The quantitative behavior of cutaneous histamine and mast cells in the hair cycles of rats

Topical Products for Human Hair Regeneration: A Comparative Study on an Animal Model

Background

Hair loss and hair growth is the subject of tremendous amount of research.

Objective

This study investigated the efficacy of three chemical treatments used in humans for hair loss, using a rat model of hair regrowth. The products tested were 2% minoxidil, Hairgrow (Dar-Al-Dawa Pharma), Aminexil, Dercos (Vichy Laboratoires), and Kerium, Anti-chute (La Roche-Posay).

Methods

Thirty-two adult female Wistar-Bratislava rats were assigned to 4 groups. Two rectangular areas (2×4 cm) were shaved on either sides of the mid dorsal line (left side - control; right side - test area). Group I was treated topically with 2% minoxidil, group II with Aminexil, and group III with Kerium. Each rat received 0.3 ml of substance applied topically to the shaved dorsal skin every day for 28 days. Rats in group IV served as sham controls receiving no treatment. Hair regrowth was evaluated by trichoscopy (with a dermatoscope), grown hair weight (from a surface area of 1 cm²), and histopathological examination for skin thickness, follicle count, and percentage of anagen induction (morphometric assessment).

Results

Treatment with 2% minoxidil significantly induced hair regrowth as assessed by trichoscopy, hair weight examination, and morphometric evaluation. Hair weight examination and morphometric assessment demonstrated the lowest hair growth effect with Aminexil among the tested products. Treatment with Kerium was found to significantly induce hair regrowth (p<0.05 as compared to the control group).

Conclusion

Our study demonstrates that hair regrowth efficacy of products recommended for human use is not similar when tested on an animal model.

Human pigmentation: A side effect adapted from a primitive organism's survival, acting through cell attachment with an affinity for the keratinocyte and for elastin: Part I

Pigmentation featured millions of years ago and perhaps began with an amoeba frightening off a predator with some agent such as dopamine to prevent its attachment for phagocytosis by an enemy. This paper suggests that the environmental forces of grip and stick deserve greater emphasis and that mechanical forces involved in grip and stick or release from attachment, all point to control of proteases underlying pigmentation. There is an affinity for elastin as a pathway for melanin to exit its peripheral location in the epidermis into lymphatics and play a humeral role in defense mechanisms. The hair follicle follows the epidermal-dermal pattern of behavior with an affinity for elastin, a controlling function of melanin and through the bulge, an influence of mechanical forces and control by protease inhibitors.

The itchy scalp--scratching for an explanation

Scalp pruritus is a common complaint that is considered a diagnostically and therapeutically challenging situation. Scalp skin has a unique neural structure that contains densely innervated hair follicles and dermal vasculature. In spite of the recent advances in our understanding of itch pathophysiology, scalp itching has not been studied as yet. In this review, we summarize the current knowledge on the neurobiology of scalp and hair follicles as well as itch mediators and provide a putative mechanism for scalp itch with special emphasis on neuroanatomy and pathophysiology.

Localization of rat FGF-5 protein in skin macrophage-like cells and FGF-5S protein in hair follicle: possible involvement of two Fgf-5 gene products in hair growth cycle regulation

It has been reported that the gene for murine fibroblast growth factor-5 (Fgf-5) is expressed in the rat hair follicle and that this expression may be associated with catagen induction (Hebert et al, 1994). In this study, we analyzed the Fgf-5 gene product in skin because the gene generates two mRNA that translate into the FGF-5 protein and a short form of the FGF-5 protein (FGF-5S) as a result of an alternative splicing (Hattori et al, 1996; Ozawa et al, 1996). Indeed, we detected both types of FGF-5 mRNA in rat skin samples. Two monoclonal anti-FGF-5 antibodies, one (E723) being specific for FGF-5 long-form protein and the other (B2B6) being reactive with both FGF-5 and FGF-5S proteins, were used to locate these proteins by immunohistochemistry. Staining of the rat skin revealed that only the B2B6 antibody reacted with hair follicles and that both antibodies reacted with macrophage-like round cells, suggesting that the product of the Fgf-5 gene in the hair follicle is FGF-5S. The immunoreactivity of the FGF-5S protein increased during early anagen VI and decreased rapidly during catagen. The density of FGF-5-positive macrophage-like cells in the dermis increased during anagen and decreased during catagen and telogen, whereas the density of these cells in the panniculus adiposus did not change during anagen and increased during catagen and telogen. There was no apparent association between the density of FGF-5-positive macrophage-like cells and that of FGF-5-negative, dendritic macrophage-like cells. Thus, the results suggest the possible involvement of FGF-5S in the hair follicle in anagen VI and catagen development and that the density of FGF-5-positive macrophage-like cells may also be associated with the hair growth cycle.

Effects of transforming growth factor beta 1 in the hair cycle

Hair follicle growth is thought to be regulated by a complex interplay of stimulatory and inhibitory signals. From among such signals, we examined the effects of transforming growth factor beta 1 (TGF beta 1) on the murine hair growth cycle. Quantitation of TGF beta 1 per wet tissue weight was performed at different stages of the hair cycle. TGF beta 1 was extracted with 10 mM HCl, and its level was measured with ELISA. The level of TGF beta 1 did not change markedly during the hair cycle. Immunohistochemical observations revealed that hair follicle cells and epidermal cells were negative for TGF beta 1 at all stages of the hair cycle. Mast cells in the dermis were positive throughout the cycle. To confirm whether the proliferation of hair follicles. Our observations suggest that TGF beta 1 is at least partly responsible for regulating hair follicles as a negative growth factor.

Soluble and insoluble collagen and elastin in the rat hair cycle

Soluble and insoluble collagen and elastin were chemically evaluated in the dorsal skin of rats during the third hair cycle. Both fractions of collagen remain unchanged during anagen, while they increase considerably in the first days of telogen to drop afterwards. Elastin content gradually increases throughout anagen and falls in telogen. The authors suggest that the increasing amounts of collagen in the first part of telogen may be responsbile for the progressive block in the downwards movements of previously growing follicles into the dermis. Elastin data could be the result of a mechanical readjustment of skin to the expansion provoked by growing follicles.

Endothelial DNA synthesis in themicrovasculature of rat skin during the hair growth cycle

Earlier studies of the vascular patterns around hair follicles revealed that actively growing follicles have an extensive microvasculature relative to that around quiescent follicles. In order to determine whether the establishment of the active perifollicular vascular pattern involves replication of endothelial and perivascular cells, we studied the 3H-thymidine labeling indices of these cells in autoradiographs of rat skin from regions containing either actively growing follicles or recently inactive follicles. In skin containing inactive follicles, the endothelial labeling index was 0.22%, a figure similar to those reported for the endothelium of small blood vessels in several other non-stimulated adult tissues. However, skin containing actively growing follicles displayed an endothelial labeling index of 2.35%. The labeling indices of perivascular cells paralleled those of the endothelial cells. Thus, endothelial and perivascular cells in vessels associated with actively growing follicles undergo significantly more DNA synthesis than those in vessels associated with inactive follicles. Replication of these cells apparently contributes to the extension of the microvascular network around growing follicles.

Modulation of dermal cell activity during hair growth in the rat

Interaction between connective tissue cells and hair growth in the rat has been studied by radioautography after in vivo and in vitro pulse labelling with thymidine, uridine, histidine, leucine and proline. The connective tissue, which surrounds and integrates the hair bulbs as a unit, contains cells of various types which have a cyclic metabolic activity. This cyclic activity is coordinated with the hair growth cycle. The number of nuclei which actively synthesize DNA in the dermal cells, mainly those of endothelial and migratory cells, significantly increases during the short and transient anagen 4 substage. RNA and protein synthesizing activities are also present in all cell types and seem modulated by the hair cycle although to a lesser degree. This data provides an important basis for the interpretation of similar studies in alopecia areata.