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Bone marrow-derived mesenchymal stem cells (BMSCs) were seeded in a three-dimensional scaffold of silk fibroin (SF) and chitosan (CS) to repair cartilage defects in the rabbit knee. Totally 54 rabbits were randomly assigned to BMSCs + SF/CS scaffold, SF/CS scaffold and control groups. A cylindrical defect was created at the patellofemoral facet of the right knee of each rabbit and repaired by scaffold respectively. Samples were prepared at 4, 8 and 12 weeks post-surgery for gross observation, hematoxylin-eosin and toluidine blue staining, type II collagen immunohistochemistry, Wakitani histology. The results showed that differentiated BMSCs proliferated well in the scaffold. In the BMSCs + SF/CS scaffold group, the bone defect was nearly repaired, the scaffold was absorbed and immunohistochemistry was positive. In the SF/CS scaffold alone group, fiber-like tissues were observed, the scaffold was nearly degraded and immunohistochemistry was weakly positive. In the control group, the defect was not well repaired and positive immunoreactions were not detected. Modified Wakitani scores were superior in the BMSCs + SF/CS scaffold group compared with those in other groups at 4, 8 and 12 weeks (P < 0.05). A SF/CS scaffold can serve as carrier for stem cells to repair cartilage defects and may be used for cartilage tissue engineering.

Background: One of the main problems associated with the development of osteochondral reparative materials is that the accurate imitation of the structure of the natural osteochondral tissue and fabrication of a suitable scaffold material for osteochondral repair are difficult. The long-term outcomes of single-or bilayered scaffolds are often unsatisfactory because of the absence of a progressive osteochondral structure. Therefore, only scaffolds with gradient pore sizes are suitable for osteochondral repair to achieve better proliferation and differentiation of the stem cells into osteochondral tissues to complete the repair of defects. Methods: A silk fibroin (SF) solution, chitosan (CS) solution, and nano-hydroxyapatite (nHA) suspension were mixed at the same weight fraction to obtain osteochondral scaffolds with gradient pore diameters by centrifugation, freeze-drying, and chemical cross-linking. Results: The scaffolds prepared in this study are confirmed to have a progressive structure starting from the cartilage layer to bone layer, similar to that of the normal osteochondral tissues. The prepared scaffolds are cylindrical in shape and have high internal porosity. The structure consists of regular and highly interconnected pores with a progressively increasing pore distribution as well as a progressively changing pore diameter. The scaffold strongly absorbs water, and has a suitable degradation rate, sufficient space for cell growth and proliferation, and good resistance to compression. Thus, the scaffold can provide sufficient nutrients and space for cell growth, proliferation, and migration. Further, bone marrow mesenchymal stem cells seeded onto the scaffold closely attach to the scaffold and stably grow and proliferate, indicating that the scaffold has good biocompatibility with no cytotoxicity. Conclusion: In brief, the physical properties and biocompatibility of our scaffolds fully comply with the requirements of scaffold materials required for osteochondral tissue engineering, and they are expected to become a new type of scaffolds with gradient pore sizes for osteochondral repair.

Tanshinone IIA (Tan IIA), a phytochemical derived from the roots of Salvia miltiorrhiza, has been shown to inhibit growth and induce apoptosis in various cancer cells. The association of its inhibitory effect on the primary malignant bone tumor, osteosarcoma, with mitochondrial dysfunction remains unclear. This study aimed to investigate the anti-proliferative effects of Tan IIA on human osteosarcoma 143B cells both in vitro and in vivo. Administration of Tan IIA to NOD-SCID mice implanted with 143B cells led to significant inhibition of tumor development. The inhibition of proliferation, migration, and invasion was observed in 143B cells treated with Tan IIA. The tumor proliferation markers, Ki67 and PCNA, were suppressed and apoptosis by TUNEL assay was activated respectively. Apoptosis in the Tan IIA-treated 143B cells and xerograft mice was associated with the activation of caspase cascade via the modulation of Bcl-2 family. The CD31 was inhibited in Tan IIA-treated xenografts to indicate anti-neovasculization. Tan IIA administration resulted in a significant decrease in the mitochondrial fusion proteins, Mfn1/2 and Opa1, as well as an increase in the fission protein Drp1. We concluded that mitochondrial dysfunction associated with dynamic change was involved in apoptosis and anti-angiogenesis elicited by Tan IIA.

Chondral and subchondral repair can be achieved using the biphase scaffold implant that permits both chondrogenesis and osteogenesis from BMSCs. This approach has the potential to be clinically used for tissue engineering implantation.

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