Articular cartilage generation applying PEG-LA-DM/PEGDM copolymer hydrogels

Background: Injuries to the human native cartilage tissue are particularly problematic because cartilage has little to
no ability to heal or regenerate itself. Employing a tissue engineering strategy that combines suitable cell sources
and biomimetic hydrogels could be a promising alternative to achieve cartilage regeneration. However, the weak
mechanical properties may be the major drawback to use fully degradable hydrogels. Besides, most of the fully
degradable hydrogels degrade too fast to permit enough extracellular matrix (ECM) production for neocartilage
formation. In this study, we demonstrated the feasibility of neocartilage regeneration using swine articular
chondrocytes photoencapsualted into poly (ethylene glycol) dimethacrylate (PEGDM) copolymer hydrogels
composed of different degradation profiles: degradable (PEG-LA-DM) and nondegradable (PEGDM) macromers in
molar ratios of 50/50, 60/40, 70/30, 80/20, and 90/10.
Methods: Articular chondrocytes were isolated enzymatically from juvenile Yorkshire swine cartilage. 6 × 107 cells
cells were added to each milliliter of macromer/photoinitiator (I2959) solution. Nonpolymerized gel containing the
cells (100 μL) was placed in cylindrical molds (4.5 mm diameter × 6.5 mm in height). The
macromer/photoinitiator/chondrocyte solutions were polymerized using ultraviolet (365 nm) light at 10 mW/cm2
for 10 mins. Also, an articular cartilaginous ring model was used to examine the capacity of the engineered
cartilage to integrate with native cartilage. Samples in the pilot study were collected at 6 weeks. Samples in the
long-term experimental groups (60/40 and 70/30) were implanted into nude mice subcutaneously and harvested at
6, 12 and 18 weeks. Additionally, cylindrical constructs that were not implanted used as time zero controls. All of
the harvested specimens were examined grossly and analyzed histologically and biochemically.
Results: Histologically, the neocartilage formed in the photochemically crosslinked gels resembled native articular
cartilage with chondrocytes in lacunae and surrounded by new ECM. Increases in total DNA, glycosaminoglycan,
and hydroxyproline were observed over the time periods studied. The neocartilage integrated with existing native
cartilage.
Conclusions: Articular cartilage generation was achieved using swine articular chondrocytes photoencapsulated in
copolymer PEGDM hydrogels, and the neocartilage tissue had the ability to integrate with existing adjacent native
cartilage.