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[Experimental study on staphylococcal enterotoxin promoting tendon-bone healing after reconstruction of anterior cruciate ligament in rabbits].

OBJECTIVE
To explore highly agglutinative staphylococcin (HAS) pomoting on tendon-bone healing after reconstruction of anterior cruciate ligament(ACL) in rabbits.


METHODS
Animal model of ACL reconstruction in 24 mature New Zealand white rabbits(3 months, 2.56 kg on average, either gender) were established using autologous digital long extensor tendon and randomly classified into 2 groups(HAS and control group), 12 rabbits for each group. HAS group was separately injected 0.1ml highly agglutinative staphylococcin immediately into tendon-bone interface during the operation and 2 days after operation. Control group was injected with the same dose of physiological saline for 3 days. All animals were sacrificed at 4, 8, and 12 weeks after operation for histological examinations. The specimens were stained with hematoxylin-eosin, picric acid-sirius red, VEGF immunohistochemistry stain, and toluidine blue to histologically analysis the total pathology changes of the tendon-bone healing tissue, the tendon bone interface morphology classification, hyperplasia and arrangement of collagen fiber, vascularization and new bone formation, respectively.


RESULTS
The Yamakado morphological interface results showed that the tissue healing at tendon-bone interface of the HAS group was better than that of the control group. The histological examination revealed that on the 4th week after operation, the tendon-bone interface of HAS group was filled with fibrous connective tissue. The proliferated fibroblasts, chondroblasts and the angiogenesis were rich. On the 8th week after operation, the healing tissue at the bone-tendon interface had developed into dense connective tissue, the neo-vessels were very rich, the collagen fibers were formed abundantly, some Sharpey's fibers spanning parts of the tendon-bone interface. On the 12th week after operation, the transition zones were full of Sharpey's fibers;the neo-vessels were not as much as the 8th weeks, but new bone formation was further increased and immature fibrocartilage appeared. For quantitative histological analysis at 4, 8 and 12 weeks after operation, the proportion of neo-vessel area and the area of now bone formation of the HAS group were all significantly higher than those of the control group(P<0.05).


CONCLUSIONS
Under the synergy of staphylococcal enterotoxin C and other active ingredients, Highly Agglutinative Staphylococcin can significantly improve the tendon-bone healing after ACL reconstruction in rabbit knees, which is expected to be a new method to improve the clinical results of ACL reconstruction.