Formation of hair follicles from a single-cell suspension of embryonic rat skin by a two-step procedure in vitro

Generation of Hair Follicle Germs In Vitro Using Human Postnatal Skin Cells

Modeling organoids with hair follicle germ-like properties provides an opportunity for developing strategies for alopecia drug discovery and replacement therapy, as well as investigating the molecular mechanisms underlying human hair follicle regeneration in vitro. Hair follicle germ reconstruction in vitro is based on dermal papilla hair-inducing abilities and the plasticity of skin epidermal keratinocytes. The current protocol describes a highly efficient approach suitable for adult human skin cell applications. This method allows to obtain hair follicle germs using tissues from one donor. Isolated and cultured for 2 weeks, adult hair follicle dermal papilla cells and skin epidermal keratinocytes self-organize in hanging drop cultures generating organoids that exhibit the features of folliculogenesis onset.

Bottom-up Nanoencapsulation from Single Cells to Tunable and Scalable Cellular Spheroids for Hair Follicle Regeneration

Cell surface engineering technology advances cell therapeutics and tissue engineering by accurate micro/nanoscale control in cell-biomaterial ensembles and cell spheroids formation. By tailoring cell surface, microgels can encapsulate cells for versatile uses. However, microgels are coated in a thick layer to house multiple cells together but not a single cell based. Besides, excessive deposition on cell surface is detrimental to cellular functions. Herein, layer-by-layer (LbL) self-assembly to encapsulate single cell using nanogel is reported, owing to its security and tunable thickness at nanoscale, and further forms cell spheroids by physical cross-linking on nanogel-coated cells for delivery. A hair follicle (HF) regeneration model where the dermal papilla cells (DPCs) are given a 3D installation to maintain its ability of HF induction during in vitro culture is studied. Dermal papilla (DP) spheroids are optimized and that LbL-DPCs aggregation is akin to primary DP is demonstrated. The markers ALP, Versican, and NCAM are examined to investigate that high-passaged (P8) DP spheroids can restore the hair induction potential, which are lost in 2D culture. New HFs are regenerated successfully by implantation of DP spheroids in vivo.

Hair Germ Model In Vitro via Human Postnatal Keratinocyte-Dermal Papilla Interactions: Impact of Hyaluronic Acid

Hair follicle (HF) reconstruction in vitro is a promising field in alopecia treatment and human HF development research. Here, we combined postnatal human dermal papilla (DP) cells and skin epidermal keratinocytes (KCs) in a hanging drop culture to develop an artificial HF germ. The method is based on DP cell hair-inducing properties and KC self-organization. We evaluated two protocols of aggregate assembling. Mixed HF germ-like structures demonstrated the initiation of epithelial-mesenchymal interaction, including WNT pathway activation and expression of follicular markers. We analyzed the influence of possible DP cell niche components including soluble factors and extracellular matrix (ECM) molecules in the process of the organoid assembling and growth. Our results demonstrated that soluble factors had little impact on HF germ generation and Ki67⁺ cell score inside the organoids although BMP6 and VD3 maintained effectively the DP identity in the monolayer culture. Aggrecan, biglycan, fibronectin, and hyaluronic acid (HA) significantly stimulated cell proliferation in DP cell monolayer culture without any effect on DP cell identity. Most of ECM compounds prevented the formation of cell aggregates while HA promoted the formation of larger organoids. In conclusion, our model could be suitable to study cell-cell and cell-niche interactions during HF reconstruction in vitro.

Comparison of Calcium and Barium Microcapsules as Scaffolds in the Development of Artificial Dermal Papillae

This study aimed to develop and evaluate barium and calcium microcapsules as candidates for scaffolding in artificial dermal papilla. Dermal papilla cells (DPCs) were isolated and cultured by one-step collagenase treatment. The DPC-Ba and DPC-Ca microcapsules were prepared by using a specially designed, high-voltage, electric-field droplet generator. Selected microcapsules were assessed for long-term inductive properties with xenotransplantation into Sprague-Dawley rat ears. Both barium and calcium microcapsules maintained xenogenic dermal papilla cells in an immunoisolated environment and induced the formation of hair follicle structures. Calcium microcapsules showed better biocompatibility, permeability, and cell viability in comparison with barium microcapsules. Before 18 weeks, calcium microcapsules gathered together, with no substantial immune response. After 32 weeks, some microcapsules were near inflammatory cells and wrapped with fiber. A few large hair follicles were found. Control samples showed no marked changes at the implantation site. Barium microcapsules were superior to calcium microcapsules in structural and mechanical stability. The cells encapsulated in hydrogel barium microcapsules exhibited higher short-term viability. This study established a model to culture DPCs in 3D culture conditions. Barium microcapsules may be useful in short-term transplantation study. Calcium microcapsules may provide an effective scaffold for the development of artificial dermal papilla.

Epidermal stem cells and skin tissue engineering in hair follicle regeneration

The reconstitution of a fully organized and functional hair follicle from dissociated cells propagated under defined tissue culture conditions is a challenge still pending in tissue engineering. The loss of hair follicles caused by injuries or pathologies such as alopecia not only affects the patients' psychological well-being, but also endangers certain inherent functions of the skin. It is then of great interest to find different strategies aiming to regenerate or neogenerate the hair follicle under conditions proper of an adult individual. Based upon current knowledge on the epithelial and dermal cells and their interactions during the embryonic hair generation and adult hair cycling, many researchers have tried to obtain mature hair follicles using different strategies and approaches depending on the causes of hair loss. This review summarizes current advances in the different experimental strategies to regenerate or neogenerate hair follicles, with emphasis on those involving neogenesis of hair follicles in adult individuals using isolated cells and tissue engineering. Most of these experiments were performed using rodent cells, particularly from embryonic or newborn origin. However, no successful strategy to generate human hair follicles from adult cells has yet been reported. This review identifies several issues that should be considered to achieve this objective. Perhaps the most important challenge is to provide three-dimensional culture conditions mimicking the structure of living tissue. Improving culture conditions that allow the expansion of specific cells while protecting their inductive properties, as well as methods for selecting populations of epithelial stem cells, should give us the necessary tools to overcome the difficulties that constrain human hair follicle neogenesis. An analysis of patent trends shows that the number of patent applications aimed at hair follicle regeneration and neogenesis has been increasing during the last decade. This field is attractive not only to academic researchers but also to the companies that own almost half of the patents in this field.

Scalable production of controllable dermal papilla spheroids on PVA surfaces and the effects of spheroid size on hair follicle regeneration

Organ size and numbers are vital issues in bioengineering for hair follicle (HF) regeneration. Murine HF dermal papilla (DP) cells are able to induce HF neogenesis when transplanted as aggregates. However, how the preparation of murine and human DP aggregates affects HF inductivity and the size of regenerated HF is yet to be determined. Here we report a scalable method for production of controllable human and rat DP spheroids in general labs for reproducible experiments. Compared with more hydrophobic polyethylene and poly(ethylene-co-vinyl alcohol), DP cells are poorly adhesive to hydrophilic polyvinyl alcohol (PVA). Seeded in PVA-coated 96-welled commercial PCR tube arrays, DP cells quickly aggregate into single spheroids with progressive compaction. Varying seeded cell numbers and culture periods enables us to control the size and cell number of the spheroids. The spheroids obtained have high viability and preserve DP characters. A proof of principle experiment was conducted to examine the size effect on the efficiency and efficacy of HF regeneration. We found that both human and rat DP spheroids are able to induce HF neogenesis and larger DP spheroids exhibit higher HF inductivity. However, the average diameter of regenerated hair fiber did not significantly change with the increasing size of transplanted DP spheroids. The result suggests that an appropriate size of DP spheroid is essential for HF inductivity, but its size cannot be directly translated to a thicker regenerated hair. Our results also have implications on the efficiency and efficacy in the regeneration of other epithelial organs.

Bioengineering the hair follicle

The hair follicle develops from the primitive embryonic epidermis as a result of complex epithelial-mesenchymal interactions. The full follicle, consisting of epithelial cylinders under control of a proximal lying mesenchymal papilla, grows in cycles giving rise to a new hair shaft during each cycle. The ability to cycle endows the follicle with regenerative properties. The evolution of hair follicle engineering began with the recognition in the early 1960's that hair follicles could be transplanted clinically into a foreign site and still grow a shaft typical of the donor site. Since that time, it has been found that the follicular papilla has hair follicle inducing properties and that the hair follicle houses within it epithelial stem cells that can respond to hair inductive signals. These findings have laid the foundation for isolating hair-forming cells, for expanding the cells in culture, and for forming new follicles in vivo.

Large-scale cultivation of transplantable dermal papilla cellular aggregates using microfabricated PDMS arrays

In this work we have developed a strategy for cultivating dermal papilla (DP) cells to form multiple arrayed spheroidal microtissues for transplantation on a micropatterned polydimethylsiloxane (PDMS)-based tissue culture polystyrene (TCPS) plate system. We also describe the behavior of dermal papilla cells on this platform and the spontaneous formation of spheroidal microtissues by DP cells. We used a hydrophobic PDMS arrayed chip as a master to separate the seeded cells in the TCPS culture plate. By controlling the cell seeding densities, a microwell with arrayed DP spheroidal microtissues was easily formed. Formation of DP microtissues was associated with overlapping multilayered cells on the microwells and low cell-substrate adhesivity on the PDMS film. The microwell environment enhanced the aggregation of DP cells into spheroidal microtissues on the TCPS culture plate. The spheroidal microtissues preserved their hair induction potential in vitro and in vivo. A large quantity of DP spheroidal microtissues could be obtained rapidly and simply using this platform. We could harvest hundreds of DP microtissues (352 microtissues) with a cell seeding density of 1×10⁶ cells well⁻¹ after 3 days cultivation in one well of a 24-well plate. This is the first demonstration of the formation of DP spheres in large quantitites.

High-throughput reconstitution of epithelial-mesenchymal interaction in folliculoid microtissues by biomaterial-facilitated self-assembly of dissociated heterotypic adult cells

The aim of this study was to develop a method for efficient production of folliculoid keratinocyte-dermal papilla (DP) microtissues to facilitate epithelial-mesenchymal interaction. The behavior of DP cells and adult keratinocytes from hairless skin on poly(ethylene-co-vinyl alcohol) (EVAL) surface was investigated. Keratinocytes, poorly adherent both to substrate and between homotypic cells, become suspended disperse cells after homotypic cell seeding. Seeded simultaneously, keratinocytes and DP cells are able to aggregate into spheroidal microtissues. Dynamical analysis shows that DP cells act as a carrier in the process due to the heterotypic intercellular adhesion. DP cells attach faster to EVAL and start to aggregate. Keratinocytes adhere to DP cells and are then carried by DP cells to form initial hybrid aggregates. Due to the high motility of DP cells, these hybrid aggregates move collectively as clusters and merge into larger spheroids which subsequently detach from the substratum and can be easily collected. Compared with random cell distribution in spheroids generated in hanging drops, these hybrid spheroids have a preferential compartmented core-shell structure: an aggregated DP cell core surrounded by a keratinocyte shell. In addition to ameliorated DP signature gene expression, keratinocytes show down-regulated epidermal terminal differentiation and enhanced follicular differentiation. Functionally, these microtissues are able to grow hairs in vivo. This work sheds light on the complex effects and dynamics of cell-cell and cell-substratum interaction in the patterning of heterotypic cells into tissue forms and is of potential to be applied to mass generation of other epithelial organ primordia in vitro.

Hair morphogenesis in vitro: formation of hair structures suitable for implantation

AIM

To develop a construct through which implanted follicular cells will efficiently cause hair regeneration for the treatment of androgenetic alopecia.

MATERIALS & METHODS

Follicular dermal and epidermal cells isolated from embryonic mouse skin were formed into aggregates. The aggregates were incubated in culture for 5-7 days and then implanted intradermally into athymic mice.

RESULTS

During culture, mixed cell aggregates developed into hair-like structures, termed 'proto-hairs'. Proto-hairs contained structures that resembled normal hair components, such as dermal papillae, hair matrix and rudimentary hair shafts. When implanted into mouse skin, they developed further into mature hair follicles capable of prolonged growth.

CONCLUSION

Mixed aggregates of murine follicular cells have the ability to develop in culture into proto-hairs that retain the ability to fully develop into hair follicles after implantation. Proto-hairs from human cells could provide a convenient and practical means by which follicular cells could be implanted for efficient hair regeneration to treat hair loss.

Self-assembly of dermal papilla cells into inductive spheroidal microtissues on poly(ethylene-co-vinyl alcohol) membranes for hair follicle regeneration

Self-aggregation is key to hair follicle (HF) induction ability of dermal papilla (DP) cells and neogenesis of HF can be achieved by transplanting DP microtissues. However, there is currently lack of a suitable system that allows efficient production of DP microtissues and analysis of DP self-aggregation in vitro. We demonstrate that, at a higher seeding cell density, poly(ethylene-co-vinyl alcohol) (EVAL) membranes facilitate DP self-assembly into many compact spheroidal microtissues that are able to induce new HFs. This self-assembling process is associated with an enhanced cell movement and a declined cell-substrate adhesivity on EVAL. A compromised cell growth is also revealed on EVAL. On the contrary, a more adherent surface allows faster cell expansion but maintains DP cells in a flat morphology. Dynamically, cell migration, intercellular collision and intercellular adhesion contribute to DP microtissue formation on EVAL. Our results suggest that, for large-scale production of DP microtissues for HF regeneration, an adhesive surface is needed for quick cell expansion and a biomaterial with a lower adhesivity is required for self-aggregation. In addition, this system can be a model for investigation of DP self-aggregation in vitro.

Effect of therapeutic macromolecules in spheroids

Recent advances in biotechnology have allowed the production of new types of macromolecular therapeutic agents (antibodies, immunotoxins, cytokines, extracellular matrix molecule (ECM) proteins, vectors) that may eventually find broad clinical applications in the treatment of human tumors and other diseases. The model of the Multicellular Tumor Spheroids (MTS) represents a valuable tool to test the therapeutic potential of these new pharmacologic agents in a 3-D context. Specific questions pertaining to the behaviour in a 3-D setting of some of the macromolecules under evaluation for in vivo applications can also be addressed in the MTS model (e.g. 'binding site barrier', role of cell-cell and cell-ECM interactions). This paper reviews the most significant contributions regarding the delivery of macromolecules to MTS, the penetration and therapeutic effects of antibodies, radiolabelled antibodies, immunotoxins and other macromolecular compounds.

Histodifferentiation of hair follicles in grafting of cell aggregates obtained by rotation culture of embryonic rat skin

We have previously reported reconstruction of hair follicles from a single cell suspension of rat fetal upper lip by a two-step culture method consisting of rotation and flotation cultures. Rotation sorted out the cells and flotation facilitated histodifferentiation. In the present study, we added grafting procedures to the previous method to see whether cell aggregates obtained this way were graftable, and whether the grafting promoted histodifferentiation. The aggregates before and after flotation were grafted, and differentiation of hair follicles comparable to those in vivo was confirmed 10 days after grafting. There was no difference in the degree of differentiation between the two kinds of grafts. The grafting procedure therefore resulted in an appreciable increase in histodifferentiation even when aggregates obtained after flotation were grafted.

Three-dimensional cell cultures: from molecular mechanisms to clinical applications

This article reviews actual advances in the development and application of three-dimensional (3-D) cell culture systems. Recent therapeutically oriented studies include characterization of multicellular-mediated drug resistance, novel ways of quantifying hypoxia, and new approaches to more efficient immunotherapy. Recent progress toward understanding the development of necrosis in tumor spheroids has been made using novel spheroid models. 3-D cultures have been used for studies on molecular mechanisms involved in invasion and metastasis, with a major focus on the role of E-cadherin. Similarly, tumor angiogenesis and the significance of vascular endothelial growth factor have been investigated in a variety of 3-D culture systems. There are many ongoing developments in tissue modeling or remodeling that promise significant progress toward the development of bioartificial liver support and artificial blood. Perhaps one of the most interesting areas of basic research with 3-D cultures is the characterization of embryoid bodies obtained from stable embryonic stem cells. These models have greatly increased the understanding of embryonic development, in particular through the notable exceptional advances in cardiogenesis.