Direct effects of minoxidil on epidermal cells in culture

Toxicological assessment of minoxidil: A drug with therapeutic potential besides alopecia

Minoxidil is regularly prescribed for alopecia, and its therapeutic potential has expanded in recent times. However, few studies have been conducted to evaluate its toxicity, and controversial findings regarding its mutagenic activities remain unsolved. This study aimed to access cytotoxic, genotoxic, and mutagenic properties of minoxidil using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, comet assay, and micronucleus test in mouse fibroblast (L929) cells and its point mutation induction potential in the Salmonella/microsome assay. Furthermore, an in vivo toxicity assessment was conducted in Caenorhabditis elegans. Minoxidil showed cytotoxicity at 2.0 mg/mL in MTT assay. Genotoxicity was observed after 3 h treatment in L929 cells using comet assay. No mutagenic effect was observed in both the micronucleus test and the Salmonella/microsome assay. The lethal dose 50 in C. elegans was determined to be 1.75 mg/mL, and a delay in body development was detected at all concentrations. In conclusion, minoxidil induces DNA damage only in early treatment, implying that this DNA damage may be repairable. This observation corroborates the absence of mutagenic activities observed in L929 cells and Salmonella typhimurium strains. However, the toxicity of minoxidil was evident in both C. elegans and L929 cells, underscoring the need for caution in its use.

In Vivo Study of the Effects of Propranolol, Timolol, and Minoxidil on Burn Wound Healing in Wistar Rats

Propranolol, timolol, and minoxidil have all shown benefits in treatment of burn injury and other skin wounds. The study evaluated their effects on full-thickness thermal skin burns in a Wistar rat model. Performed on 50 female rats; two dorsal skin burns were created on each animal. On the next day, the rats were divided into 5 groups (n = 10); each has received a specific treatment daily for 14 days: group I-topical vehicle (control), group II-topical silver sulfadiazine (SSD), group III-oral propranolol (5.5 mg) associated with topical vehicle, group IV-topical timolol 1% cream, and group V-topical minoxidil 5% cream. Wound contraction rates, malondialdehyde (MDA), glutathione (GSH, GSSG), and catalase activity in skin and/or serum were evaluated, and histopathological analyses were performed. Propranolol did not show advantages in necrosis prevention and wound contraction and healing, and did not reduce oxidative stress. It impaired keratinocyte migration, and promoted ulceration, chronic inflammation, and fibrosis, yet reducing the necrotic zone. Timolol prevented necrosis and promoted contraction and healing, increased antioxidant capacity and promoted keratinocyte migration and neo capillarization in comparison to the other treatments. Minoxidil reduced necrosis and enhanced contraction, resulting in positive outcomes after 1 week of treatment regarding local antioxidant defense, keratinocyte migration, neo capillarization, chronic inflammation, and fibrosis rates. However, after 2 weeks, it resulted in contrasting outcomes. In conclusion, topical timolol promoted wound contraction and healing, reducing local oxidative stress and improving keratinocyte migration, bringing arguments for potential benefits in skin epithelization.

Minoxidil Downregulates Interleukin-1 Alpha Gene Expression in HaCaT Cells

Introduction:

Minoxidil has been used topically to stimulate hair growth for male androgenetic alopecia (AGA) for more than 3 decades. It is currently being used for female AGA and alopecia areata (AA) as well. Although much time has passed since its first use, our understanding of its mechanism of action is highly limited. Therefore, we examined the inflammatory properties of AGA and AA, two entities in which minoxidil is being used as a therapeutic agent. We investigated the in vitro expression levels of cytokine interleukin-1 alpha (IL-1α), a potent inhibitor of hair growth, in minoxidil-treated human keratinocyte (HaCaT) cells to determine whether this molecule exerts anti-inflammatory effects.

Materials and Methods:

Cellular proliferation was examined using the Cell Proliferation Kit II (XTT) reagent. After determining a noncytotoxic concentration, HaCaT cells were treated with minoxidil. RNA was isolated from both untreated and treated cells with TRI Reagent^®. Expression of the IL-1α gene was determined by reverse transcription quantitative polymerase chain reaction analysis and is reported relative to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which served as a control.

Results:

Results are presented as IL-1α/GAPDH fold change. Minoxidil treatment downregulated IL-1α expression by 0.3433-fold compared with untreated cells (P = 0.001).

Conclusion:

This anti-inflammatory effect of minoxidil, as evidenced by significant downregulation of IL-1α gene expression in HaCaT cells, may represent one of its mechanisms of action in alopecia.

Medical treatments for male and female pattern hair loss

Male and female pattern hair loss affects a large percentage of the population, and patients frequently present for treatment of this to their dermatologist. Here we review the many treatments available for hair loss. We review the evidence for each, and outline the most effective treatment strategies for both men and women.

LEARNING OBJECTIVE

At the conclusion of this article, the reader should be able to describe the most effective treatments for hair loss, understand their mechanism(s) of action, and explain which treatments are the best in different settings.

Androgenetic alopecia

Androgenetic alopecia (AGA), or male pattern hair loss, affects approximately 50% of the male population. AGA is an androgen-related condition in genetically predisposed individuals. There is no treatment to completely reverse AGA in advanced stages, but with medical treatment (eg, finasteride, minoxidil, or a combination of both), the progression can be arrested and partly reversed in the majority of patients who have mild to moderate AGA. Combination with hair restoration surgery leads to best results in suitable candidates. Physicians who specialize in male health issues should be familiar with this common condition and all the available approved treatment options.

In the absence of streptomycin, minoxidil potentiates the mitogenic effects of fetal calf serum, insulin-like growth factor 1, and platelet-derived growth factor on NIH 3T3 fibroblasts in a K+ channel-dependent fashion

There is considerable evidence to suggest that the opening of K+ channels plays an important role in stimulating mitogenesis. K+ channel blockers have been shown to inhibit mitogenesis in vitro, mitogens increase cytosolic membrane K+ channel permeability, K+ channel openers stimulate hair growth in vivo, and the Ras/Raf signal transduction pathway induces K+ channel activity. Paradoxically, however, K+ channel openers such as minoxidil have been reported in vitro not to modulate, or even to inhibit, mitogenesis in a range of cell types. Only untherapeutic concentrations have stimulated mitogenesis. These experiments, however, appear to have been carried out in the presence of aminoglycoside antibiotics, which inhibit potassium channel activity. We now report that in the absence of aminoglycoside antibiotics, minoxidil at 10 microg/ml (0.05 mM) causes a significant stimulation of proliferation of NIH 3T3 fibroblasts maintained over a 10-d period in 5% fetal calf serum-supplemented medium. Further, we show that in the presence of 100 microg streptomycin per ml, minoxidil at 10 microg/ml produces an initial inhibition of proliferation, which apparently confirms, in NIH 3T3 fibroblasts, that the inhibition of mitogenesis by minoxidil in the presence of streptomycin is an artifact. The potentiation of NIH 3T3 cell growth by minoxidil can be attributed to the opening of potassium channels, because the potassium channel blocker tolbutamide (5 mM) or combinations of the blockers tolbutamide (1 mM)/tetraethylammonium (2 mM) or glibenclamide (1 microM)/apamin (10 nM) block the minoxidil-induced stimulation of growth. We also demonstrate that minoxidil is able to significantly potentiate the mitogenic effects of both platelet-derived growth factor and insulin-like growth factor 1 on NIH 3T3 fibroblasts in the presence of CPSR-2 (a cytokine free serum substitute). Thus we have shown that minoxidil potentiates the mitogenic effects of fetal calf serum in vitro on NIH 3T3 fibroblasts by opening potassium channels and is also able to potentiate the mitogenic effects of the growth factors platelet-derived growth factor and insulin-like growth factor 1.

Stimulation of elastin expression by minoxidil in chick skin fibroblasts

Minoxidil inhibited the proliferation of embryonic skin fibroblasts during the growth phase but not during the stationary phase. Minoxidil stimulated elastin synthesis two-fold in a dose-dependent manner at a concentration of 1 mM during the stationary phase. The stimulation of elastin synthesis paralleled a comparable increase in elastin mRNA level. These results suggest that the stimulation of elastin expression by minoxidil in skin fibroblasts was controlled at the elastin mRNA level and also suggest that its elastin-stimulating effect is not related to the suppressive effect on cell proliferation. Minoxidil appears to be a potent stimulator for elastin expression in skin fibroblasts.

Generalized hypertrichosis after treatment with topical minoxidil

Generalized hypertrichosis is a common side-effect of oral minoxidil treatment for hypertension. However, hypertrichosis is uncommon after treatment with topical minoxidil for alopecia, and normally only occurs in areas close to the site of application. A 16-year-old girl is presented who developed generalized hypertrichosis 3 months after applying topical minoxidil for treatment of diffuse alopecia in doses greater than that prescribed. Four months after discontinuing treatment, the abnormal hair gradually diminished and disappeared.

Effects of the selective protein kinase C inhibitor, Ro 31-7549, on the proliferation of cultured mouse epidermal keratinocytes

We have investigated the effects of Ro 31-7549, a selective protein kinase C (PKC) inhibitor, on DNA synthesis and proliferation in two primary mouse epidermal keratinocyte culture systems. In differentiating keratinocytes incubated in medium containing 10% serum and high calcium (approximately 0.5 mM), Ro 31-7549 blocked the inhibitory effect of the phorbol ester 12-0-tetradecanoyl-13-acetate (TPA) (a PKC activator) on keratinocyte DNA synthesis at 24 h [50% maximal response concentration (EC50) = 1 microM], consistent with inhibition of PKC-mediated differentiation. Continuous treatment of the differentiative culture system with the PKC inhibitor resulted in a marked (fourfold) stimulation of [3H]thymidine incorporation at day 7 of exposure, with an EC50 of 0.25 microM. The potencies of these effects of Ro 31-7549 are comparable to that reported for inhibition of TPA-induced platelet 47-kD protein phosphorylation [50% inhibitory concentration (IC50) = 4.4 microM]. The time course of [3H]thymidine incorporation indicated that Ro 31-7549 did not directly stimulate DNA synthesis but instead prevented the loss of proliferative capacity associated with continued culture in this medium. Maximal stimulation (2.6 times) of DNA synthesis was observed on day 4, whereas DNA synthesis at day 1 was unaffected. In a highly proliferative culture system using serum-free medium containing 25 microM calcium, TPA dose-dependently inhibited proliferation with an IC50 of approximately 0.3 mM. This antiproliferative effect of TPA was largely reversed by 0.1 microM Ro 31-7549. In the proliferative culture system, 0.75 microM Ro 31-7549 also essentially reversed the inhibition of proliferation caused by switching to high (1.0 mM) calcium. These results suggest that the loss of proliferative capacity in differentiating epidermal keratinocyte cultures may be mediated, at least in part, by PKC.

Minoxidil: inhibition of proliferation of keratinocytes in vitro

Previous studies have suggested that minoxidil stimulates growth of keratinocytes, possibly in a manner similar to the action of epidermal growth factor. Using both a short-term assay, thymidine incorporation, and a longer term assay, cell counting, to assess proliferative growth, we tested the activity of minoxidil in human keratinocyte cultures grown in 0.1 mM Ca(++). Minoxidil failed to stimulate growth in these assays. At concentrations of 5-10 micrograms per ml, minoxidil showed half-maximal inhibition of both EGF- and placental extract-stimulated thymidine incorporation. Minoxidil also inhibited proliferative growth in the presence or absence of placental extract. Direct measurement of the ability of minoxidil to compete for binding to the EGF receptor indicated that minoxidil probably does not bind to the EGF receptor. Minoxidil was not toxic, as keratinocytes continued to survive and grow, although at a slower rate, in the presence of minoxidil.

The metabolism of fibroblasts from normal and fibrotic skin is inhibited by minoxidil in vitro

The effects of minoxidil in vitro were studied using fibroblasts grown from the lesional skin of patients with lichen sclerosus et atrophicus, morphoea and from the skin of normal individuals. The proliferation of all fibroblast lines over 3 days was inhibited in proportion to the concentration of minoxidil, being 20% or less of controls at 1 mM, where cell viability was only marginally reduced (84 +/- 2% vs. 88 +/- 2% (SEM) in controls). At 5 mM there was usually a net loss of cells and only 72% of those remaining were viable. In contrast, minoxidil at 0.1-1 mM stimulated the proliferation of foreskin keratinocytes by up to 130%. Contraction of collagen lattices containing the three types of fibroblasts was inhibited by 22-26% with 1 mM minoxidil after 5 days and by 50-94% with 5 mM. Secretion of glycosaminoglycans by normal fibroblasts showed concentration-dependent reduction, being 25 +/- 6% of that of untreated cultures with 1 mM minoxidil. These findings show that minoxidil has a range of inhibitory effects on both normal and abnormal skin fibroblasts in vitro, which contrast with its stimulation of skin epithelial cells, and support suggestions that it may provide a useful topical treatment for keloids and other fibroses.

Five-year follow-up of men with androgenetic alopecia treated with topical minoxidil

Thirty-one men with androgenetic alopecia completed 4 1/2 to 5 years of therapy with 2% and 3% topical minoxidil. Hair regrowth with topical minoxidil tended to peak at 1 year with a slow decline in regrowth over subsequent years. However, at 4 1/2 to 5 years, maintenance of nonvellus hairs beyond that seen at baseline was still evident. Topical minoxidil appears to be effective in helping to maintain nonvellus hair growth in men with androgenetic alopecia.

Australian trial of topical minoxidil and placebo in early male pattern baldness

One hundred and sixty nine men with early male pattern baldness (androgenic alopecia) were treated in a random, double-blind fashion with either 2% minoxidil solution or placebo vehicle for 24 weeks, one ml applied twice daily. After 24 weeks all patients received the active solution until week 48. After 24 weeks the minoxidil treated patients had increased their non-vellus hair counts significantly more than the placebo treated group; means were 37.6 and 8.8 hairs per reference area, 95% C.I. for difference = 10.85 to 60.75. The rate of non-vellus hair regrowth was also greater among minoxidil treated patients than placebo treated patients. Nine (12.5%) evaluable minoxidil treated patients compared with 2 (2.7%) evaluable placebo treated patients reported moderate or dense hair regrowth at week 24. Minimal regrowth was reported by 18 (25%) active group and 15 (20%) placebo group patients. The investigators considered that 3 (2%) of the minoxidil group and none of the placebo group had moderate hair regrowth and that none had dense regrowth. After 48 weeks treatment 28 (23%) patients considered that they had moderate hair regrowth and the investigators considered that 14 (12%) patients had moderate regrowth. None had dense growth. No serious adverse reactions or deaths were reported. Minoxidil solution appeared to be an efficacious and safe treatment for early androgenic alopecia.

Minoxidil stimulates mouse vibrissae follicles in organ culture

Minoxidil, a potent vasodilator, stimulates the growth of terminal hair from vellus or miniaturized follicles in balding scalp. To study minoxidil's action on isolated follicles we developed and validated an organ culture system using mouse whisker follicles. Control follicles cultured without minoxidil showed macroscopic changes including kinking of the hair shafts and bending of the follicles. Necrosis was evident in the differentiating epithelial elements forming the cuticle, cortex, and inner root sheath. These abnormalities were eliminated or greatly reduced in minoxidil-treated follicles. The morphology of these follicles was consistent with the production of new hair during culture. Direct measurement demonstrated that minoxidil-treated follicles grew significantly longer than control follicles during the 3-d culture. Minoxidil increased the incorporation of radiolabeled cysteine and glycine in follicles compared with control treatment. Doses of minoxidil up to 1 mM caused increased cysteine incorporation, while higher doses were inhibitory. Experiments with labeled thymidine indicated that minoxidil induced proliferation of hair epithelial cells near the base of the follicle. Autoradiography also showed that cysteine accumulated in the keratogenous zone above the dermal papilla. These studies demonstrate that organ cultured follicles are suitable for determining minoxidil's mechanism of action and may be useful for studying other aspects of hair biology. The results also show that minoxidil's effect on hair follicles is direct. This suggests that minoxidil's action in vivo includes more than just increasing blood flow to hair follicles.

Quantitative assessment of 2% topical minoxidil in the treatment of male pattern baldness

Forty-seven men with male pattern baldness were treated in a double-blind clinical trial with topical 2% minoxidil or placebo. Twelve were randomly selected for quantitative hair measurement using the unit area trichogram and visual counting. There was no significant difference after 6 or 12 months of treatment with a 2% minoxidil solution for total hair density (THD; hair cm-2), meaningful hair density (MHD; hair greater than 40 microns in diameter greater than 30 mm in length cm-2), per cent of hair in the anagen growth phase, or the per cent of meaningful hair in the anagen growth phase. Significantly fewer hairs were recorded with the visual hair counting method, compared to values obtained from adjacent sites with the unit area trichogram. In addition, a significantly larger mean total hair count was recorded by an experienced observer, compared to an inexperienced observer. Increased pigmentation was observed within the vellus hair population of treated subjects. Our findings indicate that minoxidil appears unlikely to affect the long-term course of male pattern baldness. However, we found no significant deterioration in total hair density, or meaningful hair density in treated subjects, suggesting minoxidil may have a prophylactic effect. Further long-term studies employing the unit area trichogram are required to evaluate this finding.

Selective inhibition by minoxidil of prostacyclin production by cells in culture

The effect of minoxidil on arachidonic acid metabolism by cells in culture was studied. In bovine aorta endothelial cells, treatment with minoxidil in the presence of various stimulators of arachidonic acid metabolism was accompanied by a dose-dependent inhibition of prostacyclin production (measured as 6-keto-prostaglandin F1 alpha). Synthesis of the other cyclooxygenase products (prostaglandins E2, F2 alpha and thromboxane) was not inhibited. When the bovine aorta endothelial cells were stimulated by the Ca2+ ionophore A-23187, the inhibition was seen as early as 2 min. Minoxidil also inhibited prostacyclin production by a second cell line of bovine aorta endothelial cells (the established CPAE cell line), bovine aorta smooth muscle cells, porcine aorta endothelial cells, and rat liver cells (the C-9 cell line)--the latter, less effectively. Again, formation of all the other cyclooxygenase products studied was not inhibited. Minoxidil did not affect significantly prostaglandin E2 and F2 alpha production by newborn rat keratinocytes (the NBR cell line)--a cell that does not produce PGI2. The clinical, biochemical, and pharmacologic implications are discussed.

Response to minoxidil in severe alopecia areata correlates with T lymphocyte stimulation

Mitogen-induced T cell blastogenesis was determined in 47 patients with severe alopecia areata, before and after treatment with topical 5% minoxidil, and compared with control values. The group of 36 responders, who demonstrated terminal hair regrowth, showed significantly increased lymphocyte stimulation with concanavalin A and PHA before treatment, which decreased towards control values following hair regrowth. Lymphocytes from non-responders showed no significant differences from controls either before or after treatment. The results suggest that enhanced T cell blastogenesis may predict the response of severe alopecia areata to topical 5% minoxidil therapy.

Topical minoxidil in the treatment of male pattern alopecia

Male pattern hair loss (androgenetic alopecia) is a common problem. In fact, it affects nearly all males to some degree. Expression of the disorder is variable, and while it is never life-threatening, it often becomes a major source of consternation. The biology of the process is poorly understood, and no current therapy can halt or reverse the process. Only cosmetic surgery, which is painful, time consuming, and expensive, has been effective. In the past 7 years, since it was noted that a patient taking minoxidil for hypertension had reversal of male pattern hair loss, awareness of a possible therapeutic role for topical minoxidil in the management of this disorder has grown among physicians, scientists, and the general public. It can be concluded from available data that topical application of minoxidil is effective in providing cosmetically satisfying thickening of hair in a select group of individuals with male pattern hair loss. The drug's mechanism of action remains obscure. No serious side effects have been demonstrated with its use, however, and it is therefore advised in selected patients.

Long-term efficacy of topical minoxidil in male pattern baldness

A 24-month clinical trial, begun on a double-blind basis, was conducted in 153 men with discernible male pattern baldness of the crown with the use of either topically applied placebo, 2% minoxidil, or 3% minoxidil solution. After 4 months the patients using placebo were switched to 3% minoxidil solution. At 12 months, there were statistically significant increases in terminal hair growth within a 1-inch target area in those treated with 2% or 3% minoxidil solution, in comparison with baseline counts. However, there were few patients who had appreciable cosmetic restoration. At 12- and 24-month intervals, progressive regression or stabilization of the size of the bald area was noted in the majority of patients. This therapeutic or preventive effect was statistically significant. The data on actual target area hair counts suggested that the 2% minoxidil solution was equal to or more efficacious than the 3% minoxidil solution. Baseline vital signs and laboratory parameters remained essentially unchanged. Topical minoxidil was well tolerated, with no serious drug-related adverse reactions noted during the study.

Potential mechanisms of minoxidil-induced hair growth in alopecia areata

In vivo, topical minoxidil therapy is associated with changes in the follicular epithelium, tissue and blood lymphocyte populations, lymphocyte blastogenic response to mitogens, and perifollicular vasculature. Biopsy specimens taken from areas of terminal hair regrowth show a dose-dependent increase in hair follicle length, a decrease in tissue lymphocyte populations associated with a simultaneous increase in peripheral blood lymphocyte counts, and reopening of previously closed lumina of perifollicular vessels. Responder lymphocytes show pretreatment-increased concanavalin A and phytohemagglutinin-induced blastogenesis, which decrease toward control values after treatment. In vitro, at concentrations approximating the range of tissue levels in patients treated topically with the 5% solution, minoxidil affects both epithelial cells and lymphocytes in tissue culture. Cultured murine epithelial cells show increased cell proliferation and delayed senescence. Cultured human lymphocytes show suppression of mitogen-induced blast transformation. Differential effects on responder, nonresponder, and control lymphocytes are seen. Minoxidil may induce hair regrowth in alopecia areata by a synergistic stimulatory effect on follicular epithelium and a suppressive effect on lymphocyte-mediated immunologic phenomena. A contributing role for its vasodilatory properties must also be considered.

Topical minoxidil (3%) in extensive alopecia areata, including long-term efficacy

This study was conducted to further evaluate the safety and efficacy of 3% topical minoxidil in the treatment of extensive alopecia areata. Patients were assigned to one of two treatment regimens in a double-blind manner. One group applied 3% minoxidil to the scalp twice daily for 64 weeks; the other group applied placebo for the initial 12 weeks and then switched to 3% minoxidil for the remaining 52 weeks. Thirty male and female subjects, ages 7 to 63 years, with extensive alopecia areata affecting 25% to 100% of the scalp were enrolled, fifteen subjects to each treatment group. Twenty-four of the thirty subjects had greater than 75% scalp hair loss. At 12 weeks the group treated with 3% minoxidil had slightly more hair growth than the placebo group, but the difference was not statistically significant. At 64 weeks, thirteen of twenty subjects (65%) who began with less than full scalp involvement (25% to 99% scalp hair loss) had terminal hair growth that was incomplete or cosmetically acceptable; of these, nine (45%) were cosmetically acceptable, a response that is significant in patients with severe alopecia areata. No hair growth or only slight growth was seen in all nine patients with 100% scalp hair loss at baseline. Thus the extent of hair loss at baseline was correlated with response at 64 weeks. Twenty-one of the patients continued treatment for a second year. Of these, thirteen showed further growth, three had no further growth, and five who had cosmetically acceptable hair growth during the first year had some hair loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of minoxidil on pre- and postconfluent keratinocytes

Studies in our laboratory have shown that minoxidil prolongs the life of keratinocytes in culture and extends the time after confluence that cells can be subcultured. These data suggest that the drug reduces the rate at which cells are lost from the germinative pool and hence slows senescence. In a dose-response study with minoxidil, the maximal effect of the drug was seen at doses from 6 to 12 micrograms/ml; however, activity could be detected at doses below 1 microgram/ml. Cells subcultured during log growth failed to demonstrate that minoxidil increased the total number of generations attainable under these conditions, although as expected, epidermal growth factor extended the life span of cells. When the experiments were repeated in a keratinocyte cell line that does not require a fibroblast feeder layer, the same results were obtained, indicating that the difference observed between log phase and postconfluence growth cannot be explained by the presence of fibroblasts. Minoxidil's effect on postconfluent cells was blunted by the addition of cholera toxin to the medium, suggesting that elevation of cyclic adenosine monophosphate cannot be a mechanism, although reduction of cyclic adenosine monophosphate is a possibility. Finally, maintaining keratinocytes at a 20 to 40 mM calcium concentration greatly reduced the ability of postconfluent cells to be subcultured, in comparison with the normal calcium concentration of 2 mM. That minoxidil almost completely reversed this inhibitory effect suggests it may work by preventing cross-linking by transglutaminase, which is activated by elevated calcium concentrations.

Topical minoxidil. A preliminary review of its pharmacodynamic properties and therapeutic efficacy in alopecia areata and alopecia androgenetica

When minoxidil is administered orally for periods in excess of 1 month, hypertrichosis occurs as a side effect in a majority of patients. Consequently, topical minoxidil has been developed to try to improve hair growth in patients with alopecia areata and alopecia androgenetica. Preliminary studies have shown that topical minoxidil promotes cosmetically acceptable hair regrowth in a variable proportion of patients with alopecia areata. Data from a large multicentre trial indicate that cosmetically worthwhile results are achieved in about one-third of subjects with alopecia androgenetica after 1 year of treatment. A much higher proportion (about 80%) of patients with alopecia androgenetica exhibited some non-vellus hair regrowth after 1 year, and whether more of these patients would develop a cosmetically acceptable result with a longer treatment period is an important area of future investigation. Initial indications suggest that less severe disease is a predictor of likely response. Thus, topical minoxidil would seem to be a useful treatment modality for patients with alopecia androgenetica--a disease for which no other safe and effective drug therapy exists. Results from treating patients with alopecia areata with topical minoxidil, although encouraging, have been more variable and require further evaluation. Even though a number of questions remain to be answered about topical minoxidil (as would be expected at this stage in its development), it would seem to be the first available drug with the potential to promote substantial hair regrowth in these divergent diseases.

Topical tretinoin for hair growth promotion

Topical all-trans-retinoic acid (tretinoin) alone and in combination with 0.5% minoxidil has been tested for the promotion of hair growth in 56 subjects with androgenetic alopecia. After 1 year, the combination of topical tretinoin with 0.5% minoxidil resulted in terminal hair regrowth in 66% of the subjects studied. Tretinoin was shown to stimulate some hair regrowth in approximately 58% of the subjects studied. One female subject with pronounced alopecia for more than 20 years had regrowth of hair using only tretinoin for a period of 18 months. Tretinoin has been shown to promote and regulate cell proliferation and differentiation in the epithelium and may promote vascular proliferation. These factors are important for hair growth promotion. These preliminary results indicate that more work should be done on the role of retinoids in hair growth. The synergistic effect of retinoids in combination with a low concentration of minoxidil should also be further investigated.

Thy-1+ epidermal cells are not demonstrable in rat and human skin

Recent studies have revealed the presence of a population of Thy-1+ epidermal cells in murine epidermis. These experiments were designed to determine whether analogous Thy-1+ cell populations occur in rat and human epidermis. Thy-1+ cells could not be demonstrated in epidermal sheets derived from rat and human skin or in epidermal cell lines, KB and A431. To date, Thy-1+ epidermal cells have been observed only in murine epithelia. The cellular equivalent of the murine Thy-1+ cell in other species remains elusive.

Topical minoxidil in early male pattern baldness

One-hundred twenty-six healthy men with early male pattern baldness completed a 12-month double-blind, controlled trial of 2% and 3% topical minoxidil. Subjects were initially randomly assigned to use placebo or 2% or 3% topical minoxidil. After 4 months of study, the placebo group was crossed over to 3% topical minoxidil. Both objective measurement of hair growth by counting of vellus, terminal, and total hairs in a vertex target balding area and subjective assessment by subject and investigator were done. Treatment of subjects with topical minoxidil for 4 months resulted in a statistically significant increase in terminal hair growth in comparison with placebo therapy. In addition, subjects initially treated with placebo, when crossed over to topical minoxidil, showed a significant increase in the number of terminal hairs. No subject had a net hair loss in the target area during the study. These results indicate that topical minoxidil can increase terminal hair growth in early male pattern baldness.

The Thy-1 epidermal cell: perspective and prospective

Recently a class of cells distinguished by the presence of the cell-surface protein, Thy-I, has been discovered in the epidermis. These cells constitute a heterogeneous population such that they may be dendritic or round, and may be derived from both mesenchymal and ectodermal tissue. Phenotypically, cells with the following characteristics have been observed: Thy-I +, Vim+; Thy-I+, Vim-; Thy-I+, Ker+; Thy-I+, Ker-; Thy-I+, asialo GMI+; Thy-I+, asialo GMI-. Thy-I+ epidermal cells do not appear to be T or B lymphocytes, macrophage/monocytes or melanocytes. The Thy-I+ epidermal cell can be studied in in vivo and in vitro systems. It would appear that skin as well as the immune system contain Thy-I+ and Ia+ cells. Such cells may be prerequisite for both systems to carry out their primary defense functions.

In vitro suppression of human lymphocyte activity by minoxidil

The in vitro effect of minoxidil on normal human lymphocyte activity was studied. At a concentration of 0.1 mg/ml, minoxidil significantly inhibited phytohemagglutinin-dependent lymphocyte DNA synthesis (p less than 0.05), and at 0.01 mg/ml, 0.05 mg/ml, and 0.1 mg/ml, it suppressed mitogen-dependent production of leukocyte migration inhibition factor (p less than 0.04, p less than 0.01, and p less than 0.01, respectively), without compromising cell viability. Minoxidil thus appears to exert a suppressive effect on normal human T-lymphocytes in vitro. The physiologic relevance of these findings remains uncertain.