Mouse Models for Human Skin Transplantation: A Systematic Review

Nutritional Aspects, Chemistry Profile, Extraction Techniques of Lemongrass Essential Oil and It's Physiological Benefits

Lemongrass contains a variety of substances that are known to have antioxidant and disease-preventing properties, including essential oils, compounds, minerals, and vitamins. Lemongrass (Cymbopogon Spp.) essential oil (LGEO) has been demonstrated to ameliorate diabetes and accelerate wound healing. A member of the Poaceae family, Lemongrass, a fragrant plant, is cultivated for the extraction of essential oils including myrcene and a mixture of geranial and neral isomers of citral monoterpenes. Active constituents in lemongrass essential oil are myrcene, followed by limonene and citral along with geraniol, citronellol, geranyl acetate, neral, and nerol, which are beneficial to human health. A large part of lemongrass' expansion is driven by the plant's huge industrial potential in the food, cosmetics, and medicinal sectors. A great deal of experimental and modeling study was conducted on the extraction of essential oils. Using Google Scholar and PubMed databases, a systematic review of the literature covering the period from 1996 to 2022 was conducted, in accordance with the PRISMA declaration. There were articles on chemistry, biosynthesis, extraction techniques and worldwide demand of lemongrass oil. We compared the effectiveness of several methods of extracting lemongrass essential oil, including solvent extraction, supercritical CO2 extraction, steam distillation, hydrodistillation (HD), and microwave aided hydrodistillation (MAHD). Moreover, essential oils found in lemongrass and its bioactivities have a significant impact on human health. This manuscript demonstrates the different extraction techniques of lemongrass essential oil and its physiological benefits on diabetic wound healing, tissue repair and regeneration, as well as its immense contribution in ameliorating arthritis and joint pain.Key teaching pointsThe international market demand prediction and the pharmacological benefits of the Lemongrass essential oil have been thoroughly reported here.This article points out that different extraction techniques yield different percentages of citral and other secondary metabolites from lemon grass, for example, microwave assisted hydrodistillation and supercritical carbon dioxide extraction process yields more citral.This article highlights the concept and application of lemongrass oil in aromatherapy, joint-pain, and arthritis.Moreover, this manuscript includes a discussion about the effect of lemongrass oil on diabetic wound healing and tissue regeneration - that paves the way for further research.

The Development of an Advanced Model for Multilayer Human Skin Reconstruction In Vivo

Human skin reconstruction on immune-deficient mice has become indispensable for in vivo studies performed in basic research and translational laboratories. Further advancements in making sustainable, prolonged skin equivalents to study new therapeutic interventions rely on reproducible models utilizing patient-derived cells and natural three-dimensional culture conditions mimicking the structure of living skin. Here, we present a novel step-by-step protocol for grafting human skin cells onto immunocompromised mice that requires low starting cell numbers, which is essential when primary patient cells are limited for modeling skin conditions. The core elements of our method are the sequential transplantation of fibroblasts followed by keratinocytes seeded into a fibrin-based hydrogel in a silicone chamber. We optimized the fibrin gel formulation, timing for gel polymerization in vivo, cell culture conditions, and seeding density to make a robust and efficient grafting protocol. Using this approach, we can successfully engraft as few as 1.0 × 106 fresh and 2.0 × 106 frozen-then-thawed keratinocytes per 1.4 cm2 of the wound area. Additionally, it was concluded that a successful layer-by-layer engraftment of skin cells in vivo could be obtained without labor-intensive and costly methodologies such as bioprinting or engineering complex skin equivalents. Key features • Expands upon the conventional skin chamber assay method (Wang et al., 2000) to generate high-quality skin grafts using a minimal number of cultured skin cells. • The proposed approach allows the use of frozen-then-thawed keratinocytes and fibroblasts in surgical procedures. • This system holds promise for evaluating the functionality of skin cells derived from induced pluripotent stem cells and replicating various skin phenotypes. • The entire process, from thawing skin cells to establishing the graft, requires 54 days. Graphical overview.

Blank Spots in the Map of Human Skin: The Challenge for Xenotransplantation

Most of the knowledge about human skin homeostasis, development, wound healing, and diseases has been accumulated from human skin biopsy analysis by transferring from animal models and using different culture systems. Human-to-mouse xenografting is one of the fundamental approaches that allows the skin to be studied in vivo and evaluate the ongoing physiological processes in real time. Humanized animals permit the actual techniques for tracing cell fate, clonal analysis, genetic modifications, and drug discovery that could never be employed in humans. This review recapitulates the novel facts about mouse skin self-renewing, regeneration, and pathology, raises issues regarding the gaps in our understanding of the same options in human skin, and postulates the challenges for human skin xenografting.

Mouse Models for Human Herpesviruses

More than one hundred herpesviruses have been isolated from different species so far, with nine infecting humans. Infections with herpesviruses are characterized by life-long latency and represent a significant challenge for human health. To investigate the consequences of infections and identify novel treatment options, in vivo models are of particular relevance. The mouse has emerged as an economical small animal model to investigate herpesvirus infections. However, except for herpes simplex viruses (HSV-1, HSV-2), human herpesviruses cannot infect mice. Three natural herpesviruses have been identified in mice: mouse-derived cytomegalovirus (MCMV), mouse herpesvirus 68 (MHV-68), and mouse roseolovirus (MRV). These orthologues are broadly used to investigate herpesvirus infections within the natural host. In the last few decades, immunocompromised mouse models have been developed, allowing the functional engraftment of various human cells and tissues. These xenograft mice represent valuable model systems to investigate human-restricted viruses, making them particularly relevant for herpesvirus research. In this review, we describe the various mouse models used to study human herpesviruses, thereby highlighting their potential and limitations. Emphasis is laid on xenograft mouse models, covering the development and refinement of immune-compromised mice and their application in herpesvirus research.

Protocol for xenotransplantation of human skin and streptozotocin diabetes induction in immunodeficient mice to study impaired wound healing

Here, we present a protocol for the integration of human skin onto the backs of diabetic immunodeficient mice, providing a versatile in vivo model for mimicking and studying mechanisms involved in impaired cutaneous wound healing. This protocol includes instructions for the grafting of human skin, induction of diabetes using streptozotocin and wounding/post-wounding care of immunodeficient mice, as well as suggested downstream tissue analyses. This preclinical mouse model can be used to validate the efficacy of newly developed wound dressings. For complete details on the use and execution of this protocol, please refer to Theocharidis et al. (2022).1.

Navitoclax (ABT-263) Rejuvenates Human Skin by Eliminating Senescent Dermal Fibroblasts in a Mouse/Human Chimeric Model

Chronic senescence, such as aging, contributes to age-related tissue dysfunction and disease development. The accumulation of senescent fibroblasts and the senescence-associated secretory phenotype is particularly implicated in this process. Removal of senescent cells has been reported to prevent tissue dysfunction and to extend the life span during aging. ABT-263 (navitoclax), which inhibits antiapoptotic proteins, is a leading antiaging drug; however, its role in human skin aging is unclear. This study aimed to determine the rejuvenating effects of ABT-263 on aging skin using a human skin graft mouse model. We assessed the viability of ABT-263-treated skin fibroblasts after inducing senescence. Aged human skin was transplanted under the back skin of nude mice and injected intraperitoneally with the drug or control. Analysis of the skin specimens revealed that ABT-263 induced selective elimination of senescent dermal fibroblasts. Senescent human skin treated with ABT-263 exhibited a decrease in the number of senescent cells and in the expression of aging-related secretory phenotype molecules, such as matrix metalloproteinases and interleukins and an increase in collagen density. Our results indicate that selective removal of senescent skin cells with ABT-263 can improve the aging phenotype of human skin without side effects. ABT-263 is, thus, a novel potential therapeutic agent for skin aging.

Glutaminase inhibitors rejuvenate human skin via clearance of senescent cells: a study using a mouse/human chimeric model

Skin aging caused by various endogenous and exogenous factors results in structural and functional changes to skin components. However, the role of senescent cells in skin aging has not been clarified. To elucidate the function of senescent cells in skin aging, we evaluated the effects of the glutaminase inhibitor BPTES (bis-2-(5-phenylacetamido-1, 3, 4-thiadiazol-2-yl)ethyl sulfide) on human senescent dermal fibroblasts and aged human skin. Here, primary human dermal fibroblasts (HDFs) were induced to senescence by long-term passaging, ionizing radiation, and treatment with doxorubicin, an anticancer drug. Cell viability of HDFs was assessed after BPTES treatment. A mouse/human chimeric model was created by subcutaneously transplanting whole skin grafts from aged humans into nude mice. The model was treated intraperitoneally with BPTES or vehicle for 30 days. Skin samples were collected and subjected to reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting, and histological analysis. BPTES selectively eliminated senescent dermal fibroblasts regardless of the method used to induce senescence; aged human skin grafts treated with BPTES exhibited increased collagen density, increased cell proliferation in the dermis, and decreased aging-related secretory phenotypes, such as matrix metalloprotease and interleukin. These effects were maintained in the grafts 1 month after termination of the treatment. In conclusion, selective removal of senescent dermal fibroblasts can improve the skin aging phenotype, indicating that BPTES may be an effective novel therapeutic agent for skin aging.