Electrospun scaffolds for cartilage regeneration

University of Califomia-Riverside, Riverside, CA, United States 

In contrast, tissue-engineering approaches provide an opportunity to precisely place proper cells into the defect site in a controlled cellular microenvironment to maintain/ enhance chondrocyte phenotype and increase cell-delivery efficiency for facilitated tissue regeneration. 

To repair or replace the damaged cartilage with tissue-engineering approaches, it is important to consider the local structure of the cartilage for appropriate biomechanical functions (Wilson et al 2006). The solution of this complex problem should be based upon a combinatory effort of proper material selection, adequate cell sourcing, and incorporation of biochemical/biophysical cues (Vinatier et al., 2009). 

To engineer functional AC, the physiological requirements should closely mimic the characteristics of the native tissue in both biochemical composition and mechanical integrity. The native structure of AC comprises three primary zones including the superficial, middle and deep zones (Fig. 10.1). Each of the zones independently, yet cohesively, contribute specific functions of cartilage such as lubrication and compressive resistance, due to the organization and composition of the extracellular matrix (ECM) accompanied by cells. 

The superficial zone of AC contains the largest cell population while only being roughly 10-20% by volume. The tissue primarily acts as the area for friction reduction in the tissue (Pearle et al., 2005). In this zone, the chondrocytes have a flat morphology and run parallel to the surface of the joint along with the collagen fibers. In addition to these structural characteristics, the chondrocytes in this zone secrete lubricin, a lubricant protein, reducing friction experienced from joint movanent (Buckwalter and Mankin, 1997). 

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Levorson EJ, et al. Fabrication and characterization of multiscale electrospun scaffolds for cartilage regeneration. Biomed Mater 2013 8. 

Levorson, E.J., Raman Sreerekha, P, Chennazhi, K.P., Kasper, F.K., Nair, S.V., Mikos, A.G., 2013. Fabrication and characterization of multiscale electrospun scaffolds for cartilage regeneration. Biomedical Materials 8, 014103. 

The use of PLA alone for electrospun scaffolds in cartilage regeneration has had little to no attention probably due to the slow clearance rates of the material during rapid biodegradation, which accumulate the acidic by-products of the polymers in the native tissne. Thns, it has been typically used as a component for blends or... 

Electrospun fibers have also been researched for cartilage regeneration procedures. Thorvaldsson et al. (2(X)8) used a combination of micro- and nanofibers to create novel fiber structures. This enhanced the pore structure characteristics of the fabricated scaffold. The synthesized scaffold enhanced the human chondrocyte infiltration. Nanocomposites consisting of multiwalled carbon nanombes (MWCNTs) and PLA were fabricated using electrospinning. The nanocomposite material displayed enhanced mechanical properties and improved the chondrogenesis of MSCs (Holmes et al., 2013). 

Overall, these results demonstrate the superiority of electrospun scaffolds over typical tissue-culture plates as a cell-culture platform for cartilage regeneration. The nanofibrous structure not only enhances the phenotypic maintenance of mature chondrocytes, but also promotes the differentiation of stem cells toward chondrocytes. 

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