Poly (glycerol sebacate): a novel scaffold material for temporomandibular joint disc engineering

Abstract

The preponderance of temporomandibular joint (TMJ) disorders involving TMJ disc injury inspires the need to further explore tissue engineering strategies. The objective of this study was to examine the potential of poly (glycerol sebacate) (PGS), a biocompatible, biodegradable elastomer, as a porous scaffold material for the TMJ disc. Goat fibrochondrocytes were seeded on PGS at three seeding densities (25, 50, 100 million cells/mL scaffold), respectively, and cultured for 24 h, 2 weeks, and 4 weeks. The resulting histological, biochemical, and biomechanical properties were determined. Histological staining revealed an abundance of both collagen and glycosaminoglycans (GAG) throughout the high seeding density scaffolds at 4 weeks. There was also a significant increase in the cellular content in all groups over the four-week period, showing that the scaffolds promoted cell attachment and proliferation. The PGS scaffolds supported the deposition of large quantities of extracellular matrix, with differences noted between seeding density groups. At 4 weeks, the medium and high seeding density groups had significantly more collagen per scaffold (181±46 μg and 218±24 μg, respectively) than the low seeding density group (105±28 μg) (p<0.001). At 4 weeks, the medium and high seeding density groups also had a significantly higher GAG content per scaffold (702±253 μg and 773±187 μg, respectively), than the low seeding density group (324±73 μg) (p<0.001). The compression tangent modulus was significantly greater at 4 weeks than 24 h (123.6±86 kPa and 26.2±5 kPa, respectively) (seeding density groups combined) (p<0.001), with no differences between seeding groups at each time point. After 4 weeks, the tangent modulus of the low seeding density group was in a similar range of the goat TMJ disc (180±127 kPa compared to 304±141 kPa, respectively). The results show that cell seeding density and culture time do have an effect on both the biochemical and biomechanical properties of PGS scaffolds. These findings demonstrate that PGS has great potential as a scaffold material for TMJ disc engineering.

FIG. 1.

Gross morphology of the high seeding density poly (glycerol sebacate) (PGS) scaffolds at 24 h and 4 weeks. Color images available online at www.liebertpub.com/tea

FIG. 2.

Hematoxylin and Eosin staining of the low, medium, and high seeding density PGS scaffolds at 24 h, 2 weeks, and 4 weeks. Scale bar is 500 μm. Color images available online at www.liebertpub.com/tea

FIG. 3.

Histological staining of the PGS scaffolds. Row 1: Safranin o/fast green staining for GAG. Row 2: Picrosirius red staining for collagen. Row 3: Collagen type II immunostain. Scale bar is 250 μm. Color images available online at www.liebertpub.com/tea

FIG. 4.

Example of collagen type II-positive and -negative stain. Scale bar is 500 μm. Color images available online at www.liebertpub.com/tea

FIG. 5.

Biochemical content of PGS scaffolds at 24 h, 2 weeks, and 4 weeks: (A) cell content per construct, (B) collagen content per construct, and (C) glycosaminoglycan (GAG) content per construct. Error bars indicate average±standard deviation. The symbol (*) indicates statistical difference between groups at each time point p<0.001.

FIG. 6.

Biomechanical properties of PGS scaffolds at 24 h and 4 weeks. (A) peak stress, (B) equilibrium stress, (C) percent stress relaxation, and (D) tangent modulus. Error bars indicate average±standard deviation. The symbol (*) indicates p<0.001 for all groups between time points.