Session: 17-01-01 Research Posters

Paper Number: 72135

Start Time: Thursday, 02:25 PM

72135 - Proof of Concept Bioreactor Design: Mechanically Synced Electrical Stimulation via Piezoelectric Spinal Fusion Interbody Device on Porcine Explants 

Bone is a highly dynamic tissue that has been known to actively adapt its geometry and microstructure in response to mechanical deformation. Bone also exhibits piezoelectric properties allowing it to generate small currents under strain. Thus, bone tissue engineering (BTE) applications often employ mechanical and electrical stimulation methods to improve bone formation metrics in vitro. In a pilot ovine study, a piezoelectric spinal fusion interbody device exhibited faster bone healing properties in a shorter amount of time compared to the standard implants. However, the bone healing pathway that was triggered by this novel device is unknown. Here, the physiological mechanical loading exhibited by the ovine is synced with the negative DC output of the interbody device. This mechanism exhibits a novel form of bone stimulation, known as mechanically synced electrical stimulation (MSES). This study aims to compare the effectiveness of MSES, isolated mechanical stimulation, and isolated electrical stimulation in promoting bone modeling and remodeling. The stimulation groups are separated into four groups (1) mechanically synced electrical stimulation (MSES), (2) mechanical stimulation (M-stim), (3) electrical stimulation (E-stim), and (4) control groups with no additional stimulation. Porcine trabecular bone explants were extracted from lumbar vertebral bodies and cut to a standardized size of 7.6 mm diameter and 5 mm height. A custom three-point arm was designed as an attachment for a material testing system in order stimulate the bone explants and a piezoelectric implant simultaneously. A cyclic compressive load with a 25 N preload and 20 N magnitude was applied to the porcine explants to obtain a bulk strain around 3000 microstrain. After digestion of the porcine explants, the chosen metrics include cellular proliferation quantification via a PicoGreen Assay, identification of upregulation and/or downregulation via Polymerase Chain Reaction (PCR) of key molecules (SOST, β-catenin, and LEF1) in the Wnt pathway, and enzyme-linked immunosorbent assay (ELISA) for early and late differentiation osteogenesis markers such as alkaline phosphatase (ALP). The objective of this study is to determine the effects of MSES compared to isolated mechanical and isolated electrical loading on porcine explants. Understanding the bone healing pathway triggered by the piezoelectric spinal fusion interbody device will enable a more targeted healing mechanism. The findings from this study will be used for further research into a clinically relevant biomimetic bioreactor. The bioreactor will help facilitate the transition from benchtop to bedside of orthopedic devices so that less time is spent on designs that could ultimately hinder patients.  

Presenting Author: Victoria Drapal University of Kansas

Authors:

Victoria Drapal University of Kansas
Jordan Gamble University of Kansas
Lisa Friis University of Kansas
Jennifer Robinson University of Kansas