Isolation and culture of amelanotic melanocytes from human hair follicles

Culturing of Melanocytes from the Equine Hair Follicle Outer Root Sheath

Hair follicles harbor a heterogeneous regenerative cell pool and represent a putative low-to-non-invasively available source of stem cells. We previously reported a technology for culturing human melanocytes from the hair follicle outer root sheath (ORS) for autologous pigmentation of tissue engineered skin equivalents. This study translated the ORS technology to horses. We de-veloped a culture of equine melanocytes from the ORS (eMORS) from equine forelock hair follicles cultured by means of an analogue human hair follicle-based in vitro methodology. The procedure was adjusted to equine physiology by addition of equine serum to the culture medium. The hair follicles were isolated by macerating forelock skin rests, enzymatically digested and subjected to air-medium-interface cultivation method. The procedure resulted in differentiated equine melanocytes, which exhibited typical morphology, presence of melanosomes, expression of cytoskeleton proteins vimentin, α-SMA, Sox2, S100ß and tyrosinase as well as tyrosinase activity followed by production of melanin. According to all assessed parameters, eMORS could be ranked as partially melanotic melanocytes. The results of the study offer an experimental base for further insight into hair follicle biology in equine and for comparative studies of hair follicles across different species.

Isolation and enrichment of melanocytes from human corneal limbus using CD117 (c-Kit) as selection marker

Limbal melanocytes (LM) are located in the basal epithelial layer of the corneoscleral limbus and interact with adjacent limbal epithelial progenitor cells. The exploration of their biological role in the maintenance of the limbal stem cell niche has been limited by the difficulty of LM isolation and cultivation. Here, we report on a facile protocol for the efficient isolation and enrichment of pure populations of human LMs by fluorescence-activated cell sorting (FACS) using antibodies raised against the cell surface marker CD117 (c-Kit). The enriched LMs retain self-renewal capacity and sustained melanin production, and are suitable to study the potential of LMs in stem cell-based corneal tissue engineering.

Hair Follicle as a Source of Pigment-Producing Cells for Treatment of Vitiligo: An Alternative to Epidermis?

To discuss the advantages and limitations of hair follicle-derived cell transplantation (FCT) in vitiligo, compared to the epidermal cell transplantation (ECT), and the knowledge gap which is required to be bridged. The papers relevant to the purpose was reviewed. Surgical approaches for treating vitiligo are based on the idea of replenishing lost melanocytes. Skin and hair follicles as the main sources of melanocytes have been applied for this purpose transferring the whole tissue or tissue-derived cell suspension to the vitiligo lesions. Considering the differences between hair follicle and epidermis in terms of the constituting cell populations, phenotype and function of melanocytes, and micro-environmental factors, different response of vitiligo patients to treatment with FCT or ECT would be expected theoretically. However, there is currently a lack of evidence on such a difference. However, ECT appears to be a more feasible, less time-consuming, and more comfortable treatment for both physicians and patients. Although the current evidence has not shown a significant difference between ECT and FCT in terms of efficacy, ECT appears to be more feasible specifically in the treatment of large lesions. However, further randomized controlled clinical trials with larger sample sizes and longer follow-up durations are required to be conducted to draw a definite conclusion on comparing FCT with ECT in terms of the safety, efficacy, durability of the therapeutic effects, and indications in vitiligo patients.

The biology of human hair greying

Hair greying (canities) is one of the earliest, most visible ageing-associated phenomena, whose modulation by genetic, psychoemotional, oxidative, senescence-associated, metabolic and nutritional factors has long attracted skin biologists, dermatologists, and industry. Greying is of profound psychological and commercial relevance in increasingly ageing populations. In addition, the onset and perpetuation of defective melanin production in the human anagen hair follicle pigmentary unit (HFPU) provides a superb model for interrogating the molecular mechanisms of ageing in a complex human mini-organ, and greying-associated defects in bulge melanocyte stem cells (MSCs) represent an intriguing system of neural crest-derived stem cell senescence. Here, we emphasize that human greying invariably begins with the gradual decline in melanogenesis, including reduced tyrosinase activity, defective melanosome transfer and apoptosis of HFPU melanocytes, and is thus a primary event of the anagen hair bulb, not the bulge. Eventually, the bulge MSC pool becomes depleted as well, at which stage greying becomes largely irreversible. There is still no universally accepted model of human hair greying, and the extent of genetic contributions to greying remains unclear. However, oxidative damage likely is a crucial driver of greying via its disruption of HFPU melanocyte survival, MSC maintenance, and of the enzymatic apparatus of melanogenesis itself. While neuroendocrine factors [e.g. alpha melanocyte-stimulating hormone (α-MSH), adrenocorticotropic hormone (ACTH), ß-endorphin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH)], and micropthalmia-associated transcription factor (MITF) are well-known regulators of human hair follicle melanocytes and melanogenesis, how exactly these and other factors [e.g. thyroid hormones, hepatocyte growth factor (HGF), P-cadherin, peripheral clock activity] modulate greying requires more detailed study. Other important open questions include how HFPU melanocytes age intrinsically, how psychoemotional stress impacts this process, and how current insights into the gerontobiology of the human HFPU can best be translated into retardation or reversal of greying.

Laminin-511-E8 promotes efficient in vitro expansion of human limbal melanocytes

Limbal melanocytes, located in the basal epithelial layer of the corneoscleral limbus, represent essential components of the corneal epithelial stem cell niche, but, due to difficulties in their isolation and cultivation, their biological roles and potential for stem cell-based tissue engineering approaches have not been comprehensively studied. Here, we established a protocol for the efficient isolation and cultivation of pure populations of human limbal melanocytes, which could be expanded at high yield by using recombinant laminin (LN)-511-E8 as culture substrate. Co-cultivation of limbal melanocytes with limbal epithelial stem/progenitor cells on fibrin hydrogels pre-incubated with LN-511-E8 resulted in multilayered stratified epithelial constructs within ten days. By reproducing physiological cell–cell and cell–matrix interactions of the native niche environment, these biomimetic co-culture systems provide a promising experimental model for investigating the functional roles of melanocytes in the limbal stem cell niche and their suitability for developing advanced epithelial grafts for ocular surface surface reconstruction.

Melanocyte Chitosan/Gelatin Composite Fabrication with Human Outer Root Sheath-Derived Cells to Produce Pigment

The hair follicle serves as a melanocyte reservoir for both hair and skin pigmentation. Melanocyte stem cells (MelSCs) and melanocyte progenitors reside in the bulge/sub-bulge region of the lower permanent portion of the hair follicle and play a vital role for repigmentation in vitiligo. It would be beneficial to isolate MelSCs in order to further study their function in pigmentary disorders; however, due to the lack of specific molecular surface markers, this has not yet been successfully accomplished in human hair follicles (HuHF). One potential method for MelSCs isolation is the “side population” technique, which is frequently used to isolate hematopoietic and tumor stem cells. In the present study, we decided to isolate HuHF MelSCs using “side population” to investigate their melanotic function. By analyzing mRNA expression of TYR, SOX10, and MITF, melanosome structure, and immunofluorescence with melanocyte-specific markers, we revealed that the SP-fraction contained MelSCs with an admixture of differentiated melanocytes. Furthermore, our in vivo studies indicated that differentiated SP-fraction cells, when fabricated into a cell-chitosan/gelatin composite, could transiently repopulate immunologically compromised mice skin to regain pigmentation. In summary, the SP technique is capable of isolating HuHF MelSCs that can potentially be used to repopulate skin for pigmentation.

Convenient methodology for extraction and subsequent selective propagation of mouse melanocytes in culture from adult mouse skin tissue

Mouse melanoma B16-BL6 cells are useful cells for cancer metastatic studies. To understand the metastatic principle at molecular levels, it is necessary to carry out experiments in which cancer cells and their normal counterparts are compared. However, unlike normal human melanocytes, preparation of normal mouse melanocytes is quite difficult due to the lack of marketing and insufficient information on an established protocol for primary culture of mouse melanocytes. In this study, we aimed to establish a convenient method for primary culture of mouse melanocytes on the basis of the protocol for human melanocytes. The main obstacles to preparing pure mouse melanocytes are how to digest mouse skin tissue and how to reduce the contamination of keratinocytes and fibroblasts. The obstacles were overcome by collagenase digestion for skin specimens, short time trypsinization for separating melanocytes and keratinocytes, and use of 12-O-Tetradecanoylphorbol 13-acetate (TPA) and cholera toxin in the culture medium. These supplements act to prevent the proliferation of keratinocytes and fibroblasts, respectively. The convenient procedure enabled us to prepare a pure culture of normal mouse melanocytes. Using enriched normal mouse melanocytes and cancerous B16-BL6 cells, we compared the expression levels of melanoma cell adhesion molecule (MCAM), an important membrane protein for melanoma metastasis, in the cells. The results showed markedly higher expression of MCAM in B16-BL6 cells than in normal mouse melanocytes.

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Collagenase efficiently extracts skin cells.

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Short trypsinization greatly helps an enrichment of mouse melanocytes in culture.

Hair & skin derived progenitor cells: In search of a candidate cell for regenerative medicine

BACKGROUND & OBJECTIVES

Skin is an established tissue source for cell based therapy. The hair follicle has been introduced later as a tissue source for cell based therapy. The ease of tissue harvest and multipotent nature of the resident stem cells in skin and hair follicle has promoted basic and clinical research in this area. This study was conducted to evaluate skin stem cells (SSCs) and hair follicle stem cells (HFSCs) as candidate cells appropriate for neuronal and melanocyte lineage differentiation.

METHODS

In this study, SSCs and hair follicle stem cells (HFSCs) were expanded in vitro by explant culture method and were compared in terms of proliferative potential and stemness; differentiation potential into melanocytes and neuronal lineage.

RESULTS

SSCs were found to be more proliferative in comparison to HFSCs, however, telomerase activity was more in HFSCs in comparison to SSCs. Capacity to differentiate into two lineages of ectoderm origin (neuronal and melanocyte) was found to be different. HFSCs cells showed more propensities towards melanocyte lineage, whereas SSCs were more inclined towards neuronal lineage.

INTERPRETATION & CONCLUSIONS

The study showed that SSCs had differential advantage over the HFSCs for neuronal cell differentiation, whereas, the HFSCs were better source for melanocytic differentiation.

Human melanocytes form a PAX3-expressing melanocyte cluster on Matrigel by the cell migration process

BACKGROUND

The interactions between human epidermal melanocytes and their cellular microenvironment are important in the regulation of human melanocyte functions or in their malignant transformation into melanoma. Although the basement membrane extracellular matrix (BM-ECM) is one of major melanocyte microenvironments, the effects of BM-ECM on the human melanocyte functions are not fully explained at a molecular level.

OBJECTIVE

This study was aimed to characterize the molecular and cellular interactions between normal human melanocytes (NHMs) and BM-ECM.

METHODS

We investigated cell culture models of normal human melanocytes or melanoma cells on three-dimensional (3D) Matrigel to understand the roles of the basement membrane microenvironment in human melanocyte functions. Melanogenesis and melanobast biomarker expression in both primary human melanocytes and melanoma cells on 3D Matrigel were evaluated.

RESULTS

We found that NHMs migrated and formed reversible paired box 3 (PAX3) expressing cell clusters on three-dimensional (3D) Matrigel. The melanogenesis was significantly decreased in the PAX3 expressing cell cluster. The expression profile of PAX3, SOX10, and MITF in the melanocyte cluster on 3D Matrigel was similar to that of melanoblasts. Interestingly, PAX3 and SOX10 showed an inverse expression profile in NHMs, whereas the inverse expression pattern of PAX3 and SOX10 was disrupted in melanoma MNT1 and WM266-4 cells.

CONCLUSION

The human melanocyte culture on 3D Matrigel provides an alternative model system to study functions of human melanoblasts. In addition, this system will contribute to the elucidation of PAX3-related tumorigenic mechanisms to understand human melanoma.

Differentiating the stem cell pool of human hair follicle outer root sheath into functional melanocytes

Bench-to-Bedside concepts for regenerative therapy place significant weight on noninvasive approaches, with harvesting of the starting material as a header. This is particularly important in autologous treatments, which use one's bodily constituents for therapy. Precisely the stretch between obtaining therapeutic elements invasively and noninvasively places non-intrusive "sampling" rather than "biopsy" in the center of the road map of developing an autologous regenerative therapy. We focus on such a noninvasively available source of adult stem cells that we carry with us throughout our life, available at our fingertips-or shall we say hair roots, by a simple plucking of hair: the human hair follicle. This chapter describes an explant procedure for cultivating melanocytes differentiated from the stem cell pool of the hair follicle Outer Root Sheath (ORS). In vivo, the most abundant derivatives of the heterogeneous ORS stem cell pool are epidermal cells-melanocytes and keratinocytes which complete their differentiation-either spontaneously or upon picking up regenerative cues from damaged skin-and migrate from the ORS towards the adjacent regenerating area of the epidermis. We have taken advantage of the ORS developmental potential by optimizing explant primary culture, expansion and melanogenic differentiation of resident ORS stem cells towards end-stage melanocytes in order to obtain functional melanocytes noninvasively for the purposes of transplantation and use them for the treatment of depigmentation disorders. Our protocol specifies sampling of hair with their ORS, follicle medium-air interface primary culture, stimulation of cell outgrowth, adherent culture and differentiation of ORS stem cells and precursors towards fully functional melanocytes. Along with cultivation, we describe selection techniques for establishing and maintaining a pure melanocyte population and methods suitable for determining melanocyte identity.

Primary culture of human face skin melanocytes for the study of hyperpigmentation

Facial epidermal pigmentation and skin tumors can be caused by UV exposure and other physical and chemical irritations. In this report we describe the primary culture of melanocytes from human face skin. The ability to culture these melanocytes will enable their morphological and biological properties to be investigated. Skin specimens were obtained from patients who had undergone lower blepharoplasty procedures. Digestion with neutral protease and trypsin was used to obtain single cell suspensions of epidermal cells. The cells were cultured in M254 medium supplemented with human melanocyte growth solution. Cell morphology was observed using inverted microscopy. Melanocytes were positively identified using both L-DOPA staining and S-100 protein immunohistochemical staining. Immunofluorescence was used to confirm the expression of tyrosinase-related protein-1, a melanocyte-specific protein. The cellular ultrastructure of the melanocytes was observed by transmission electron microscopy. The cultured human melanocytes from face skin were multi-dendritic, and many mature melanosomes were observed. Therefore, using a specific culture medium, melanocytes from face skin can be successfully cultured and made available for further investigations.

Extracted hair follicle outer root sheath cell suspension for pigment cell restoration in vitiligo

Vitiligo surgery has come up a long way from punch skin grafts to epidermal cell suspension and latest to the extracted hair follicle outer root sheath cell suspension (EHF-ORS-CS) transplantation. The progressive development from one technique to the other is always in a quest for the best. In the latest development- EHF-ORS-CS, which is an enriched source of follicular inactive melanocyte (melanocyte stem cells), seems to be a good addition to the prevailing cell-based therapies for vitiligo; however, need to be explored further in larger, and preferably randomized blinded studies. This review discusses the principle, technical details, and stem cell composition of hair follicular outer root sheath cell suspension.

Optimization of the method for the culture of melanocyte precursors from hair follicles and their activation by 1,25-dihydroxyvitamin D3

The melanocytes in vitiligo repigmentation are derived predominantly from melanocyte precursors (MPs) present in the outer root sheath (ORS) of hair follicles. The methods currently used for culturing MPs are unstable, and the cultured cells have the capacity to produce melanin. These factors are problematic when conducting in vitro studies to investigate the mechanism of repigmentation. Although 1,25-dihydroxyvitamin D3 (VID) has been demonstrated to be highly effective in the treatment of vitiligo in the clinic, its precise mode of action has yet to be elucidated. In the present study, the method for the culture of MPs from the ORS of hair follicles was optimized and the ability of VID to activate MPs was investigated. The results suggested that the MPs cultured using the optimized method mainly exhibited bipolar morphology. The cells proliferated well and were negative for 3,4-dihydroxy-L-phenylalanine (DOPA) staining. Transmission electron microscopy revealed that the cytoplasm of the MPs contained numerous stage I and stage II melanosomes; however, stage III and IV melanosomes were not observed. Following VID treatment, the MPs showed increased dendritic morphology, the cells stained positive for DOPA and stage III and IV melanosomes appeared in the cells. Western blotting revealed that microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1) and TRP-2 were expressed in the MPs and that VID increased the expression levels of MITF, TYR and TRP-1. However, the levels of MITF, TYR and TRP-1 in the MPs prior to and following VID treatment were significantly lower compared with those in cultured epidermal melanocytes, while the levels of TRP-2 in these three groups were not significantly different. Subsequent to VID treatment, the TYR activity in the MPs increased significantly, as did the corresponding melanin levels. In conclusion, the present study successfully optimized the method for MP culture. The MPs demonstrated no significant TYR activity or melanin synthesis; therefore, the MP cultures exhibited the features of MPs in vivo. In addition, VID significantly promoted the differentiation of MPs.

Culture of amelanotic melanocytes derived from human fetal hair follicles

Human melanocyte stem cells (MSCs) or melanoblasts are not well-investigated owing to the devoid of suitable culture system. Establishing cell lines of MSCs and/or their progenies from human hair follicles will provide a better opportunity to satisfy clinical needs and to enable a deeper understanding of hair-related diseases. In the present study, we cultured melanocytes derived from human fetal hair follicles, perform immunocytochemistry and Fontana Masson staining on them, and employed atomic force microscopy (AFM) and scanning electron microscopy to observe their subtle morphologies. The results show that the cultured melanocytes have a bipolar or tripolar appearance, which obviously differ from cultured epidermal melanocytes. Compared to cells derived from adult human hair follicles, these cells display a high proliferative capability and exhibit a clonal growth behavior. At the second passage, all these cells were positive for immunocytochemical staining with the NKI/beteb monoclonal antibody and Fontana Masson staining. Under AFM, the cells exhibited rounded, oval, triangular, or quadrangular perikarya, from which two or three dendrites arose. The dendritic arbor was not homogeneous but appeared as spindle-shaped dendritic swellings, knob-like processes, without any filopodia arising from the dendrites or the cell body. Without using a feeder layer, we successfully obtained the clonal growth of melanocytes from human fetal HFs, suggesting that the medium was suitable for the growth of MSCs and their progenies.

Improved method of differentiation, selection and amplification of human melanocytes from the hair follicle cell pool

Hair root harbours a complex cell pool with an immense developmental potential. Several lineages, including skin, can be differentiated from the multipotent to pluripotent cells of outer root sheath (ORS) of hair follicle. Outer root sheath presents the most opulent non-invasively gained adult stem cell source known. For the purposes of cultivating melanocytes designated for graft-based treatments of depigmentation disorders, we have established an ex vivo/in vitro cultivation method by introducing several methodological improvements to the ORS explant method of Dieckmann. As a result, we gained a higher, purer yield of differentiated melanocytes in half the time (at least 10(6) of 95% pure cells in 4 weeks). This reliable cultivation procedure begins with the epilation of 60 hairs and yields high numbers of ORS melanocytes that could be used for grafting applications. The procedure not only utilises the developmental potential of hair root cell pool and favors differentiation into melanocytes, but also contributes to the general trend of minimal-to-non-invasive strategies for regenerative medicine.

Using human hair follicle-derived keratinocytes and melanocytes for constructing pigmented tissue-engineered skin

BACKGROUND

Traditional tissue-engineered skin does not produce a satisfactory long-term result because it lacks natural skin pigmentation and leads to discolored cosmetically unpleasing skin that only functions to cover the body of patients. Additionally, the cell sources for tissue-engineered skin are generally derived from normal skin, which is often limited in patients with skin defects.

METHODS

In this study, hair follicle melanocytes and keratinocytes were isolated from human scalp. The melanocytes were co-cultured with keratinocytes until the second passage and then purified. Purified melanocytes and keratinocytes were seeded onto the chitosan-gelatin membrane for 1 week to construct pigmented tissue-engineered skin. The pigmented skin equivalent was used to resurface the skin defect in nude mice. Four weeks after grafting, skin biopsies were harvested to take hematoxylin and eosin staining and immunohistochemistry staining of Melan-A and HLA-ABC.

RESULTS

Large quantities of purified melanocytes can be obtained with co-culture method. The hematoxylin and eosin staining of repaired skin biopsy demonstrated that the tissue-engineered skin can repair skin defects successfully. Engineered skin contained pigmentation and stained positive for Melan-A and HLA-ABC, which confirmed the presence of melanocytes and its sources were of human origin.

CONCLUSION

This study demonstrated the possibility of constructing pigmented tissue-engineered skin with human hair follicle-derived keratinocytes and melanocytes, which brings a promising method to make up for the deficiency of traditional tissue-engineered skin and provides an alternative treatment for depigmentation diseases.

The distributions of type IV collagen alpha chains in basement membranes of human epidermis and skin appendages

Distributions of type IV collagen alpha chains in the basement membrane (BM) of human skin and its appendages were analyzed by immunofluorescent microscopy using chain-specific monoclonal antibodies. The basement membrane beneath the epidermis contained [alpha1(IV)](2)alpha2(IV) and [alpha5(IV)](2)alpha6(IV) but no alpha3(IV)alpha4(IV)alpha5(IV); this held true for at the eccrine sweat glands and glandular ducts, sebaceous glands, hair follicles, and arrector muscles of hair. The secretary portion of the eccrine sweat glands was rich in [alpha1(IV)](2) alpha2(IV) and had less [alpha5(IV)](2)alpha6(IV), while [alpha5(IV)](2) alpha6(IV) was abundant in the ductal portion. In the subepidermal zone, alpha5(IV)/alpha6(IV) chain negative spots (1.9-15.0 microm) were frequently observed. Triple staining samples (Mel.2, alpha2(IV) and alpha5(IV) chains) showed that about 50% of epidermal melanocytes colocalized with such spots. Results suggest that these alpha5(IV)/alpha6(IV) chain negative spots of the subepidermal basement membrane have a particular relationship with melanocytes and are sites for certain interactions between the two.

A modified method for purifying amelanotic melanocytes from human hair follicles

We describe a modified method for establishing long-term pure cultures of amelanotic melanocytes (AMMC) derived from human hair follicles. Normal human corpse scalp (just after death, 1 h) was transected 1 mm below the epidermis, and hair follicles in the remaining dermis were isolated by a two-step enzyme treatment. Hair follicle cell suspensions were prepared by 0.50% trypsin treatment for 30 min and cultured in an optimized melanoblast proliferation nature mitogen medium. Cells attached to the substratum were mostly amelanotic melanocytic in character with small, bipolar shapes in the early stage; only a few keratinocytes and rare fibroblasts were observed. Keratinocytes were easily removed by differential trypsinization. After the third passage, the proliferating cells were all amelanotic melanocytes as confirmed by immunostaining with polyclonal antibodies to alphaPEP7h, which recognized the tyrosinase protein located on melanosomes and NKI/beteb, which is a pre-melanosomal antigen against synthetic peptides corresponding to the carboxyl termini of human melanosomal protein GP100. Cultured AMMC were highly positive to L-dopa reactivity after the addition of IBMX to the culture medium for 7 days. Many stage I and II melanosomes and occasional stage III melanosomes without stage IV melanosomes were found in the cytoplasm by transmission electron microscope. This modified technique is potentially more suitable for cultivating amelanotic melanocytes. The availability of pure cultures of hair-follicle amelanotic melanocytes will facilitate investigations of the roles of those cells in migration and differentiation during treatment of vitiligo.