RESUMO
The effects of low intensity pulsed ultrasound (LIPUS) on proliferation and chondrogenic differentiation of human mesenchymal stem cells (hMSCs) seeded on 3D printed poly-(ethylene glycol)-diacrylate (PEG-DA) scaffolds with varying pore geometries (square and hexagonal channels) were investigated. The scaffold with square pores resulted in higher hMSC growth and chondrogenic differentiation than a solid or a hexagonally porous scaffold. The optimal LIPUS parameters at 1.5 MHz were found to be 100 mW/cm2 and 20% duty cycle. LIPUS stimulation increased proliferation by up to 60% after 24 hr. For chondrogenesis, we evaluated key cartilage biomarkers abundant in cartilage tissue; glycosaminoglycan (GAG), type II collagen and total collagen. LIPUS stimulation enhanced GAG synthesis up to 16% and 11% for scaffolds with square and hexagonal patterns, respectively, after 2 weeks. Additionally, type II collagen production increased by 60% and 40% for the same patterns, respectively under LIPUS stimulation after 3 weeks. These results suggest that LIPUS stimulation, which has already been approved by FDA for treatment of bone fracture, could be a highly efficient tool for tissue engineering in combination with 3D printing and hMSCs to regenerate damaged cartilage tissues.