Mechanically adjustable and degradable scaffolds for the treatment of articular cartilage defects

Abstract

Articular cartilage (AC) has long been known as the tissue that “once destroyed, is not repaired”. Damage to the AC may impair joint function, leading to osteoarthritis, joint destruction, and ultimately, joint replacement. Although current surgical procedures to repair AC defects may decrease the pain and restore the joint function in the short term, they are unable to restore the long term mechanical stability and durability of authentic AC. Tissue engineering holds great promises to repair cartilage defects. As yet, there are still significant challenges that need to be overcome for the design and fabrication of structural supports to direct the repair of AC. So far, no synthesized tissue-engineered cartilage can mimic the long-term mechanical stability and durability of the authentic AC. Based on tissue engineering, structural supports were developed by electrospinning biodegradable polymers into scaffolds that exhibit a mechanical environment similar to the native AC. Two types of scaffolds were developed: poly(3-hydroxybutyrate)/poly(3 hydroxyoctanoate) [P(3HB)/P(3HO)], and chitosan/poly(ethylene oxide) (PEO) crosslinked with genipin. For the P(3HB)/P(3HO) scaffolds, the fibril size decreased and the stiffness increased with increasing composition of P(3HO). Using P(3HB)/P(3HO) at a ratio of 1:0.25, a fibril size that was sixfold larger than the collagen fibrils, and a stiffness of 868 ± 540 kPa, which was comparable to the stiffness of human AC, was obtained. In addition, the degradation of this scaffold was accompanied with the formation of new cartilage. For the chitosan/PEO scaffolds, the fibril size decreased and the stiffness increased with higher genipin concentration. The overall fibril size was approximately twofold larger than the collagen fibrils. Unfortunately, the mesh size was too small to allow cell migration into the scaffolds, which resulted in low formation of neo-cartilage. Taken together, the electrospinning of P(3HB)/P(3HO) at a ratio of 1:0.25 demonstrated promising results to serve as supporting scaffolds towards an effective treatment for AC defects, thus, minimising the risk of developing secondary osteoarthritis. The blends of P(3HB)/P(3HO) can be developed into a toolbox with diverse structures, mechanical and degradation properties to meet the requirements of structural supports for various tissue engineering applications, such as for bone repair and cardiovascular stents.

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ORCID for Martin Stolz: orcid.org/0000-0002-0732-0811

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