Collagen Degradation by Host-derived Enzymes during Aging

TLDR

Incompletely infiltrated collagen fibrils in acid‑etched dentin are susceptible to degradation. The study hypothesizes that collagen degradation in acid‑etched dentin can occur over time without bacteria, driven by slowly released host‑derived matrix metalloproteinases. Partially demineralized collagen matrices from human dentin were stored in artificial saliva, with controls in inhibitor‑containing saliva or mineral oil, and retrieved at 24 h, 90 days, and 250 days to assess degradation. After 250 days, experimental specimens showed almost complete destruction of DCM, whereas control specimens and those treated with enzyme inhibitors or mineral oil retained intact collagen layers, and dentin powder exhibited low collagenolytic activity that was inhibited by protease inhibitors or chlorhexidine.

Abstract

Incompletely infiltrated collagen fibrils in acid-etched dentin are susceptible to degradation. We hypothesize that degradation can occur in the absence of bacteria. Partially demineralized collagen matrices (DCMs) prepared from human dentin were stored in artificial saliva. Control specimens were stored in artificial saliva containing proteolytic enzyme inhibitors, or pure mineral oil. We retrieved them at 24 hrs, 90 and 250 days to examine the extent of degradation of DCM. In the 24-hour experimental and 90- and 250-day control specimens, we observed 5- to 6-μm-thick layers of DCM containing banded collagen fibrils. DCMs were almost completely destroyed in the 250-day experimental specimens, but not when incubated with enzyme inhibitors or mineral oil. Functional enzyme analysis of dentin powder revealed low levels of collagenolytic activity that was inhibited by protease inhibitors or 0.2% chlorhexidine. We hypothesize that collagen degradation occurred over time, via host-derived matrix metalloproteinases that are released slowly over time.