This study sought to detect the pathological changes of anterior cruciate ligament (ACL) and medial collateral ligament (MCL) under injury stretch. Bone-ACL-Bone (B-ACL-B) and B-MCL-B complexes were isolated from 20 male Wister rats, and were immersed in phosphate buffered saline. The complexes were stretched with 10% or 20% strain for 10 min or 30 min. After being stretched, the specimens were fixed in 10% buffered formalin, then mounted in paraffin. Sections were stained with Alcian blue-PAS and HE. The following results were found: In the control group, the matrix in ACL contained much more GAGs, as compared with that in MCL. When stretched with 10%, most of the fibroblasts in ACL were elongated like spindles in shape, and some pyknotic nuclei were found increased with stretching time. With 20% strain, ACL showed disruption in parts of collagen fibrils and lysis. But MCL was often torn at its tibia end. The injury can be detected in pathological slices under microscope, even this injury can not be found with naked eye. This injury first starts with the disturbance of the nucleus in the ligament, but following further stretching, it will extend to the rupture of collagen fibrils, and the serious injury of the fibroblasts is especially bad to the repair of the ligament.
Animals ; Anterior Cruciate Ligament ; pathology ; Anterior Cruciate Ligament Injuries ; Male ; Medial Collateral Ligament, Knee ; injuries ; pathology ; Rats ; Rats, Wistar ; Stress, Mechanical

Objective This study detects the expression of secreted frizzled-related protein 1 (SFRP1) in healthy patients and patients with chronic periodontitis (CP) and explores the relationship between SFRP1 and the occurrence and development of CP. Methods First, 28 patients forming the CP group were further divided into mild, moderate, and severe CP subgroups according to clinical attachment loss (CAL) data. Ten healthy volunteers were recruited in the control group. Gingival crevi-cular fluid (GCF) was collected from all of the patients, and the concentration of SFRP1 in the GCF samples was detected using enzyme-linked immunosorbent assay. Next, gingival lesions were obtained from 22 patients in the CP group and healthy gingival tissues were obtained from the 10 healthy patients in the control group. Immunohistochemical analysis for SFRP1 was used to analyze the correlation between the expression of SFRP1 and the severity of CP based on staining intensities. Results The concentration of SFRP1 in GCF samples taken from of the CP group (281.07 ng·L-1±33.37 ng·L-1) was signifi-cantly higher than that in samples taken from the control group (245.30 ng·L-1±35.69 ng·L-1) (P<0.05). A significant positive correlation was observed between the concentration of SFRP1 in GCF and CAL (r=0.651, P<0.001). Furthermore, the SFRP1 scores in the CP groups (4.500±0.913) were significantly higher than those in the control group (2.800±1.135) (P<0.001). SFRP1 scores did not vary significantly among the CP subgroups (P>0.05). Conclusion SFRP1 expression in the CP groups was significantly higher than that in the control group. Thus, SFRP1 may play a significant role in the development of CP.