Sphere formation restores and confers hair-inducing capacity in cultured mesenchymal cells

Fabrication of heterocellular spheroids with controllable core-shell structure using inertial focusing effect for scaffold-free 3D cell culture models

Three-dimensional (3D) cell culture models capable of emulating the biological functions of natural tissues are pivotal in tissue engineering and regenerative medicine. Despite progress, the fabrication ofin vitroheterocellular models that mimic the intricate structures of natural tissues remains a significant challenge. In this study, we introduce a novel, scaffold-free approach leveraging the inertial focusing effect in rotating hanging droplets for the reliable production of heterocellular spheroids with controllable core-shell structures. Our method offers precise control over the core-shell spheroid's size and geometry by adjusting the cell suspension density and droplet morphology. We successfully applied this technique to create hair follicle organoids, integrating dermal papilla cells within the core and epidermal cells in the shell, thereby achieving markedly enhanced hair inducibility compared to mixed-structure models. Furthermore, we have developed melanoma tumor spheroids that accurately mimic the dynamic interactions between tumor and stromal cells, showing increased invasion capabilities and altered expressions of cellular adhesion molecules and proteolytic enzymes. These findings underscore the critical role of cellular spatial organization in replicating tissue functionalityin vitro. Our method represents a significant advancement towards generating heterocellular spheroids with well-defined architectures, offering broad implications for biological research and applications in tissue engineering.

Twist2 contributes to skin regeneration and hair follicle formation in mouse fetuses

Unlike adult mammalian wounds, early embryonic mouse skin wounds completely regenerate and heal without scars. Analysis of the underlying molecular mechanism will provide insights into scarless wound healing. Twist2 is an important regulator of hair follicle formation and biological patterning; however, it is unclear whether it plays a role in skin or skin appendage regeneration. Here, we aimed to elucidate Twist2 expression and its role in fetal wound healing. ICR mouse fetuses were surgically wounded on embryonic day 13 (E13), E15, and E17, and Twist2 expression in tissue samples from these fetuses was evaluated via in situ hybridization, immunohistochemistry, and reverse transcription-quantitative polymerase chain reaction. Twist2 expression was upregulated in the dermis of E13 wound margins but downregulated in E15 and E17 wounds. Twist2 knockdown on E13 left visible marks at the wound site, inhibited regeneration, and resulted in defective follicle formation. Twist2-knockdown dermal fibroblasts lacked the ability to undifferentiate. Furthermore, Twist2 hetero knockout mice (Twist + /-) formed visible scars, even on E13, when all skin structures should regenerate. Thus, Twist2 expression correlated with skin texture formation and hair follicle defects in late mouse embryos. These findings may help develop a therapeutic strategy to reduce scarring and promote hair follicle regeneration.

Fetal Fibroblast Transplantation via Ablative Fractional Laser Irradiation Reduces Scarring

Scar treatments include fractional laser treatment, cell transplantation, surgery, skin needling, and dermal fillers. Fractional laser treatments are used to reduce scarring and blurring. Cell transplantation is promising, with mature fibroblasts and adipose-derived stem cells being used clinically, while embryonic fibroblasts are used experimentally. Herein, we developed a combination of ablative CO₂ (carbon dioxide) fractional laser and cell transplantation for the treatment of scars. Eight-week-old male C57Bl/6 mice were used to create a full-layer skin defect in the back skin and create scars. The scar was then irradiated using a CO₂ fractional laser. The cells were then transplanted onto the scar surface and sealed with a film agent. The transplanted cells were GFP-positive murine fetal fibroblasts (FB), fetal fibroblasts with a long-term sphere-forming culture (LS), and fetal skin with a short-term sphere-forming culture (SS). After transplantation, green fluorescent protein (GFP)-positive cells were scattered in the dermal papillary layer and subcutis in all the groups. LS significantly reduced the degree of scarring, which was closest to normal skin. In conclusion, the combination of ablative fractional laser irradiation and fetal fibroblast transplantation allowed us to develop new methods for scar treatment.

Melatonin increases growth properties in human dermal papilla spheroids by activating AKT/GSK3β/β-Catenin signaling pathway

Background

Melatonin, a neurohormone, maybe involved in physiological processes, such as antioxidation, anti-inflammation, and hair growth. In the present study, we investigated the effects of melatonin on proliferation and intracellular signaling in DP cells using a three-dimensional (3D) spheroid culture system that mimics the in vivo hair follicle system.

Methods

DP cells were incubated in monolayer (2D) and 3D spheroid culture systems. The expression levels of melatonin receptors in DP cells were analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blotting. The effect of melatonin on the hair-inductive property of DP cells was analyzed using a WST-1-based proliferation assay, determination of DP spheroid size, expression analysis of DP signature genes, and determination of β-catenin stabilization in DP cells. The AKT/GSK3β/β-catenin signaling pathway associated with melatonin-induced β-catenin stabilization in DP cells was investigated by analyzing changes in upstream regulator proteins, including AKT, GSK3β, and their phosphorylated forms.

Results

The expression levels of the melatonin receptors were higher in human DP cells than in human epidermal keratinocytes and human dermal fibroblast cells. Comparing the expression level according to the human DP cell culture condition, melatonin receptor expression was upregulated in the 3D culture system compared to the traditional two-dimensional monolayer culture system. Cell viability analysis showed that melatonin concentrations up to 1 mM did not affect cell viability. Moreover, melatonin increased the diameter of DP cell 3D spheroids in a dose-dependent manner. Immunoblotting and qRT-PCR analysis revealed that melatonin upregulated the expression of hair growth-related genes, including alkaline phosphatase, bone morphogenetic protein 2, versican, and wingless-int 5A, in a melatonin receptor-dependent manner. Cell fractionation analysis showed that melatonin increased the nuclear localization of β-catenin. This result correlated with the increased transcriptional activation of T-cell factor/lymphoid enhancer factor-responsive luciferase induced by melatonin treatment. Interestingly, melatonin induced the phosphorylation of protein kinase B/AKT at serine 473 residue and GSK-3β at serine 9 residue. To determine whether AKT phosphorylation at serine 473 induced β-catenin nuclear translocation through GSK3β phosphorylation at serine 9, the PI3K/AKT inhibitor LY294002 was cotreated with melatonin. Immunoblotting showed that LY294002 inhibited melatonin-induced phosphorylation of GSK3β at serine 9 residue and β-catenin activation.

Conclusion

Collectively, this report suggests that melatonin promotes growth properties by activating the AKT/GSK3β/β-catenin signaling pathway through melatonin receptors.

Ginsenoside Rg4 Enhances the Inductive Effects of Human Dermal Papilla Spheres on Hair Growth Via the AKT/GSK-3β/β-Catenin Signaling Pathway

Ginsenoside Rg4 is a rare ginsenoside that is naturally found in ginseng, and exhibits a wide range of biological activities including antioxidant and anti-inflammatory properties in several cell types. The purpose of this study was to use an in vivo model of hair follicle (HF)-mimic based on a human dermal papilla (DP) spheroid system prepared by three-dimensional (3D) culture and to investigate the effect of Rg4 on the hair-inductive properties of DP cells. Treatment of the DP spheroids with Rg4 (20 to 50 μg/ml) significantly increased the viability and size of the DP spheres in a dose-dependent manner. Rg4 also increased the mRNA and protein expression of DP signature genes that are related to hair growth including ALP, BMP2, and VCAN in the DP spheres. Analysis of the signaling molecules and luciferase reporter assays further revealed that Rg4 induces the activation of phosphoinositide 3-kinase (PI3K)/AKT and the inhibitory phosphorylation of GSK3β, which activates the WNT/β-catenin signaling pathway. These results correlated with not only the increased nuclear translocation of β-catenin following the treatment of the DP spheres with Rg4 but also the significant elevation of mRNA expression of the downstream target genes of the WNT/β-catenin pathway including WNT5A, β-catenin, and LEF1. In conclusion, these results demonstrated that ginsenoside Rg4 promotes the hair-inductive properties of DP cells by activating the AKT/GSK3β/β-catenin signaling pathway in DP spheres, suggesting that Rg4 could be a potential natural therapy for hair growth.

Cellular Nanofiber Structure with Secretory Activity-Promoting Characteristics for Multicellular Spheroid Formation and Hair Follicle Regeneration

Multicellular spheroids can mimic the in vivo microenvironment and maintain the unique functions of tissues, which has attracted great attention in tissue engineering. However, the traditional culture microenvironment with structural deficiencies complicates the culture and collection process and tends to lose the function of multicellular spheroids with the increase of cell passage. In order to construct efficient and functional multicellular spheroids, in this study, a chitosan/polyvinyl alcohol nanofiber sponge which has an open-cell cellular structure is obtained. The hair follicle (HF) regeneration model was employed to evaluate HF-inducing ability of dermal papilla (DP) multicellular spheroids which formed on the cellular structure nanofiber sponge. Through structural fine-tuning, the nanofiber sponge has appropriate elasticity for the creation of a three-dimensional dynamic microenvironment to regulate cellular behavior. The cellular structure nanofiber sponge tilts the balance of cell-substratum and cell-cell interactions to a state which is more conducive to the formation of controllable multicellular spheroids in a short time. More importantly, it improves the secretory activity of high-passaged dermal papilla cells and restores their intrinsic properties. Experiments using BALB/c nude mice show that cultured DP multicellular spheroids could effectively enhance HF-inducing ability. This novel system provides a simple and efficient strategy for multicellular spheroid formation and HF regeneration.

Tissue engineering strategies for human hair follicle regeneration: How far from a hairy goal?

The demand for an efficient therapy for alopecia disease has fueled the hair research field in recent decades. However, despite significant improvements in the knowledge of key processes of hair follicle biology such as genesis and cycling, translation into hair follicle replacement therapies has not occurred. Great expectation has been recently put on hair follicle bioengineering, which is based on the development of fully functional hair follicles with cycling activity from an expanded population of hair‐inductive (trichogenic) cells. Most bioengineering approaches focus on in vitro reconstruction of folliculogenesis by manipulating key regulatory molecular/physical features of hair follicle growth/cycling in vivo. Despite their great potential, no cell‐based product is clinically available for hair regeneration therapy to date. This is mainly due to demanding issues that still hinder the functionality of cultured human hair cells. The present review comprehensively compares emergent strategies using different cell sources and tissue engineering approaches, aiming to successfully achieve a clinical cure for hair loss. The hurdles of these strategies are discussed, as well as the future directions to overcome the obstacles and fulfill the promise of a “hairy” feat.

Surface Tension Guided Hanging-Drop: Producing Controllable 3D Spheroid of High-Passaged Human Dermal Papilla Cells and Forming Inductive Microtissues for Hair-Follicle Regeneration

Human dermal papilla (DP) cells have been studied extensively when grown in the conventional monolayer. However, because of great deviation from the real in vivo three-dimensional (3D) environment, these two-dimensional (2D) grown cells tend to lose the hair-inducible capability during passaging. Hence, these 2D caused concerns have motivated the development of novel 3D culture techniques to produce cellular microtissues with suitable mimics. The hanging-drop approach is based on surface tension-based technique and the interaction between surface tension and gravity field that makes a convergence of liquid drops. This study used this technique in a converged drop to form cellular spheroids of dermal papilla cells. It leads to a controllable 3Dspheroid model for scalable fabrication of inductive DP microtissues. The optimal conditions for culturing high-passaged (P8) DP spheroids were determined first. Then, the morphological, histological and functional studies were performed. In addition, expressions of hair-inductive markers including alkaline phosphatase, α-smooth muscle actin and neural cell adhesion molecule were also analyzed by quantitative RT-PCR, immunostaining and immunoblotting. Finally, P8-DP microtissues were coimplanted with newborn mouse epidermal cells (EPCs) into nude mice. Our results indicated that the formation of 3D microtissues not only endowed P8-DP microtissues many similarities to primary DP, but also confer these microtissues an enhanced ability to induce hair-follicle (HF) neogenesis in vivo. This model provides a potential to elucidate the native biology of human DP, and also shows the promising for the controllable and scalable production of inductive DP cells applied in future follicle regeneration.

Hair Induction by Cultured Mesenchymal Cells Using Sphere Formation

Isolated dermal cells possess the capacity to induce hair growth. The cells cannot be expanded while they retain the capacity for hair induction, and lose their potential immediately after cultivation. Sphere-forming multipotent cells derived from the dermis (skin-derived precursors [SKPs]) possess hair-inducing activity. These observations provide two possibilities for the determination of the capacity for hair induction: capacity is dependent on either identity as a dermal cell or on the process of sphere formation. We developed a method that demonstrates cultivated mesenchymal cells derived from dermis and lung tissue possess in vivo hair-inducing capacity via sphere formation.

Cells or signals: which moves to drive skin pattern formation?

During its development, the skin produces an array of evenly spaced hair follicles. How the location of each follicle is determined to produce this pattern has been the subject of study and speculation for several decades. A central unresolved issue is the extent to which movement of scattered, precommitted follicle cells might play a role in this process. Xavier et al. now report the identification of subpopulations of dermal cells in developing sheep skin which are positive for Delta1 expression, suggesting that these cells may represent precommitted dermal papilla cells and that dermal Notch pathway signalling plays a role in hair follicle patterning.

Controllable production of transplantable adult human high-passage dermal papilla spheroids using 3D matrigel culture

We have succeeded in culturing human dermal papilla (DP) cell spheroids and developed a three-dimensional (3D) Matrigel (basement membrane matrix) culture technique that can enhance and restore DP cells unique characteristics in vitro. When 1 × 10(4) DP cells were cultured on the 96-well plates precoated with Matrigel for 5 days, both passage 2 and passage 8 DP cells formed spheroidal microtissues with a diameter of 150-250 μm in an aggregative and proliferative manner. We transferred and recultured these DP spheroids onto commercial plates. Cells within DP spheres could disaggregate and migrate out, which was similar to primary DP. Moreover, we examined the expression of several genes and proteins associated with hair follicle inductivity of DP cells, such as NCAM, Versican, and α-smooth muscle actin, and confirmed that their expression level was elevated in the spheres compared with the dissociated DP cells. To examine the hair-inducing ability of DP spheres, hair germinal matrix cells (HGMCs) and DP spheres were mixed and cultured on Matrigel. Unlike the dissociated DP cells and HGMCs cocultured in two dimensions, HGMCs can differentiate into hair-like fibers under the induction of the DP spheres made from the high-passage cells (passage 8) in vitro. We are the first to show that passage 3 human HGMCs differentiate into hair-like fibers in the presence of human DP spheroids. These results suggest that the 3D Matrigel culture technique is an ideal culture model for forming DP spheroids and that sphere formation partially models the intact DP, resulting in hair induction, even by high-passage DP cells.

Enrichment and characterization of human dermal stem/progenitor cells by intracellular granularity

Adult stem cells from the dermis would be an attractive cell source for therapeutic purposes as well as studying the process of skin aging. Several studies have reported that human dermal stem/progenitor cells (hDSPCs) with multipotent properties exist within the dermis of adult human skin. However, these cells have not been well characterized, because methods for their isolation or enrichment have not yet been optimized. In the present study, we enriched high side scatter (SSC(high))-hDSPCs from normal human dermal fibroblasts using a structural characteristic, intracellular granularity, as a sorting parameter. The SSC(high)-hDSPCs had high in vitro proliferation properties and expressed high levels of SOX2 and S100B, similar to previously identified mouse SOX2+ hair follicle dermal stem cells. The SSC(high)-hDSPCs could differentiate into not only mesodermal cell types, for example, adipocytes, chondrocytes, and osteoblasts, but also neuroectodermal cell types, such as neural cells. In addition, the SSC(high)-hDSPCs exhibited no significant differences in the expression of nestin, vimentin, SNAI2, TWIST1, versican, and CORIN compared with non-hDSPCs. These cells are therefore different from the previously identified multipotent fibroblasts and skin-derived progenitors. In this study, we suggest that hDSPCs can be enriched by using characteristic of their high intracellular granularity, and these SSC(high)-hDSPCs exhibit high in vitro proliferation and differentiation potentials.

Generating CK19-positive cells with hair-like structures from Wharton's jelly mesenchymal stromal cells

Wharton's jelly mesenchymal stromal cells (WJMSCs) are considered mesenchymal, multipotent, and capable of differentiating into cells of mesodermal origin. Ectodermal differentiation from mesenchymal cells has been recently reported. Herein, we show for the first time that we can generate cytokeratin 19-positive cells and hair-like structures from WJMSCs in vitro using 2 separate methodologies that utilize osteogenic media to induce WJMSCs to undergo osteogenic differentiation. In one method, WJMSCs were seeded on a matrix isolated from Wharton's jelly following decellularization. In the other method, WJMSCs were cultured to form spheroids. Our findings demonstrate that WJMSCs may have the capacity for ectodermal differentiation.