GROWTH FACTORS IN HAIR ORGAN DEVELOPMENT AND THE HAIR GROWTH CYCLE

A basic knowledge of the hair growth cycle is needed to evaluate disorders of hair growth. This chapter presents a broad overview of the physiology and evaluation of hair growth, as well as discussions of specific types of alopecia. The epidemiology, pathogenesis, diagnosis, and treatment of androgenetic alopecia, the most common type of nonscarring hair loss, are covered. Diffuse hair shedding is generalized hair loss over the entire scalp. Diagnosis and treatment of telogen effluvium, anagen arrest (anagen effluvium), and other causes of diffuse hair shedding are covered in detail. Alopecia areata, typically characterized by patchy hair loss; cicatricial alopecia, which results from permanent scarring of the hair follicles; and miscellaneous causes of hair loss are also discussed. Tables list the causes of diffuse and cicatricial alopecia, telogen effluvium, and miscellaneous chemicals and categories of drugs that can cause alopecia, as well as miscellaneous causes of hair loss. Included is an algorithm outlining the approach to diagnosing nonscarring alopecia, as well as a variety of clinical photographs. This review contains 9 highly rendered figures, 6 tables, and 42 references.

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Transfection of rat dermal papilla cells with a gene encoding a temperature-sensitive polyomavirus large T antigen generates cell lines retaining a differentiated phenotype

Journal of Cell Science ◽

10.1242/jcs.107.7.1761 ◽

1994 ◽

Vol 107 (7) ◽

pp. 1761-1772

Author(s):

W. Filsell ◽

J.C. Little ◽

A.J. Stones ◽

S.P. Granger ◽

S.A. Bayley

Keyword(s):

Cell Lines ◽

Hair Growth ◽

Dermal Papilla ◽

Growth Cycle ◽

T Antigen ◽

Temperature Sensitive ◽

Early Passage ◽

Gene Encoding ◽

Dermal Papilla Cells ◽

Dermal Papilla Cell

The dermal papilla is a discrete group of cells at the base of the hair follicle and is implicated in controlling the hair growth cycle. Early passage dermal papilla cells can induce hair growth in vivo, but, upon further culturing, this property is lost. In order to study the events occurring in hair induction, a representative dermal papilla cell line was required. We have transfected passage 1 rat vibrissa dermal papilla cells with a polyomavirus large T gene encoding a temperature-sensitive T antigen, and generated permanent cell lines in which the immortalizing function can be switched off by temperature shift. The cells established without crisis, resembled cells in the starting population, and retained the aggregative properties of early passage dermal papilla cells. Growth studies were performed on the immortalized cell lines, which showed that transferring the cells to the restrictive temperature for the large T gene product resulted in cell senescence or quiescence, and changes in morphology. Implantation of cell pellets into the ears of immunologically compatible rats showed that the immortal cells retained hair-inductive ability. Cytokines are believed to have an important role in the control of hair growth. The pattern of cytokine gene expression in the immortal cell lines was compared with early passage dermal papilla cells and a non-hair-inducing dermal papilla cell line, using reverse transcriptase-polymerase chain reaction. Epidermal growth factor, tumour necrosis factor, and interleukin-1a were detected in the immortalized and non-hair-inducing dermal papilla cell lines, but were absent in passage 2 dermal papilla cells. All other cytokines examined were detected in all the cell types under study. These results demonstrate that the polyomavirus large Ttsa-immortalized dermal papilla cell lines are very similar to passage 2 dermal papilla cells and thus provide a good model for hair growth studies. Cytokine expression profiles indicate that the expression of several cytokines may be implicated in hair induction. Further studies are under way to investigate the relationship between cytokine expression and the hair growth cycle.

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