Contraction of collagen lattices by skin fibroblasts from dystrophic recessive epidermolysis bullosa and other dermatoses

Recessive epidermolysis bullosa simplex phenotype reproduced in vitro: ablation of keratin 14 is partially compensated by keratin 17

Recessive epidermolysis bullosa simplex (REBS) is characterized by generalized cutaneous blistering in response to mechanical trauma. This results from fragility of the basal keratinocytes that lack keratin tonofilaments because of homozygote null mutation in the keratin 14 gene. REBS patients display in addition focal dyskeratotic skin lesions with histology of epidermolytic hyperkeratosis (EHK) and tonofilament clumping in the suprabasal layers of the epidermis. In this study we examined whether it is possible to mimic in vitro the bullous and dyskeratotic cellular phenotype. For this purpose, fibroblasts from nondyskeratotic (K14-/-) and dyskeratotic (K14-/-) skin of a REBS patient and fibroblasts from a healthy donor (K14+/+) were isolated and incorporated into collagen matrices. Subsequently, fresh biopsies originating from the nondyskeratotic and dyskeratotic skin of the patient and from a healthy donor were placed onto the collagen matrices and cultured at the air-liquid interface. Epidermal morphogenesis was evaluated on the basis of tissue morphology and the expression of a series of keratins. The results of the present study indicate that basal cell vacuolization in REBS can be mimicked in vitro but not the EHK. Fibroblasts seem to play an important regulatory role in establishing the REBS phenotype. These findings suggest that wild-type fibroblasts may enhance the stability of K14-/- keratinocytes in vitro.

Phenytoin reduces the contraction of recessive dystrophic epidermolysis bullosa fibroblast populated collagen gels

Recessive dystrophic epidermolysis bullosa (RDEB) is a group of genetic disorders in which blistering occurs below the basement membrane, in many cases resulting in extensive scar formation, contractures and mitten deformities. Our aim was to compare quantitatively the contraction forces generated by normal and RDEB fibroblats and to investigate the effect of Phenytoin (5,5-diphenyl-2,4-imidazolidinedione, sodium salt; PHT). PHT is an anticonvulsant agent, that causes fibrosis as a side effect. This study utilised conventional untethered fibroblast populated collagen lattice contraction and a quantitative force measurement instrument, the culture force monitor (CFM). The RDEB cell lines were hypercontractile, generating 2.5 times the force of normal fibroblasts, though they appeared morphologically normal. In untethered collagen gels PHT (20 micrograms/ml) significantly reduced contraction of both normal and RDEB fibroblasts over 7 days. Pre-treatment of RDEB cells for 5 days also produced a 40% reduction in contraction as measured in the CFM. One suggested mechanism of PHT action is through inhibition of matrix metalloproteinase activity, but the similar effects of PHT and Colchicine (an inhibitor of microtubule polymerisation) in the CFM, indicate that it may act on contraction through disruption of microfilaments and changes to cell shape. These findings show that isolated RDEB fibroblasts retain the hypercontractile features of many of the patient's lesion sites and imply that local application of PHT may have a therapeutic effect in controlling contraction.

Fibroblast contraction of collagen matrices with and without covalently bound hyaluronan

Hyaluronan, which is found in high concentrations in fetal tissues, has been suggested to play a major role in preventing scar formation in fetal wounds. We have developed a floating collagen fibrillar matrix (CFM) made out of reconstituted type I collagen for the purpose of evaluating the ability of hyaluronan to inhibit the fibroblast induced contraction of the matrix. When hyaluronan is covalently bound to collagen it appears to better support fibroblast proliferation and matrices are less contractible by these cells than when hyaluronan interacts only ionically. When hyaluronan is bridged between collagen fibrils by a network of extensive covalent crosslinks, contractibility by fibroblasts is abolished. These modified collagen matrices may prove to be very useful in the development of bioprostheses and implants.

Variability in the retraction of collagen lattices by scleroderma fibroblasts--relationship to protein synthesis and clinical data

Skin fibroblasts from 18 scleroderma patients were seeded into collagen lattices and their ability to retract their substratum was compared with that of control fibroblasts from healthy donors. When considered as a whole, scleroderma fibroblasts retracted lattices earlier and more intensely than controls. Analysis of individual results demonstrated that morphea and diffuse systemic sclerosis (dSSc) fibroblasts had different kinetics of lattice retraction. Fibroblasts which contracted lattices more intensely than controls were found to produce increased levels of fibronectin. A comparison of the retraction of collagen lattices by fibroblasts from involved (IS) and uninvolved skin (US) of the same patients (n = 4) showed that those from IS retracted the lattices more than fibroblasts from normal donors, whereas a high variability was found with fibroblasts from US. The increased retraction of collagen lattices seems to be a feature of the more severe forms of scleroderma.

Collagen telopeptides (cross-linking sites) play a role in collagen gel lattice contraction

Solubilized interstitial collagens will form a fibrillar, gel-like lattice when brought to physiologic conditions. In the presence of human dermal fibroblasts the collagen lattice will contract. The rate of contraction can be determined by computer-assisted planemetry. The mechanisms involved in contraction are as yet unknown. Using this system it was found that the rate of contraction was markedly decreased when collagen lacking telopeptides was substituted for native collagen. Histidinohydroxylysinonorleucine (HHL) is a major stable trifunctional collagen cross-link in mature skin that involves a carboxyl terminal, telopeptide site 16c, the sixteenth amino acid residue from the carboxy terminal of the telopeptide region of alpha 1 (I) in type I collagen. Little, if any, HHL was present in native, purified, reconstituted, soluble collagen fibrils from 1% acetic acid-extracted 2-year-old bovine skin. In contrast, HHL cross-links were present (0.22 moles of cross-link per mole of collagen) in lattices of the same collagen contracted by fibroblasts. However, rat tail tendon does not contain HHL cross-links, and collagen lattices made of rat tail tendon collagen are capable of contraction. This suggests that telopeptide sites, and not mature HHL cross-links per se, are essential for fibroblasts to contract collagen lattices. Beta-aminopropionitrile fumarate (BAPN), a potent lathyrogen that perturbs collagen cross-linking by inhibition of lysyl oxidase, also inhibited the rate of lattice cell contraction in lattices composed of native collagen. However, the concentrations of BAPN that were necessary to inhibit the contraction of collagen lattices also inhibited fibroblast growth suggestive of cellular toxicity. In accordance with other studies, we found no inhibition of the rate of lattice contraction when fibronectin-depleted serum was used. Electron microscopy of contracted gels revealed typical collagen fibers with a characteristic axial periodicity. The data provide evidence that collagen telopeptide sites play a role in collagen gel lattice contraction.

Heterogeneity in dermatosparaxis is shown by contraction of collagen gels

Dermal fibroblasts from sheep exhibiting a mild form of dermatosparaxis were able to contract reconstituted, fibrillar collagen gels at the same rate as control dermal fibroblasts, indicating a normal interaction between the cells and a collagenous matrix. An extract from dermatosparactic skin was shown, after partial purification, to have N-proteinase activity, although the level of activity was much lower than found in normal skin. These data show that dermatosparaxis is a heterogeneous disease, since in the severe forms of the disease the defect has been characterized as an absence of N-proteinase and an inability of the cells to interact with and contract collagen gels.

Fibroblast-keratinocyte interactions in psoriasis: failure of psoriatic fibroblasts to stimulate keratinocyte proliferation in vitro

We have tested in two ways the hypothesis that dermal fibroblasts direct the hyperproliferation of the overlying epidermis in psoriasis. First, culture medium from psoriatic and from normal skin fibroblasts was added to monolayer cultures of foreskin keratinocytes. Second, psoriatic and normal fibroblasts embedded in hydrated collagen lattices were co-cultured with monolayers of foreskin keratinocytes. There was no evidence in either study that psoriatic fibroblast products could stimulate the proliferation of the keratinocytes, or that normal fibroblast products inhibited their proliferation. A positive control for the fibroblasts was provided by leucocyte supernatants, which stimulated keratinocyte proliferation by up to 65%. Our data do not support a primary role for dermal fibroblasts in psoriasis.

Failure of a helium-neon laser to affect components of wound healing in vitro

The red light of a helium-neon (He-Ne) laser has been reported to stimulate wound healing and cell growth. To investigate the nature of its influence on wound healing we have studied seven components of the healing process in vitro: human skin fibroblast, epithelial and endothelial cell proliferation, cellular migration from skin explants, collagen lattice contraction, collagen synthesis and glycosaminoglycans (GAG) secretion. We used a 5 mW He-Ne laser emitting a I mm diameter beam of wavelength 633 nm. Cellular proliferation was not affected by irradiation three times a day for 3 days. There was no effect on cellular migration or on the rate of collagen lattice contraction. The rate of collagen synthesis, measured as the incorporation of 3H-proline into collagenase-sensitive protein, was no greater than that of controls and GAG secretion did not increase in the irradiated group. We have not found any significant effects of He-Ne irradiation.

Quantitative evaluation of the factors affecting the process of fibroblast-mediated collagen gel contraction by separating the process into three phases

Kinetics of collagen gel contraction by fibroblasts cultured in vitro was examined in detail for quantitative analysis. The process of collagen gel contraction was not expressed by a simple function of time. It appeared to consist of three distinct phases; a lag phase before the initiation of contraction, a rapid contraction phase and a slow contraction phase. Factors affecting the gel contraction can be classified into four groups. The first group includes increase in cell number, in culture temperature or in serum concentration, which strengthened the contraction in all the three phases, suggesting that they affected cellular activity particularly in interacting with collagen. The second group repressed the later two phases of contraction but not the first lag phase, typically increase in collagen concentration and a low dose of nocodazole or colcemid. Increasing population doubling levels of fibroblasts belongs to the third group which caused a reduced lag time but no change in the later two phases. Cytochalasin D at a low dose (0.03-0.1 microgram/ml) is another example of the third group which shortened the lag time. The last group did not change the contraction curves. Donor age of fibroblasts isolated from the skin is an example of this group. The rate of rapid contraction in the second phase was always found to be closely correlated with the degree of contraction at the end of the third phase, in a whole set of the factors above mentioned. The results suggest that the extent of the later two phases might be a reflection of the same cellular activity, particularly cytokinetical one. The lag time is directly related to the time for cells to become elongate in shape as observed by using the video-microscopy, suggesting that the lag phase is also governed by cytokinetical activity. The two cytokinetical activities are closely related, but may be distinct, since the factors affecting the collagen gel contraction can be differentiated into four groups.

Contraction of collagen lattices by skin fibroblasts: drug-induced changes

A range of dermatologically useful drugs were added to human skin fibroblasts cultured in collagen lattices to assess possible effects on the rate of lattice contraction. Vitamin C, Vitamin E, phenytoin, sodium salicylate, D-penicillamine and dibutyryl c-AMP had no significant effect. Chlorhexidine acetate at 10 micrograms/ml arrested contraction after 24 h but this was related to its cytotoxicity. The antibiotics griseofulvin (2-16 micrograms/ml) and cycloheximide (5-30 micrograms/ml) caused dose-related inhibitions of contraction without affecting fibroblast viability. Four corticosteroids at 10 micrograms/ml inhibited contraction, clobetasol propionate having the greatest effect. On the other hand 4 retinoids at 10(-5) M enhanced contraction by up to 20%. As lattice contraction appears to model the contraction of skin wounds and there are broad parallels between the effects shown here of antiseptics, corticosteroids and the retinoids, and their reported influence on healing wounds, the lattice system may be a useful pharmacological screen for new compounds.

Toxicity of the anthraquinone glycoside P-1894B for human skin fibroblasts

P-1894B inhibits prolyl hydroxylase in vitro and has been proposed as a topical treatment for dermal fibrosis. The drug had similar effects on two fibroblast lines from normal human skin and one line from a patient with lichen sclerosus et atrophicus. Exposure of logarithmically-growing cell monolayers for 72 h caused dose-dependent inhibition of proliferation at 0.05-0.5 microgram/ml but time-dependent cell death at 1-50 micrograms/ml. The epithelial cell line NCTC 2544 gave a similar result. Collagen lattices containing normal fibroblasts contracted more slowly in the presence of the drug at 0.1-0.5 microgram/ml, but this was clearly related to loss of viability. Collagen synthesis by monolayer cultures was unaffected at 0.05 and 0.1 microgram/ml P-1894B in one line of normal fibroblasts, but was reduced by 40% and 15%, respectively, in the other. The concentrations of P-1894B reported to be active against prolyl hydroxylase are therefore lethal to cultured skin cells. Although the effective use of dithranol as a topical anti-psoriatic agent, despite its cytotoxicity in vitro, is encouraging for P-1894B, further toxicological studies are imperative.