Isolation of intact collagen fibrils from healing ligament

The inability to isolate intact collagen fibrils has limited the study of their growth and structure. Although intact fibrils have been isolated from echinoderms and from embryonic chick tissues, no method has previously succeeded in isolating intact collagen fibrils from a postfoetal vertebrate tissue. Having previously observed that gentamicin weakens rat tail tendon, we hypothesized that gentamicin may weaken interfibrillar bonds and that intact collagen fibrils might be isolated from tissue treated with gentamicin. In this study medial collateral knee ligaments of Sprague Dawley rats were transected and then harvested 24, 48 or 96 h postoperatively. These specimens were placed in gentamicin or phosphate-buffered saline for 72 h, vortexed for 1 h, incubated in gentamicin for an additional 24 h, and vortexed again for 1 h. Negatively stained specimens were examined with a transmission electron microscope. The phosphate-buffered saline specimens yielded only broken fibrils. The,gentamicin specimens yielded both broken and intact fibrils. The latter had tapering ends and consisted of molecules orientated such that their amino termini pointed toward the tip and their carboxy termini pointed toward a short central region where the molecular polarity reversed.