Chondrocyte source for cartilage regeneration in an immature animal: Is iliac apophysis a good alternative?

In vitro and in vivo investigation of chitosan/silk fibroin injectable interpenetrating network hydrogel with microspheres for cartilage regeneration

Articular cartilage is an avascular and almost acellular tissue with limited self-regenerating capabilities. Although injectable hydrogels have garnered a lot of attention as a promising treatment, a biocompatible hydrogel with adequate mechanical properties is yet to be created. In this study, an interpenetrating network hydrogel comprised of chitosan and silk fibroin was created through electrostatic and hydrophobic bonds, respectively. The polymeric network of the scaffold combined an effective microenvironment for cell activity with enhanced mechanical properties to address the current issues in cartilage scaffolds. Furthermore, microspheres (MS) were utilized for a controlled release of methylprednisolone acetate (MPA), around ~75 % after 35 days. The proposed scaffolds demonstrated great mechanical stability with ~0.047 MPa compressive moduli and ~145 kPa compressive strength. Moreover, the degradation rate of the samples (~45 % after 35 days) was optimized to match neo-cartilage formation. Furthermore, the use of natural biomaterials yielded good biocompatibility with ~76 % chondrocyte viability after 7 days. According to gross observation after 12 weeks the defect site of the treated groups was filled with minimally discernible boundary. These results were confirmed by histopathology assays were the treated groups showed higher chondrocyte count and collagen type II expression.

Long-Term Evaluation of Allogenic Chondrocyte-Loaded PVA-PCL IPN Scaffolds for Articular Cartilage Repair in Rabbits

OBJECTIVE

This study tested the long-term efficacy of two synthetic scaffolds for osteochondral defects and compare the outcomes with that of an established technique that uses monolayer cultured chondrocytes in a rabbit model.

METHODS

Articular cartilage defect was created in both knees of 18 rabbits and divided into three groups of six in each. The defects in first group receiving cells loaded on Scaffold A (polyvinyl alcohol-polycaprolactone semi-interpenetrating polymer network (Monophasic, PVA-PCL semi-IPN), the second on Scaffold B (biphasic, PVA-PCL incorporated with bioglass as the lower layer), and the third group received chondrocytes alone. One animal from each group was sacrificed at 2 months and the rest at 1 year. O'Driscoll's score measured the quality of cartilage repair.

RESULTS

The histological outcome had good scores (22, 20, and 19) for all three groups at 2 months. At 1-year follow-up, the chondrocyte alone group had the best scores (mean 20.0 ± 1.4), while the group treated by PVA-PCL semi-IPN scaffolds fared better (mean 15 ± 4.2) than the group that received biphasic scaffolds (mean 11.8 ± 5.9). In all three groups, defects treated without cells scored less than the transplant.

CONCLUSION

These results indicate that while these scaffolds with chondrocytes perform well initially, their late outcome is disappointing. We propose that for all scaffold-based tissue repairs, a long-term evaluation should be mandatory. The slow degrading scaffolds need further modifications to improve the milieu for long-term growth of chondrocytes and their hyaline phenotype for the better incorporation of tissue-engineered constructs.

Bone marrow extract as a growth supplement for human iliac apophyseal chondrocyte culture

Background & objectives:

Human bone marrow is rich in various growth factors which may support the chondrocyte growth. This study was conducted to compare the culture characteristics of human growth plate chondrocyte in foetal bovine serum (FBS) and human autologous bone marrow extract (BME) in monolayer culture.

Methods:

Iliac crest apophyseal cartilage was harvested from four donors, aged between two and nine years, undergoing hip surgery. Chondrocytes were propagated under two culture conditions, with 10 per cent FBS and 10 per cent autologous BME harvested from the same donors. Cells were harvested at 7, 14 and 21 days to assess viability, morphology, cell count and immunocytochemistry.

Results:

With an initial seeding density of 2500 cells/cm², the average yield in monolayer cultured with FBS was 3.35 × 10⁵, 5.9 × 10⁵, 14.1 × 10⁵ and BME was 0.66 × 10⁵, 1.57 × 10⁵ and 3.48 × 10⁵ at 7, 14 and 21 days, respectively. Viability was 98.21 per cent with FBS and 97.45 per cent with BME at 21 days. In BME supplemented cultures, hyaline phenotype was maintained up to 21 days. The yield was higher in the FBS supplemented group; however, the phenotype could not be maintained by the FBS group as long as BME group.

Interpretation & conclusions:

Autologous BME was found to be a safer alternative to FBS for human studies. BME could maintain the hyaline phenotype for a longer time. Ways to enhance the cell yield needs to be explored in future studies.

High Quality of Infant Chondrocytes in Comparison with Adult Chondrocytes for Cartilage Tissue Engineering

BACKGROUND

Tissue engineering is used for the treatment of many diseases, and the ideal cell source for cartilage tissue engineering is chondrocytes. The main limitation of chondrocyte is the low number of cells in cartilage tissue engineering. This study investigated a suitable cell source with high proliferation rate to obtain a large number of chondrocytes.

METHODS

Adult cartilage tissue samples were obtained from adult patients undergoing surgical procedure, and infant cartilage tissue samples were obtained from polydactyly surgical waste. After isolation and expansion of chondrocytes, the proliferation rate was evaluated by calculating population doubling time (PDT) and MTT assay for both types of cells. Cartilage film was prepared with sheets of over confluent chondrocytes. The cartilage tissue film from infant and adult chondrocytes were evaluated histologically and by immunefluorescent staining collagen type 2.

RESULTS

PDT and MTT assays revealed that the growth rate of the infant chondrocytes was significantly higher than adult chondrocytes. Histological findings showed that sheets were thicker in the cartilage film of infant chondrocytes and they had more extracellular matrix between the sheets of cells than the cartilage film of adult chondrocytes. The findings of the immunofluorescent staining of cartilage film indicated that collagen type II film of polyductily was more positive than adult chondrocytes.

CONCLUSION

The recent study presented a new cell source to overcome the limitation of low number of chondrocytes for cell therapy of cartilage defects in adults and also sheets of cells able to overcome the problems of scaffolds.

Enhanced encapsulation of chondrocytes within a chitosan/hyaluronic acid hydrogel: a new technique

Two encapsulation techniques for rabbit chondrocytes in chitosan/hyaluronic acid gel have been compared. The standard technique involves the cross-linking of chitosan and hyaluronic acid at 2:1 (w/w). In the modified technique, cells were initially added to 33% of hyaluronic acid dialdehyde and the gelation process was completed with the remaining 67%. This minimised the cell loss and improved the encapsulation of the cells. By the third week, the modified technique showed better seeding density, with matrix synthesis (per scaffold) of 11 μg as compared to 1.1 μg in the current technique. Relative expression of collagen II with the current technique and the modified technique were 6.4% and ~1,600% respectively. The modified technique was superior for matrix synthesis and maintenance of phenotype.

Viability, proliferation and phenotype maintenance in cryopreserved human iliac apophyseal chondrocytes

Cryopreservation preserves cells at low temperature and creates a reserve for future use while executing the clinical translation. Unlike articular chondrocyte, cryopreservation protocol and its outcome are not described in iliac apophyseal chondrocytes, a potential source of chondrocytes in cartilage engineering. This study for the first time describes the cryopreservation of human iliac apophyseal chondrocytes. Four cartilage samples were procured from iliac crests of children undergoing hip surgery after consent. The total chondrocyte yield was divided into two groups. First group was grown as monolayer while second group was cryopreserved following the slow cooling method in the medium containing 10 % Dimethyl sulfoxide for 3 months. Group two cells were also grown as a monolayer following thawing. Viability, time to confluence, population doubling time and phenotype maintenance were compared for both the groups. Viability was 65.75 % after 3 months of cryopreservation at -196 °C, as compared to 94.19 % for fresh chondrocytes (p = 0.001). Fresh and cryopreserved cells reached confluence on 10th and 15th day of culture respectively. Population doubling time was significantly more in fresh than cryopreserved chondrocytes on 10th (p = 0.0006) and 15th day (p = 0.0002) in culture. Both fresh and cryopreserved cells maintain their chondrocyte phenotype as assessed by immunocytochemistry. Relative gene expression by real time polymerase chain reaction showed similar upregulation of mRNA of Collagen 2, SOX 9, Aggrecan and Collagen 1 in cryopreserved chondrocyte as compared to fresh chondrocyte. Iliac apophyseal chondrocytes cryopreserved for 3 months maintained the phenotype successfully 2 weeks after thawing in culture. The viability and proliferation rates after thawing were adequate for a clinical translation of these cells.