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

Minoxidil decreases collagen I deposition and tissue-like contraction in clubfoot-derived cells: a way to improve conservative treatment of relapsed clubfoot?

AIM

Clubfoot is a congenital deformity affecting the musculoskeletal system, resulting in contracted and stiff tissue in the medial part of the foot. Minoxidil (MXD) has an inhibitory effect on lysyl hydroxylase, which influences the quality of extracellular matrix crosslinking, and could therefore be used to reduce the stiffness and to improve the flexibility of the tissue. We assessed the in vitro antifibrotic effects of minoxidil on clubfoot-derived cells.

METHODS

Cell viability and proliferation were quantified by xCELLigence, MTS, and LIVE/DEAD assays. The amount of collagen I deposited into the extracellular matrix was quantified using immunofluorescence with subsequent image segmentation analysis, hydroxyproline assay, and Second Harmonic Generation imaging. Extracellular matrix contraction was studied in a 3D model of cell-populated collagen gel lattices.

RESULTS

MXD concentrations of 0.25, 0.5, and 0.75 mM inhibited the cell proliferation in a concentration-dependent manner without causing a cytotoxic effect. Exposure to ≥0.5 mM MXD resulted in a decrease in collagen type I accumulation after 8 and 21 days in culture. Changes in collagen fiber assembly were observed by immunofluorescence microscopy and nonlinear optical microscopy (second harmonic generation). MXD also inhibited the contraction of cell-populated collagen lattices (0.5 mM by 22%; 0.75 mM by 28%).

CONCLUSIONS

Minoxidil exerts an in vitro inhibitory effect on the cell proliferation, collagen accumulation, and extracellular matrix contraction processes that are associated with clubfoot fibrosis. This study provides important preliminary results demonstrating the potential relevance of MXD for adjuvant pharmacological therapy in standard treatment of relapsed clubfoot.

Pseudoacromegaly induced by the long-term use of minoxidil

Acromegaly is an endocrine disorder caused by chronic excessive growth hormone secretion from the anterior pituitary gland. Significant disfiguring changes occur as a result of bone, cartilage, and soft tissue hypertrophy, including the thickening of the skin, coarsening of facial features, and cutis verticis gyrata. Pseudoacromegaly, on the other hand, is the presence of similar acromegaloid features in the absence of elevated growth hormone or insulin-like growth factor levels. We present a patient with pseudoacromegaly that resulted from the long-term use of minoxidil at an unusually high dose. This is the first case report of pseudoacromegaly as a side effect of minoxidil use.

The induction by topical minoxidil of increased fenestration in the perifollicular capillary wall

We report the induction by topical minoxidil of increased fenestration in the perifollicular capillary wall. Male 30-day-old Wistar rats were divided into two groups, i.e. an experimental group which received 4% minoxidil solution topically on the dorsal skin, and a control group which received only vehicle solution topically. Using transmission electron microscopy, follicular and subepidermal capillaries and dermal fibres were compared between both groups. There were no obvious differences in subepidermal capillaries or dermal fibres between the two groups. However, topically applied minoxidil increased fenestration in follicular capillary walls around anagen hair bulbs.

Minoxidil-induced alteration of corneal topography after radial keratotomy

PURPOSE

To determine the antiproliferative effect of minoxidil on human corneal epithelium (hCE) proliferation in vitro and to assess whether topical minoxidil can significantly alter corneal topography after radial keratotomy (RK) by inhibiting myofibroblast activity in the keratotomy wound.

SETTING

Corneal Research Laboratory, University of Chicago, Illinois, USA.

METHODS

In the in vitro evaluation, proliferating hCE was exposed to minoxidil (0.1 to 2.0 mM) for 96 hours to determine the minimum inhibitory dose. Human corneal epithelium cell proliferation was assessed by the incorporation of bromodeoxyuridine (BRDU) into DNA. In the in vivo analysis, eight New Zealand albino rabbits had an eight-incision bidirectional RK on one eye and were divided into two groups. The control eyes (n = 3) received tobramycin and dexamethasone (TobraDex), ciprofloxacin hydrochloride (Ciloxan), and balanced salt solution (BSS) drops four times a day for 3 weeks, while the treatment eyes (n = 5) received TobraDex, Ciloxan, and minoxidil 1.0 mM drops four times daily for 3 weeks. The net change in corneal curvature at 3 weeks was analyzed with corneal topography. Myofibroblast activity in the keratotomy wound was assessed using alpha smooth muscle actin staining techniques.

RESULTS

At concentrations of 1.0 mM and above, minoxidil caused a statistically significant, dose-dependent reduction in hCE cellular proliferation ranging from 29 to 44% (P < .05). Minoxidil (1.0 mM) caused a statistically significant central corneal flattening effect of 4.66 diopters (D) after RK in the treatment eyes compared with 1.11 D in the control eyes (P = .05). Histologically, minoxidil-treated keratotomy wounds lacked cells with contractile elements consistent with myofibroblast differentiation. Corneal epithelial wound healing was similar in both groups.

CONCLUSION

At the appropriate dose, topical minoxidil may be a useful adjunctive treatment that can reduce the number of undercorrections after mini-RK without apparent toxicity to the corneal epithelium.

Aggressive polyfibromatosis: a 10 year follow-up

Polyfibromatosis syndrome is a condition characterized by the occurrence of several cutaneous fibrotic conditions including Dupuytren's contracture and keloid formation. A 10 year follow-up of a patient with an aggressive type of polyfibromatosis associated with erosive arthropathy is presented. The underlying pathogenesis and management of this uncommon condition is discussed.

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.

The effect of minoxidil analogues and metabolites on the contraction of collagen lattices by human skin fibroblasts

Minoxidil, in addition to its effect on hypertension and hair growth, has been proposed as a potential antifibrotic agent. Minoxidil inhibits the contraction of collagen lattices by human fibroblasts in vitro. However, the mechanism of inhibition is unknown. As minoxidil is metabolised in the body to minoxidil glucuronide and minoxidil sulphate, we investigated the potencies of these metabolites to inhibit collagen lattice contraction. We also studied selected analogues of minoxidil to assess the influence of certain functional groups in the inhibition. The major metabolite, minoxidil glucuronide, proved to be inactive, whereas minoxidil sulphate was considerably more active than minoxidil. In terms of the structural analogues, the substitution of one amino group by a methyl group resulted in loss of the inhibitory activity; removal of the nitroxide oxygen led to stronger inhibition than with minoxidil. Further studies are planned to learn more about a possible role for minoxidil in wound contraction.

Skin fibroblast activity in pretibial myxoedema and the effect of octreotide (Sandostatin) in vitro

The accumulation of glycosaminoglycans in the skin in pretibial myxoedema appears to be a response by local fibroblasts to a stimulating factor in the patient's serum, but the identity of the factor, its ability to stimulate skin fibroblasts as opposed to cultured thyroid cells, and the specificity of its effect to pretibial skin fibroblasts, are all controversial. We have studied fibroblasts cultured from the lesional skin of two women with pretibial myxoedema, and compared their proliferation and secretion of glycosaminoglycans with those of fibroblasts from the patients' forearms and from the forearm skin of two normal subjects. We found that in the presence of the patients' sera all six lines of fibroblasts secreted more glycosaminoglycans [205 +/- 21% (SD)] than with normal human sera (147 +/- 19%), or fetal calf serum (100%). Fibroblast proliferation showed the same pattern of differences: patients' sera 142 +/- 22%; normal human sera 116 +/- 9%, and fetal calf serum 100%. These experiments confirm the presence of a serum factor in pretibial myxoedema which is capable of stimulating the activity of skin fibroblasts in vitro, and show that its effects are not restricted to fibroblasts from pretibial skin or to those grown from the skin of the patients. Proliferation of normal fibroblasts cultured in medium supplemented with fetal calf serum was reduced by Sandostatin (octreotide), but it failed to inhibit their secretion of glycosaminoglycans. In contrast, secretion of glycosaminoglycans by a patient's pretibial skin fibroblasts was almost completely inhibited by 1 mM minoxidil. In the presence of patients' sera Sandostatin (0.1-10 micrograms/ml) reduced secretion of glycosaminoglycans by about 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Current dermatologic therapy

This article reviews therapeutic advances reported in the English-language literature during 1991. Readers should review the original article in full before attempting any experimental or controversial therapy.