Dermal-epidermal membrane systems by using human keratinocytes and mesenchymal stem cells isolated from dermis

Extracellular vesicles selective capture by peptide-functionalized hollow fiber membranes

Recently, membrane devices and processes have been applied for the separation and concentration of subcellular components such as extracellular vesicles (EVs), which play a diagnostic and therapeutic role in many pathological conditions. However, the separation and isolation of specific EV populations from other components found in biological fluids is still challenging. Here, we developed a peptide-functionalized hollow fiber (HF) membrane module to achieve the separation and enrichment of highly pure EVs derived from the culture media of human cardiac progenitor cells. The strategy is based on the functionalization of PSf HF membrane module with BPt, a peptide sequence able to bind nanovesicles characterized by highly curved membranes. HF membranes were modified by a nanometric coating with a copoly azide polymer to limit non-specific interactions and to enable the conjugation with peptide ligand by click chemistry reaction. The BPt-functionalized module was integrated into a TFF process to facilitate the design, rationalization, and optimization of EV isolation. This integration combined size-based transport of species with specific membrane sensing ligands. The TFF integrated BPt-functionalized membrane module demonstrated the ability to selectively capture EVs with diameter < 200 nm into the lumen of fibers while effectively removing contaminants such as albumin. The captured and released EVs contain the common markers including CD63, CD81, CD9 and syntenin-1. Moreover, they maintained a round shape morphology and structural integrity highlighting that this approach enables EVs concentration and purification with low shear stress. Additionally, it achieved the removal of contaminants such as albumin with high reliability and reproducibility, reaching a removal of 93%.

Injectable hydrogel harnessing foreskin mesenchymal stem cell-derived extracellular vesicles for treatment of chronic diabetic skin wounds

Chronic skin wounds are a serious complication of diabetes with a high incidence rate, which can lead to disability or even death. Previous studies have shown that mesenchymal stem cells derived extracellular vesicles (EVs) have beneficial effects on wound healing. However, the human foreskin mesenchymal stem cell (FSMSCs)-derived extracellular vesicle (FM-EV) has not yet been isolated and characterized. Furthermore, the limited supply and short lifespan of EVs also hinder their practical use. In this study, we developed an injectable dual-physical cross-linking hydrogel (PSiW) with self-healing, adhesive, and antibacterial properties, using polyvinylpyrrolidone and silicotungstic acid to load FM-EV. The EVs were evenly distributed in the hydrogel and continuously released. In vivo and vitro tests demonstrated that the synergistic effect of EVs and hydrogel could significantly promote the repair of diabetic wounds by regulating macrophage polarization, promoting angiogenesis, and improving the microenvironment. Overall, the obtained EVs-loaded hydrogels developed in this work exhibited promising applicability for the repair of chronic skin wounds in diabetes patients.

Cellular human tissue-engineered skin substitutes investigated for deep and difficult to heal injuries

Wound healing is an important function of skin; however, after significant skin injury (burns) or in certain dermatological pathologies (chronic wounds), this important process can be deregulated or lost, resulting in severe complications. To avoid these, studies have focused on developing tissue-engineered skin substitutes (TESSs), which attempt to replace and regenerate the damaged skin. Autologous cultured epithelial substitutes (CESs) constituted of keratinocytes, allogeneic cultured dermal substitutes (CDSs) composed of biomaterials and fibroblasts and autologous composite skin substitutes (CSSs) comprised of biomaterials, keratinocytes and fibroblasts, have been the most studied clinical TESSs, reporting positive results for different pathological conditions. However, researchers' purpose is to develop TESSs that resemble in a better way the human skin and its wound healing process. For this reason, they have also evaluated at preclinical level the incorporation of other human cell types such as melanocytes, Merkel and Langerhans cells, skin stem cells (SSCs), induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs). Among these, MSCs have been also reported in clinical studies with hopeful results. Future perspectives in the field of human-TESSs are focused on improving in vivo animal models, incorporating immune cells, designing specific niches inside the biomaterials to increase stem cell potential and developing three-dimensional bioprinting strategies, with the final purpose of increasing patient's health care. In this review we summarize the use of different human cell populations for preclinical and clinical TESSs under research, remarking their strengths and limitations and discuss the future perspectives, which could be useful for wound healing purposes.

Nano- and Micro-Porous Chitosan Membranes for Human Epidermal Stratification and Differentiation

The creation of partial or complete human epidermis represents a critical aspect and the major challenge of skin tissue engineering. This work was aimed at investigating the effect of nano- and micro-structured CHT membranes on human keratinocyte stratification and differentiation. To this end, nanoporous and microporous membranes of chitosan (CHT) were prepared by phase inversion technique tailoring the operational parameters in order to obtain nano- and micro-structured flat membranes with specific surface properties. Microporous structures with different mean pore diameters were created by adding and dissolving, in the polymeric solution, polyethylene glycol (PEG Mw 10,000 Da) as porogen, with a different CHT/PEG ratio. The developed membranes were characterized and assessed for epidermal construction by culturing human keratinocytes on them for up to 21 days. The overall results demonstrated that the membrane surface properties strongly affect the stratification and terminal differentiation of human keratinocytes. In particular, human keratinocytes adhered on nanoporous CHT membranes, developing the structure of the corneum epidermal top layer, characterized by low thickness and low cell proliferation. On the microporous CHT membrane, keratinocytes formed an epidermal basal lamina, with high proliferating cells that stratified and differentiated over time, migrating along the z axis and forming a multilayered epidermis. This strategy represents an attractive tissue engineering approach for the creation of specific human epidermal strata for testing the effects and toxicity of drugs, cosmetics and pollutants.

Double porous poly (Ɛ-caprolactone)/chitosan membrane scaffolds as niches for human mesenchymal stem cells

In this paper, we developed membrane scaffolds to mimic the biochemical and biophysical properties of human mesenchymal stem cell (hMSC) niches to help direct self-renewal and proliferation providing to cells all necessary chemical, mechanical and topographical cues. The strategy was to create three-dimensional membrane scaffolds with double porosity, able to promote the mass transfer of nutrients and to entrap cells. We developed poly (Ɛ-caprolactone) (PCL)/chitosan (CHT) blend membranes consisting of double porous morphology: (i) surface macrovoids (big pores) which could be easily accessible for hMSCs invasion and proliferation; (ii) interconnected microporous network to transfer essential nutrients, oxygen, growth factors between the macrovoids and throughout the scaffolds. We varied the mean macrovoid size, effective surface area and surface morphology by varying the PCL/CHT blend composition (100/0, 90/10, 80/20, 70/30). Membranes exhibited macrovoids connected with each other through a microporous network; macrovoids size increased by increasing the CHT wt%. Cells adhered on the surfaces of PCL/CHT 100/0 and PCL/CHT 90/10 membranes, that are characterized by a high effective surface area and small macrovoids while PCL/CHT 80/20 and PCL/CHT 70/30 membranes with large macrovoids and low effective surface area entrapped cells inside macrovoids. The scaffolds were able to create a permissive environment for hMSC adhesion and invasion promoting viability and metabolism, which are important for the maintenance of cell integrity. We found a relationship between hMSCs proliferation and oxygen uptake rate with surface mean macrovoid size and effective surface area. The macrovoids enabled the cell invasion into the membrane and the microporosity ensured an adequate diffusive mass transfer of nutrients and metabolites, which are essential for the long-term maintenance of cell viability and functions.

Characterization of Dermal Stem Cells of Diabetic Patients

Diabetic foot ulcers (DFUs) are lesions that involve loss of epithelium and dermis, sometimes involving deep structures, compartments, and bones. The aim of this work is to investigate the innate regenerative properties of dermal tissue around ulcers by the identification and analysis of resident dermal stem cells (DSCs). Dermal samples were taken at the edge of DFUs, and genes related to the wound healing process were analyzed by the real-time PCR array. The DSCs were isolated and analyzed by immunofluorescence, flow cytometry, and real-time PCR array to define their stemness properties. The gene expression profile of dermal tissue showed a dysregulation in growth factors, metalloproteinases, collagens, and integrins involved in the wound healing process. In the basal condition, diabetic DSCs adhered on the culture plate with spindle-shaped fibroblast-like morphology. They were positive to the mesenchymal stem cells markers CD44, CD73, CD90, and CD105, but negative for the hematopoietic markers CD14, CD34, CD45, and HLA-DR. In diabetic DSCs, the transcription of genes related to self-renewal and cell division were equivalent to that in normal DSCs. However, the expression of CCNA2, CCND2, CDK1, ALDH1A1, and ABCG2 was downregulated compared with that of normal DSCs. These genes are also related to cell cycle progression and stem cell maintenance. Further investigation will improve the understanding of the molecular mechanisms by which these genes together govern cell proliferation, revealing new strategies useful for future treatment of DFUs.