Establishment of Three Types of Immortalized Human Skin Stem Cell Lines Derived from the Single Donor

Genome-wide association studies in the Japanese population identified genetic loci and target gene associated with epidermal turnover

The epidermis is an essential organ for life by retaining water and as a protective barrier. The epidermis is maintained through metabolism, in which basal cells produced from epidermal stem cells differentiate into spinous cells, granular cells and corneocytes, and are finally shed from the epidermal surface. This is epidermal turnover, and with aging, there is a decline in epidermis function. Other factors that may affect epidermal turnover include ultraviolet damage and genetic factors. These genetic factors are of particular interest as little is known. Although recent skin-focused genome-wide association studies (GWAS) have been conducted, the genetic regions associated with epidermal turnover are almost uninvestigated. Therefore, we conducted a GWAS on epidermal turnover in the Japanese population, using the corneocyte area, which correlates to the rate of epidermal turnover, as an indicator. As a result, rs2278431 (p = 1.29 × 10-7 ) in 19q13.2 was associated with corneocyte size. Furthermore, eQTL analysis suggested that rs2278431 was related to the SPINT2 gene. In addition, SPINT2 knockdown studies using epidermal keratinocytes revealed that SPINT2 is involved in keratinocyte proliferation and in corneocyte size regulation in reconstructed epidermis. These results suggest that rs2278431 is involved in the expression of SPINT2 and affects epidermal turnover.

Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention

Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.

Injectable decellularized dental pulp matrix-functionalized hydrogel microspheres for endodontic regeneration

The sufficient imitation of tissue structures and components represents an effective and promising approach for tissue engineering and regenerative medicine applications. Dental pulp disease is one of the most common oral diseases, although functional pulp regeneration remains challenging. Herein, we propose a strategy that employs hydrogel microspheres incorporated with decellularized dental pulp matrix-derived bioactive factors to simulate a pulp-specific three-dimensional (3D) microenvironment. The dental pulp microenvironment-specific microspheres constructed by this regenerative strategy exhibited favorable plasticity, biocompatibility, and biological performances. Human dental pulp stem cells (hDPSCs) cultured on the constructed microspheres exhibited enhanced pulp-formation ability in vitro. Furthermore, the hDPSCs-microcarriers achieved the regeneration of pulp-like tissue and new dentin in a semi-orthotopic model in vivo. Mechanistically, the decellularized pulp matrix-derived bioactive factors mediated the multi-directional differentiation of hDPSCs to regenerate the pulp tissue by eliciting the secretion of crucial bioactive cues. Our findings demonstrated that a 3D dental pulp-specific microenvironment facilitated by hydrogel microspheres and dental pulp-specific bioactive factors regenerated the pulp-dentin complex and could be served as a promising treatment option for dental pulp disease. STATEMENT OF SIGNIFICANCE: Injectable bioscaffolds are increasingly used for regenerative endodontic treatment. Despite their success related to their ability to load stem cells, bioactive factors, and injectability, conventional bulk bioscaffolds have drawbacks such as ischemic necrosis in the central region. Various studies have shown that ischemic necrosis in the central region can be corrected by injectable hydrogel microspheres. Unfortunately, pristine microspheres or microspheres without dental pulp-specific bioactive factor would oftentimes fail to regulate stem cells fates in dental pulp multi-directional differentiation. Our present study reported the biofabrication of dental pulp-derived decellularized matrix functionalized gelatin microspheres, which contained dental pulp-specific bioactive factors and have the potential application in endodontic regeneration.

The Role of Cell-Based Therapies in Acute Burn Wound Skin Repair: A Review

Tissue engineering solutions for skin have been developed over the last few decades with a focus initially on a two-layered structure with epithelial and dermal repair. An essential element of skin restoration is a source of cells capable of differentiating into the appropriate phenotype. The need to repair areas of skin when traditional techniques were not adequate addressed led to cell based therapies being developed initially as a laboratory-based tissue expansion opportunity, both as sheets of cultured epithelial autograft and in composite laboratory-based skin substitutes. The time to availability of the cell-based therapies has been solved in a number of ways, from using allograft cell-based solutions to the use of point of care skin cell harvesting for immediate clinical use. More recently pluripotential cells have been explored providing a readily available source of cells and cells which can express the broad range of phenotypes seen in the mature skin construct. The lessons learnt from the use of cell based techniques has driven the exploration of the use of 3D printing technology, with controlled accurate placement of the cells within a specific printed construct to optimise the phenotypic expression and tissue generation.

Melanin accumulation in dermal stem cells deteriorates their exosome-mediated skin basement membrane construction in solar lentigo

Solar lentigo (SL) is a hyperpigmented macule that occurs in sun-exposed areas and is characterized by the accumulation of melanin pigment in the epidermis. On the contrary, melanin-incorporated macrophages have also been identified in the dermis, which is thought to be caused by melanin transfer due to disruption of the basement membrane, but the detailed mechanism remains unclear. In this study, we analysed SL lesions by pathological methods and examined the mechanism of melanin accumulation in the dermis using cultured skin models in vitro. First, we observed a significant decrease in type IV collagen (COL4), a major component of the basement membrane, in SL lesions. The basement membrane is known to be formed by the interaction of keratinocytes and dermal cells. Therefore, we constructed skin models containing fibroblasts or dermal stem cells and examined their effects on basement membrane formation. The results showed a markedly enhanced production of COL4 mediated by dermal stem cell-derived exosomes. The analysis of melanin localization in the SL dermis revealed that CD163-positive macrophages and CD271-positive dermal stem cells both took up melanin pigment. Exosomes of dermal stem cells incorporating melanosomes were less effective in promoting COL4 expression. These findings suggest that while the promotion of COL4 production in keratinocytes by dermal stem cell-derived exosomes is important for maintaining basement membrane homeostasis, this mechanism is disrupted in SL lesions, leading to chronic melanin accumulation in the dermis.

Enhanced Type I Collagen Synthesis in Fibroblasts by Dermal Stem/Progenitor Cell-Derived Exosomes

The self-duplication and differentiation of dermal stem cells are essential for the maintenance of dermal homeostasis. Fibroblasts are derived from dermal stem cells and produce components of connective tissue, such as collagen, which maintains the structure of the dermis. Cell-cell communication is required for the maintenance of tissue homeostasis, and the role of exosomes in this process has recently been attracting increasing attention. Dermal stem cells and fibroblasts have been suggested to communicate with each other in the dermis; however, the underlying mechanisms remain unclear. In the present study, we investigated communication between dermal stem/progenitor cells (DSPCs) and fibroblasts via exosomes. We collected exosomes from DSPCs and added them to a culture of fibroblasts. With the exosomes, COL1A1 mRNA expression was up-regulated and dependent on the Akt phosphorylation. Exosomes collected from fibroblasts did not show the significant up-regulation of COL1A1 mRNA expression. We then performed a proteomic analysis and detected 74 proteins specific to DSPC-derived exosomes, including ANP32B related to Akt phosphorylation. We added exosomes in which ANP32B was knocked down to a fibroblast culture and observed neither Akt phosphorylation nor enhanced type I collagen synthesis. Additionally, an immunohistochemical analysis of skin tissues revealed that ANP32B expression levels in CD271-positive dermal stem cells were lower in old subjects than in young subjects. These results suggest that DSPCs promote type I collagen synthesis in fibroblasts by secreting exosomes containing ANP32B, which may contribute to the maintenance of skin homeostasis; however, this function of DSPCs may decrease with aging.