Immortalized rat whisker dermal papilla cells cooperate with mouse immature hair follicle buds to activate type IV procollagenases in collagen matrix coculture: correlation with ability to promote hair follicle development in nude mouse grafts

Building complex tissues: high-throughput screening for molecules required in hair engineering

A fully functional model of hair reconstitution remains elusive because of the complexity of cellular organization and the number of molecular interactions that must be approximated. In this issue, Havlickova et al. (2009) report a significant contribution to hair engineering with their human folliculoid microsphere assay.

Isolation and short-term culture of primary keratinocytes, hair follicle populations and dermal cells from newborn mice and keratinocytes from adult mice for in vitro analysis and for grafting to immunodeficient mice

Protocols for preparing and culturing primary keratinocytes from newborn and adult mouse epidermis have evolved over the past 35 years. This protocol is now routinely applied to mice of various genetic backgrounds for in vitro studies of signaling pathways in differentiation and cell transformation, and for assessing the in vivo phenotype of altered keratinocytes in grafts of cells on immunodeficient mice. Crucial in the development and application of the procedure was the observation that keratinocytes proliferate in media of low calcium concentration, but rapidly commit to differentiation at calcium concentrations >0.07 mM after the initial attachment period. Preparing primary keratinocytes from ten newborn mice requires 2-3 h of hands-on time. Related procedures are also provided: preparing immature hair follicle buds, developing dermal hair follicles and fibroblasts from newborn mice, preparing primary keratinocytes from adult mice and grafting cell mixtures on athymic nude mice.

Establishment of SV40T-transformed human dermal papilla cells and identification of dihydrotestosterone-regulated genes by cDNA microarray

BACKGROUND

Recent studies suggest that androgens are the main regulator of changes in human hair growth, and dermal papilla (DP) is known to secret factors which regulate the growth and activity of the cells in the follicle in response to androgens. However, published data of androgen-regulated genes in human dermal papilla cells is limited and genome-wide large scale screening has not been reported.

OBJECTIVE

To identify the dihydrotestosterone (DHT)-regulated genes in human dermal papilla cells.

METHODS

SV40T-transformed human dermal papilla cell line (SV40T-DPC) was established and DHT-regulated genes were screened by cDNA microarray analysis.

RESULTS

SV40T-DPC maintained early passage morphology and expressed functional androgen receptors. cDNA microarray followed by RT-PCR analysis showed that a number of genes are regulated by DHT in SV40T-DPC.

CONCLUSION

The DHT-regulated genes reported in this study may be involved in androgen-mediated regulation of hair growth.

Thymosin beta4 increases hair growth by activation of hair follicle stem cells

Thymosin beta4, a 43-amino acid polypeptide that is an important mediator of cell migration and differentiation, also promotes angiogenesis and wound healing. Here, we report that thymosin beta4 stimulates hair growth in normal rats and mice. A specific subset of hair follicular keratinocytes in mouse skin expresses thymosin beta4 in a highly coordinated manner during the hair growth cycle. These keratinocytes originate in the hair follicle bulge region, a niche for skin stem cells. Rat vibrissa follicle clonogenic keratinocytes, closely related, if not identical, to the bulge-residing stem cells, were isolated and their migration and differentiation increased in the presence of nanomolar concentrations of thymosin beta4. Expression and secretion of the extracellular matrix-degrading enzyme matrix metalloproteinase-2 were increased by thymosin beta4. Thus, thymosin beta4 accelerates hair growth, in part, due to its effect on critical events in the active phase of the hair follicle cycle, including promoting the migration of stem cells and their immediate progeny to the base of the follicle, differentiation, and extracellular matrix remodeling.

Identification of androgen-regulated genes in SV40-transformed human hair dermal papilla cells

BACKGROUND

Androgens are major regulators of human hair growth, which exert their effect on follicular epithelium via the mesenchyme-derived dermal papilla (DP) cells. However, very few data are available with regard to the genes regulated by androgen in DP cells.

OBJECTIVE

To investigate the differentially expressed genes by androgen in DP cells.

METHODS

Human hair DP cells were cultured and transformed with SV40 T antigen. Using cDNA representational difference analysis, androgen-regulated genes in SV40-transformed dermal papilla (SDP) cells were identified.

RESULTS

SDP cells revealed extended lifespan as compared with primary cultured DP cells. SDP cells expressed androgen receptor (AR) and showed androgen responsiveness. cDNA representational difference analysis followed by Northern blot analysis showed that heat shock cognate protein, Hsc70 was differentially expressed by dihydrotestosterone (DHT) treatment in SV40-transformed DP cells.

CONCLUSION

These results suggest that Hsc70 may be involved in androgen action on DP cells.

Expression patterns of the transcription factor AP-2alpha during hair follicle morphogenesis and cycling

AP-2alpha is a member of a family of transcription factors expressed in cells of the epithelial and neural crest lineage. AP-2alpha plays an essential role in embryonic development and in regulation of epithelial gene transcription. To further characterize the role of AP-2alpha in skin biology, we assessed its expression in the skin of C57BL/6J mice during defined stages of hair follicle morphogenesis and cycling. During early hair follicle morphogenesis, AP-2alpha was upregulated in the epidermal placode, in the basal keratinocytes of the hair follicle bud, and then in the inner root sheath. The follicular papilla cells underwent a brief upregulation of AP-2alpha expression during the initiation of hair shaft formation and active hair follicle downward growth. Completion of hair follicle morphogenesis was associated with a marked reduction of AP-2alpha immunoreactivity in the lower portion of the hair follicle including both epithelial and mesenchymal compartments. In adolescent mouse skin, consistently strong AP-2alpha expression was found in the basal keratinocytes of the epidermis, in the hair follicle infundibulum, and in the sebocytes. In the follicular papilla, AP-2alpha was weakly expressed in telogen, significantly upregulated in early anagen, then gradually declined, and reappeared again in middle catagen. In the inner root sheaths, AP-2alpha expression was detected during early and middle anagen and during middle catagen stages. Prominent AP-2alpha expression was also seen in the zone of club hair formation. Therefore, AP-2alpha upregulation in both epithelial and mesenchymal hair follicle compartments was coordinated with initiation of major remodeling processes. Our findings support the use of the hair follicle as a model to explore the role of AP-2alpha in physiologic remodeling of developing organs and in reciprocal ectodermal-mesenchymal interactions.

Prostaglandin-induced hair growth

Latanoprost, used clinically in the treatment of glaucoma, induces growth of lashes and ancillary hairs around the eyelids. Manifestations include greater thickness and length of lashes, additional lash rows, conversion of vellus to terminal hairs in canthal areas as well as in regions adjacent to lash rows. In conjunction with increased growth, increased pigmentation occurs. Vellus hairs of the lower eyelids also undergo increased growth and pigmentation. Brief latanoprost therapy for 2-17 days (3-25.5 microg total dosage) induced findings comparable to chronic therapy in five patients. Latanoprost reversed alopecia of the eyelashes in one patient. Laboratory experiments with latanoprost have demonstrated stimulation of hair growth in mice and in the balding scalp of the stumptailed macaque, a primate that demonstrates androgenetic alopecia. The increased number of visible lashes is consistent with the ability of latanoprost to induce anagen (the growth phase) in telogen (resting) follicles while inducing hypertrophic changes in the involved follicles. The increased length of lashes is consistent with the ability of latanoprost to prolong the anagen phase of the hair cycle. Correlation with laboratory studies suggests that initiation and completion of latanoprost hair growth effects occur very early in anagen and the likely target is the dermal papilla.

Proliferation and differentiation of organoid hair follicle cells co-cultured with fat cells in collagen gel matrix culture

Using rat skin, we studied the influence of fat cells on the proliferation and differentiation of organoid hair follicle cells in a three-dimensional collagen gel matrix culture system. We cultured organoid hair follicles embedded in collagen gel under each of the following three conditions: cell-free collagen gel for control experiments (condition 1); co-culture with fat cells in close apposition (condition 2); and co-culture with fat cells in spatial separation (condition 3). Outgrowths of epithelial cells from the organoid hair follicles associated with perifollicular proliferation of fibroblasts were observed under conditions 1 and 3. Under condition 2, proliferation of both organoid hair follicle cells and fibroblasts was inhibited, but differentiation of the hair follicle cells appeared to be accelerated. Fat cells are considered to have an inhibitory effect on the proliferation of perifollicular fibroblasts, which might have resulted in the inhibition of hair follicle cell proliferation and also in the better maintenance of normal follicular structure and integrity, allowing for hair-type differentiation to proceed. A direct accelerating effect of fat cells on hair follicle differentiation may also have been responsible. In a physiological state (co-culture with keratinocytes on the collagen gel), similar results were observed under conditions 1 and 2. The different findings under conditions 2 and 3 may be due to either of two possibilities: either the concentration gradient of the soluble factors released from fat cells, acting on either the hair follicle cells or the perifollicular fibroblasts as an inhibitor of proliferation, caused the difference in the results, or direct contact between the organoid hair follicle cells and fat cells may have influenced the accelerating effect of fat cells on the differentiation of hair follicle cells.

Human hair follicle regeneration following amputation and grafting into the nude mouse

In this study we investigated the capacity of the human hair follicle to regenerate a fiber-forming bulb after its amputation. We removed the bases from terminal follicles from a variety of sites and transplanted the follicles onto athymic mice, either still attached to a skin graft or as subcutaneous implants of individual follicles. External hair growth was observed on the skin grafts, and histology of the follicles revealed restoration of dermal papillae and follicle bulb structures. This result suggests that the capacity of hair follicles to regenerate their lower structures after removal, which was first demonstrated on whisker follicles, may be a general phenomenon. It emphasizes the importance of specific cellular subpopulations within the follicle and the role of dermal-epidermal interactions in adult follicle activities.

Dermal-epidermal interactions. Adult follicle-derived cell populations and hair growth

Intrinsic dermal-epidermal interactions are central to the development and growth of hair. This article describes investigations into the inductive properties of specific dermal and epidermal cell populations from adult follicles by means of cell culture and in vivo implantation. It highlights the inductive powers of cultured dermal papilla cells and the more recent finding that the germinative epidermal cells of the lower follicle also can stimulate hair growth. How the reconstruction of a hair follicle from its constituent parts has been achieved is described. The significance of these findings is considered with reference to human hair growth, tissue engineering, and the prospects for elucidating the molecular signalling mechanisms that underpin dermal-epidermal interplay.