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Updated: Nov 21, 2025
Preparation of Intact Bovine Tail Intervertebral Discs for Organ Culture
Published on: February 2, 2012
LIPUS far-field exposimetry system for uniform stimulation of tissues in-vitro: development and validation with
Devante A Horne1, Peter D Jones, Matthew S Adams
1Department of Orthopaedic Surgery, University of California, San Francisco, United States of America. The UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley, and University of California, San Francisco, United States of America. Thermal Therapy Research Group, Radiation Oncology Department, University of California, San Francisco, United States of America.
Abstract:
Therapeutic Low-intensity Pulsed Ultrasound (LIPUS) has been applied clinically for bone fracture healing and has been shown to stimulate extracellular matrix (ECM) metabolism in numerous soft tissues including intervertebral disc (IVD). In-vitro LIPUS testing systems have been developed and typically include polystyrene cell culture plates (CCP) placed directly on top of the ultrasound transducer in the acoustic near-field (NF). This configuration introduces several undesirable acoustic artifacts, making the establishment of dose-response relationships difficult, and is not relevant for targeting deep tissues such as the IVD, which may require far-field (FF) exposure from low frequency sources. The objective of this study was to design and validate an in-vitro LIPUS system for stimulating ECM synthesis in IVD-cells while mimicking attributes of a deep delivery system by delivering uniform, FF acoustic energy while minimizing reflections and standing waves within target wells, and unwanted temperature elevation within target samples. Acoustic field simulations and hydrophone measurements demonstrated that by directing LIPUS energy at 0.5, 1.0, or 1.5 MHz operating frequency, with an acoustic standoff in the FF (125-350 mm), at 6-well CCP targets including an alginate ring spacer, uniform intensity distributions can be delivered. A custom FF LIPUS system was fabricated and demonstrated reduced acoustic intensity field heterogeneity within CCP-wells by up to 93% compared to common NF configurations. When bovine IVD cells were exposed to LIPUS (1.5 MHz, 200 μs pulse, 1 kHz pulse frequency, and ISPTA = 120 mW cm-2) using the FF system, sample heating was minimal (+0.81 °C) and collagen content was increased by 2.6-fold compared to the control and was equivalent to BMP-7 growth factor treatment. The results of this study demonstrate that FF LIPUS exposure increases collagen content in IVD cells and suggest that LIPUS is a potential noninvasive therapeutic for stimulating repair of tissues deep within the body such as the IVD.
