Bone marrow-derived cells from the footprint infiltrate into the repaired rotator cuff.

BACKGROUND: Cells from the bone marrow are considered important during the rotator cuff repair process, but the kinetics of bone marrow-derived cells in this process is unknown. PURPOSE: To analyze the kinetics of bone marrow cells during the rotator cuff repair process, to review whether or not they are histologically involved in rotator cuff healing, and to analyze the biomechanics of the repaired tissues. METHODS: Bone marrow chimeric rats that express green fluorescent protein (GFP) only in bone marrow- and circulation-derived cells were created. Bilateral supraspinatus tendons were separated from the greater tuberosity of the humeral head to produce a rotator cuff transection model. Drilling into the bone marrow was performed in the greater tuberosity of the right humerus and the supraspinatus tendon was repaired (drilling group), while the supraspinatus tendon was repaired on the left shoulder without drilling (control group). We examined the histology of the rotator cuff, the ultimate force-to-failure, and the proportion of GFP-positive cells in the repaired rotator cuff at 2, 4 and 8 weeks after surgery. RESULTS: Mesenchymal cells were observed in the repaired rotator cuff at 2 weeks in both groups. There were more GFP-positive cells in the drilling group than the control group at 2, 4 and 8 weeks. The ultimate force-to-failure was significantly higher in the drilling group than the control group at 4 and 8 weeks. CONCLUSION: Bone marrow-derived cells passed through holes drilled in the humerus footprint, infiltrated the repaired rotator cuff and contributed to postsurgical rotator cuff healing.

Positive effect on bone fusion by the combination of platelet-rich plasma and a gelatin ß-tricalcium phosphate sponge: a study using a posterolateral fusion model of lumbar vertebrae in rats.

We developed a novel method for bone fusion by combining platelet-rich plasma (PRP) and a gelatin ß-tricalcium phosphate (ß-TCP) sponge. The PRP is an autologous concentration of platelets that includes several growth factors. The gelatin ß-TCP sponge comprises gelatin and ß-TCP, thus enabling the sustained release of growth factors and osteoconduction. To evaluate this method, we generated a posterolateral fusion model of lumbar vertebrae in rats and divided it into five groups by implanting the following materials between transverse processes of vertebrae, (1) the gelatin ß-TCP sponge with PRP (PRP sponge), (2) the gelatin ß-TCP sponge with platelet-poor plasma, (3) gelatin hydrogel with PRP, (4) autologous iliac bone (autograft), and (5) no material was implanted as a control. The assessment of bone fusion by a radiographic assessment, a biomechanical test, microcomputed tomography, and histological evaluations demonstrated that there were no significant differences between the PRP sponge and the autograft groups regarding the osteogenic effect. Subsequent examinations revealed that no significant differences existed between the PRP sponge and the autograft groups in either biomechanical stiffness or the bone volume over time; whereas the radiographic and histological composition underwent similar changes in the fusion process. These results indicate that the PRP sponge could, therefore, be potentially useful as an attractive and less invasive method for bone fusion.

Characterization of in vivo effects of platelet-rich plasma and biodegradable gelatin hydrogel microspheres on degenerated intervertebral discs.

We have previously shown that administration of platelet-rich plasma-impregnated gelatin hydrogel microspheres (PRP-GHMs) into a degenerated intervertebral disc (IVD) markedly suppresses progression of IVD degeneration. In the current study, we characterized the in vivo effects of PRP-GHM treatment in a degenerated IVD model in rabbit. On magnetic resonance images, the IVD height was significantly greater after treatment with PRP-GHMs compared with phosphate-buffered saline-impregnated GHMs, PRP without GHMs, and needle puncture only. Water content was also preserved in PRP-GHM-treated IVDs. Consistent with this observation, the mRNA expression of proteoglycan core protein and type II collagen was significantly higher after PRP-GHM treatment compared with other treatment groups. No proliferating cells were found in the nucleus pulposus and inner annulus fibrosus in any groups, but the number of apoptotic cells in the nucleus pulposus after PRP-GHM treatment was significantly lower than that after other treatments. These results provide an improved understanding of the therapeutic effects of PRP-GHM treatment of degenerated IVDs.