymal stem cells therapy against skin flaps necrosis

Mesenchymal stem cells (MSCs), multipotential cells that reside within the bone marrow, can be induced to differentiate into various cells, such as osteoblasts, adipocytes, chondrocytes, vascular endothelial progenitor cells, and other cell types. MSCs are being widely studied as potential cell therapy agents due to their angiogenic properties, which have been well established by in vitro and in vivo researches. Within this context, MSCs therapy appears to hold substantial promise, particularly in the treatment of conditions involving skin grafts, pedicle flaps, as well as free flaps described in literatures. The purpose of this review is to report the new advances and mechanisms underlying MSCs therapy against skin flaps necrosis.

Efficacy of nanofibrous conduits in repair of long-segment sciatic nerve defects

Our previous studies have histomorphologically confirmed that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit can be used to repair 30-mm-long sciatic nerve defects. However, the repair effects on rat behaviors remain poorly understood. In this study, we used nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit and autologous sciatic nerve to bridge 30-mm-long rat sciatic nerve gaps. Within 4 months after surgery, rat sciatic nerve functional recovery was evaluated per month by behavioral analyses, including toe out angle, toe spread analysis, walking track analysis, extensor postural thrust, swimming test, open-field analysis and nociceptive function. Results showed that rat sciatic nerve functional recovery was similar after nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit and autologous nerve grafting. These findings suggest that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) conduit is suitable in use for repair of long-segment sciatic nerve defects.