Comparison of Human Dermal Fibroblasts and HaCat Cells Cultured in Medium with or without Serum via a Generic Tissue Engineering Research Platform

New Skin-Relevant Cell Coculture Model With Stratum Corneum-Like Layer

Two-dimensional (2D) cell culture is an important tool in the discovery of skin-active agents. Fibroblasts and keratinocytes, more rarely fibroblast-keratinocyte cocultures, are usually used for that purpose, where test compounds are added by mixing with the overlaying growth medium. However, such an approach is suboptimal because it lacks the stratum corneum component. The stratum corneum acts as a selective gatekeeper and opposes the intradermal permeation of many compounds that are bioactive when placed in direct contact with cells. One solution is to use reconstituted epidermis, but this approach is costly and time consuming. Here, a model is proposed, where the simplicity and convenience of the 2D cell culture is combined with the advantage of a hydrophobic barrier reminiscent of the skin horny layer. This model was tested with skin-relevant solvents, as well as with "naked" hydrophilic and encapsulated compounds. Cell viability and collagen stimulation were used as readouts. The results showed that the incorporation of a stratum corneum-substitute barrier on top of a 2D cell culture reduced the cytotoxicity of a common cosmetic solvent, dimethyl isosorbide (DMI), in cell culture and modified the bioactivity of the added actives (magnesium ascorbyl phosphate [MAP] and oligomeric proanthocyanidins [OPCs]/levan biopolymer), which became dependent on their ability to penetrate through a lipidic layer. Taken together, these results indicate a better physiological relevance of this cell culture model in workflows aimed at the discovery and analysis of skin-active compounds than conventional 2D systems.

Integrated Experimental and Mathematical Exploration of Modular Tissue Cultures for Developmental Engineering

Developmental engineering (DE) involves culturing various cells on modular scaffolds (MSs), yielding modular tissues (MTs) assembled into three-dimensional (3D) tissues, mimicking developmental biology. This study employs an integrated approach, merging experimental and mathematical methods to investigate the biological processes in MT cultivation and assembly. Human dermal fibroblasts (HDFs) were cultured on tissue culture plastics, poly(lactic acid) (PLA) discs with regular open structures, or spherical poly(methyl methacrylate) (PMMA) MSs, respectively. Notably, HDFs exhibited flattened spindle shapes when adhered to solid surfaces, and complex 3D structures when migrating into the structured voids of PLA discs or interstitial spaces between aggregated PMMA MSs, showcasing coordinated colonization of porous scaffolds. Empirical investigations led to power law models simulating density-dependent cell growth on solid surfaces or voids. Concurrently, a modified diffusion model was applied to simulate oxygen diffusion within tissues cultured on solid surfaces or porous structures. These mathematical models were subsequently combined to explore the influences of initial cell seeding density, culture duration, and oxygen diffusion on MT cultivation and assembly. The findings underscored the intricate interplay of factors influencing MT design for tissue assembly. The integrated approach provides insights into mechanistic aspects, informing bioprocess design for manufacturing MTs and 3D tissues in DE.

Secretome profile of TNF-α-induced human umbilical cord mesenchymal stem cells unveils biological processes relevant to skin wound healing

Aim: To profile and study the proteins responsible for the beneficial effect of the TNF-α-induced human umbilical cord mesenchymal stem cells (hUCMSCs) secretome in wound healing. Methods: The hUCMSCs secretome was generated with (induced) or without (uninduced) TNF-α and was subsequently analyzed by liquid chromatography-mass spectrometry, immunoassay and in vitro scratch assay. Results: Proteomic analysis revealed approximately 260 proteins, including 51 and 55 unique proteins in the induced and uninduced secretomes, respectively. Gene ontology analysis disclosed that differential proteins in the induced secretome mainly involved inflammation-related terms. The induced secretome, consisting of higher levels of FGFb, VEGF, PDGF and IL-6, significantly accelerated wound closure and enhanced MMP-13 secretion in HaCaT keratinocytes. Conclusion: The secretome from induced hUCMSCs includes factors that promote wound closure.

Toxicity evaluation of Pinus radiata D.Don bark wax for potential cosmetic application

Radiata pine bark is a widely available organic waste, requiring alternative uses due to its environmental impact on soil, fauna, and forest fires. Pine bark waxes could be used as cosmetic substitutes, but their toxicity requires evaluation since pine bark may contain toxic substances or xenobiotics, depending on the extraction process. This study evaluates the toxicity of radiata pine bark waxes obtained through various extraction methods on human skin cells grown in vitro. The assessment includes using XTT to evaluate mitochondrial activity, violet crystal dye to assess cell membrane integrity, and ApoTox-Glo triple assay to measure cytotoxicity, viability, and apoptosis signals. Pine bark waxes extracted via T3 (acid hydrolysis and petroleum ether incubation) and T9 (saturated steam cycle, alkaline hydrolysis, and petroleum ether incubation) exhibit non-toxicity up to 2% concentration, making them a potential substitute for petroleum-based cosmetic materials. Integrating the forestry and cosmetic industries through pine bark wax production under circular economy principles could promote development while replacing petroleum-based materials. Extraction methodology affects pine bark wax toxicity in human skin cells due to the retention of xenobiotic compounds including methyl 4-ketohex-5-enoate; 1-naphthalenol; dioctyl adipate; eicosanebioic acid dimethyl ester; among others. Future research will investigate whether the extraction methodology alters the molecular structure of the bark, affecting the release of toxic compounds in the wax mixture.

Adding a new dimension: Multi-level structure and organization of mixed-species Pseudomonas aeruginosa and Staphylococcus aureus biofilms in a 4-D wound microenvironment

Biofilms in wounds typically consist of aggregates of bacteria, most often Pseudomonas aeruginosa and Staphylococcus aureus, in close association with each other and the host microenvironment. Given this, the interplay across host and microbial elements, including the biochemical and nutrient profile of the microenvironment, likely influences the structure and organization of wound biofilms. While clinical studies, in vivo and ex vivo model systems have provided insights into the distribution of P. aeruginosa and S. aureus in wounds, they are limited in their ability to provide a detailed characterization of biofilm structure and organization across the host-microbial interface. On the other hand, biomimetic in vitro systems, such as host cell surfaces and simulant media conditions, albeit reductionist, have been shown to support the co-existence of P. aeruginosa and S. aureus biofilms, with species-dependent localization patterns and interspecies interactions. Therefore, composite in vitro models that bring together key features of the wound microenvironment could provide unprecedented insights into the structure and organization of mixed-species biofilms. We have built a four-dimensional (4-D) wound microenvironment consisting of a 3-D host cell scaffold of co-cultured human epidermal keratinocytes and dermal fibroblasts, and an in vitro wound milieu (IVWM); the IVWM provides the fourth dimension that represents the biochemical and nutrient profile of the wound infection state. We leveraged this 4-D wound microenvironment, in comparison with biofilms in IVWM alone and standard laboratory media, to probe the structure of mixed-species P. aeruginosa and S. aureus biofilms across multiple levels of organization such as aggregate dimensions and biomass thickness, species co-localization and spatial organization within the biomass, overall biomass composition and interspecies interactions. In doing so, the 4-D wound microenvironment platform provides multi-level insights into the structure of mixed-species biofilms, which we incorporate into the current understanding of P. aeruginosa and S. aureus organization in the wound bed.

Strategically designed SPEEK nanofibrous scaffold with tailored delivery ofresveratrolfor skin wound regeneration

Electro-spinnable polymeric materials can easily form two-dimensional (2D) nanofibrous scaffolds improving biochemical functionalities specially in the area of skin wound healing and nanomedicine, but it has been hard to achieve this on a highly mechanically stable biopolymer, Poly ether ether ketone (PEEK), due to its intrinsic hydrophobicity and chemical inertness. Herein, we demonstrated a novel nanomedicine healing system consisting of sulphonated poly ether ether ketone combined withresveratrol(SPEEK+RSV), which could act as an effective 2D nano bio-materialin vitroandin vivo, without observable cytotoxicity. The fabricated nanocomposites exhibited enriched skin cell proliferation and adhesion as confirmed from the results of MTT, cell adhesion and live-dead assay. Results of SEM analysis showed a uniform nano-sized distribution with adequate pore size and porosity % facilitating a desired breathable environment at the wound site. The results of FT-IR, tensile studies and TGA analyses confirmed the presence of appropriate bonds and improved mechanical stability of theRSVincorporated nanofibrous scaffold. Results of anti-microbial analysis portrayed good potentiality of the fabricated nanofibers in treating wounds colonized with bacterial infections. Controlled drug release of resveratrol established the bio-compatibility of the nanofibers in skin wound regeneration.In vivoanalysis assessed in female Wistar rats enabled complete wound closure with 100 % wound contraction within 16 days. Results of histopathology analysis through H-E and MT staining presented the re-surfing of the wound environment with regeneration of epithelium, granulation tissue and collagen. Thus, the fabricated 2D nanofibrous scaffold incorporated with pharmaceutical RSV bio-medicine perceptively mimicked skin ECM convincingly aiding the progression of skin wound regeneration mechanism.

Integration of a microfluidic multicellular coculture array with machine learning analysis to predict adverse cutaneous drug reactions

Adverse cutaneous reactions are potentially life-threatening skin side effects caused by drugs administered into the human body. The availability of a human-specific in vitro platform that can prospectively screen drugs and predict this risk is therefore of great importance to drug safety. However, since adverse cutaneous drug reactions are mediated by at least 2 distinct mechanisms, both involving systemic interactions between liver, immune and dermal tissues, existing in vitro skin models have not been able to comprehensively recapitulate these complex, multi-cellular interactions to predict the skin-sensitization potential of drugs. Here, we report a novel in vitro drug screening platform, which comprises a microfluidic multicellular coculture array (MCA) to model different mechanisms-of-action using a collection of simplistic cellular assays. The resultant readouts are then integrated with a machine-learning algorithm to predict the skin sensitizing potential of systemic drugs. The MCA consists of 4 cell culture compartments connected by diffusion microchannels to enable crosstalk between hepatocytes that generate drug metabolites, antigen-presenting cells (APCs) that detect the immunogenicity of the drug metabolites, and keratinocytes and dermal fibroblasts, which collectively determine drug metabolite-induced FasL-mediated apoptosis. A single drug screen using the MCA can simultaneously generate 5 readouts, which are integrated using support vector machine (SVM) and principal component analysis (PCA) to classify and visualize the drugs as skin sensitizers or non-skin sensitizers. The predictive performance of the MCA and SVM classification algorithm is then validated through a pilot screen of 11 drugs labelled by the US Food and Drug Administration (FDA), including 7 skin-sensitizing and 4 non-skin sensitizing drugs, using stratified 4-fold cross-validation (CV) on SVM. The predictive performance of our in vitro model achieves an average of 87.5% accuracy (correct prediction rate), 75% specificity (prediction rate of true negative drugs), and 100% sensitivity (prediction rate of true positive drugs). We then employ the MCA and the SVM training algorithm to prospectively identify the skin-sensitizing likelihood and mechanism-of-action for obeticholic acid (OCA), a farnesoid X receptor (FXR) agonist which has undergone clinical trials for non-alcoholic steatohepatitis (NASH) with well-documented cutaneous side effects.

Reduced serum methods for contact-based coculture of human dermal fibroblasts and epidermal keratinocytes

Direct contact-based coculture of human dermal fibroblasts and epidermal keratinocytes has been a long-standing and challenging issue owing to different serum and growth factor requirements of the two cell types. Existing protocols employ high serum concentrations (up to 10% fetal bovine serum), complex feeder systems and a range of supplemental factors. These approaches are technically demanding and labor intensive, and pose scientific and ethical limitations associated with the high concentrations of animal serum. On the other hand, serum-free conditions often fail to support the proliferation of one or both cell types when they are cultured together. We have developed two reduced serum approaches (1-2% serum) that support the contact-based coculture of human dermal fibroblasts and immortalized keratinocytes and enable the study of cell migration and wound closure.

Human bone marrow mesenchymal stem cell-derived exosomes stimulate cutaneous wound healing mediates through TGF-β/Smad signaling pathway

BACKGROUND

Cutaneous wound healing represents a morphogenetic response to injury and is designed to restore anatomic and physiological function. Human bone marrow mesenchymal stem cell-derived exosomes (hBM-MSC-Ex) are a promising source for cell-free therapy and skin regeneration.

METHODS

In this study, we investigated the cell regeneration effects and its underlying mechanism of hBM-MSC-Ex on cutaneous wound healing in rats. In vitro studies, we evaluated the role of hBM-MSC-Ex in the two types of skin cells: human keratinocytes (HaCaT) and human dermal fibroblasts (HDFs) for the proliferation. For in vivo studies, we used a full-thickness skin wound model to evaluate the effects of hBM-MSC-Ex on cutaneous wound healing in vivo.

RESULTS

The results demonstrated that hBM-MSC-Ex promote both two types of skin cells' growth effectively and accelerate the cutaneous wound healing. Interestingly, we found that hBM-MSC-Ex significantly downregulated TGF-β1, Smad2, Smad3, and Smad4 expression, while upregulated TGF-β3 and Smad7 expression in the TGF-β/Smad signaling pathway.

CONCLUSIONS

Our findings indicated that hBM-MSC-Ex effectively promote the cutaneous wound healing through inhibiting the TGF-β/Smad signal pathway. The current results provided a new sight for the therapeutic strategy for the treatment of cutaneous wounds.

Delineating cell behavior and metabolism of non-melanoma skin cancer in vitro

Non-melanoma skin cancers - basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) - are the most frequent forms of malignant neoplasm in humans worldwide. The etiology of these carcinomas is multifactorial. In addition to the harmful effect of UV light, altered cross-talk between neoplastic epithelial cells and the supporting dermal fibroblasts contributes to the regulation of tumor cell behavior, growth and survival. Metabolic cooperation between these cell types allows them to adapt and react to changes in their surrounding microenvironment by modifying their cellular bioenergetics and biosynthesis. We characterized the growth, behavior, and metabolic activity of human BCC cells, E-cadherin-competent SCC cells and E-cadherin-suppressed SCC cells in the presence or absence of dermal fibroblasts. In mono-cultures and co-cultures, BCC and SCC cells demonstrated distinct morphology, growth and organizational patterns. These tumor cells also exhibited unique patterns of consumption and secretion profiles of glucose, lactate, acetate, glutamine, glutamate, and pyruvate. In comparison to mono-cultures, growth of fibroblasts with either BCC cells or SCC cells enriched the cell growth environment, allowed for metabolic cooperation between these two cell types, and resulted in alterations in the metabolic profiles of the co-cultures. These alterations were affected by the cancer cell type, culture confluence and the composition of the growth medium. Characterizing the bioenergetics of BCC and SCC cells in the context of tumor-stromal interactions is not only important for further understanding of tumor pathogenesis, but also can illuminate potential new targets for novel, metabolic-based therapies for non-melanoma skin cancers.

Processed eggshell membrane powder regulates cellular functions and increase MMP-activity important in early wound healing processes

Avian eggshell membrane (ESM) is a natural biomaterial that has been used as an alternative natural bandage to cure wounds, and is available in large quantities from egg industries. We have previously demonstrated that processed eggshell membrane powder (PEP), aiming to be used in a low cost wound healing product, possesses anti-inflammatory properties. In this study, we further investigated effects of PEP on MMP activities in vitro (a dermal fibroblast cell culture system) and in vivo (a mouse skin wound healing model). Three days incubation with PEP in cell culture led to rearrangement of the actin-cytoskeleton and vinculin in focal adhesions and increased syndecan-4 shedding. In addition, we observed increased matrix metalloproteinase type 2 (MMP-2) enzyme activation, without effects on protein levels of MMP-2 or its regulators (membrane type 1 (MT1)-MMP and tissue inhibitor of matrix metalloproteinase type 2 (TIMP-2). Longer incubation (10 days) led to increased protein levels of MMP-2 and its regulators. We also observed an increased alpha-smooth muscle actin (α-SMA) production, suggesting an effect of PEP on myofibroblast differentiation. In vivo, using the mouse skin wound healing model, PEP treatment (3 days) increased MMP activity at the wound edges, along with increased MMP-2 and MMP-9 protein levels, and increased keratinocyte cell proliferation. Altogether, our data suggest PEP stimulates MMP activity, and with a positive effect on early cellular events during wound healing.