Scurvy; a comparison between ultrastructural and biochemical changes observed in cultured fibroblasts and the collagen they synthesise.
Earlier biochemical investigations of cultured 3T6 fibroblasts have shown that ascorbate deficiency has no effect on the synthesis of collagen protein quantitatively but does produce inhibition of the critical post-translational hydroxylation of collagen essential for normal fibrogenesis and of formation of hydroxylysine-derived cross-links. This ultrastructural study on the same 3T6 fibroblast system demonstrates that ascorbate deficiency does not affect the cell morphology, particularly that of the protein synthetic or secretory apparatus, but does prevent the deposition of typical 640A degrees banded collagen fibres; instead, finer, unbanded fibrils--presumably collagenous--are deposited extracellularly. This confirms the earlier biochemical findings as wll as presenting a new finding--the inability of ascorbate-deficient cells to lay down normal collagen fibrils; possible mechanisms are considered in terms of the known biochemical lesions. The tissue culture findings are also compared with those observed in vivo in the scorbutic guinea-pig, where other workers have reported biochemical and ultrastructural evidence that collagen synthesis is inhibited. The apparently paradoxical observations in the two systems are considered; we conclude that the tissue culture system demonstrates the primary collagenous lesion which is perhaps obscured in vivo by secondary effects--nevertheless the two approaches are complementary.
D000818:Animals; D001206:Ascorbic Acid Deficiency / Q000378:metabolism / Q000473:pathology*; D003094:Collagen / Q000096:biosynthesis*; D003238:Connective Tissue / Q000648:ultrastructure*; D005347:Fibroblasts / Q000648:ultrastructure; D066298:In Vitro Techniques; D008854:Microscopy, Electron
D003094:Collagen