Fabrication of an integrated cartilage/bone joint prosthesis and its potential application in joint replacement

Mechanism of Abnormal Chondrocyte Proliferation Induced by Piezo1-siRNA Exposed to Mechanical Stretch

Objective

To investigate the effect of small interfering RNA targeting mechanosensitive ion channel protein Piezo1 (Piezo1-siRNA) on abnormal chondrocyte proliferation exposed to mechanical stretch.

Methods

Construct and screen effective Piezo1-siRNA sequences and explore an appropriate method to transfect lentiviral vector into chondrocytes exposed to mechanical stretch. Western blot and RT-PCR were used to detect the mRNA and protein expression of Piezo1, Kif18A, and β-tubulin, respectively. Flow cytometry was used to measure the changes in the chondrocyte cycle. The proliferation of chondrocyte was evaluated by cell counting kit-8.

Results

According to the mRNA and protein expression of Piezo1, the effective siRNA sequence was successfully screened. Compared with the 0 h group, mechanical stretch upregulated the expression of Piezo1, Kif18A, and β-tubulin, resulting in chondrocyte cycle arrest and eventually inhibiting chondrocyte proliferation. Moreover, Piezo1-siRNA transfection effectively blocks this process and promotes the proliferation of chondrocyte.

Conclusion

Piezo1-siRNA can reduce the inhibition of chondrocyte proliferation induced by mechanical stretch via downregulating the expression of Kif18A and inhibiting the depolymerization of microtubules. Piezo1-siRNA plays a protective role in chondrocytes, which provides a potential method for the treatment of OA under abnormal mechanical stimulation.

In vivo evaluation of porous nanohydroxyapatite/polyamide 66 struts in a goat cervical fusion model

The hollow cylindrical nanohydroxyapatite/polyamide 66 strut (n-HA/PA66) has been used clinically for anterior cervical reconstruction. However, rates of occurrence of a “radiolucent gap” between the dense strut and adjacent endplates were reported. The aim of this in vivo study was to evaluate the viability and advantages of the novel porous n-HA/PA66 strut. The goat C3/4 partial discectomy and fusion model was built, and two groups of n-HA/PA66 struts were implanted into C3/4: group 1, porous n-HA/PA66 strut; and group 2, hollow cylindrical n-HA/PA66 strut filled with autogenous cancellous bone. CT evaluation was performed to assess the fusion status after 12 and 24 weeks. The cervical spines were harvested. Histomorphological analysis was performed to determine new bone formation. Biomechanical testing was performed to determine range of motion (ROM). CT confirmed the disappearance of the boundary of the porous strut and host bone, while the radiolucent gap remained clearly discernible in the dense strut group. The mean CT fusion scores of the porous group were significantly higher. Histologic evaluation showed that the porous struts promoted better osteointegration. Calcein fluorochrome labelling indicated faster bone ingrowth in the porous struts. Biomechanical tests revealed that the porous struts had significantly reduced micromotion. The porous n-HA/PA66 strut could offer interesting potential for cervical reconstruction after corpectomy.

Nanohydroxyapatite Reinforced Chitosan Composite Hydrogel with Tunable Mechanical and Biological Properties for Cartilage Regeneration

With the continuous quest of developing hydrogel for cartilage regeneration with superior mechanobiological properties are still becoming a challenge. Chitosan (CS) hydrogels are the promising implant materials due to an analogous character of the soft tissue; however, their low mechanical strength and durability together with its lack of integrity with surrounding tissues hinder the load-bearing application. This can be solved by developing a composite chitosan hydrogel reinforced with Hydroxyapatite Nanorods (HANr). The objective of this work is to develop and characterize (physically, chemically, mechanically and biologically) the composite hydrogels loaded with different concentration of hydroxyapatite nanorod. The concentration of hydroxyapatite in the composite hydrogel was optimized and it was found that, reinforcement modifies the hydrogel network by promoting the secondary crosslinking. The compression strength could reach 1.62 ± 0.02 MPa with a significant deformation of 32% and exhibits time-dependent, rapid self-recoverable and fatigue resistant behavior based on the cyclic loading-unloading compression test. The storage modulus value can reach nearly 10 kPa which is needed for the proposed application. Besides, composite hydrogels show an excellent antimicrobial activity against Escherichia coli, Staphylococcus aureus bacteria's and Candida albicans fungi and their cytocompatibility towards L929 mouse fibroblasts provide a potential pathway to developing a composite hydrogel for cartilage regeneration.