Age-related changes in the mitogenic activity of heparin-binding growth factors in rat sera

Inhibitory effects of human serum on human fetal skin fibroblast migration: migration-inhibitory activity and substances in serum, and its age-related changes

In order to clarify the environmental factors modulating cell migration, we investigated the effects of human serum on cell migration, and found that serum from adult donors strongly (by 48%) suppressed the migration of human fetal skin fibroblasts into a denuded area in a cell monolayer. Human serum from old donors inhibited cell migration more strongly than that from adult donors. Next, we investigated the properties of migration-inhibitory activity of human serum and serum proteins in order to identify migration-inhibitory substances. Human serum from adult donors strongly suppressed the migration of human fetal skin fibroblasts, although it stimulated cell proliferation more strongly than fetal bovine serum (FBS), indicating that the inhibitory effects of human serum on cell migration was not due to its toxic effects. The inhibition of cell migration by human serum was concentration dependent. It was demonstrated that the inhibition did not depend on the inhibitory effects of human serum on collagen synthesis. The migration-inhibitory activity was seen in fractions over 100 kDa, as determined by an ultrafiltration membrane, and no inhibitory activity was observed in fractions under 100 kDa. On the other hand, it was not detected either in fractions over 100 kDa or under 100 kDa in FBS. Among the over 100 kDa human serum proteins examined, gamma-globulin, alpha2-macroglobulin, and low density lipoprotein (LDL) suppressed fibroblast migration in a concentration-dependent manner. However, among the three, cell migration-inhibiting activity of gamma-globulin almost disappeared when cell migration was conducted in 10% FBS-supplemented medium. These results indicated that alplha2-macroglobulin and LDL were candidate substances for cell migration-inhibiting activity in human serum.

The effects of ageing on wound healing: immunolocalisation of growth factors and their receptors in a murine incisional model

A number of reports suggest that the process of ageing impairs wound repair and that strategies to manipulate the age-related wound healing environment are necessary in order to stimulate repair. The process of cutaneous wound repair is controlled by growth factors in an autocrine and paracrine fashion: it is therefore surprising that the localisation of specific growth factors and their receptors has not been documented in wound healing with respect to chronological age. In this study the temporal profile of growth factor and receptor immunostaining was assessed within acute incisional wounds in an ageing mouse colony. A delay in appearance of platelet derived growth factor (PDGF) A and B isoforms, and PDGF-alpha and -beta receptors was evident with increasing animal age, paralleled by a similar finding for epidermal growth factor (EGF) and EGF receptor. Transforming growth factor (TGF)-beta 1 and 2 isoforms were increased at all time points in the wounds of younger animals, but the TGF-beta 3 isoform increased in intensity from d 7 postwounding in the old mice wounds, and basic fibroblast growth factor (bFGF) from d 14. The quantity and distribution patterns of the various growth factors and their receptors may explain the age-related differences in wound healing speed and quality, and possibly suggest new therapeutic targets for manipulating wound healing in the aged.

Effects of aging and dietary restriction on activity of monkey serum in promoting fibroblast migration

In order to determine whether serum modified cellular aging in vivo, we previously studied the effects of serum from various mammals of different ages on cell functions such as proliferation and migration, and reported that cell migration was more greatly inhibited by serum from old donors than cell proliferation [1]. Moreover, since dietary restriction has been reported to extend lifespan and slow the aging rate of some animals [2], we wondered whether sera from dietary restricted and control monkeys of various ages might exhibit reduced aging effects on cell migration. When serum from young adult (3-5 years old) monkeys was added to plain medium, the migration of human fetal skin fibroblasts was very strongly inhibited compared to FBS. Surprisingly, sera from adult (6-11 years old) and old (more than 18 years old) monkeys caused significantly less migration-inhibitory activity than serum from young adult monkeys although sera from adult and old monkeys were much more inhibitory to cell migration than FBS. Dietary restriction only caused marginal effects on serum migration-promoting activity in a few monkey groups. The inhibition of cell migration caused by monkey serum was not brought about by cytotoxic effects since monkey serum stimulated cell proliferation as well as fetal bovine serum. These results indicate that the effects of aging on monkey serum migration-promoting activity are much more pronounced than those of dietary restriction.