The fate and role of bone graft-derived cells after autologous tendon and bone transplantation into the bone tunnel.

BACKGROUND: Grafting bone between the tendon graft and the bone tunnel in anterior cruciate ligament reconstruction increases the mechanical strength of the tendon graft. However, the biological role of the bone graft is unclear. The purpose of this research was to elucidate the role of bone graft cells after autologous tendon graft into the bone tunnel with an autologous bone graft in green fluorescent protein (GFP) transgenic rats. METHODS: The Achilles tendons of Sprague-Dawley (SD) wild-type rats and bone of GFP rats were harvested and transplanted into bone tunnels drilled in the femurs at the knees of SD rats. The femurs were harvested at 1, 2, and 4 weeks after transplantation and histologically investigated using hematoxylin and eosin staining and immunostaining of heat shock protein 47 (HSP47), macrophages, and type I and type III collagens. Biomechanical tests were performed on the tendon graft 2 and 4 weeks after transplantation to evaluate the ultimate force to failure. RESULTS: A small number of GFP-positive cells was seen in the tendon graft 2 weeks after transplantation. The cell count in the tendon graft was increased at 4 weeks after transplantation. HSP47-positive cells and macrophage-stained cells present in the tendon graft corresponded with the GFP-positive cells. By 2 weeks after transplantation, the relative areas of immunostained type I and III collagens in the tendon graft had declined significantly in the bone graft group compared to the control. The ultimate failure load in the bone graft group was higher than that in the control group at both 2 and 4 weeks after transplantation. CONCLUSIONS: This research showed that, within 4 weeks of transplantation, bone graft cells migrate to the tendon graft, where they differentiate into cells involved in collagen production and macrophages. Bone graft cells may contribute to the early stage remodeling of tendon grafts.

Utility of delayed gadolinium-enhanced MRI (dGEMRIC) for qualitative evaluation of articular cartilage of patellofemoral joint.

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) was used for the measurement of relative proteoglycan depletion of articular cartilage in the patellofemoral (PF) joint following a proprietary protocol, which was compared with the X-ray images, proton density weighted MR images (PDWI) and arthroscopic findings. The study examined 30 knees. The ages ranged from 16 to 74 (average 40.3) years. The Gd-DTPA(2-)containing contrast medium was used in a single dose. The subjects were made to exercise the knee joint for 10 min; and MR images were taken 2 h after intravenous injection of contrast medium. T1-calculated images were produced and the region of interest (ROI) was set as follows. (1) ROI1: entire articular cartilage in a slice through the center of the patella. (2) ROI2: low signal region in T1-calculated images, which were set in a blind fashion by two observers. (3) ROI3: articular cartilage on one side that includes ROI2 where low signal region were detected (medial or lateral). ROI3 was set to examine the contrast of ROI2 with surrounding articular cartilage. The average T1 values of ROI1 was 393.5+/-33.6 ms for radiographic grade 0 and 361.3+/-11.1 ms for grade I, which showed a significant difference (P=0.036). The T1 value of ROI2 was 351.6+/-28.2 ms for grade I, 361.9+/-38.3 ms for grade II, 362.1+/-67.7 ms for grade III, and 297.8+/-54.1 ms for grade IV according to arthroscopic Outerbridge classification. All cases, that demonstrated decrease of T1 values on dGEMRIC (ROI2), showed abnormal arthroscopic or direct viewing findings. The ratio (ROI3/ROI2) in cases of only slight damage classified as Outerbridge grade I (6 cases) was an average of 1.04+/-0.02 and was 1.0 or greater in all cases, thereby indicating well-defined contrast with the surrounding cartilage. The diagnosis of damage in articular cartilage was possible in all 16 cases with radiographic K-L grade I on dGEMRIC, while the intensity changes were not found in 10 of 16 cases on PDWI. The dGEMRIC with a single-dose would be useful on a diagnosis of the area demonstrating early relative proteoglycan depletion in the articular cartilage of the PF joint prior to any discernible changes in the subchondral bone on X-ray images and exceeds to plain MR images for examining deterioration of articular cartilage.