Altered rates of collagen synthesis in in vitro aged human lung fibroblasts

Breastfeeding and the risk of childhood cancer: a systematic review and dose-response meta-analysis

BACKGROUND

The aim of this study was to quantitatively summarize the available evidence on the association of breastfeeding with the risk of childhood cancer.

METHODS

A literature search of PubMed and Embase databases was performed to identify eligible observational studies published from inception to July 17, 2020. The categorical and dose-response meta-analysis was conducted by pooling relative risk (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression and stratification analysis. Sensitivity analysis and publication bias test were also carried out.

RESULTS

Forty-five articles involving 475,579 individuals were included in the meta-analysis. Among the thirty-three studies on the association between breastfeeding and risk of childhood leukemia, the pooled risk estimates were 0.77 (95% CI, 0.65-0.91) and 0.77 (95% CI 0.63-0.94) for ever versus non/occasional breastfeeding and longest versus shortest breastfeeding duration group, respectively. There was clear indication for non-linear dose-response relationship between breastfeeding duration and the risk of childhood leukemia (P non-linear < 0.001). The most protective effect (OR, 0.66, 95% CI 0.62-0.70) was observed at a breastfeeding duration of 9.6 months. Four studies examined, the association between breastfeeding and risk of childhood neuroblastoma, and significant inverse associations were consistently observed in both the comparisons of ever breastfeeding versus non/occasional breastfeeding (OR = 0.59, 95% CI 0.44-0.81) and longest versus shortest breastfeeding (OR = 0.61, 95% CI 0.44-0.83). However, no associations of breastfeeding with risk of other cancers were found.

CONCLUSIONS

Our study supports a protective role of breastfeeding on the risk of childhood leukemia, also suggesting a non-linear dose-response relationship. Further studies are warranted to confirm the association between breastfeeding and risk of childhood neuroblastoma.

Utility of the Teslar Facial Massager for Skin Elasticity and the Mechanism of its Effects

The Teslar is a facial massager that emits a weak electric current, where users have reported a beneficial effect on skin elasticity with continued use. Accordingly, we conducted a clinical utility study and a comprehensive gene analysis, with cultured human fibroblasts to investigate the utility and mechanism of this treatment. In this clinical utility study, we found significant improvement in skin elasticity in Teslar treatments, compared to controls after two weeks of treatment. In cell experiments, we found that adenosine triphosphate synthesis and collagen contraction were promoted in fibroblasts cultured in type I collagen gel, following Teslar treatment. We considered that Teslar treatment exerted a structurally regenerative effect on the dermal matrix, based on the results of GeneChip® Expression Analysis. In particular, we demonstrated that Teslar treatment promotes type I collagen mRNA expression and fibulin-5/DANCE (Developmental arteries and neural crest EGF (epidermal growth factor)-like) mRNA expression and protein levels, which are reduced with aging. We also found increases in LTBP-3 (Latent TGF-β binding protein-3) and CSPG4 (Chondroitin sulfate proteoglycan 4) mRNA expression levels. Based on these results, we considered that Teslar treatment promoted dermal regeneration and recovery of skin elasticity.

Effect of erythromycin A and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts

Thinning of the dermis is the principal histological change in atrophic skin disorders and aged skin. It is caused due to a decreased amount of collagen in the dermis. Macrolides have been reported to exert various pharmacological activities, including anti-inflammatory activity, tumor angiogenesis inhibition and growth inhibition of fibroblasts, in addition to antimicrobial activity. In this study, we investigated the effects of erythromycin A (EMA) and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts. Dermal fibroblasts were cultured with 10(-9) M-10(-5) M EMA or EM201, and collagen production was measured by incubation with radioactive proline, SDS-polyacrylamide gel electrophoresis and fluorography. mRNA levels were measured by Northern blots analysis, and to investigate transcriptional levels luciferase assays were also performed. The results showed that both EMA and EM201 increased collagen production and type I collagen mRNA level (to a maximum of 200% with EMA and 250% with EM201) in a dose-dependent manner in cultured dermal fibroblasts. Transcription of the type I collagen gene was also increased by both macrolides. These results suggest that EMA and EM201 have the potential to improve the thinning of the dermis in atrophic skin disorders and aged skin.

TGF-beta1-induced cardiac myofibroblasts are nonproliferating functional cells carrying DNA damages

TGF-beta1 induces differentiation and total inhibition of cardiac MyoFb cell division and DNA synthesis. These effects of TGF-beta1 are irreversible. Inhibition of MyoFb proliferation is accompanied with the expression of Smad1, Mad1, p15Ink4B and total inhibition of telomerase activity. Surprisingly, TGF-beta1-activated MyoFbs are growth-arrested not only at G1-phase but also at S-phase of the cell cycle. Staining with TUNEL indicates that these cells carry DNA damages. However, the absolute majority of MyoFbs are non-apoptotic cells as established with two apoptosis-specific methods, flow cytometry and caspase-dependent cleavage of cytokeratin 18. Expression in MyoFbs of proliferative cell nuclear antigen even in the absence of serum confirms that these MyoFbs perform repair of DNA damages. These results suggest that TGF-beta1-activated MyoFbs can be growth-arrested by two checkpoints, the G1/S checkpoint, which prevents cells from entering S-phase and the intra-S checkpoint, which is activated by encountering DNA damage during the S phase or by unrepaired damage that escapes the G1/S checkpoint. Despite carrying of the DNA damages TGF-beta1-activated MyoFbs are highly functional cells producing lysyl oxidase and contracting the collagen matrix.

Energetic stress induces premature aging of diploid human fibroblasts (Wi-38) in vitro

Oxidative phosphorylation is the main endogenous source for the generation of reactive oxygen species (ROS). In order to investigate the influence of enhanced ROS production on the in vitro senescence of Wi-38 fibroblasts, cells were cultivated in medium with elevated (hypertonic) NaCl concentrations. The number of active Na(+)/K(+)-ATPase molecules per cell was found to be increased. A rise in both respiration and glycolysis as evidenced by the increases in oxygen and glucose consumption and lactate production was revealed. Cells stayed alive in medium with NaCl concentrations of up to 0.30 M and could be adapted to growth under these hypertonic conditions (high-NaCl tolerant cells). These cells exhibited an increased cell size and protein content. A growing number of cells showed stress fibers and granulation. The proliferation rate and the maximum number of cumulative population doublings of these high-NaCl tolerant cultures were reduced and saturation density was decreased. Thus, these cells under energetic stress due to increased energy requirements for active ion transport expressed features typical for aging in vitro. We conclude therefore that energetic stress induces premature aging in human diploid fibroblasts.

Changes in collagen metabolism in response to endothelin-1: evidence for fibroblast heterogeneity

Endothelin-1 (Et-1) is a 21-amino acid peptide primarily synthesized by endothelial cells. It was originally classified as a potent vasoconstrictor but recent evidence suggests that it also possesses a wide variety of non-vascular actions. It stimulates fibroblast and smooth muscle cell proliferation and it has been shown to stimulate fibroblast collagen metabolism. However, studies on its ability to regulate collagen production remain incomplete, and its effect on post-translational processing of procollagen has not been studied. This report details the effect of Et-1 on the rates of procollagen synthesis and degradation in two fibroblast cell lines; human foetal lung (HFL-1) and whole foetal rat fibroblasts (Rat 2). Fibroblast cultures were incubated for 24 hr in the presence or absence of Et-1 before procollagen metabolism was determined by measuring hydroxyproline. Non-collagen metabolism was also determined in these cultures from the uptake of tritiated phenylalanine. Et-1 stimulated procollagen synthesis in HFL-1 fibroblasts and reduced synthesis in Rat 2 cells. The response was dose dependent with the greatest effect at 1.10(-6) M Et-1 for both cell types (155 +/- 6% of control (mean +/- SD, n = 6, P < 0.01) and 61 +/- 4% of control (n = 4, P < 0.01) for HFL-1 and Rat 2 fibroblasts, respectively). Non-collagen protein synthesis was increased to 148 +/- 5% of control (P < 0.05) at 1.10(-6) M Et-1. Non-collagen protein synthesis remained unaffected in the HFL-1 fibroblast cultures. Procollagen degradation, expressed as a proportion of total procollagen synthesis, was decreased in HFL-1 fibroblasts (control, 29 +/- 2%; Et-1, 1.10(-6) M; 21 +/- 2%; P < 0.01), and increased in Rat 2 fibroblasts (control 42 +/- 1%; Et-1, 1.10(-6) M; 49 +/- 1%; P < 0.01). Blocking of the EtA receptor for Et-1, using the receptor antagonist-BQ123, abolished the effect of Et-1 on procollagen metabolism in both cell types. These results suggest that different populations of fibroblasts exhibit heterogeneous responses to Et-1. It is concluded that Et-1 may play an important role in the extent and distribution of fibrosis seen in diseases associated with the overproduction of Et-1.

Age-related alterations in collagen and total protein metabolism determined in cultured rat dermal fibroblasts: age-related trends parallel those observed in rat skin in vivo

The cultured fibroblast has been extensively used as a model system to study aging. However, few studies have examined the veracity of observations obtained in cultured fibroblasts aged in vitro to those made in animal tissues in vivo. This paper compares age-related alterations in collagen metabolism measured in cultured cells with previously reported results in the aging rat (Mays et al. (1991) Biochem. J. 276, 307-313). Age-related changes in collagen synthesis in rat skin fibroblasts in vitro over 30 population doublings were determined based on the production of hydroxy-[14C]proline. Degradation of newly synthesized collagen was based on the appearance of free hydroxy-[14C]proline in the culture system. Total protein synthesis rates were based on the incorporation of [14C]proline into proteins. In vitro rates of collagen synthesis decreased 5-fold over 30 population doublings (P < 0.05). Degradation of newly synthesized collagen increased from 33.0 +/- 0.8% (n = 4, SEM) to 45.2 +/- 1.1% (n = 4; P < 0.05) over the same period, with a maximum after 25 population doublings of 55.8 +/- 1.1% (n = 4). Total protein synthesis rates decreased by one-half over 30 population doublings (P < 0.05). The results indicated that collagen production decreased as cells aged in vitro and that this was due to both changes in synthesis and degradation. The results demonstrate that age-related alterations in collagen and total protein metabolism of skin fibroblasts in culture were similar to those reported previously for skin in vivo, suggesting that for studies of these processes, fibroblasts in culture provide an appropriate model.

In vitro biosynthesis of type I and III collagens by human dermal fibroblasts from donors of increasing age

A quantitative study of type I and type III collagen production was carried out on primary cultures of human dermal fibroblasts. Cultures were initiated from facial and mammary skin of 29 women aged between 19 and 68 years. Secreted and cell-associated collagen levels were determined by an enzyme linked immunosorbent assay (ELISA). We found that the secretion of type I and type III collagen decreased linearly with age (r = 0.432; P = 0.0193 and r = 0.502; P = 0.0147, respectively). There was a 29% loss in secretion ability for type I and type III collagen over the 49-year period studied. Furthermore, no significant linear age-related decrease was observed for type I and type III collagen associated with the cellular fraction. The influence of body site was also analysed. We observed a significant linear age-related decrease in type I collagen secretion by mammary skin cells (P = 0.0183 and r = 0.618) as well as facial skin cells (P = 0.0037 and r = 0.699). Furthermore, only mammary skin fibroblasts showed a significant linear age-related decrease in secreted type III collagen (P = 0.106 and r = 0.513). No age-related variations in cell-associated collagen were found.

Differential extracellular matrix gene expression by fibroblasts during their proliferative life span in vitro and at senescence

Increasing evidence supports the idea that the finite proliferative life span of normal fibroblasts is a differentiation-like phenomenon. If this were correct, an ordered sequence of differential gene expression should be associated with the in vitro progression of cells from low passage to high passage (senescence). To define the pattern of expression of fibroblast differentiation-associated genes during this in vitro progression, we have determined the temporal pattern of expression of extracellular matrix (ECM) genes in Syrian hamster dermal fibroblasts as a function of passage level and percentage of proliferative life span in vitro. Steady-state mRNA levels were determined by Northern and dot blot analyses of total cellular RNA hybridized with cDNA probes specific for fibronectin, procollagen alpha 1III, and procollagen alpha 1I. Cells were analyzed at 24 hr postconfluence to minimize the presence of actively proliferating cells, and because maximal levels of fibronectin, alpha 1III, and alpha 1I mRNAs were observed 24 hr postconfluence. Unique, multiphasic patterns of expression of each of these ECM components were observed as the cells progressed from low passage to high passage. As the cells reached midhigh passage, fibronectin mRNA levels increased. This midpassage increase in fibronectin was followed by an increase in the level of alpha 1III mRNA as the cells reached the end of their in vitro proliferative life span, and then alpha 1I when the cells entered the postmitotic senescent phase, at which time the level of fibronectin mRNA also declined. A similar overlapping cascade pattern of up-regulation of these genes is seen during development and wound repair. This suggests that as cultured fibroblasts reach the end of their proliferative life span, they reinitiate a gene expression program used in tissue development and repair.

Cellular ageing related proteins secreted by human fibroblasts

Fibroblast secreted proteins participate in the formation of extracellular matrix. Extracellular matrix affects growth factor action, mediates cell adhesion and supports cell growth. Structural and quantitative characteristics of secreted proteins are modified in a similar manner, during both in vivo and in vitro cellular ageing. Such ageing related modifications may either be directly controlled by primary ageing causes, or evolve from a reformation of the extracellular matrix induced by a few ageing defects in key proteins such as fibronectin. They may result in the further inhibition of cell adhesion, cell stimulation by growth factors and, eventually, of cell proliferative ability.

Ultrastructure of dermal fibroblasts during development and aging: relationship to in vitro senescence of dermal fibroblasts

One approach to understanding the relationship between in vitro cellular senescence and in vivo aging is to define the development and aging of cells in vivo and then to compare these in vivo properties with the in vitro behavior of the same cells. The Syrian hamster is being used as an experimental aging model to investigate the intrinsic developmental program of dermal fibroblasts in vivo (proliferation, extracellular matrix (ECM) production, quiescence, and reactivation during wound repair) in order to determine whether the in vivo differentiation program and mature function of these cells is related to their in vitro proliferation and senescence pattern. The ultrastructure of dermal fibroblasts from midfetal development through old age is described, and a working hypothesis of the development and aging of dermal fibroblasts is proposed as a framework for further evaluation of the relationship between in vitro proliferative capacity of dermal fibroblasts and in vivo developmental and age-related changes in the dermis.

Minocycline-treatment of diabetic rats normalizes skin collagen production and mass: possible causative mechanisms

Daily minocycline-treatment of streptozotocin-induced diabetic rats not only prevented a diabetes-caused atrophy of skin collagen mass (10-mos old rats), but also normalized skin collagen mass to match that of growing (ca. 1%/d) non-diabetic controls (4- and 5-mos old rats). The causative mechanism by which minocycline-treatment normalizes skin collagen mass must, in part, be related to a general anabolic effect on growth (body weight) because the effect on skin collagen mass correlates strongly to that on body weight. Consequently, a minocycline-stimulated increase of a systemic factor (such as insulin-like growth factor) is not unlikely. The anabolic effect of minocycline-treatment of diabetic rats is also expressed as a normalized cellular ribosome mass (an index of total protein synthetic capacity) and a normalized absolute rate of collagen production. (Calculation of an absolute rate was justified by an apparent maximum saturation of the prolyl-tRNA pool(s) of skin, maximum saturation obtained by the pool-flooding approach). The normalized skin ribosome amount does not, however, explain a selective effect of minocycline-treatment on collagen production as opposed to that for non-collagen protein, this selective effect measured as relative collagen production. To explain such selectivity, the inhibition of diabetes-induced excess skin collagenase activity seems unlikely. (This inference is based on results from a preliminary study indicating that recently [less than 2 h] synthesized collagen is not degraded by the excess collagenase in skin of diabetic rats). Thus, the principal collagen fraction acted on by pathologically excess collagenase might be collagen at a later stage (greater than 2 h after synthesis) in its life cycle. (Another possibility for the selective effect of minocycline on collagen production, as yet untested, is reduced intracellular procollagen degradation.) Overall, this is the first study aimed at discerning the mechanism(s) by which minocycline-treatment enhances the rate of collagen production in tissues of a diabetic rat. For future studies, the extent to which the positive effect on growth, ribosome mass, and rate of collagen production contributes to the change of collagen mass must, along with the known minocycline-inhibition of collagenase activity, be quantified. Such quantification is a prerequisite for evaluating the chemotherapeutic efficacy of minocycline-treatment on collagen-degradative diseases.

Cellular senescence revisited: a review

The field of cellular senescence (cytogerontology) is reviewed. The historical precedence for investigation in this field is summarized, and placed in the context of more recent studies of the regulation of cellular proliferation and differentiation. The now-classical embryonic lung fibroblast model is compared to models utilizing other cell types as well as cells from donors of different ages and phenotypes. Modulation of cellular senescence by growth factors, hormones, and genetic manipulation is contrasted, but newer studies in oncogene involvement are omitted. A current consensus would include the view that the life span of normal diploid cells in culture is limited, is under genetic control, and is capable of being modified. Finally, embryonic cells aging in vitro share certain characteristics with early passage cells derived from donors of increasing age.

Comparison of the use of isotopic proline vs leucine to measure protein synthesis in cultured fibroblasts

Compartmentation of the amino acid precursor pools for protein synthesis in cultured cells can substantially complicate measurements of synthesis rates. This is particularly true for nonessential amino acids such as proline, an amino acid often used in isotopic form to measure collagen synthesis. We have made a comparative study of this problem in cultured IMR-90 fibroblasts using isotopic proline and leucine to measure total protein and collagen synthesis. 3H-leucine in the extracellular (EC) medium equilibrates with tRNA-leucine at an EC concentration of 0.4 mM in both dividing and stationary cells. Thus, under these experimental conditions there is no complicating compartmentation of leucine for protein synthesis. Equilibration of EC and tRNA-bound 3H-proline, however, does not occur even when the EC concentration is in the mM range, based upon simultaneous measurements of synthesis rates using 3H-proline and 3H-leucine together. Furthermore, significant changes in EC proline concentration and specific activity occur over short time intervals (2 hr) if the initial EC proline concentration is below 0.2 mM. Thus, the use of isotopic proline to measure protein synthesis introduces substantial interpretive problems. Serum deprivation causes changes in both total collagen synthesis and the percent of protein synthesis devoted to collagen when measured with either 14C-leucine or 3H-proline. At the same time, isotopic proline remains the better choice for measuring percent collagen synthesis.

Synthesis of cytoskeletal and contractile proteins by cultured IMR-90 fibroblasts

Models of the assembly of cytoskeletal and contractile proteins of eukaryotic cells require quantitative information about the rates of synthesis of individual component proteins. We applied the dual isotope technique of Clark and Zak (1981, J. Biol. Chem., 256:4863-4870) to measure the synthesis rates of cytoskeletal and contractile proteins in stationary and growing cultures of IMR-90 fibroblasts. Fibroblast proteins were labeled to equilibrium with [14C]leucine over several days, at the end of which there was a 4-h pulse with [3H]leucine. Fractional synthesis rates (percent per hour) were calculated from the 3H/14C ratio of cell protein extracts or protein purified by one- or two-dimensional polyacrylamide gel electrophoresis and the 3H/14C ratio of medium-free leucine. The average fractional synthesis rate for total, SDS- or urea-soluble; Triton-soluble; and cytoskeletal protein extracts in stationary cells each was approximately 4.0%/h. The range of values for the synthesis of individual proteins from total cell extracts or cytoskeletal extracts sliced from one-dimensional gels was similar, though this range was greater than that for major proteins of Triton-soluble protein extracts. Three specific cytoskeletal proteins--actin, vimentin, and tubulin--were synthesized at similar rates that were significantly slower than the average fractional synthesis rate for total protein. Myosin, on the other hand, was synthesized faster than average. Synthesis rates were the same for beta-and gamma-actin and polymerized (cytoskeletal extract) vs. Triton-soluble actin. The same was true for alpha- and beta-tubulin and two different forms of vimentin. Synthesis rates were uniformly higher in growing cells, though the same pattern of differential rates was observed as for stationary cells. Synthesis rates in growing cells were higher than the rate necessary to maintain the growth rate, even for those cytoskeletal proteins being synthesized slowly. Therefore, there appears to be some turnover of these cytoskeletal elements even during growth. We conclude that proteins in cytoskeletal extracts may have nonuniform rates of synthesis, but at least one important subclass of cytoskeletal proteins that comprise filament subunits have the same synthesis rates.