An efficient method for isolation of hair papillae and follicle epithelium from human scalp specimens

Epidermal/Dermal Separation Techniques and Analysis of Cell Populations in Human Skin Sheets

Human skin consists of three compartments, each endowed with a particular structure and the presence of several immune and nonimmune cells that together comprise a protective shield and orchestrate multiple processes in the skin. Appropriate processing of human skin samples acquired from healthy volunteers or patients is essential for successful analysis in basic, translational, and clinical research to obtain accurate and reliable results, despite differences between individuals. From the wide range of available assays and methods, it is necessary to select the suitable method for separation of skin compartments, which will provide preservation or high viability of skin cells or whole structures that will be analyzed or further processed. In this paper, we review and discuss skin separation methods and compare their features such as processing time, cell viability, location of the basement membrane after detachment of the epidermis from the dermis, and their application. Furthermore, we visualize different cell populations and structures in epidermal and dermal sheets using confocal microscopy. It is aimed to provide an overview of the optimal processing of human skin samples and their possible application.

Tight Junction barriers in human hair follicles - role of claudin-1

Barrier function of hair follicles (HFs) is of great interest because they might be an entry port for allergens/pathogens, but could on the other hand be used for drug delivery or vaccination. Therefore we investigated tight junction (TJ) barrier function in human HFs. We show that there is a TJ barrier in the outermost living layer bordering to the environment from the infundibulum to the lower central part and between Henle’s and Huxles layer of anagen HFs. In club hair typical for catagen and telogen HFs a TJ barrier is found surrounding the club. This demonstrates that there is a continuous TJ barrier along interfollicular epidermis and HFs in different phases of HF cycle. However, interestingly, in cell culture experiments we can show that barrier is less tight in HF keratinocytes compared to interfollicular keratinocytes. Knock-down of the TJ protein claudin-1, which we demonstrate here to be less expressed in HFs of lesional atopic dermatitis skin, results in impaired barrier function, decreased proliferation and increased apoptosis of hair keratinocytes. This is in line with a hair growth phenotype in claudin-1 deficient patients (NISCH syndrome) and corresponding knock-out mice and indicates an important role of claudin-1 in HF barrier function and growth.

Hair follicle regeneration in skin grafts: current concepts and future perspectives

The repair and management of full-thickness skin defects resulting from burns and chronic wounds remain a significant unmet clinical challenge. For those skin defects exceeding 50%-60% of total body surface area, it is impractical to treat with autologous skin transplants because of the shortage of donor sites. The possibility of using tissue-engineered skin grafts for full-thickness wound repair is a promising approach. The primary goal of tissue-engineered skin grafts is to restore lost barrier function, but regeneration of appendages, such as hair follicles, has to be yet achieved. The successful regeneration of hair follicles in immunodeficient mice suggests that creating human hair follicles in tissue-engineered skin grafts is feasible. However, many limitations still need to be explored, particularly enriching isolated cells with trichogenic capacity, maintaining this ability during processing, and providing the cells with proper environmental cues. Current advances in hair follicle regeneration, in vitro and in vivo, are concisely summarized in this report, and key requirements to bioengineer a hair follicle are proposed, with emphasis on a three-dimensional approach.

Dermal papilla cells induce keratinocyte tubulogenesis in culture

The ability of dermal papilla (DP) cells to induce hair growth was reported in many studies. However, early stages of hair follicle development and signals that govern this process are poorly understood. Therefore, an in vitro model may be a convenient system to study epithelial-mesenchymal interactions and early stages of epidermal morphogenesis, especially in humans. To investigate the role of DP cells in epidermal morphogenesis we modified the method of isolation of DP cells from hair follicle of human scalp and developed the three-dimensional model of epidermal morphogenesis. Isolated DP cells were able to differentiate in adipogenic and osteogenic directions and retained activity of alkaline phosphatase (AP) for seven passages in culture. DP cells were able to induce tubule-like structures in three-dimensional model in vitro and to reorganize collagen matrix. Prolonged cultivation of DP cells has been a big problem because of the loss of hair follicle-inducing ability and growth activity after several passages. To solve this problem we immortalized DP cells by the transfection of the human telomerase reverse transcriptase cDNA (hTERT). Immortalized DP-hTERT cells retained AP activity and demonstrated low ability to osteogenic differentiation. The conditioned medium collected from actively proliferated cells as well as DP-hTERT cells themselves were capable to induce tubulogenesis after prolonged keratinocyte cultivation.

Hair follicle reformation induced by dermal papilla cells from human scalp skin

To investigate the possibility of hair follicle reformation induced by dermal papilla cells in vivo and in vitro. Dermal papilla cells, dermal sheath cells obtained from human scalp skin by enzyme digestion were mixed with collagen to form mesenchymal cell-populated collagen gels. Superior and inferior epithelial cells and bulb matrical cells were then cultured on these gels by organotypic culture to recombine bilayer artificial skins. Dermal papilla cells and outer root sheath keratinocytes were mingled together and transplanted under subcutaneous tissue of the dorsal skin of nude mice. The results of histologic examination was observed with HE stain. These recombinants by organotypic culture all reformed bilayer structure like nature skin. Hair follicle-like structure reformation was found in dermal sheath cell-populated collagen gel when combined with superior or inferior epithelial cells. Dermal papilla cells also induced superior and inferior epithelial cells to form hair follicle on nude mice. Low passage dermal papilla cells mixed with hair follicle epithelial cells reformed many typical hair follicle structures and produced hair fibres after transplantation on nude mice. The dermal part of hair follicle, such as dermal papilla cells and dermal sheath cells, has the ability to induce hair follicle formation by interaction with the epithelial cells of hair follicle.

Enzyme digestion to isolate and culture human scalp dermal papilla cells: a more efficient method

In this study, we show a more efficient method for isolation and cultivation of dermal papilla cells from hair follicles of human scalp skin. The dermal partments of low hair follicles were pulled out from cutaneous fat and the bulb epithelium was teased out from the fibrous sheath with attached dermal papilla by applying gentle pressure with the tip of an occal forceps. When these fibrous sheaths were entirely digested into isolated cells by collagenase D but the dermal papillae were justly to be digested, collagenase D was discarded and the dermal papillae were isolated completely out from the resuspension solution by repeated low-speed centrifugation and transferred to another dish for free-floating culture. This procedure markedly simplifies the steps of isolated dermal papilla operation and relieves the laborious tension. Furthermore, dermal papillae could be isolated on a large-scale and remained intact. After collagenase digestion, the dermal papillae showed very high adherent rate and quicker growth than that of microdissection, which suggests that the definition factor of dermal papilla cell migration was relaxed and some structure had been activated or exposed. The cells exhibited a multi-layer forming property and spread-out growth style. They showed positive with alcian blue, with toluidine blue O for different gradient pH and PAS, which was similar to the staining results of in situ dermal papilla. It suggests that the culture papilla cells still synthesize and excrete neutral and acid mucopolysaccharides. Our results demonstrate that the papilla cells in culture condition still remain the ability to synthesize the specific extracellular matrix components of in situ dermal papilla, which supports the concept that the dermal papilla cell, a highly specialized fibroblast, especially is involved in hair growth regulation.

Proliferative potential of different keratinocytes of plucked human hair follicles

We have examined colony-forming ability, localization of colony-forming cells, and in vitro life spans of outer root sheath keratinocytes of different fragments of adult human plucked hair follicles. These were shown by immunohistochemical staining for cytokeratins and integrins to contain a preserved basal cell layer. By microdissection, five fragments of the outer root sheath (B1, B2, B3-1, B3-2, B4) were separated, dispersed by trypsin into single cell suspensions, and grown on human feeder fibroblasts. All fragments gave rise to at least some colonies, but colony-forming ability was mostly marked in the intermediate part (B2) and the lower half of the central part (B3-1); approximately 60% of colony-forming cells of a hair follicle localized to the fragment B3-1 and 28% to the fragment B3-2 (upper half of the central part, including bulge). To compare the in vitro life spans of cells from the various fragments, we subcultured isolated keratinocytes under identical conditions. The longest was found in the fragment B3-2 and the shortest in the fragment B1 (bulb). Moreover, the differentiation state of the native cells and the cells of all cultures were studied during their whole life spans by immunocytochemical analysis of various proliferation and differentiation markers. Surprisingly, keratinocytes of all fragments, as shown by expression of high-molecular-weight cytokeratins and filaggrin, were capable of terminal differentiation. These data indicate that cells with long life spans are localized in central parts of the outer root sheath close to the bulge area and that cells with high colony-forming ability are localized in the lower central parts. The latter are usually removed by plucking and may therefore not represent stem cells but rather cells important for hair growth during a single cycle. Cells with long life spans--also included in plucked hair follicles--may be immediate progeny of stem cells that will be segregated in the bulge area. Finally, our results are important for gene transfer and stem cell gene therapy in genodermatoses, because plucked hair follicles are easily available and keratinocytes close to the bulge area should be used selectively.