Serum regulation of collagen biosynthesis in human diploid fibroblasts

A new dermal equivalent: The use of dermal fibroblast culture alone without exogenous materials

BACKGROUND

During the past decade, several kinds of skin equivalents have been developed. However, the dermal equivalents have all contained exogenous materials, which can be difficult to obtain and a source of infections.

OBJECTIVES

The aim of this study was to develop a new dermal equivalent by culturing dermal fibroblasts alone without exogenous materials and to evaluate its applicability in vitro and in vivo.

METHODS

The postconfulent cultures of dermal fibroblasts in serum containing medium, that was supplemented with epidermal growth factor, insulin, hydrocortisone, transferrin and triiodothyronine for 3 weeks, produced a fibrous sheet that was visible macroscopically. To construct a skin equivalent, epidermal keratinocytes were cultured on the top of the fibrous sheet at the air-liquid interface. To evaluate its fate in vivo, the fibrous sheet was grafted into a nude mouse.

RESULTS

Histologically, the fibrous sheet showed dermis-like tissue that consisted of an extracellular matrix around dermal fibroblasts, and revealed collagen fibers by Masson-trichrome staining. The components of dermal matrix such as type I collagen, type III collagen, elastin, fibrillin-1 and fibronectin were diffusely expressed. Some collagen fibrils were found by electron microscopy. In the skin equivalent, a multilayered epidermis with a horny layer was formed. Some differentiation markers (keratin 1 and 10, and involucrin) and the components of basement membrane (beta4 integrin chain, type IV and VII collagens) were expressed in a similar fashion to those in normal skin in vivo. Ultrastructurally, basement membrane zone such as hemidesmosomes, lamina lucida and lamina densa was found, although it was still incomplete. When the fibrous sheet was grafted in vivo, it revealed blood vessels that were derived from the nude mouse, and persisted for 4 weeks.

CONCLUSION

These findings demonstrated that a new dermal equivalent, closely resembling a dermis in vivo, could be constructed by culturing dermal fibroblasts alone in a special culture medium. In addition, the dermal equivalent may be useful for experimental and clinical purposes, such as the reconstruction of a skin equivalent in vitro and grafting in vivo.

ACE inhibitor and angiotensin II type 1 receptor blocker differently regulate ventricular fibrosis in hypertensive diastolic heart failure

BACKGROUND

Promoted myocardial stiffening has a crucial role in the transition to overt diastolic heart failure (DHF) in hypertensive hearts and is attributed to progressive ventricular fibrosis. Previous studies revealed the effects of an angiotensin II type 1 receptor blocker (ARB) and an angiotensin-converting enzyme inhibitor (ACEI) on the synthesis and degradation of collagens in the other phenotype of heart failure, systolic heart failure, which has a different pathophysiology; however, little is known about their effects in DHF.

OBJECTIVE

To investigate effects of an ACEI and an ARB on the regulatory system of ventricular fibrosis in hypertensive DHF.

DESIGN AND METHODS

Dahl salt-sensitive rats fed a diet containing 8% NaCl from age 7 weeks (DHF model) were divided into three groups: six untreated rats, six rats treated with a subdepressor dose of an ARB, candesartan cilexetil (1 mg/kg per day), from age 8 weeks, and six rats treated with a subdepress or dose of an ACEI, temocapril hydrochloride (0.2 mg/kg per day), from age 8 weeks. Six Dahl salt-sensitive rats fed on normal chow served as controls. Data were collected when animals were aged 20 weeks.

RESULTS

The administration of an ARB or an ACEI inhibited ventricular fibrosis to the same degree. The ACEI decreased the level of type I collagen mRNA, but the decrease was less than that induced by the ARB. The difference in collagen synthesis was probably cancelled out by that in degradation: both in-vitro and in-situ zymography showed that gelatinase activity was greater in the rats treated with the ACEI than in those treated with the ARB.

CONCLUSIONS

An ARB and an ACEI inhibited ventricular fibrosis through different mechanisms in hypertensive DHF.

Temperature-dependent enhancement of cell proliferation and mRNA expression for type I collagen and HSP70 in primary cultured goldfish cells

Goldfish (Carasius auratus) primary culture cells derived from caudal fin were incubated over a temperature range of 20-35 degrees C. The population doubling time of cells cultured at 20, 25, 30 and 35 degrees C were 34, 29, 17 and 14 h, respectively. Interestingly, cDNA-representational difference analysis revealed type I collagen alpha chain (colalpha(I)) as a candidate for a warm temperature-specific gene. mRNA levels of colalpha(I) increased with an increase of incubation temperature and days of culture. Furthermore, the cell growth rate and colalpha(I) mRNA levels were rapidly changed following temperature shifts. To examine the effects of culture temperature shift on the cellular physiological states, mRNA levels of HSP70 were additionally investigated. HSP70 mRNA levels in the cells cultured at 30 and 35 degrees C were again 2-3 times higher than those at 20 and 25 degrees C. When the culture temperature was shifted from 20 to 35 degrees C, HSP70 mRNA levels were rapidly increased within 1 h. Subsequently, mRNA levels of the 35 degrees C-treated cells decreased, but remained doubled compared with those of the 20 degrees C-treated cells, even 4 h following the temperature shift. When the culture temperature was lowered from 35 to 20 degrees C, HSP70 mRNA levels decreased to about 70% of the original levels in 4 h. These results indicate that goldfish cells cultured at different temperatures easily develop temperature-associated steady physiological states within 4 h of temperature shifts.

Angiotensin II type 1 and endothelin type A receptor antagonists modulate the extracellular matrix regulatory system differently in diastolic heart failure

OBJECTIVE

Ventricular fibrosis plays a pivotal role in the development of diastolic heart failure and is a therapeutic target; however, the effects of pharmacological interventions on the extracellular matrix (ECM) regulatory system in diastolic heart failure remain to be clarified.

DESIGN AND METHODS

Dahl salt-sensitive rats fed on a diet containing 8% NaCl from age 7 weeks--a hypertensive diastolic heart failure model--were divided into untreated rats, rats treated with angiotensin II type 1 (AT1) receptor antagonist and those treated with endothelin type A (ETA) receptor antagonist.

RESULTS

Ventricular fibrosis progressed in the untreated rats, with increases in mRNA levels of type I collagen, matrix metalloproteinase-2, -9 and -13, and tissue inhibitor of metalloproteinase-1 and -2. Both antagonists attenuated ventricular fibrosis to the same degree. AT1 receptor blockade decreased the type I collagen mRNA level more than ETA receptor blockade. ETA receptor blockade did not decrease the matrix metalloproteinase-2 mRNA level that was decreased by AT1 receptor blockade, and decreased the tissue inhibitor of metalloproteinase-2 mRNA level that was not affected by AT1 receptor blockade. These led to a higher ratio of matrix metalloproteinase-2 to tissue inhibitor of metalloproteinase-2 mRNA levels and a greater 72-kDa gelatinase activity in the rats treated with ETA receptor antagonist than in those treated with AT1 receptor antagonist, and may well cancel out the lesser decline in collagen synthesis, resulting in the equivalent attenuation of ventricular fibrosis.

CONCLUSIONS

AT1 receptor and ETA receptor antagonists provide their beneficial effects on the ECM through different modulation of its regulatory system.

Spl phosphorylation induced by serum stimulates the human alpha2(I) collagen gene expression

Serum has been known to stimulate collagen production by dermal fibroblasts. As part of an ongoing study of the molecular mechanisms of collagen production, we have investigated transcriptional regulation of the human alpha2(I) collagen gene by serum in human dermal fibroblasts. Serum responsive elements were mapped by deletion analysis between bp -353 and -264, and between -148 and -108 in the alpha2(I) collagen promoter. Further functional analysis of the alpha2(I) collagen promoter containing various substitution mutations revealed that serum stimulation of this promoter is mediated equally by a GC-rich region located between bp -303 and -271 and by the TCCTCC motif located between bp -123 and -128, both of which constitute binding sites for transcription factor Spl and Sp3. No differences were observed in electrophoretic mobility shift assays between unstimulated and serum stimulated fibroblasts. The Spl inhibitor mithramycin blocked stimulation of the alpha2(I) collagen promoter activity by serum. Furthermore, immunoprecipitation analysis showed that serum stimulation increased Spl phosphorylation. In conclusion, this study characterized response elements that mediate serum stimulation of the human alpha2(I) collagen promoter and suggests that serum stimulation was mediated via Sp1/Sp3 binding sites in this promoter.

Effects of platelet-derived growth factor isoforms on human lung fibroblast proliferation and procollagen gene expression

Platelet-derived growth factor (PDGF), a potent mitogen for fibroblasts, is a potentially important cytokine in the pathogenesis of fibroproliferative disorders of lung. Different isoforms of PDGF include a heterodimer composed of A and B chains and homodimers composed of A or B chains. The biological significance of the different isoforms is unknown, but they have been shown to differ in their mitogenic potency in some systems. Their effects on other fibroblast functions have not been fully examined. We undertook this study to determine the effect of PDGF isoforms on human lung fibroblast proliferation and procollagen synthesis. Cultured lung fibroblasts (IMR-90, WI-38, GeNA) were incubated in the presence of varying concentrations of highly purified PDGF-AB obtained from platelets or recombinant PDGF-AA or -BB homodimers. Incorporation of [3H]thymidine was determined as a measure of mitogenic activity. Fetal lung fibroblasts (IMR-90, WI-38) and an adult fibroblast strain (GeNA) responded similarly to the different isoforms, with maximum mitogenic activity observed at 5-10 ng/mL. Cell cycle analysis using three additional normal adult lung fibroblast strains indicated that all PDGF isoforms stimulated similar proportions of cells to cycle over a 7-day period. Fibroblast procollagen synthesis, measured after pulse labeling with [3H]proline, was not increased even at concentrations of the PDGF isoforms that were maximally mitogenic. Moreover, steady-state levels of alpha 1(I) and alpha 1(III) procollagen mRNA levels, determined by northern analysis and dot blot hybridization, were not changed after exposure to any of the PDGF isoforms. While all PDGF isoforms are potent mitogens for fetal and adult lung fibroblasts, it was concluded that they do not directly stimulate procollagen gene expression or procollagen synthesis in vitro. The results suggest that PDGF isoforms are potentially important mitogens for lung fibroblasts, but other factors are likely to be involved in the stimulation of fibroblast procollagen synthesis that is observed in fibroproliferative disorders of lung.

Collagen synthesis in fibroblasts from human colon: regulatory aspects and differences with skin fibroblasts

The purpose of this study was to examine regulation of collagen synthesis in human colon fibroblasts and compare the results from colon fibroblasts with those obtained in fibroblasts from human skin. The effects of interleukin-1 beta, tumour necrosis factor alpha, interferon gamma, transforming growth factor-beta, dexamethasone, and the calcium ionophore A23187 were investigated. All compounds were tested both in the absence and in the presence of fetal calf serum in the culture medium. The process of collagen synthesis in fibroblasts from colon and skin appears to be affected differently by these regulatory compounds. The most pronounced differences were that the relative collagen synthesis increased in dermal fibroblasts and decreased in colon fibroblasts upon addition of serum. In the presence of serum, interleukin-1 beta inhibited collagen synthesis in skin fibroblasts but not in colon fibroblasts. Dexamethasone suppressed the relative collagen synthesis in skin fibroblasts but not in colon fibroblasts. Transforming growth factor-beta stimulated the collagen synthesis in dermal fibroblasts in the presence of serum, but inhibited the process in colon fibroblasts. Because fibroblasts are the primary sources of collagen needed during wound repair, these results may offer (part of) the explanation why wounds in skin and intestine appear to behave differently under certain conditions.

Increased collagen gene expression in vascular smooth muscle cells cultured in serum or isoleucine deprived medium

The relationship between type I and type III collagen gene expression and the growth state of cultured bovine vascular smooth muscle cells has been investigated. Growth was modulated by incubation of subconfluent cultures of smooth muscle cells in media containing concentrations of fetal calf serum ranging from 10% to 0.5%. As the serum concentration was lowered, the doubling time increased from 17 hours to 70 hours, and collagen mRNA levels increased as judged by Northern blot analysis. The levels of induction were 5- to 15-fold for alpha 1(I), 2- to 3-fold for alpha 2(I), and 4- to 7-fold for alpha 1(III). Metabolic cell labelling with precursor amino acids indicated that type I and type III procollagen synthesis was elevated approximately 2-fold as growth slowed. A similar 2-fold increase occurred upon translation of isolated RNAs in a rabbit reticulocyte cell-free system. Nuclear run-on analysis indicated that increased collagen transcription can account for part of the increase in mRNA levels following incubation in lowered fetal calf serum. To further examine the influence of proliferation on collagen gene expression, smooth muscle cells were cultured in isoleucine-free medium, which resulted in quiescence within 36 hours. Induction of collagen mRNA levels was observed within 24 hours of incubation in isoleucine-free medium. Thus, collagen gene expression increases as the growth of vascular smooth muscle cells is slowed by either deprivation of growth factors or essential amino acids. Regulation is mediated at several sites, including gene transcription and mRNA translation, and possibly post-transcriptional steps.

Response to epidermal growth factor of skin fibroblasts from donors of varying age is modulated by the extracellular matrix

The present study was undertaken to investigate the effect of epidermal growth factor (EGF) on the biosynthetic activity of skin fibroblasts from donors of varying age and the modulation of their response to this growth factor by culture in a three-dimensional extracellular matrix. When cultured in monolayer on plastic or at the surface of a collagen gel, EGF specifically inhibited collagen synthesis whatever the age of the donor (from 17 to 84 years, n = 11). This inhibition was paralleled by a significant decrease in the steady-state level of procollagen type I mRNAs. When embedded in a three-dimensional floating collagen lattice, EGF stimulated the non-collagen protein (NCP) synthesis in fibroblasts from younger donors (5 out of 6) while fibroblasts from the older ones were not affected. Collagen production by fibroblasts from younger donors was not inhibited as in monolayer (some being even stimulated) while that of the older donors was inhibited as observed in monolayer. The steady-state level of procollagen type I mRNA was not modified by EGF in the three-dimensional culture. No significant difference was observed in the affinity and the number of EGF receptors of the fibroblasts on plastic or embedded in a collagen lattice between young and aged donors. Our results suggest that the environment of the cells can modulate the reactivity to EGF and reveal differences related to in vivo aging.

Growth-dependent modulation of type I collagen production and mRNA levels in cultured human skin fibroblasts

Five human skin fibroblast lines were studied for type I collagen production and type I procollagen mRNA levels through the different growth phases. The cells were plated at low density and followed for 11 days at daily intervals through the stages of rapid growth and visual confluency until the cultures reached stationary growth phase. Each day one culture flask was labeled with [3H]proline for 24 h, and analyzed for production of radiolabeled type I collagen into culture medium. The cell layers were counted and subjected to isolation of cytoplasmic RNA and determination of type I procollagen mRNA levels. The results revealed an approx. 2-fold increase in procollagen production and mRNA levels when the cells reached visual confluency. Thereafter the synthesis rates and mRNA levels remained relatively constant, although a decreasing tendency of both parameters was observed upon further culturing. The results confirm that determination of cell density is important when cell cultures are used for measurement of collagen synthesis or mRNA levels. For determination of pro alpha 2(I) collagen mRNA an 1193 bp cDNA clone was constructed using RNA extracted from human fetal calvaria. Sequencing of the clone revealed some nucleotide and amino acid differences between the previously published sequences. This suggests the presence of more individual variation in procollagen coding sequences than expected.

Collagen synthesis by human fibroblasts. Regulation by transforming growth factor-beta in the presence of other inflammatory mediators

We have examined the combined effects of transforming growth factor-beta (TGF-beta), serum and gamma-interferon (gamma-IFN) on collagen synthesis by fibroblasts and compared the response of fibroblast subpopulations to TGF-beta. Human diploid fibroblasts were treated with TGF-beta alone and with serum of gamma-IFN. Cells were labelled with radioactive amino acids, and collagen production was measured as collagenase-digestible radioactivity. Collagen mRNA was determined by a solution-hybridization assay using procollagen-alpha 1[I] cDNA clone HF 677. The results showed that either serum or TGF-beta increased incorporation, collagen production and mRNA by fibroblasts approx. 2-fold; however, collagen synthesis relative to total protein synthesis and collagen mRNA relative to total polyadenylated [poly(A)+] RNA were not affected. Only serum activated cell growth. Collagen production increased approx. 4-fold in cells exposed to both TGF-beta and serum, and this increase was equal to that expected for an additive effect by both components. Treatment with gamma-IFN decreased collagen production and collagen mRNA to 44 and 40% respectively, whereas total incorporation and poly(A)+ RNA were affected only marginally. Cells exposed simultaneously to both gamma-IFN and TGF-beta produced less collagen and contained less mRNA than did those treated with TGF-beta alone. The gamma-IFN decreased collagen synthesis in control and TGF-beta-treated cultures to a similar extent, and TGF-beta increased collagen synthesis 2-fold in cells pre-treated with gamma-IFN. Fibroblast strains obtained in medium containing plasma-derived serum synthesized approximately half as much collagen as did cells derived from the same explant in the presence of fresh human serum, and TGF-beta stimulated collagen production and mRNA in both cell strains. We conclude that TGF-beta, serum and gamma-IFN regulate collagen synthesis by independent mechanisms, and that the combined action of these components plays a significant role in regulating collagen synthesis during wound healing and tissue repair.

Pentoxifylline inhibits normal human dermal fibroblast in vitro proliferation, collagen, glycosaminoglycan, and fibronectin production, and increases collagenase activity

Fibroblasts from normal human adult skin were cultured in vitro in the presence and absence of different concentrations of pentoxifylline or a pentoxifylline analog, A81-3138 (10(-1)-10(3) micrograms/ml). Similar concentration dependent reductions in normal proliferation of fibroblasts in fetal calf serum-driven subconfluent cultures were detected following treatment with pentoxifylline or A81-3138. Fibroblasts assayed as confluent cultures produced sub-normal amounts of collagen, glycosaminoglycans (GAGs), and fibronectin in a fashion dependent upon the concentration of pentoxifylline. In contrast, fibroblasts exposed to pentoxifylline elaborated double the collagenase activity produced by normal, untreated fibroblasts. The reduced proliferation and reduced synthetic activities were not due to a lethal toxic effect on fibroblasts by pentoxifylline and A81-3138, nor was the reduction in collagen synthesis simply due to an inability to secrete newly synthesized intracellular collagen. Unlike pentoxifylline-induced inhibition of collagen and fibronectin production, which was detected only in cultures supplemented with serum, pentoxifylline inhibits, to a similar degree, both constitutive and serum-driven production of GAGs. The addition of IL1 beta (2.5 and 10.0 U/ml) to serum-driven fibroblast cultures resulted in greater proliferation, which was inhibitable by the presence of pentoxifylline and A81-3138 as anti-fibrotic agents in certain disorders of fibrosis.

Effect of relaxin on the phenotype of collagens synthesized by cultured rabbit chondrocytes

The effect of porcine relaxin on rabbit articular and growth plate chondrocytes in primary culture was investigated by measurement of total collagen production and analysis of the phenotypes of newly synthesized collagen chains. A 24-h treatment of monolayer articular and multilayer growth plate chondrocytes with 2 micrograms per ml relaxin had no effect on total DNA and did not significantly modify the amount of [3H]proline-labelled collagen chains secreted by the cells. However, polyacrylamide gel electrophoresis demonstrated relevant modifications in relaxin treated chondrocytes. A significant increase was observed in the proportion of type III collagen and in the intensity of the band corresponding to alpha 2I chains. Two-dimensional peptide mapping of CNBr-cleaved molecules indicated that the band that was identified as alpha 1II on monodimensional gels contained a significant proportion of alpha 1I collagen chains, as demonstrated by the presence of alpha 1I cyanogen bromide-digested peptides. The intensity of this band was increased by relaxin treatment. Furthermore, total RNA analysis by slot blot and Northern blot techniques showed a dose-dependent stimulation of alpha 1I and alpha 1III mRNA levels after incubation with increased relaxin concentrations, but no change in the amount of alpha 1II mRNA. These results suggested that when added to cartilage cells in vitro, relaxin modulated the expression of type I, type II and type III collagen genes by amplifying the dedifferentiation process.