Poultry Science 1994; 73:663-669
Use of this material approved
Poultry Science Association, ©1994

Influence of Manganese Deficiency on the Characteristics of Proteoglycans of Avian Epiphyseal Growth Plate Cartilage
A. C.-H. LIU, B. S. HEINRICHS, and R. M. LEACH, JR.

ABSTRACT

The need for manganese for normal skeletal development appears to be related to its role in proteoglycan biosynthesis. The purpose of this research was to characterize the proteoglycans synthesized under conditions of manganese deficiency. The proteoglycans were extracted from epiphyseal growth plate cartilage and the monomers separated by cesium chloride density gradient centrifugation followed by column chromatography. The proteoglycan monomers from normal cartilage contained primarily (92%) chondroitin sulfate side chains with keratan sulfate being a minor (8%) component. Manganese deficiency reduced the total amount of cartilage proteoglycans. Of the monomers present in deficient cartilage, the majority (75%) were similar to those found in normal cartilage. Cartilage from deficient chicks also contained a second monomer fraction (25%) characterized by a reduced carbohydrate content. Thus, in addition to a reduction in total proteoglycan content, manganese deficiency results in qualitative changes in the proteoglycans present in epiphyseal growth plate cartilage.

Manganese has been demonstrated to be an essential element for many species of animals and is presumed to be essential for humans. If manganese deficiency occurs during fetal development or early postnatal life, severe impairment of skeletal development can occur (Leach, 1988). The primary effect is decreased endochondral bone growth, resulting in chondrodystrophy (dwarfism). The role of manganese in normal epiphyseal cartilage metabolism appears to be centered around its involve-ment in the biosynthesis of proteoglycans, which are major constituents of cartilage extracellular matrix (Leach, 1986). Proteoglycans occur in the extracellular matrix as complex aggregates containing proteoglycan monomers, hyaluronic acid, and link proteins (Hascall, 1988). The proteoglycan monomer is comprised of a protein core with a large number of glycosaminoglycan side chains. Manganese is a co-factor for glycosyltransferases, enzymes involved in the synthesis of the glycosaminoglycan side chains (Leach, 1986).

The purpose of this research was to determine the characteristics of the proteoglycans isolated from manganese deficient cartilage. The research addressed the question: Is there a reduced number of normal proteoglycan molecules or are abnormal proteoglycan molecules produced under conditions of manganese deficiency?

In conclusion, the proteoglycans of normal epiphyseal growth plate cartilage that were isolated using CsCl density gradient centrifugation were characterized by large amounts (92%) of chondroitin sulfate side chains and a smaller amount (8%) of keratan sulfate side chains. Manganese deficiency substantially reduced the total proteoglycan content. Of the proteoglycan monomers that were present, the majority (75%) were similar to those found in normal cartilage. However, a second monomer fraction (25%) was found to be reduced in carbohydrate content, suggesting the presence of either smaller side chains or fewer side chains per molecule of core protein.

Hascall, V.C., 1988. Proteoglycans: The chondroitin sulfate/keratin sulfate proteoglycan of cartilage. Pages 189-198 in: Institute for Scientific Information Atlas of Science, BioChemistry. Vol. 1. Institute for Scientific Information, Philadelphia, PA.

Leach, R.M., Jr., 1986. Mn(II) and glycosyltransferases essential for skeletal development. Pages 81-91 in: Manganese in Metabolism and Enzyme Function. B.L. Schramm, and F.W Wedler, ed. Academic Press, New York, NY.

Leach, R.M. Jr., 1988. The role of trace elements in the development of cartilage matrix. Pages 267-271 in. Trace Elements in Man and Animals 6. L. Hurley, C.L. Keen, B. Lonnerdal, and R.B. Rucker, ed. Plenum Publishing Corp., New York, NY.