To determine the characteristics of magnetic resonance (MR) signals of normal growing cartilage and identify the difference in transverse relaxation times between physeal and epiphyseal cartilage in vivo. 24 distal femora of 12 two-week-old piglets were imaged on a 1.5 Tesla GE MR scanner. Comparison was made between signal intensity on MR images and the structure shown in corresponding histologic sections. T2 values were measured in eight piglets by means of multiecho spin-echo sequences. Our results showed that MR imaging delineated five regions between the secondary ossification center and the metaphysis, which histologically correspond to the zone of provisional calcification of the secondary ossification center, physis of the secondary ossification center, epiphyseal cartilage, physis and zone of provisional calcification. The T2 value in the physeal cartilage was much larger than that in the epiphyseal cartilage (P<0.05). It is concluded that MRI findings could differentiate the different regions of growing cartilage. T2 is longer in physeal than in epiphyseal cartilage, perhaps reflecting differences in water binding by proteoglycans.
Animals, Newborn ; Femur/anatomy & histology ; Femur/growth & development ; Femur/metabolism ; Growth Plate/*anatomy & histology ; Growth Plate/*growth & development ; Growth Plate/metabolism ; *Magnetic Resonance Imaging ; Osteogenesis/physiology ; Swine

The purpose of this study is to define the appearance of normal epiphyseal and metaphyseal marrow and normal changes of marrow due to fatty conversion on Gadolinium (Gd)-enhanced MR Imaging. Unenhanced and enhanced T1-weighted MR imaging were performed in proximal and distal femoral ends of 8 healthy piglets at the ages of 2, 4, 6 and 8 weeks, respectively. The changes with age in signal intensity and enhancement ratio of the epiphyseal and metaphyseal marrow with age were examined. The correlation of MRI characteristics with histological findings was studied. Our study showed that marrow of the metaphysis and of periphery of the 2nd ossification center were well vascularized hematopoietic marrow and had great enhancements. The enhancement ratio of metaphysis was greater than that of epiphyseal marrow and both enhancement ratios degraded gradually with age. The central regions of the epiphyseal ossification center and of the diaphysis were of fatty marrow and had little enhancement. It is concluded that on Gd-enhanced MR imaging the hematopoietic marrow of metaphysis and of periphery of the 2nd ossification center had greater enhancement than that of fatty marrow of central region of the 2nd ossification center. All of their enhancements decreased gradually with age.
Epiphyses/*anatomy & histology ; Femur/anatomy & histology ; Femur/*growth & development ; Gadolinium/*diagnostic use ; Growth Plate/*anatomy & histology ; Growth Plate/blood supply ; Growth Plate/growth & development ; Image Enhancement ; Magnetic Resonance Imaging ; Swine ; Swine, Miniature

To determine the characteristics of magnetic resonance (MR) signals of normal growing cartilage and identify the difference in transverse relaxation times between physeal and epiphyseal cartilage in vivo. 24 distal femora of 12 two-week-old piglets were imaged on a 1.5 Tesla GE MR scanner. Comparison was made between signal intensity on MR images and the structure shown in corresponding histologic sections. T2 values were measured in eight piglets by means of multiecho spin-echo sequences. Our results showed that MR imaging delineated five regions between the secondary ossification center and the metaphysis, which histologically correspond to the zone of provisional calcification of the secondary ossification center, physis of the secondary ossification center, epiphyseal cartilage, physis and zone of provisional calcification. The T2 value in the physeal cartilage was much larger than that in the epiphyseal cartilage (P<0.05). It is concluded that MRI findings could differentiate the different regions of growing cartilage. T2 is longer in physeal than in epiphyseal cartilage, perhaps reflecting differences in water binding by proteoglycans.
Animals ; Animals, Newborn ; Femur ; anatomy & histology ; growth & development ; metabolism ; Growth Plate ; anatomy & histology ; growth & development ; metabolism ; Magnetic Resonance Imaging ; Osteogenesis ; physiology ; Swine

PURPOSE: The purpose of this study was to investigate the effects of transplantation of an in vitro-generated, scaffold-free, tissue-engineered cartilage tissue analogue (CTA) using a suspension chondrocyte culture in a rabbit growth-arrest model. MATERIALS AND METHODS: We harvested cartilage cells from the articular cartilage of the joints of white rabbits and made a CTA using a suspension culture of 2x107 cells/mL. An animal growth plate defect model was made on the medial side of the proximal tibial growth plate of both tibias of 6-week-old New Zealand white rabbits (n=10). The allogenic CTA was then transplanted onto the right proximal tibial defect. As a control, no implantation was performed on the left-side defect. Plain radiographs and the medial proximal tibial angle were obtained at 1-week intervals for evaluation of bone bridge formation and the degree of angular deformity until postoperative week 6. We performed a histological evaluation using hematoxylin-eosin and Alcian blue staining at postoperative weeks 4 and 6. RESULTS: Radiologic study revealed a median medial proximal tibial angle of 59.0degrees in the control group and 80.0degrees in the CTA group at 6 weeks. In the control group, statistically significant angular deformities were seen 3 weeks after transplantation (p<0.05). On histological examination, the transplanted CTA was maintained in the CTA group at 4 and 6 weeks postoperative. Bone bridge formation was observed in the control group. CONCLUSION: In this study, CTA transplantation minimized deformity in the rabbit growth plate injury model, probably via the attenuation of bone bridge formation.
Animals ; *Bone Transplantation ; Cartilage/anatomy & histology ; Cell Culture Techniques ; Cells, Cultured ; Chondrocytes/*cytology/transplantation ; Growth Plate/anatomy & histology/*surgery ; *Mesenchymal Stem Cell Transplantation ; Rabbits ; Tibia/*surgery ; Tissue Engineering ; Transplantation, Autologous/methods ; Transplantation, Homologous

OBJECTIVETo compare the histological features of the thoracic vertebral body growth plates (VBGPs) of rats at different ages and assess their proliferative capability.

METHODSThe thoracic VBGPs obtained from rats aged 1 day and 1, 4, 8, 16 and 28 weeks were identified using safranin O-fast green staining, and the height of the hypertrophic zone, proliferative zone, and resting zone were measured. The chondrocytes were isolated from these VBGPs with a modified trypsin-collagenase type II digestion method for primary culture in vitro. The expressions of proliferating cell nuclear antigen (PCNA) mRNA and protein was detected by real time-PCR and Western blotting, respectively.

RESULTSThe 1-day- and 1-week-old rats showed significantly greater hypertrophic zone and proliferative zone in the VBGPs than older rats (P<0.01); the proliferative zone was significantly greater in rats aged 4 weeks than in those aged 28 weeks (P<0.05). The resting zone was obviously greater in rats aged 1 day and 1 week than in older rats (P<0.05), and also greater in rats aged 4 weeks than in those aged 16 and 28 weeks (P<0.05). Obvious ossification in the resting zone occurred at 16 weeks, and most of the resting zone became ossified at 28 weeks. The expression of PCNA decreased at both the mRNA and protein levels as the rats grew.

CONCLUSIONThe 3 zones of VBGPs are greater in rats aged 1 day and 1 week than in older ones. Ossification in the resting zone begins at 16 weeks, and till 28 weeks, most of the resting zone is ossified. The proliferation ability of VBGP chondrocytes decreases with the increase of age of the rats.

Age Factors ; Animals ; Animals, Newborn ; Cell Proliferation ; Cells, Cultured ; Chondrocytes ; cytology ; Growth Plate ; anatomy & histology ; cytology ; Male ; Proliferating Cell Nuclear Antigen ; analysis ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Thoracic Vertebrae ; growth & development