Fibroblast growth factor and epidermal growth factor in hair development.

Hair follicles arise in developing skin as a result of a complex of interactions that are likely to be mediated by diffusible, cell- and matrix-bound factors. Growth factors such as fibroblast growth factor (FGF) and epidermal growth factor (EGF) have been implicated in the control of epidermal and mesenchymal cell function, and it is likely that they also affect proliferation and differentiation of the cells of the cutaneous appendages during development. Immunolocalization of basic FGF adjacent to areas of proliferation in developing and in mature follicles suggests that this factor may regulate the mitotic activity of epithelially-derived cells; acidic FGF, on the other hand, appears in the differentiating cells of the follicle bulb and may therefore participate in the formation of structural components of the follicle or of the fiber. EGF has been identified as a potent modulator of cellular growth and is also present during follicle differentiation. These factors may act through autocrine and paracrine mechanisms because their receptors are also found on epidermally derived and mesenchymal structures in the skin. We have studied the effects of these growth factors on hair follicle development in the newborn mouse. Daily injections for 1 week after birth resulted in significant changes in the morphogenesis of the hair follicle population. Histologic examination of skin of FGF-treated mice suggested that the growth factor had affected hair follicle initiation and development, which resulted in a significant delay in the first and subsequent hair cycles when compared to control animals. Because aFGF and bFGF are not readily diffusible, these effects remained confined to the area of treatment. In contrast, EGF affected the whole body coat of the treated animals, induced hyperkeratinization of the skin, and caused a significant delay in hair follicle development.

Localization of epidermal growth factor immunoreactivity in sheep skin during wool follicle development.

Interactions among the cells and matrices of the epidermis and mesenchyme of skin are essential for hair follicle initiation and development. The identification of receptors for epidermal growth factor (EGF) on epithelial components of the follicle during growth has suggested that the ligand participates in some of these events. We have used affinity-purified antibodies together with an alkaline phosphatase detection procedure to investigate the distribution of EGF in the skin of the sheep during wool follicle formation. Immunoreactivity was restricted to the periderm and intermediate layers of fetal epidermis at 55 d of gestation, when the first wave of wool follicles are initiated. This particular distribution persisted during subsequent development but never became associated with the basal cells of the epidermis. The activity was lost around 118 d, coinciding with sloughing of the periderm. No immunoreactivity was found in the plugs or the dermal condensations of the developing follicles. At approximately 105 d of gestation, however, reactions were detected in the outer root sheath as the follicles matured and in the differentiating cells of the sebaceous glands. A similar distribution pattern was also noted at 140 d, just prior to birth, and in adult animals, indicating that EGF was sequestered and perhaps synthesized within the follicle. The presence of immunoreactive material was also associated with the pilary canals and the skin surface, suggesting that this may have had its origin in the sebaceous glands. We examined this using a radioreceptor assay for EGF. Material washed from the skin surface and sebaceous gland extracts were found to displace 125I-EGF from rat liver membranes, in parallel with mouse EGF.

Association of versican with dermal matrices and its potential role in hair follicle development and cycling.

Versican is a member of the group of aggregating proteoglycans involved in matrix assembly and structure and in cell adhesion. We examined changes in the distribution of versican in mammalian skin, with emphasis on hair follicle development and cycling. In adult human skin, immunostaining for versican appeared predominantly in the dermis, with intense staining of the reticular dermis. Weak staining was observed at the dermoepidermal junction and the connective tissue sheath of hair follicles. Versican expression was also noted in the reticular dermis of rat skin, within dermal papillae, and possibly associated with follicle basement membranes. During mouse hair follicle development, versican was not expressed until the hair follicles were beginning to produce fibers. With follicle maturation, versican expression intensified in the dermal papillae, reaching a maximum at the height of the growth phase (anagen), after which it diminished as the end of this phase approached. Versican immunoreactivity in the papillae decreased further during catagen and was absent from these structures during telogen. However, intense staining for versican was then observed in the neck regions of telogen follicles. As the follicles entered the next hair cycle, versican disappeared from the necks and was again seen in the dermal papillae when follicles began producing fibers. This type of expression continued throughout subsequent hair cycles and is unlike any other dermal papilla component. The results of this study are consistent with a distinct supportive role for versican in the follicle matrices during hair follicle morphogenesis and cycling.

Hair growth induction: roles of growth factors.

The hair follicles of eutheria arise during fetal life as a consequence of interactions between the cells and matrices of the epidermis and mesenchyme. In some instances, communication may be mediated by growth factors, receptors, and similar molecules. We have focused on epidermal growth factor and fibroblast growth factor, since both are expressed in skin, where they are presumed to perform regulatory functions. In sheep, EGF receptors are located on skin epithelia. An EGF-like protein was detected by immunochemistry in fetal epidermis but was not associated with the cells of developing wool follicles. During subsequent development the molecule was associated with the sebaceous glands and the outer root sheath. If the ORS may be considered a source of stem cells for the proliferating matrix, EGF may act as a differentiation factor, determining cell fates by cell contact mechanisms similar to those in invertebrates. FGF was localized in the epidermis and basal lamina and in follicle plugs during morphogenesis. At maturity, FGF was found in the ORS and in the region of the basal lamina of the follicle bulb, suggesting a role in bulb proliferation and fiber growth.

Cultivation of mesenchymal cells derived from the skin and hair follicles of the sheep: the involvement of peptide factors in growth regulation.

Mesenchymal components of skin and vibrissa follicles of the sheep have been introduced into culture. Outgrowths of cells were obtained from explants of the dermal papilla, follicular capsule, dermal sheath and the reticular region of the dermis. Following trypsinization, the cells were successfully propagated as monolayers through several passages. As numbers increased, both the papilla and sheath cells displayed aggregative behaviour. Capsular and dermal fibroblasts did not aggregate but became aligned into polarized arrays, the cells appearing to exert tractional forces on each other and the surface of the culture dish. In general, cell proliferation was promoted by fetal bovine serum (FBS), epidermal growth factor (EGF) and fibroblast growth factor (FGF), although the extents of the responses varied amongst the different types. Dermal fibroblasts underwent the greatest increase in numbers in the presence of FBS. The sheath and papilla cells, by contrast, were more responsive to EGF than dermal fibroblasts, with capsular fibroblasts displaying an intermediate response. Intense EGF immunoreactivity was detected in Western immunoblots of freshly isolated capsular tissue. The presence of EGF-like activity in capsular extracts was confirmed by radioreceptor assay, suggesting a specific autocrine or paracrine function for the growth factor in the local follicular environment. Mitogenic responses to FGF were approximately equivalent in all cell types when compared with controls. The similarities in aggregative behaviour and proliferative responses displayed by the dermal sheath and papilla cells suggest that they may be members of a lineage which diverged from that giving rise to the other mesenchymal derivatives during early follicle development.

Fibroblast growth factor influences the development and cycling of murine hair follicles.

The effects of basic fibroblast growth factor (bFGF) on the development of hair follicles in neonatal mouse skin were examined. Newborn mice (B6C3-based strain) were given daily subcutaneous injections of bFGF and bovine serum albumin (BSA) for 7 days. By Day 9, distinct areas of hairless, unpigmented skin were observed surrounding the sites treated with bFGF. This phenomenon persisted until about 14-16 days of age when the emergence of hair in the bald patches was first seen. Hair growth continued in the treated regions until they were mostly covered at 18-20 days of postnatal age. Control sites injected with BSA only were indistinguishable from the surrounding pigmented, hairy skin at all ages. Histological examination of skin from various ages of bFGF-treated mice suggested that the growth factor had affected both the initiation and the development of the hair follicles. This resulted in a significant delay in the first and subsequent hair cycles when compared to control animals injected with BSA only.

Distribution of acidic and basic fibroblast growth factors in ovine skin during follicle morphogenesis.

Acidic and basic fibroblast growth factors (aFGF and bFGF) have been localized by immunochemistry in ovine skin during wool follicle morphogenesis. At 40 days of gestation, prior to the appearance of follicle primordia, bFGF immunoreactivity was detected in the intermediate and periderm layers of the epidermis and at the dermal-epidermal junction. Antibodies to aFGF did not bind to skin at this age. During early follicle formation, at 76 days of gestation, both FGFs were found in the epidermis and associated with the follicle primordia. Antibodies to aFGF, in particular, bound to the basal cells of the epidermis and the follicle cell aggregations. With the development of epidermal plugs, bFGF was confined to the intermediate layers of the epidermis and the dermal-epidermal junction, whereas aFGF staining was associated with the cells of the epidermis and the plugs. At 90 days, when many different stages of follicle development were in evidence, immunoreactivity for both FGFs was associated with the cells of the elongating epidermal column, particularly those adjacent to the dermal-epidermal junction. During follicle maturation, bFGF was found in the suprabasal layer of the epidermis, in the outer root sheath of the follicle and in the basement membrane zone surrounding the bulb matrix. Conversely, strong staining for aFGF was observed in the epidermis and pilary canal contiguous with the epidermis, and in cells of the upper bulb matrix of the follicle in the region of the keratogenous zone. Western blotting of extracts of mature follicles that had been isolated from the skin showed the presence of a major aFGF immunoreactive band with an apparent molecular mass of 27 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Two-dimensional analysis of gliadin proteins associated with quality in durum wheat: chromosomal location of genes for their synthesis.

Two-dimensional electrophoresis was used to fractionate the gliadin proteins from the endosperm of durum wheat. The increased resolution of the system, as compared with single-dimensional analysis, accentuated the heterogeneity of the proteins. This resolution, coupled with the use of aneuploid lines of the cultivar 'Langdon', permitted identification of the chromosomes controlling synthesis of the major protein components. Homoeologous Group 1 chromosomes controlled omega- and gamma-gliadin synthesis and the Group 6 chromosomes 6A and 6B controlled alpha- and beta-gliadins. Chromosome 1B was primarily responsible for the two groups of protein-polypeptides associated with strong or weak gluten characteristics of durum wheat. However, some of these proteins were controlled by chromosome 1A. In the beta-gliadin region several hybrid bands, whose chromosomal control was not identified by electrophoresis alone, were specified primarily by genes on chromosome 6B, although chromosome 6A was also involved. Control of some other hybrid bands could not be determined. Chromosomes in Groups 2, 3, 4, 5 and 7 were not implicated in the synthesis of the gliadin proteins of durum wheat.