title: Enhanced depth-independent chondrocyte proliferation and phenotype maintenance in an ultrasound bioreactor and an assessment of ultrasound dampening in the scaffold.
abstract: Chondrocyte-seeded scaffolds were cultured in an ultrasound (US)-assisted bioreactor, which supplied the cells with acoustic energy around resonance frequencies (~5.0 MHz). Polyurethane-polycarbonate (BM), chitosan (CS) and chitosan-n-butanol (CSB) based scaffolds with varying porosities were chosen and the following US regimen was employed: 15 kPa and 60 kPa, 5 min per application and 6 applications per day for 21 days. Non-stimulated scaffolds served as control. For BM scaffolds, US stimulation significantly impacted cell proliferation and depth-independent cell population density compared to controls. The highest COL2A1/COL1A1 ratios and ACAN mRNA were noted on US-treated BM scaffolds compared to controls. A similar trend was noted on US-treated cell-seeded CS and CSB scaffolds, though COL2A1/COL1A1 ratios were significantly lower compared to BM scaffolds. Expression of Sox-9 was also elevated under US and paralleled the COL2A1/COL1A1 ratio. As an original contribution, a simplified mathematical model based on Biot theory was developed to understand the propagation of the incident US wave through the scaffolds and the model analysis was connected to cellular responses. Scaffold architecture influenced the distribution of US field, with the US field being the least attenuated in BM scaffolds, thus coupling more mechanical energy into cells, and leading to increased cellular activity.
authors: Department of Chemical Engineering, 207L Othmer Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0643, USA.
authors: Sanjukta
authors: S
authors: Guha Thakurta
authors: Department of Chemical Engineering, 207L Othmer Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0643, USA.
authors: Mikail
authors: M
authors: Kraft
authors: Department of Chemical Engineering, 207L Othmer Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0643, USA.
authors: Hendrik J
authors: HJ
authors: Viljoen
authors: Department of Chemical Engineering, 207L Othmer Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0643, USA. Electronic address: asubramanian2@unl.edu.
authors: Anuradha
authors: A
authors: Subramanian
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D019149:Bioreactors; D015153:Blotting, Western; D002356:Cartilage / Q000378:metabolism; D002417:Cattle; D002452:Cell Count; D049109:Cell Proliferation; D048430:Cell Shape; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D024043:Collagen Type II / Q000378:metabolism; D005786:Gene Expression Regulation; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008954:Models, Biological; D009928:Organ Specificity / Q000235:genetics; D010641:Phenotype; D016062:Porosity; D054457:Tissue Scaffolds / Q000737:chemistry*; D014465:Ultrasonics
chemical_list: D015415:Biomarkers; D024043:Collagen Type II
keywords: Bioreactor; Chondrocyte; Low-intensity continuous ultrasound; Tissue engineering; Ultrasound dampening