PURPOSE: This study was designed to measure time-dependent changes in muscle excursion and collagen content after tenotomy, and to analyze the correlation between muscle excursion and collagen content in a rabbit model. MATERIALS AND METHODS: Twenty-four rabbits underwent tenotomy of the second extensor digitorum longus (EDL) muscles on the right legs and were randomly assigned to three groups based on the period of time after tenotomy (2, 4, and 6 weeks). The second EDL muscles on left legs were used as controls. At each time after tenotomy, passive muscle excursion and collagen content, determined by hydroxyproline content, were measured bilaterally, and the ratio of each value to the normal one was used. RESULTS: The mean ratio of muscle excursion after tenotomy to the value of the control decreased in a time-dependent fashion: 92.5% at 2 weeks, 78.6% at 4 weeks, and 55.1% at 6 weeks. The mean ratio of hydroxyproline content in muscle to the value of the control increased in a time-dependent fashion: 119.5% at 2 weeks, 157.3% at 4 weeks, and 166.6% at 6 weeks. There was a significant negative correlation between the ratio of hydroxyproline content in muscle after tenotomy to the control values and the ratio of muscle excursion after tenotomy to the control values (r=-0.602, p=0.002). CONCLUSION: The decrease in muscle excursion seems to correlate with the increase in collagen content in the muscle in a time-dependent fashion following tenotomy.
Animals ; Collagen/*metabolism ; Hydroxyproline/metabolism ; Muscle, Skeletal/*metabolism ; Rabbits ; Tendon Injuries/*metabolism ; Tendons ; Tenotomy ; Time Factors

Experiments have been performed to investigate why the biomechanical strength of repaired tendons is lower than that of the normal tendon when the engineered tendons are implanted in vivo to replace the tendon defects. We seeded the primary culture tendon cells derived from Roman chickens' digital flexor tendons on the degradable polyglycolic acid meshes to construct tissue-engineered tendons. The flexor tendon defects (0.5 cm-0.8 cm) excised in second digit bilaterally in 20 Roman chickens, had been repaired with the constructed tissue-engineered tendons. The samples of repaired tendons were collected at 2, 4, 6 and 8 weeks after operation. Tests for scaffold weight, hydroxyproline content, and mechanical strength of the samples were performed. We found that from 2 weeks to 8 weeks afteroperation, the weight of the scaffolds decreased significantly, almost disappearing at 8 weeks; the hydroxyproline content determining the total collagen content increased gradually without significance; mechanically, both energy at break and tensile strength showed a tendency of drastic decrease at first 4 weeks afteroperation and a gradual increase afterwards, but the tensile strength at 8 weeks afteroperation was only 23% of that of the normal tendon. We conclude that the lower biomechanical strength of repaired tendons is owing to the serious mismatch between scaffold degradation and collagen synthesis.
Achilles Tendon ; injuries ; Animals ; Biocompatible Materials ; metabolism ; Bioprosthesis ; Cell Culture Techniques ; Chickens ; Collagen ; metabolism ; Female ; Prosthesis Implantation ; Tendon Injuries ; surgery ; Tendons ; cytology ; Tensile Strength ; Tissue Engineering ; methods

OBJECTIVESSurgical repair of Achilles tendon (AT) rupture should immediately be followed by active tendon mobilization. The optimal time as to when the mobilization should begin is important yet controversial. Early kinesitherapy leads to reduced rehabilitation period. However, an insight into the detailed mechanism of this process has not been gained. Proteomic technique can be used to separate and purify the proteins by differential expression profile which is related to the function of different proteins, but research in the area of proteomic analysis of AT 3 days after repair has not been studied so far.

METHODSForty-seven New Zealand white rabbits were randomized into 3 groups. Group A (immobilization group, n equal to 16) received postoperative cast immobilization; Group B (early motion group, n equal to 16) received early active motion treatments immediately following the repair of AT rupture from tenotomy. Another 15 rabbits served as control group (Group C). The AT samples were prepared 3 days following the microsurgery. The proteins were separated employing two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). PDQuest software version 8.0 was used to identify differentially expressed proteins, followed by peptide mass fingerprint (PMF) and tandem mass spectrum analysis, using the National Center for Biotechnology Information (NCBI) protein database retrieval and then for bioinformatics analysis.

RESULTSA mean of 446.33, 436.33 and 462.67 protein spots on Achilles tendon samples of 13 rabbits in Group A, 14 rabbits in Group B and 13 rabbits in Group C were successfully detected in the 2D-PAGE. There were 40, 36 and 79 unique proteins in Groups A, B and C respectively. Some differentially expressed proteins were enzyme with the gel, matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We successfully identified 9 and 11 different proteins in Groups A and B, such as GAPDH, phosphoglycerate kinase 1, pro-alpha-1 type 1 collagen, peroxiredoxin 1, alpha-1-antiproteinase E a-1 and MAD2L1 binding protein, etc. And some with the molecular chaperone, oxidative stress, energy metabolism, signal transduction, coupled with the tendon cell expression and protein synthesis, proliferate, differentiate and are closely related to the AT healing. The GAPDH protein was further validated through Western blotting. It was indicated that some differentially expressed proteins were involved in various metabolism pathways and may play an important role in initial healing of AT rupture.

CONCLUSIONDifferentially expressed proteins in rabbit healing AT model may contribute to 3 days healing of AT rupture through a new mechanobiological mechanism due to the application of postoperative early kinesitherapy.

Achilles Tendon ; injuries ; Animals ; Blotting, Western ; Computational Biology ; Electrophoresis, Gel, Two-Dimensional ; Exercise Therapy ; Glyceraldehyde-3-Phosphate Dehydrogenases ; analysis ; Male ; Proteins ; analysis ; Rabbits ; Rupture ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ; Tendon Injuries ; metabolism ; rehabilitation ; surgery ; Wound Healing ; physiology

OBJECTIVETo study the effect of continuous passive motion (CPM) on basic fibroblast growth factor (b-FGF) expression during tendon-bone repair in rabbits and explore the role of stress in the postoperative repair after acute rotator cuff injury.

METHODSSixteen rabbits randomized into CPM group (n=8) and non-CPM group (n=8) were subjected to surgically induced acute rupture of the supraspinatus tendon and subsequent surgical repair, with another two rabbits serving as the control. Two weeks after the operation, the rabbits in CPM group underwent CPM training, and those in non-CPM group were normally fed only. At 2, 4, 6, and 8 weeks after the operation, 2 rabbits from each group were sacrificed and the tissue samples were obtained for detecting the changes in b-FGF expression.

RESULTSTwo weeks after the operation, b-FGF expression was detected in both groups, and the CPM group showed slightly higher and more diffusive expression. At 4 weeks, b-FGF expression was significantly higher and distributed over a greater area in CPM group and in the non-CPM group. A large number of fibroblasts positive for b-FGF expression were identified in CPM group, aligning in parallel with the tendon membrane. At 6 weeks, b-FGF in the CPM group showed no obvious changes but that in the non-CPM group became lightened. At 8 weeks, b-FGF expression was reduced in both groups, which was more obvious in the non-CPM group.

CONCLUSIONCPM can promote b-FGF expression to enhance type III collagen synthesis at the tendon-bone interface in early stage of tendon-bone repair following acute rupture of supraspinatus tendon in rabbits, thereby contributing to tendon-bone recovery after rotator cuff injury.

Animals ; Bone Remodeling ; drug effects ; physiology ; Fibroblast Growth Factor 2 ; metabolism ; Male ; Postoperative Period ; Rabbits ; Random Allocation ; Range of Motion, Articular ; Rupture ; surgery ; Tendon Injuries ; rehabilitation ; surgery ; Tendons ; metabolism ; Wound Healing ; physiology