Bioengineered skin substitutes: key elements and novel design for biomedical applications

A focused review on three-dimensional bioprinting technology for artificial organ fabrication

Three-dimensional (3D) bioprinting technology has attracted a great deal of interest because it can be easily adapted to many industries and research sectors, such as biomedical, manufacturing, education, and engineering. Specifically, 3D bioprinting has provided significant advances in the medical industry, since such technology has led to significant breakthroughs in the synthesis of biomaterials, cells, and accompanying elements to produce composite living tissues. 3D bioprinting technology could lead to the immense capability of replacing damaged or injured tissues or organs with newly dispensed cell biomaterials and functional tissues. Several types of bioprinting technology and different bio-inks can be used to replicate cells and generate supporting units as complex 3D living tissues. Bioprinting techniques have undergone great advancements in the field of regenerative medicine to provide 3D printed models for numerous artificial organs and transplantable tissues. This review paper aims to provide an overview of 3D-bioprinting technologies by elucidating the current advancements, recent progress, opportunities, and applications in this field. It highlights the most recent advancements in 3D-bioprinting technology, particularly in the area of artificial organ development and cancer research. Additionally, the paper speculates on the future progress in 3D-bioprinting as a versatile foundation for several biomedical applications.

A suspended layer additive manufacturing approach to the bioprinting of tri-layered skin equivalents

Skin exhibits a complex structure consisting of three predominant layers (epidermis, dermis, and hypodermis). Extensive trauma may result in the loss of these structures and poor repair, in the longer term, forming scarred tissue and associated reduction in function. Although a number of skin replacements exist, there have been no solutions that recapitulate the chemical, mechanical, and biological roles that exist within native skin. This study reports the use of suspended layer additive manufacturing to produce a continuous tri-layered implant, which closely resembles human skin. Through careful control of the bioink composition, gradients (chemical and cellular) were formed throughout the printed construct. Culture of the model demonstrated that over 21 days, the cellular components played a key role in remodeling the supporting matrix into architectures comparable with those of healthy skin. Indeed, it has been demonstrated that even at seven days post-implantation, the integration of the implant had occurred, with mobilization of the adipose tissue from the surrounding tissue into the construct itself. As such, it is believed that these implants can facilitate healing, commencing from the fascia, up toward the skin surface-a mechanism recently shown to be key within deep wounds.

Future applications of 3D bioprinting: A promising technology for treating recessive dystrophic epidermolysis bullosa

Three-dimensional (3D) bioprinting is a rapidly developing technology that has the potential to initiate a paradigm shift in the treatment of skin wounds arising from burns, ulcers and genodermatoses. Recessive dystrophic epidermolysis bullosa (RDEB), a severe form of epidermolysis bullosa, is a rare genodermatosis that results in mechanically induced blistering of epithelial tissues that leads to chronic wounds. Currently, there is no cure for RDEB, and effective treatment is limited to protection from trauma and extensive bandaging. The care of chronic wounds and burns significantly burdens the healthcare system, further illustrating the dire need for more beneficial wound care. However, in its infancy, 3D bioprinting offers therapeutic potential for wound healing and could be a breakthrough technology for the treatment of rare, incurable genodermatoses like RDEB. This viewpoint essay outlines the promise of 3D bioprinting applications for treating RDEB, including skin regeneration, a delivery system for gene-edited cells and small molecules, and disease modelling. Although the future of 3D bioprinting is encouraging, there are many technical challenges to overcome-including optimizing bioink and cell source-before this approach can be widely implemented in clinical practice.

Human umbilical cord mesenchymal stem cells in type 2 diabetes mellitus: the emerging therapeutic approach

The umbilical cord has been proved to be an easy-access, reliable, and useful source of mesenchymal stem cells (MSC) for clinical applications due to its primitive, immunomodulatory, non-immunogenic, secretory and paracrine, migratory, proliferative, and multipotent properties. This set of characteristics has recently attracted great research interest in the fields of nanotechnology and regenerative medicine and cellular therapy. Accumulating evidence supports a pronounced therapeutic potential of MSC in many different pathologies, from hematology to immunology, wound-healing, tissue regeneration, and oncology. Diabetes mellitus, branded the epidemic of the century, is considered a chronic metabolic disorder, representing a major burden for health system sustainability and an important public health challenge to modern societies. The available treatments for type 2 diabetes mellitus (T2DM) still rely mainly on combinations of oral antidiabetic agents with lifestyle and nutritional adjustments. Despite the continuous development of novel and better hypoglycemic drugs, their efficacy is limited in the installment and progression of silent T2DM complications. T2DM comorbidities and mortality rates still make it a serious, common, costly, and long-term manageable disease. Recently, experimental models, preclinical observations, and clinical studies have provided some insights and preliminary promising results using umbilical cord MSCs to treat and manage diabetes. This review focuses on the latest research and applications of human-derived umbilical cord MSC in the treatment and management of T2DM, exploring and systematizing the key effects of both umbilical cord MSC and its factor-rich secretome accordingly with the major complications associated to T2DM.

Biologic and Synthetic Cellular and/or Tissue-Based Products and Smart Wound Dressings/Coverings

Cellular and/or tissue-based products (CTPs) have advanced greatly in the past several decades and improve the ability to heal wounds more efficiently. Products can be characterized as nonviable cells, tissue based, animal; nonviable cells, tissue based, human; viable human cells, cultured in vitro, animal substrate; viable human cells, cultured in vitro, synthetic substrate; viable human cells, noncultured, intact tissue. There are approximately 77 different CTPs at the time of this writing, with many more being investigated. Cellular and/or tissue-based product selection, application, postapplication course, and patient selection depend on patient attributes, CTP specifications, and surgeon preference.

Bioengineered Skin Intended for Skin Disease Modeling

Clinical use of bioengineered skin in reconstructive surgery has been established for more than 30 years. The limitations and ethical considerations regarding the use of animal models have expanded the application of bioengineered skin in the areas of disease modeling and drug screening. These skin models should represent the anatomical and physiological traits of native skin for the efficient replication of normal and pathological skin conditions. In addition, reliability of such models is essential for the conduction of faithful, rapid, and large-scale studies. Therefore, research efforts are focused on automated fabrication methods to replace the traditional manual approaches. This report presents an overview of the skin models applicable to skin disease modeling along with their fabrication methods, and discusses the potential of the currently available options to conform and satisfy the demands for disease modeling and drug screening.

Annexin A12-26 Treatment Improves Skin Heterologous Transplantation by Modulating Inflammation and Angiogenesis Processes

Skin graft successful depends on reduction of local inflammation evoked by the surgical lesion and efficient neovascularization to nutrition the graft. It has been shown that N-terminal portion of the Annexin A1 protein (AnxA1) with its anti-inflammatory properties induces epithelial mucosa repair and presents potential therapeutic approaches. The role of AnxA1 on wound healing has not been explored and we investigated in this study the effect of the peptide Ac2-26 (N-terminal AnxA1 peptide Ac2-26; AnxA1_2-26) on heterologous skin scaffolds transplantation in BALB/c mice, focusing on inflammation and angiogenesis. Treatment with AnxA1_2-26, once a day, from day 3-60 after scaffold implantation improved the take of the implant, induced vessels formation, enhanced gene and protein levels of the vascular growth factor-A (VEGF-A) and fibroblast influx into allograft tissue. It also decreased pro- while increasing anti-inflammatory cytokines. The pro-angiogenic activity of AnxA1_2-26 was corroborated by topical application of AnxA1_2-26 on the subcutaneous tissue of mice. Moreover, treatment of human umbilical endothelial cells (HUVECs) with AnxA1_2-26 improved proliferation, shortened cycle, increased migration and actin polymerization similarly to those evoked by VEGF-A. The peptide treatment instead only potentiated the tube formation induced by VEGF-A. Collectively, our data showed that AnxA1_2-26 treatment favors the tissue regeneration after skin grafting by avoiding exacerbated inflammation and improving the angiogenesis process.

Polylactic acid (PLA) controlled delivery carriers for biomedical applications

Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.

MALDI-MSI for the analysis of a 3D tissue-engineered psoriatic skin model

MALDI-MS Imaging is a novel label-free technique that can be used to visualize the changes in multiple mass responses following treatment. Following treatment with proinflammatory cytokine interleukin-22 (IL-22), the epidermal differentiation of Labskin, a living skin equivalent (LSE), successfully modeled psoriasis in vitro. Masson's trichrome staining enabled visualization and quantification of epidermal differentiation between the untreated and IL-22 treated psoriatic LSEs. Matrix-assisted laser desorption ionization mass spectrometry imaging was used to observe the spatial location of the psoriatic therapy drug acetretin following 48 h treatments within both psoriatic and normal LSEs. After 24 h, the drug was primarily located in the epidermal regions of both the psoriatic and nonpsoriatic LSE models whereas after 48 h it was detectible in the dermis.

Wound-healing potential of human umbilical cord blood-derived mesenchymal stromal cells in vitro--a pilot study

BACKGROUND AIMS

Our previous studies demonstrated that human bone marrow-derived mesenchymal stromal cells have great potential for wound healing. However, it is difficult to clinically utilize cultured stem cells. Recently, human umbilical cord blood-derived mesenchymal stromal cells (hUCB-MSCs) have been commercialized for cartilage repair as a first cell therapy product that uses allogeneic stem cells. Should hUCB-MSCs have a superior effect on wound healing as compared with fibroblasts, which are the main cell source in current cell therapy products for wound healing, they may possibly replace fibroblasts. The purpose of this in vitro study was to compare the wound-healing activity of hUCB-MSCs with that of fibroblasts.

METHODS

This study was particularly designed to compare the effect of hUCB-MSCs on diabetic wound healing with those of allogeneic and autologous fibroblasts. Healthy (n = 5) and diabetic (n = 5) fibroblasts were used as the representatives of allogeneic and autologous fibroblasts for diabetic patients in the control group. Human UCB-MSCs (n = 5) were used in the experimental group. Cell proliferation, collagen synthesis and growth factor (basic fibroblast growth factor, vascular endothelial growth factor and transforming growth factor-β) production were compared among the three cell groups.

RESULTS

Human UCB-MSCs produced significantly higher amounts of vascular endothelial growth factor and basic fibroblast growth factor when compared with both fibroblast groups. Human UCB-MSCs were superior to diabetic fibroblasts but not to healthy fibroblasts in collagen synthesis. There were no significant differences in cell proliferation and transforming growth factor-β production.

CONCLUSIONS

Human UCB-MSCs may have greater capacity for diabetic wound healing than allogeneic or autologous fibroblasts, especially in angiogenesis.

Recent accomplishments in wound healing

The challenge to balance limited resources with infinite demand has encouraged an evolution in the way health care services are managed and operated. Chronic wound management is complex and prolonged, and places a considerable financial burden on health services. A typical driver of cost includes the necessity to change dressings on a regular basis. Over the last few decades, several scientific and biological advances have furthered the development of wound care products and facilitated wound management. This article investigates some of the major advancements that have occurred within the wound-care arena during the last 5 years and how these advancements are being translated to provide better delivery of clinical care to patients.