Acid phosphatase activity and intracellular collagen degradation by fibroblasts in vitro

Abstract

Human gingival fibroblasts were cultured with collagen fibrils. The precise process of collagen phagocytosis and the relationship between acid phosphatase activity and intracellular degradation of collagen were investigated by cytochemical methods at the ultrastructural level. The collagen fibrils were first engulfed at one end by cellular processes, or the cell membrane wrapped itself around the middle of the fibrils. Collagen phagocytosis induced acid phosphatase activity in the fibroblast Golgi-endoplasmic reticulum-lysosome system. By application of the tracer lanthanum, deposits were observed in the intercellular spaces and along the fibrils being phagocytosed. At this stage, primary lysosomes were seen in close proximity to the collagen being engulfed, but no signs of fusion were observed. When the fibrils had been interiorized in whole or in part, they ultimately became enclosed within phagosomes, and no tracer was observed along the interiorized portion of the fibrils. Primary lysosomes then fused with these collagen-containing phagosomes to form phagolysosomes. Collagen degradation occurred within these bodies even though the end of a fibril might have protruded outside of the cell. These results suggest that selective and controlled phagocytosis of collagen and intracellular digestion of it may play a central role in the physiological remodeling and metabolic breakdown of the collagen of connective tissues.

Membranous complexes characteristic of melanocytes derived from patients with Hermansky–Pudlak syndrome type 1 are macroautophagosomal entities of the lysosomal compartment

“…Secondary lysosomes and macroautophagosomes contain acid phosphatase, a lysosomal enzyme that in part functions to degrade contents such as collagen within these structures (Dunn, 1990b; Yajima, 1986). Acid phosphatase activity was assessed in HPS‐1 melanocytes at the electron microscopic level using the technique developed by Gomori (1952).…”

Phagocytosis and intracellular digestion of collagen, its role in turnover and remodelling

“…Several studies demonstrated acid phosphatase activity in the electron-dense type of vacuoles, indicating the presence of lysosomal enzymes ( Fig. 2; Deporter & Ten Cate, 1973;Beertsen et aI., 1978;Everts et al, 1985b;Yajima, 1986Yajima, , 1988. Some authors localized the enzyme also in electron-translucent vacuoles (Beertsen et al, 1978).…”

Methylcellulose cell culture as a new cytotoxicity test system for biomaterials

“…We hypothesize that the fibroblasts interact with HDSC by production and release of, e.g., proteolytic enzymes (such as collagenase) [28][29][30][31] into the culture gel, reaching HDSC by diffusion, resulting in its degradation. The molecular structure of (cytotoxic) degradation products may depend on the available binding sites on the collagen for proteolytic enzymes.…”