Bioingeniería cutánea: aplicaciones preclínicas y clínicas

Plasma-Based Scaffold Containing Bone-Marrow Mononuclear Cells Promotes Wound Healing in a Mouse Model of Pressure Injury

Pressure injuries, or pressure ulcers, are a common problem that may lead to infections and major complications, besides being a social and economic burden due to the costs of treatment and hospitalization. While surgery is sometimes necessary, this also has complications such as recurrence or wound dehiscence. Among the newer methods of pressure injury treatment, advanced therapies are an interesting option. This study examines the healing properties of bone marrow mononuclear cells (BM-MNCs) embedded in a plasma-based scaffold in a mouse model. Pressure ulcers were created on the backs of mice (2 per mouse) using magnets and assigned to a group of ulcers that were left untreated (Control, n = 15), treated with plasma scaffold (Plasma, n = 15), or treated with plasma scaffold containing BM-MNC (Plasma + BM-MNC, n = 15). Each group was examined at three time points (3, 7, and 14 days) after the onset of treatment. At each time point, animals were subjected to biometric assessment, bioluminescence imaging, and tomography. Once treatment had finished, skin biopsies were processed for histological and wound healing reverse transcription polymerase chain reaction (RT-PCR) array studies. While wound closure percentages were higher in the Plasma and Plasma + BM-MNC groups, differences were not significant, and thus descriptive data are provided. In all individuals, the presence of donor cells was revealed by immunohistochemistry on posttreatment onset Days 3, 7, and 14. In the Plasma + BM-MNC group, less inflammation was observed by positron emission tomography-computed tomography (PET/CT) imaging of the mice at 7 days, and a complete morphometabolic response was produced at 14 days, in accordance with histological results. A much more pronounced inflammatory process was observed in controls than in the other two groups, and this persisted until Day 14 after treatment onset. RT-PCR array gene expression patterns were also found to vary significantly, with the greatest difference noted between both treatments at 14 days when 11 genes were differentially expressed.

Role of Cultured Skin Fibroblasts in Regenerative Dermatology

The skin, as the largest organ, covers the entire outer part of the body, and since this organ is directly exposed to microbial, thermal, mechanical and chemical damage, it may be destroyed by factors such as acute trauma, chronic wounds or even surgical interventions. Cell therapy is one of the most important procedures to treat skin lesions. Fibroblasts are cells that are responsible for the synthesis of collagen, elastin, and the organization of extracellular matrix (ECM) components and have many vital functions in wound healing processes. Today, cultured autologous fibroblasts are used to treat wrinkles, scars, wounds and subcutaneous atrophy. The results of many studies have shown that fibroblasts can be effective and beneficial in the treatment of skin lesions. On the other hand, skin substitutes are used as a regenerative model to improve and regenerate the skin. The use of these alternatives, restorative medicine and therapeutic cells such as fibroblasts has tremendous potential in the treatment of skin diseases and can be a new window for the treatment of diseases with no definitive treatment. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description ofthese Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Tie-Over Bolster Pressure Dressing Improves Outcomes of Skin Substitutes Xenografts on Athymic Mice

The efficacy of skin substitutes is established for the treatment of burn injuries, but its use is not limited to this condition. This technology has the potential to improve the treatment of various conditions by offering highly advanced and personalized treatments. In vivo studies are challenging but essential to move to clinical use in humans. Mice are the most widely used species in preclinical studies, but the main drawback of this model is the limited surface area of the graft in long-term transplantation studies caused by the displacement and the contraction of the graft. We improved the conventional surgical procedures by stabilizing the chamber covering the graft with intramuscular sutures and by adding a tie-over bolster dressing. The current study was therefore performed to compare outcomes of skin grafts between the conventional and optimized skin graft model. Human self-assembled skin substitutes (SASSs) were prepared and grafted to athymic mice either by the conventional method or by the new grafting method. Graft healing and complications were assessed using digital photographs on postoperative days 7, 14, and 21. Similar structure and organization were observed by histological staining. The new grafting method reduced medium and large displacement events by 1.26-fold and medium and large contraction events by 1.8-fold, leading to a 1.6-fold increase in graft surface area compared to skin substitutes grafted with the usual method. This innovation ensures better reproducibility and consistency of skin substitute transplants on mice.

Bioprinting and plastic compression of large pigmented and vascularized human dermo-epidermal skin substitutes by means of a new robotic platform

Extensive availability of engineered autologous dermo-epidermal skin substitutes (DESS) with functional and structural properties of normal human skin represents a goal for the treatment of large skin defects such as severe burns. Recently, a clinical phase I trial with this type of DESS was successfully completed, which included patients own keratinocytes and fibroblasts. Yet, two important features of natural skin were missing: pigmentation and vascularization. The first has important physiological and psychological implications for the patient, the second impacts survival and quality of the graft. Additionally, accurate reproduction of large amounts of patient’s skin in an automated way is essential for upscaling DESS production. Therefore, in the present study, we implemented a new robotic unit (called SkinFactory) for 3D bioprinting of pigmented and pre-vascularized DESS using normal human skin derived fibroblasts, blood- and lymphatic endothelial cells, keratinocytes, and melanocytes. We show the feasibility of our approach by demonstrating the viability of all the cells after printing in vitro, the integrity of the reconstituted capillary network in vivo after transplantation to immunodeficient rats and the anastomosis to the vascular plexus of the host. Our work has to be considered as a proof of concept in view of the implementation of an extended platform, which fully automatize the process of skin substitution: this would be a considerable improvement of the treatment of burn victims and patients with severe skin lesions based on patients own skin derived cells.

Tissue engineering in dermatology - from lab to market

Tissue Engineering is a branch of regenerative medical technology which helps replace damaged tissue using appropriate scaffolding, living cells, and growth factors. Using tissue engineering products can be a promising method for treating skin lesions such as wounds and deep burns. The interaction and interconnection of cells within the bio-culture medium or within a three-dimensional scaffold provides the conditions for tissue regeneration and subsequent healing of skin wounds. Tissue engineering in the field of dermatology has evolved over time from a single application of skin cells or biopolymer scaffolds to the use of cell and scaffold combinations for the treatment, repair, and closure of acute and chronic skin wounds. It has evolved. This technology has reached a point where most products are accepted, and the body rejects a small number, which strengthens the tissue engineering market. In this article, we aimed to review and study the market of this field by reviewing various articles on tissue engineering in the field of dermatology. Tissue-engineered skin substitutes are future options for wound healing and tissue regeneration strategies.

Formulation and Evaluation of Microwave-Modified Chitosan-Curcumin Nanoparticles-A Promising Nanomaterials Platform for Skin Tissue Regeneration Applications Following Burn Wounds

Improved physicochemical properties of chitosan-curcumin nanoparticulate carriers using microwave technology for skin burn wound application are reported. The microwave modified low molecular weight chitosan variant was used for nanoparticle formulation by ionic gelation method nanoparticles analyzed for their physicochemical properties. The antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa cultures, cytotoxicity and cell migration using human dermal fibroblasts-an adult cell line-were studied. The microwave modified chitosan variant had significantly reduced molecular weight, increased degree of deacetylation and decreased specific viscosity. The nanoparticles were nano-sized with high positive charge and good dispersibility with entrapment efficiency and drug content in between 99% and 100%, demonstrating almost no drug loss. Drug release was found to be sustained following Fickian the diffusion mechanism for drug release with higher cumulative drug release observed for formulation (F)2. The microwave treatment does not render a destructive effect on the chitosan molecule with the drug embedded in the core of nanoparticles. The optimized formulation precluded selected bacterial strain colonization, exerted no cytotoxic effect, and promoted cell migration within 24 h post application in comparison to blank and/or control application. Microwave modified low molecular weight chitosan-curcumin nanoparticles hold potential in delivery of curcumin into the skin to effectively treat skin manifestations.

Engineered Skin Tissue Equivalents for Product Evaluation and Therapeutic Applications

The current status of skin tissue equivalents that have emerged as relevant tools in commercial and therapeutic product development applications is reviewed. Due to the rise of animal welfare concerns, numerous companies have designed skin model alternatives to assess the efficacy of pharmaceutical, skincare, and cosmetic products in an in vitro setting, decreasing the dependency on such methods. Skin models have also made an impact in determining the root causes of skin diseases. When designing a skin model, there are various chemical and physical considerations that need to be considered to produce a biomimetic design. This includes designing a structure that mimics the structural characteristics and mechanical strength needed for tribological property measurement and toxicological testing. Recently, various commercial products have made significant progress towards achieving a native skin alternative. Further research involve the development of a functional bilayered model that mimics the constituent properties of the native epidermis and dermis. In this article, the skin models are divided into three categories: in vitro epidermal skin equivalents, in vitro full-thickness skin equivalents, and clinical skin equivalents. A description of skin model characteristics, testing methods, applications, and potential improvements is presented.

Human Reconstructed Skin in a Mouse Model

Currently, no ideal in vivo skin model, to exactly mimic the native human skin, has been utilized for laboratory and clinical application. Here, we describe a method to in vivo reconstitute a human skin model, so-called hRSK, by using culture-expanded skin cells. We grafted a mixture of dissociated human epidermal and dermal cells onto an excision wound on the back of immunodeficient mouse to generate the hRSK, and the hRSK, containing epidermis, dermis, and subcutis and also appendages such as hair follicles, histologically mirrors in situ human skin.

Genetic diagnosis of epidermolysis bullosa: recommendations from an expert Spanish research group

Epidermolysis bullosa (EB) is a rare genetic disease that causes mucocutaneous fragility. It comprises a clinically and genetically heterogeneous group of disorder characterized by spontaneous or contact/friction-induced blistering. EB is classified into 4 types-simplex, junctional, dystrophic, and Kindler syndrome-and 30 subtypes. The disease is caused by defects in proteins implicated in dermal-epidermal adhesion. At least 19 genes have been characterized and more than 1000 mutations identified, thus rendering diagnosis complex. Molecular diagnosis of EB is the last stage of a laborious process that starts with a detailed clinical history compilation and careful procurement of a skin fresh biopsy that includes an area where the epidermis detaches from the dermis. The detachment area makes it possible to establish the cleavage plane by antigen mapping and, in the best scenario, to identify a single candidate gene to search for pathogenic mutations. The results of the molecular diagnosis enable the physician to provide appropriate genetic counseling (inheritance pattern, risk of recurrence, and options for prenatal and preimplantation diagnosis) and implement subsequent preventive programs, as well as to establish a reasonable clinical prognosis facilitating access to specific therapy and rehabilitation. Lastly, molecular diagnosis is essential for the participation of patients in clinical trials, a critical issue given the current incurable status of EB. The present guidelines aim to disseminate the procedure for diagnosing EB in our laboratory and thus avoid suboptimal or incomplete clinical diagnoses. The recommendations we provide are the result of more than 10 years' experience in the molecular diagnosis of EB in Spain.

Proof of concept of a new autologous skin substitute for the treatment of deep wounds in dogs

Autologous skin grafts are effective for the repair of large skin wounds, but the availability of large amounts of skin is often limited. Through bioengineering, several autologous skin substitutes have been developed for use in human clinical practice. However, few skin substitutes are available for use in animals. The aim of this study was to develop and assess an engineered autologous skin substitute for the treatment of deep wounds in veterinary medicine. Canine keratinocytes and fibroblasts were isolated after double enzyme digestion from 8mm punch biopsies from four healthy Beagle dogs. Skin substitutes were constructed on a fibrin-based matrix and grafting capacity was assessed by xenografting in six athymic mice. Bioengineered autologous skin was assessed clinically in two dogs with large deep skin wounds. The canine skin construct was ready for use within 12-14days after the initial biopsy specimens were obtained. Grafting capacity in this model was confirmed by successful grafting of the construct in athymic mice. In both dogs, grafts were established and permanent epithelialisation occurred. Histological studies confirmed successful grafting. This full thickness skin substitute developed for the management of large skin defects in dogs appears to be a safe and useful tool for clinical veterinary practice. Further studies are needed to validate its efficacy for the treatment of deep wounds.

An advanced mouse model for human skin wound healing

Here, we report a model for studying wound repair based on skin regenerated from human tissue culture-expanded cells. The reconstituted skin (hRSK) responds to injury similar to that of intact human skin, and its constituent cells contribute to the healing process. As we have demonstrated that hRSK composed of GFP-labelled cells also heals "normally," we believe this model will be useful in analysing the wound repair process using genetically modified human cells.

Three-dimensional bio-printing equipment technologies for tissue engineering and regenerative medicine

Three-Dimensional (3D) printing technologies have been widely used in the medical sector for the production of medical assistance equipment and surgical guides, particularly 3D bio-printing that combines 3D printing technology with biocompatible materials and cells in field of tissue engineering and regenerative medicine. These additive manufacturing technologies can make patient-made production from medical image data. Thus, the application of 3D bio-printers with biocompatible materials has been increasing. Currently, 3D bio-printing technology is in the early stages of research and development but it has great potential in the fields of tissue and organ regeneration. The present paper discusses the history and types of 3D printers, the classification of 3D bio-printers, and the technology used to manufacture artificial tissues and organs.

Fibroblast sources: Where can we get them?

Fibroblasts are cells widely used in cell culture, both for transient primary cell culture or permanent as transformed cell lines. Lately, fibroblasts become cell sources for use in disease modeling after cell reprogramming because it is easily accessible in the body. Fibroblasts in patients will maintain all genetic background during reprogramming into induced pluripotent stem cells. In spite of their large use, fibroblasts are obtained after an invasive procedure, a superficial punch skin biopsy, collected under patient's local anesthesia. Taking into consideration the minimum patient's discomfort during and after the biopsy procedure, as well as the aesthetics aspect, it is essential to reflect on the best site of the body for the biopsy procedure combined with the success of getting robust fibroblast cultures in the lab. For this purpose, we compared the efficiency of four biopsy sites of the body (skin from eyelid, back of the ear, abdominal cesarean scar and groin). Cell proliferation assays and viability after cryopreservation were measured. Our results revealed that scar tissue provided fibroblasts with higher proliferative rates. Also, fibroblasts from scar tissues presented a higher viability after the thawing process.

Innovative therapeutic strategies for recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is among the most serious rare skin diseases. It is also the rare skin disease for which most effort has been expended in developing advanced therapeutic interventions. RDEB is caused by collagen VII deficiency resulting from COL7A1 mutations. Therapeutic approaches seek to replenish collagen VII and thus restore dermal-epidermal adhesion. Therapeutic options under development include protein therapy and different cell-based and gene-based therapies. In addition to treating skin defects, some of these therapies may also target internal mucosa. In the coming years, these novel therapeutic approaches should substantially improve the quality of life of patients with RDEB.

Remote diffuse reflectance spectroscopy sensor for tissue engineering monitoring based on blind signal separation

In this study the first results on evaluation and assessment of grafted bioengineered skin substitutes using an optical Diffuse Reflectance Spectroscopy (DRS) system with a remote optical probe are shown. The proposed system is able to detect early vascularization of skin substitutes expressing the Vascular Endothelial Growth Factor (VEGF) protein compared to normal grafts, even though devitalized skin is used to protect the grafts. Given the particularities of the biological problem, data analysis is performed using two Blind Signal Separation (BSS) methods: Principal Component Analysis (PCA) and Independent Component Analysis (ICA). These preliminary results are the first step towards point-of-care diagnostics for skin implants early assessment.

New experimental models of skin homeostasis and diseases

Homeostasis, whose regulation at the molecular level is still poorly understood, is intimately related to the functions of epidermal stem cells. Five research groups have been brought together to work on new in vitro and in vivo skin models through the SkinModel-CM program, under the auspices of the Spanish Autonomous Community of Madrid. This project aims to analyze the functions of DNA methyltransferase 1, endoglin, and podoplanin in epidermal stem cell activity, homeostasis, and skin cancer. These new models include 3-dimensional organotypic cultures, immunodeficient skin-humanized mice, and genetically modified mice. Another aim of the program is to use skin-humanized mice to model dermatoses such as Gorlin syndrome and xeroderma pigmentosum in order to optimize new protocols for photodynamic therapy.

Transplantation of autologous minced bladder mucosa for a one-step reconstruction of a tissue engineered bladder conduit

Surgical intervention is sometimes needed to create a conduit from the abdominal wall to the bladder for self-catheterization. We developed a method for tissue engineering a conduit for bladder emptying without in vitro cell culturing as a one-step procedure. In a porcine animal model bladder, wall tissue was excised and the mucosa was minced to small particles. The particles were attached to a tube in a 1 : 3 expansion rate with fibrin glue and transplanted back by attaching the tube to the bladder and through the abdominal wall. Sham served as controls. After 4-5 weeks, conduits were assessed in respect to macroscopic and microscopic appearance in 6 pigs. Two pigs underwent radiology before termination. Gross examination revealed a patent conduit with an opening to the bladder. Histology and immunostaining showed a multilayered transitional uroepithelium in all cases. Up to 89% of the luminal surface area was neoepithelialized but with a loose attachment to the submucosa. No epithelium was found in control animals. CT imaging revealed a patent channel that could be used for filling and emptying the bladder. Animals that experienced surgical complications did not form conduits. Minced autologous bladder mucosa can be transplanted around a tubular mold to create a conduit to the urinary bladder without in vitro culturing.