Fibrin improves skin wound perfusion in a diabetic rat model

Advancements in 3D skin bioprinting: processes, bioinks, applications and sensor integration

This comprehensive review explores the multifaceted landscape of skin bioprinting, revolutionizing dermatological research. The applications of skin bioprinting utilizing techniques like extrusion-, droplet-, laser- and light-based methods, with specialized bioinks for skin biofabrication have been critically reviewed along with the intricate aspects of bioprinting hair follicles, sweat glands, and achieving skin pigmentation. Challenges remain with the need for vascularization, safety concerns, and the integration of automated processes for effective clinical translation. The review further investigates the incorporation of biosensor technologies, emphasizing their role in monitoring and enhancing the wound healing process. While highlighting the remarkable progress in the field, critical limitations and concerns are critically examined to provide a balanced perspective. This synthesis aims to guide scientists, engineers, and healthcare providers, fostering a deeper understanding of the current state, challenges, and future directions in skin bioprinting for transformative applications in tissue engineering and regenerative medicine.

Spatially Guided Construction of Multilayered Epidermal Models Recapturing Structural Hierarchy and Cell-Cell Junctions

A current challenge in three-dimensional (3D) bioprinting of skin equivalents is to recreate the distinct basal and suprabasal layers and to promote their direct interactions. Such a structural arrangement is essential to establish 3D stratified epidermis disease models, such as for the autoimmune skin disease pemphigus vulgaris (PV), which targets the cell-cell junctions at the interface of the basal and suprabasal layers. Inspired by epithelial regeneration in wound healing, we develop a method that combines 3D bioprinting and spatially guided self-reorganization of keratinocytes to recapture the fine structural hierarchy that lies in the deep layers of the epidermis. Here, keratinocyte-laden fibrin hydrogels are bioprinted to create geographical cues, guiding dynamic self-reorganization of cells through collective migration, keratinocyte differentiation and vertical expansion. This process results in a region of self-organized multilayers (SOMs) that contain the basal to suprabasal transition, marked by the expressed levels of different types of keratins that indicate differentiation. Finally, we demonstrate the reconstructed skin tissue as an in vitro platform to study the pathogenic effects of PV and observe a significant difference in cell-cell junction dissociation from PV antibodies in different epidermis layers, indicating their applications in the preclinical test of possible therapies.

The effects of oral mucosa-derived heterotopic fibroblasts on cutaneous wound healing

An intriguing observation that has recently found support through clinical and experimental studies is that wounds of the oral mucosa tend to display faster healing and result in less scarring than in the skin. We aimed to investigate the potential of heterotopic oral mucosal fibroblasts in cutaneous wounds while determining the main differences between wounds conditioned with either the oral mucosa or dermis-derived human fibroblasts. A total of 48 nude mice were divided into four groups: control, sham, dermal fibroblast (DF), and oral fibroblast (OF). Fibroblasts were isolated, cultured, and seeded onto fibrin scaffolds for transfer to full-thickness dorsal wounds. Cell viability, wound area, healing rate, vascularization, cellular proliferation, dermal thickness, collagen architecture, and subtypes were evaluated. Both cell groups had a viability of 95% in fibrin gel prior to transfer. None of the wounds fully epithelialized on day 10, while all were epithelialized by day 21, which resulted in scars of different sizes and quality. Healing rate and scars were similar between the control and sham groups, whereas fastest healing and least scarring were noted in the OF group. Dermal thickness was highest in the DF group, which was also supported by highest levels of collagen types I and III. Proliferative cells and vascular density were highest in the OF group. DF result in healing through a thick dermal component, while oral fibroblasts result in faster healing and less scarring through potentially privileged angiogenic and regenerative gene expression.

Ferulic acid loaded microspheres reinforced in 3D hybrid scaffold for antimicrobial wound dressing

Here we report the preparation of biomimetic fibrin/chitosan/keratin hybrid scaffolds with a synergistic combination of ferulic acid loaded silica microspheres for antimicrobial wound dressing applications. The infrared and X-ray powder diffraction studies confirm the homogenous nature of the prepared hybrid scaffolds without any major interactions between the constituents. The developed hybrid scaffolds show good thermal, porosity, compression and water uptake properties. Scanning electron microscopic analysis shows that the as-synthesized ferulic acid loaded silica microspheres exhibit an average size of 35 ± 10 μm and also exposes the smooth surface with interconnected porosity in the prepared hybrid scaffolds. The incorporated ferulic acid loaded silica microspheres hybrid scaffolds show effective antimicrobial activity against the common wound pathogens. In vitro NIH3T3 fibroblast cell culture and drug release studies reveal that the prepared hybrid scaffolds have enhanced cell proliferation and adhesion with a prolonged drug release for about 72 h. In vitro wound healing and actin cytoskeleton analysis reveal that the incorporated ferulic acid loaded silica microspheres in fibrin/chitosan/keratin hybrid scaffolds facilitates cell growth and migration to damaged area through cell-cell interactions. These results suggest that the prepared hybrid scaffolds with ferulic acid loaded silica microspheres have great potential for soft tissue engineering applications particularly for the treatment of chronic and infected wounds.

Strategies to use fibrinogen as bioink for 3D bioprinting fibrin-based soft and hard tissues

Fibrin gel has been widely used for engineering various types of tissues due to its biocompatible nature, biodegradability, and tunable mechanical and nanofibrous structural properties. Despite their promising regenerative capacity and extensive biocompatibility with various tissue types, fibrin-based biomaterials are often notoriously known as burdensome candidates for 3D biofabrication and bioprinting. The high viscosity of fibrin (crosslinked form) hinders proper ink extrusion, and its pre-polymer form, fibrinogen, is not capable of maintaining shape fidelity. To overcome these limitations and empower fibrinogen-based bioinks for fibrin biomimetics and regenerative applications, different strategies can be practiced. The aim of this review is to report the strategies that bring fabrication compatibility to these bioinks through mixing fibrinogen with printable biomaterials, using supporting bath supplemented with crosslinking agents, and crosslinking fibrin in situ. Moreover, the review discusses some of the recent advances in 3D bioprinting of biomimetic soft and hard tissues using fibrinogen-based bioinks, and highlights the impacts of these strategies on fibrin properties, its bioactivity, and the functionality of the consequent biomimetic tissue. Statement of Significance Due to its biocompatible nature, biodegradability, and tunable mechanical and nanofibrous structural properties, fibrin gel has been widely employed in tissue engineering and more recently, used as in 3D bioprinting. The fibrinogen's poor printable properties make it difficult to maintain the 3D shape of bioprinted constructs. Our work describes the strategies employed in tissue engineering to allow the 3D bioprinting of fibrinogen-based bioinks, such as the combination of fibrinogen with printable biomaterials, the in situ fibrin crosslinking, and the use of supporting bath supplemented with crosslinking agents. Further, this review discuss the application of 3D bioprinting technology to biofabricate fibrin-based soft and hard tissues for biomedical applications, and discuss current limitations and future of such in vitro models.

Topical Topiramate Improves Wound Healing in an Animal Model of Hyperglycemia

Wound healing is severely affected in hyperglycemia and other metabolic conditions. Finding new therapeutic approaches that accelerate wound healing and improve the quality of the scar may reduce the morbidity commonly associated with skin lesions in diabetes. This study evaluated the effect of topical topiramate (TPM) on wound healing in C57 mice. Streptozotocin-induced hyperglycemic mice were subjected to a wound on the back and randomly allocated for treatment with either vehicle or topical TPM cream (2%) once a day for 14 days. Polymerase chain reaction, Western blotting, and microscopy were performed for the analysis. TPM improved wound healing (complete resolution at Day 10, 98% ± 5 for TPM vs. 81% ± 28 for vehicle), increased organization and deposition of collagen Type I, and enhanced the quality of the scars as determined by microscopy. In addition, TPM modulated the expression of cytokines and proteins of the insulin-signaling pathway: In early wound-healing stages, expression of interleukin-10, an anti-inflammatory marker, increased, whereas at the late phase, the pro-inflammatory markers tumor necrosis factor-α and monocyte chemoattractant protein-1 increased and there was increased expression of a vascular endothelial growth factor. Proteins of the insulin-signaling pathway were stimulated in the late wound-healing phase. Topical TPM improves the quality of wound healing in an animal model of hyperglycemia. The effect of TPM is accompanied by modulation of inflammatory and growth factors and proteins of the insulin-signaling pathway. Therefore, topical TPM presents as a potential therapeutic agent in skin wounds in patients with hyperglycemia.

Advances in Protein-Based Materials: From Origin to Novel Biomaterials

Biomaterials play a very important role in biomedicine and tissue engineering where they directly affect the cellular activities and their microenvironment . Myriad of techniques have been employed to fabricate a vast number natural, artificial and recombinant polymer s in order to harness these biomaterials in tissue regene ration , drug delivery and various other applications. Despite of tremendous efforts made in this field during last few decades, advanced and new generation biomaterials are still lacking. Protein based biomaterials have emerged as an attractive alternatives due to their intrinsic properties like cell to cell interaction , structural support and cellular communications. Several protein based biomaterials like, collagen , keratin , elastin , silk protein and more recently recombinant protein s are being utilized in a number of biomedical and biotechnological processes. These protein-based biomaterials have enormous capabilities, which can completely revolutionize the biomaterial world. In this review, we address an up-to date review on the novel, protein-based biomaterials used for biomedical field including tissue engineering, medical science, regenerative medicine as well as drug delivery. Further, we have also emphasized the novel fabrication techniques associated with protein-based materials and implication of these biomaterials in the domain of biomedical engineering .

Plasticity of oral mucosal cell sheets for accelerated and scarless skin wound healing

OBJECTIVES

Wound healing is generally faster and associated with less scarring in the oral mucosa than in the skin. Although rarely studied, oral mucosa equivalents may contribute to rapid, scarless cutaneous wound healing. Therefore, we examined the potential utility of our newly developed oral mucosal cell sheet in skin wound healing.

MATERIALS AND METHODS

Oral mucosa and skin samples were obtained from surgical patients and Sprague-Dawley rats. Keratinocytes and fibroblasts were primarily cultured for in vitro cell expansion. Mucosa and skin equivalents were produced with a mixture of cultured fibroblasts and autologous fibrin from plasma and seeding keratinocytes. Mucosal and skin cell sheets were transplanted in full-thickness excisional wounds of rat skin with control wounds. Gross, histological, and molecular characteristics of wound healing according to different postsurgical days were compared in control and cell sheet-covered wounds.

RESULTS

Keratinocytes and fibroblasts derived from the oral mucosa were cultured faster than those derived from the skin. The in vitro-engineered oral mucosa and skin equivalents were successfully produced using complete autologous mucosa or skin and plasma fibrin, showing similarity to the histological characteristics of the skin or mucosa. In the in vivo rat model, the oral mucosal and skin cell sheet promoted wound healing with early wound closure and less scarring. The cell sheet-treated wounds showed lower TGF-β1, α-smooth muscle actin, and fibronectin mRNA expression than the control wounds.

CONCLUSIONS

The oral mucosal cell sheet demonstrated in vivo tissue plasticity through good adaptation to skin wounds, contributing to accelerated and scarless healing.

Recent advances in biomaterials for the treatment of diabetic foot ulcers

Diabetes mellitus is one of the most challenging epidemics facing the world today, with over 300 million patients affected worldwide. A significant complication associated with diabetes is hyperglycemia, which impairs wound healing. The rise in the diabetic patient population in recent years has precipitated an increase in the incidence and prevalence of chronic diabetic wounds, most commonly the diabetic foot ulcer. Although foot ulcers are difficult to treat due to their complicated pathology, outcomes have improved with the development of increasingly sophisticated biomaterials that accelerate healing. In this review, we describe recently developed biomaterials that elicit healing through cell-material interactions and/or the sustained delivery of drugs. These tunable therapeutic systems increase angiogenesis, collagen deposition, cell proliferation, and growth factors concentrations, while decreasing inflammation and enzymatic degradation of the extracellular matrix. As the field of biomaterials for wound healing continues to mature, we expect to witness a broader range of clinical options that will speed healing times and improve patient quality of life.