Magnetic resonance imaging of hyaline cartilage regeneration in neocartilage graft implantation

CaAlg hydrogel containing bone morphogenetic protein 4-enhanced adipose-derived stem cells combined with osteochondral mosaicplasty facilitated the repair of large osteochondral defects

PURPOSE

Cartilage repair presents a challenge to clinicians and researchers. A more effective procedure that can produce hyaline-like cartilage is needed for articular cartilage repair. Mosaic osteochondral grafts for large osteochondral defects often show poor integration between the grafts and the surrounding normal cartilage, leading to defective cracks filled with fibrous tissue instead of hyaline-like cartilage. In the present study, we aimed to repair the defective cracks with a calcium alginate (CaAlg) hydrogel containing bone morphogenetic protein 4 (BMP4)-enhanced adipose-derived stem cells (ADSCs).

METHODS

ADSCs were transduced with BMP4 (B-ADSCs). The expression of BMP4 and type II collagen was confirmed using an enzyme-linked immunosorbent assay (ELISA). Swine models of large cartilage defects of the knee were constructed and received one of the four treatments: mosaicplasty only, mosaicplasty with the CaAlg hydrogel, mosaicplasty with the CaAlg hydrogel containing ADSCs, or mosaicplasty with the CaAlg hydrogel containing B-ADSCs injected into the defective cracks. Outcomes were evaluated at 12 and 24 weeks after surgery.

RESULTS

The in vitro study showed that the osteogenic and chondrogenic activities of the B-ADSCs were enhanced compared with those of the control. In vivo, in the group that received mosaicplasty-containing B-ADSCs, osteochondral tissue was completely integrated with an intact surface. Additionally, the histological scores of the mosaicplasty-containing B-ADSCs group were significantly higher than those of the other groups. Biomechanical examination confirmed that the neocartilage possessed properties similar to those of normal cartilage.

CONCLUSIONS

Mosaicplasty and hydrogel containing B-ADSCs promoted the repair of large cartilage defects by regenerating hyaline cartilage and repairing dead spaces between osteochondral grafts and donor-site defects, thus improving the feasibility and success rate of one-stage complete repair surgery for large osteochondral defects. This proposed method provides a novel and effective means for the repair of large articular osteochondral defects.

Sequential alterations in magnetic resonance imaging findings after autologous osteochondral mosaicplasty for young athletes with osteochondritis dissecans of the humeral capitellum

BACKGROUND

The goal of osteochondral mosaicplasty (mosaicplasty) against osteochondritis dissecans of the humeral capitellum (capitellar OCD) is to allow patients to return to their sports activities without functional disturbance of the affected elbow. Consequently, the rehabilitation protocol and the interval before returning to sports activities must be established. Although surgeons need this type of data for establishing sequential alterations of grafts in the elbow, no such data have been published.

HYPOTHESIS

The findings of magnetic resonance imaging (MRI) improve with increasing time after mosaicplasty for capitellar OCD.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Ten young male athletes with advanced lesions of capitellar OCD, treated with mosaicplasties, underwent MRI scans at 3, 6, and 12 months, postoperatively. The surgical technique involved obtaining small-sized cylindrical osteochondral grafts from the lateral periphery of the femoral condyle at the level of the patellofemoral joint and transplanting them to the capitellar lesion. The MRI findings were semiquantitatively assessed according to the scoring system of Henderson et al (4, normal; 16, no repair).

RESULTS

At 12 months, all patients returned to their competitive level of sports without any disturbances of the operated elbow. Fluid surrounding the graft was found in all patients at 3 months and 4 patients at 6 months. The grafts were all well seated within the recipient sites, with no MRI evidence of graft loosening at 12 months. The overall MRI scores significantly improved from 3 to 12 months.

CONCLUSION

The MRI findings indicate that the graft incorporation to the surrounding tissues occurs around or after 6 months, postoperatively. This finding suggests that rehabilitation precautions be taken for up to 6 months after mosaicplasty for young athletes with capitellar OCD.

The use of fibrin based matrices and fibrin microbeads (FMB) for cell based tissue regeneration

BACKGROUND

Due to its good cell attachment capabilities and promotion of cell migration, fibrin serves as an interim cell-binding matrix in wounded tissues. Due to their fast degradation, unprocessed fibrin matrices have limited use in tissue engineering.

OBJECTIVE

To describe stable fibrin-based matrices for isolation, growth and delivery of stem cells for implantation to enhance tissue regeneration.

METHODS

Fibrin microbeads (FMB) were produced by moderate-heat condensation of fibrin particles in oil without compromising the cell binding capability of the fibrin.

RESULTS

Mesenchymal stem cells (MSC) were separated from different sources at much higher yields with FMB. They were further expanded on them in suspension without trypsinization and passages. Cells on FMB could be induced to differentiate into different phenotypes, such as bone and cartilage. This enabled implantation of the cells on FMB for cell-based tissue regeneration.

CONCLUSIONS

FMB technology provides a simple and effective method for cell separation, expansion in suspension and delivery for tissue regeneration.

The synergistic effects of microfracture, perforated decalcified cortical bone matrix and adenovirus-bone morphogenetic protein-4 in cartilage defect repair

We reported a technique for articular cartilage repair, consisting of microfracture, a biomaterial scaffold of perforated decalcified cortical bone matrix (DCBM) and adenovirus-bone morphogenetic protein-4 (Ad-BMP4) gene therapy. In the present study, we evaluated its effects on the quality and quantity for induction of articular cartilage regeneration. Full-thickness defects were created in the articular cartilage of the trochlear groove of rabbits. Four groups were assigned: Ad-BMP4/perforated DCBM composite (group I); perforated DCBM alone without Ad-BMP4 (group II); DCBM without perforated (group III) and microfracture alone (group IV). Animals were sacrificed 6, 12 and 24 weeks postoperation. The harvested tissues were analyzed by magnetic resonance image, scanning electron microscope, histological examination and immunohistochemistry. Group I showed vigorous and rapid repair leading to regeneration of hyaline articular cartilage at 6 weeks and to complete repair of articular cartilage and subchondral bone at 12 weeks. Groups II and III completely repaired the defect with hyaline cartilage at 24 weeks, but group II was more rapid than group III in the regeneration of repair tissue. In group IV the defects were concave and filled with fibrous tissue at 24 weeks. These findings demonstrated that this composite biotechnology can rapidly repair large areas of cartilage defect with regeneration of native hyaline articular cartilage.

Magnetic resonance imaging characterization of osteochondral defect repair in a goat model at 8 T

OBJECTIVE

This study was performed to non-invasively visualize and characterize osteochondral (OC) repair in ex vivo goat stifles using an 8 T magnetic resonance imaging (MRI) scanner and to compare the MR morphology with images obtained from 1.5 T, gross morphology and histology.

METHODS

Mature, neutered male goats were assigned to an 8-week (n = 4) or 16-week (n = 4) study period. Two cylindrical OC defects (7 mm diameter, full cartilage thickness and 1mm into subchondral bone) were surgically created in the right stifle: one in the medial femoral condyle (MFC) and the other in the trochlear groove (TG). The implant matrices (non-woven or foam) were secured in the defect using a bottom anchored fixation device (FD). The contralateral left stifles served as time zero controls. At the day of necropsy, implants were placed at both defect sites (MFC and TG) on the normal left stifles. Following necropsy, the ex vivo goat stifles (intact and encapsulated) were disarticulated. Within 24 h postnecropsy, MR scans of the stifles along the mid-sagittal plane of the OC defect were acquired at 8 T and 1.5 T. MR relaxation times, T1 and T2, were measured at the region of repair tissue (RT) and adjacent native cartilage. Immediately after MR imaging, the stifles were dissected, grossly examined, and a sagittal OC block corresponding to the MR region of interest was prepared for formalin fixation.

RESULTS

The high-resolution MR images enabled visualization of cartilage and bone integrity surrounding the implant as well as delineating the margins of RT/implant matrix and the FD. On spin echo sequence, the RT variably appeared as high, intermediate or low MR signal intensity; whereas, the FD always appeared as low signal intensity. In general, the MR signal intensity of 8-week RT was slightly higher compared to 16-week RT; however, there was no difference in RT morphology of stifles implanted with the non-woven matrix or foam matrix. Subchondral sclerosis appeared as low signal intensity. The 8 T MR images showed better delineation of the stifle tissues compared to the images acquired at 1.5 T. The T2 relaxation time of the RT appears to indicate (inconclusive due to small number of samples) a slight variation in the RT type between 8 weeks and 16 weeks. At both study times, the defects grossly appeared whitish to reddish but did not have the characteristic hyaline appearance typical of articular cartilage (AC). The gross appearance of the MFC and TG RT differed, which was predominantly mottled and recessed with fissuring of adjacent native AC in the MFC. Histologically, the RT of both 8-week and 16-week postsurgical defects predominantly comprised fibrovascular connective tissue with only few samples showing the presence of fibrocartilaginous and/or hypertrophic chondrocytes within the defect RT at 8 weeks. Also, compared to 8-week, the 16-week RT appeared to be more fibrotic.

CONCLUSION

Using 8 T scanner, high-resolution MR images of ex vivo encapsulated goat stifles confirmed the capability of high-field MR imaging to distinguish the defect RT from the FD and adjacent joint tissues. The extent of OC repair and adjacent bone lesions (at 8 weeks and 16 weeks) observed in the MR images compared well with those observed on the corresponding histological sections.

Influence of species and anatomical location on chondrocyte expansion

BACKGROUND

Bovine articular cartilage is often used to study chondrocytes in vitro. It is difficult to correlate in vitro studies using bovine chondrocytes with in vivo studies using other species such as rabbits and sheep. The aim of this investigation was to study the effect of species, anatomical location and exogenous growth factors on chondrocyte proliferation in vitro.

METHODS

Equine (EQ), bovine (BO) and ovine (OV) articular chondrocytes from metacarpophalangeal (fetlock (F)), shoulder (S) and knee (K) joints were cultured in tissue culture flasks. Growth factors (rh-FGFb: 10 ng/ml; rh-TGFbeta: 5 ng/ml) were added to the cultures at days 2 and 4. On day 6, cells were counted and flow cytometry analysis was performed to determine cell size and granularity. A three factor ANOVA with paired Tukey's correction was used for statistical analysis.

RESULTS

After 6 days in culture, cell numbers had increased in control groups of EQ-F, OV-S, OV-F and BO-F chondrocytes. The addition of rh-FGFb led to the highest increase in cell numbers in the BO-F, followed by EQ-F and OV-S chondrocytes. The addition of rh-TGFbeta increased cell numbers in EQ-S and EQ-F chondrocytes, but showed nearly no effect on EQ-K, OV-K, OV-S, OV-F and BO-F chondrocytes. There was an overall difference with the addition of growth factors between the different species and joints.

CONCLUSION

Different proliferation profiles of chondrocytes from the various joints were found. Therefore, we recommend performing in vitro studies using the species and site where subsequent in vivo studies are planned.