Effects of maturation and aging on the pressure-bearing region of the plantaris longus tendon of the bullfrog ( L ithobates catesbeianus).

ABSTRACT The plantaris longus tendon (PLT) in bullfrog develops a fibrocartilage-like tissue in the area that is functionally subject to compressive forces. The aim of this study was to analyze the modifications of the pressure-bearing region in bullfrog PLT with different ages (7, 180, and 1,080 days after the end of metamorphosis) using histomorphometric, ultrastructural and biochemical methods. Weak basophilia and cells with a fibroblastic phenotype were observed in the compression region at 7 days of age. On the other hand, a large area of intense tissue basophilia associated with a chondroblast-like cell population was noted at the other ages. Collagen fibers exhibited a three-dimensional network-like arrangement at all ages. The number of connective tissue cells increased between 7 and 180 days of age and was reduced in older animals. The 180-day-old animals presented a well-developed pericellular matrix rich in proteoglycans. The mean diameter of collagen fibrils increased from 7 to 180 days and was the same at 1,080 days. Glycosaminoglycan content was higher in 7-day-old animals. A higher amount of hydroxyproline was observed at 180 and 1,080 days. The swelling test showed a significant increase of wet weight in 7-day-old animals. In conclusion, the alterations that occur in the pressure-bearing of bullfrog PLT are the result of physiological alterations of the animal with the maturation and aging. Microsc. Res. Tech. 77:797-805, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]