Lysozyme in Epiphyseal Cartilage

Abstract

Embryonic mouse femoral cartilage, like the epiphyseal cartilage of the calf scapula, contains large amounts of lysozyme . The addition of egg white lysozyme to organ cultures of embryonic mouse femurs induces unique alterations in the gross and microscopic morphology of the femurs . The sites of these alterations are precisely related to the natural distribution of lysozyme in calf scapula . If the exogenous lysozyme is withdrawn from the culture, the morphological changes disappear, accompanied by a resumption or derepression of growth . The effect on growth is evident only in 17-day embryos . These observations support the idea that lysozyme has a physiological role in cartilage, perhaps related to a regulatory mechanism in bone formation .

Lysozyme in Epiphyseal Cartilage

“…This locus appears to be particularly specialized since not only lysozyme, but also specific proteinpolysaccharides (34,35) and chlorides, are concentrated there (36) . It is also the area where exogenous lysozyme is specifically bound (12,14) . The functional significance of this anatomic specialization remains obscure .…”

“…It has been suggested that this role involves regulation of the reactivity of certain of the anionic polysacchariderich macromolecules of cartilage by the cationic lysozyme molecule (12)(13)(14) .…”

Electron Microscopic Studies of Cartilage Matrix Using Lysozyme as a Vital Stain

“…It is known to precipitate cartilage polysaccharides and their parent mucoproteins under physiological conditions (11) and to complex with these compounds when added to organ cultures of preosseous cartilage (2-4) . It does not degrade mammalian polysaccharides (12) and does not significantly affect the growth or calcification of epiphyseal cartilage in organ culture (2)(3)(4) . The technique of short-term organ culture in the presence of added LYS also appeared to offer the advantage that the problem of diffusion of the molecule into the tissue during the process of fixation, which occurs with some other techniques, might be considerably mitigated .…”

“…A possible approach to this problem could be the use of larger cations which would at least fix portions of the polysaccharide chains in an extended state . On the basis of previous studies (1)(2)(3)(4), LYS appeared to be a good candidate for such a cation . It is a wellcharacterized, commercially available protein with an isoelectric point of 11 .2 .…”

“…During the course of a series of studies which had as their aim the elucidation of the role of lysozyme in cartilage metabolism (1)(2)(3)(4), it was found that, when egg white lysozyme (LYS) was added to organ cultures of ossifying cartilage (cartilage which contains an epiphyseal growth plate) but not nonossifying cartilage (cartilage which does not contain a growth plate), the lysozyme bound to cartilage matrix in specific anatomic sites . In recent years a number of techniques, including staining with lanthanum and bismuth salts (5,6), ruthenium red (7), and colloidal iron (8), as well as the addition of cetylpyridinium chloride to fixatives (9), have been used for the visualization of mucopolysaccharides for electron microscopy .…”