The effects of posterior cruciate ligament rupture on the biomechanical and histological characteristics of the medial collateral ligament: an animal study.

BACKGROUND: To investigate the effect of complete rupture of the posterior cruciate ligament (PCL) on the biomechanics and histology of the medial collateral ligament (MCL). MATERIALS AND METHODS: Seventy-two male rabbits were randomly divided into two groups: the ruptured group was treated with complete PCL amputation, while the intact group was only subjected to PCL exposure without amputation. Eighteen rabbits were randomly sacrificed at 8, 16, 24, and 40 weeks after the operation, and their specimens were processed for mechanical tensile testing, nano-indentation experiments, hematoxylin-eosin (HE) staining, and picrosirius-polarization staining. RESULTS: There was no significant difference in the length and maximum displacement of the MCL between the ruptured group and the intact group at each time point. The maximum load of the ruptured group was significantly smaller than that of the intact group at 40 W. The elastic modulus and micro-hardness of the ruptured group increased significantly at 24 W and decreased significantly at 40 W. At 16 W and 24 W after PCL rupture, the number of type I collagen fibers and type III collagen fibers in the MCL of the ruptured group was significantly increased compared with that of the intact group. While the type I collagen fibers of the ruptured group were significantly decreased compared with the intact group at 40 W, there was no significant difference in type III collagen fibers between the ruptured group and the intact group. CONCLUSION: PCL rupture has no significant effect on the mechanical and histological properties of MCL in a short period of time under physiological loading, but the histological and mechanical properties of MCL decrease with time.

The therapeutic effects of earthworm extract on deep second-degree burn wound healing.

BACKGROUND: To investigated the effect of earthworm extract (EE) on deep second-degree burn wound healing process. METHODS: A burn wound model was created on the mice's skin and was subject to different treatments: the control group received no treatment; the Jingwanhong (JWH: a well-established, widely used external ointment for treating burn wounds) group was treated with 0.1 g of JWH cream and spray it on the wound surface; the EE group was treated with 0.1 mL of EE solution. All the mice were sacrificed at 3, 7, 11, and 15 days after injury (n=6/group/time point). Macroscopic observation, wound healing rate (WHR), wound healing time (WHT), water content (WC), hydroxyproline (Hyp) content, histological, and hematological analyses were performed at the burn wound sites. RESULTS: Better, faster burn wound healing in the JWH and EE groups than the control group at 15 days after injury were detected at the wound sites. Compared to the control group, the EE group had higher WHR, shorter WHT, lower WC, higher Hyp content, more fibroblasts, fibrocytes, and capillary endothelial cells; in addition, they showed greater capillary endothelial cell grouping at the wound sites during the healing process. This group also showed more platelets, white blood cells (WBCs), and neutrophilic granulocytes in serum at the early stages after burn injury. CONCLUSIONS: EE could effectively promote skin wound healing by decreasing edema, suppressing fibrosis, activating angiogenesis and epithelial regeneration, inhibiting scar formation, and reducing the risk of infection. Thus, it could be made into a promising healing agent for burn wound.