Protein-restricted maternal diet during lactation decreases type I and type III tropocollagen synthesis in the skin of mice offspring.

We investigated the effects of a low protein (LP) maternal diet during lactation on type I and III tropocollagen synthesis in infant mouse skin. The LP diet decreased the levels of type I and III tropocollagen proteins and COL1A1 and COL3A1 mRNA. Thus, the protein composition of the maternal perinatal diet may influence the skin health of offspring.

Branched-chain amino acids regulate type I tropocollagen and type III tropocollagen syntheses via modulation of mTOR in the skin.

Branched-chain amino acids (BCAAs) exhibit many physiological functions. However, the potential link and mechanism between BCAA and skin function are unknown. We examined the effects of deletion of branched-chain α-keto acid dehydrogenase kinase (BDK), a key enzyme in BCAA catabolism, on type I and III tropocollagen syntheses in mice. Leucine and isoleucine levels were significantly lower in the skin of BDK-KO mice compared with wild-type mice. No changes in valine concentrations were observed. The levels of type I and III tropocollagen proteins and mRNAs (COL1A1 and COL3A1) were significantly lower in the skin of BDK-KO mice compared with wild-type mice. The phosphorylation of p70 S6 kinase, which indicates mammalian target of rapamycin (mTOR) activation, was reduced in the skin of BDK-KO mice compared with wild-type mice. These findings suggest that deficiencies of leucine and isoleucine reduce type I and III tropocollagen syntheses in skin by suppressing the action of mTOR.

Accelerating effect of soy peptides containing collagen peptides on type I and III collagen levels in rat skin.

Two weeks of feeding soy peptides containing 2% collagen peptides increased the levels of type I and III tropocollagen and their mRNAs. In contrast, the diet did not increase the mRNA levels of rat hyaluronan synthases, serine palmitoyltransferase (the rate-limiting enzyme of ceramide synthesis), and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (the key enzyme of cholesterol synthesis). These results suggest that feeding of soy peptides with collagen peptides specifically enhanced the tropocollagen level in the skin.

An electron microscopic study of collagen formation in the dental pulp of the human premolar and rat incisor.

Collagen secretion and maturation were investigated at the ultrastructural level. Pulp tissue from the continuously growing incisor of the rat provided excellent material for studying the secretory aspects of the tropocollagen. More mature human pulp material proved valuable in viewing the collagen fibril. A networklike arrangement of fibroblasts and fibrocytes was noted. Various types of cell junction were found in all specimens. The finding of a nexus junction was particularly interesting. It is hypothesized that connected cell systems rather than single cells might be the functional units involved in collagen formation.

The influence of diabetes mellitus and hypercorticism on the wound healing of experimental myocardial infarction in rats.

In diabetic and glucocorticoid-treated rats myocardial infarction is produced by coronary artery ligation. After the ligation was performed the animals were given 3H-thymidine or 3H-proline at different times. The following parameters were determined: number of DNA- and tropocollagen-synthesizing connective-tissue cells both at the infarction border and infarction site; mean silver-grain density above the nuclei or cells; number of mitoses. The labelling and mitotic indices as well as the standard deviation (in percent) from the mean values were calculated. The following results were obtained: 1. The retarded formation of collagen fibres in diabetic animals is caused by a reduced number of tropocollagen-synthesizing fibroblasts and by a diminished synthesizing performance of the individual cells. 2. Glucocorticoids have a pronounced inhibitory effect on granulation-tissue formation, The 3H--thymidine indices are strikingly low. The synthesis of collagen precursors in the fibroblasts is reduced. The release of tropocollagen from the connective-tissue cells is slowed down.

[Autoradiographic study of the rate of collagen synthesis under conditions of stimulation of the wound process]. / Avtoradiograficheskoe issledovanie skorosti sinteza kollagena v usloviiakh stimuliatsii ranevogo protsessa.

A study was made of the rate of the tropocollagen synthesis by the granulation tissue fibroblasts and of its passage into the intercellular space in control animals and under conditions of stimulation of the wound process by potassium orotate, one of the pyrimidine series derivatives. It appeared that the process of tropocollagen synthesis became accelerated under the effect of the stimulant; collagen fiber precursor appeared in the intercellular space earlier than in control and became included into the fibrous structures of the granulation tissue, this correlating with the intensification of the RNA synthesis in the fibroblast nuclei and an accelerated passage of the newly-synthesized RNA from the nucleus into the cell cytoplasm under analogous conditions. There was noted no sharp excess of collagen in the granulation tissue of animals given potassium orotate.

The influence of age on the wound healing of experimental myocardial infarction in rats.

In 6-weeks-old, 5-months-old and 21-months-old rats myocardial infarction was induced by coronary artery ligature. After performing the ligature the animals were administered 3H-thymidine, 3H-proline or 35S-sulphate at different times. The following parameters were determined: number of DNA- and tropocollagen-synthesizing connective tissue cells at the infarction border and at the infarction site; mean silver grain density above the nuclei or cells; duration of a cycle; number of mitoses, and incorporation of radioactive sulphate at the infarction site. In addition, the labelling and mitotic indices as well as the percentage of the standard deviation from the mean values were estimated. The following results were obtained: 1. The rate of granulation tissue formation in the necrotic zone is determined by the mitotic activity of the cells. With advancing age the cell cycles are being prolonged which results in retardation of wound healing. 2. The disturbed DNA-replication in old age is not associated with a time shift in the occurrence of the mitotic and labelling peaks. 3. With advancing age the number of fibroblasts synthesizing collagen precursors decreases. There exists no age-dependence of the 3H-proline incorporation rate, of the intracellular transport, of the synthesis of collagen precursor and of the release of labelled tropocollagen. In all age-groups under study these processes last approximately 4 hours. 4. Collagen fibre formation is accompanied by an increased synthesis of acid mucopolysaccharides. In infarction callosities the content of acid mucopolysaccharides mostly is constant. 5. The proliferating endothelial cells have a pronounced metabolic activity and a markedly short generation time.

A transport form of collagen from embryonic tendon: electron microscopic demonstration of an NH 2 -terminal extension and evidence suggesting the presence of cystine in the molecule (chick embryo-tropocollagen-gel filtration).

When cells were isolated from chickembryo tendons and incubated in vitro for 2-6 hr, essentially all the newly-synthesized collagen was recovered from the incubation medium as a transport form larger than tropocollagen. Experiments in which cells were incubated with [(14)C]cystine suggested that the transport form contained cystine and that it was, in part, stabilized by disulfide bonds. Electron microscopy of segment-long-spacing aggregates prepared from the transport form of collagen showed that the native molecule differed from tropocollagen in that it had an extension of about 13 nm (130 A) at the NH(2)-terminal end.