<p>Bone is a highly dynamic tissue that has been known to actively adapt its geometry and microstructure&nbsp;in response&nbsp;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&nbsp;<i>in vitro</i>.&nbsp;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&nbsp;standard implants.&nbsp;However, the bone healing pathway that was triggered by this novel device is unknown.&nbsp;Here, the&nbsp;physiological&nbsp;mechanical&nbsp;loading&nbsp;exhibited by the ovine&nbsp;is synced with the&nbsp;negative&nbsp;DC&nbsp;output of the interbody device. This mechanism&nbsp;exhibits&nbsp;a novel form of bone stimulation, known as mechanically synced electrical stimulation (MSES).&nbsp;This study aims to compare the effectiveness of MSES, isolated mechanical stimulation, and isolated electrical stimulation in promoting bone modeling&nbsp;and&nbsp;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&nbsp;three-point&nbsp;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&nbsp;microstrain.&nbsp;After digestion of the porcine explants,&nbsp;the&nbsp;chosen&nbsp;metrics&nbsp;include&nbsp;cellular&nbsp;proliferation&nbsp;quantification&nbsp;via a&nbsp;PicoGreen&nbsp;Assay,&nbsp;identification of&nbsp;upregulation and/or&nbsp;downregulation&nbsp;via&nbsp;Polymerase Chain Reaction (PCR)&nbsp;of key molecules (SOST, β-catenin, and LEF1) in the&nbsp;Wnt&nbsp;pathway, and enzyme-linked immunosorbent assay (ELISA)&nbsp;for early and late differentiation osteogenesis markers such as&nbsp;alkaline phosphatase (ALP).&nbsp;The objective of this study is to determine the effects of MSES compared to isolated mechanical and isolated electrical loading on porcine explants.&nbsp;Understanding the bone healing pathway triggered by the piezoelectric spinal fusion interbody device&nbsp;will enable a more targeted&nbsp;healing mechanism.&nbsp;The findings from this study will be used for further research into a clinically relevant biomimetic bioreactor.&nbsp;The bioreactor will help&nbsp;facilitate the transition from benchtop to bedside of orthopedic devices so that less time is spent&nbsp;on designs that could ultimately hinder patients.&nbsp;&nbsp;</p>

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

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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