A preliminary In Vitro viability study of an electrically active hernia mesh on mouse fibroblasts

Abstract

Hernias occur when part of an organ, typically the intestines, protrudes through a disruption of the fascia in the abdominal wall, leading to patient pain, discomfort, and surgical intervention. Over one million hernia repair surgeries occur annually in the USA, but globally, hernia surgeries can exceed 20 million. Standard practice includes hernia repair mesh to help hold the compromised tissue together, depending on where the fascial disruption is located and the patient’s condition. However, the recurrence rate for hernias after using the most common type of hernia mesh, synthetic, is currently high. Physiological-level electrical stimulation (ES) has shown beneficial effects in improving healing in soft tissue regeneration. Piezoelectric materials can produce low-level electrical signals from mechanical loading to help speed healing. Combining the novelty of piezo elements to create an electrically active hernia repair mesh for faster healing prospects is explored in this study through simulated transcutaneous mechanical loading of the piezo element with therapeutic ultrasound. A tissue phantom was developed using Gelatin #0 and Metamucil® to better simulate a clinical application of the therapeutic ultrasound loading modality. The cellular viability of varying ultrasound intensities and temporal effects was analyzed. Overall, minimal cytotoxicity was observed across all experimental groups during the ultrasound intensity and temporal viability studies.

Computational analysis of electrical stimulation to promote tissue healing for hernia repair at varying mesh placement planes

“…This stimulation and electric field the tissues would experience could aid in improved tissue integration and quicker healing, based on the current understanding of the effects electrical stimulation has in vitro. [7][8][9]19 The addition of lowlevel electrical signals experienced in the targeted healing tissue could enhance native tissue integration with the mesh, thus reducing hernia repair recurrence rates.…”

“…The ultrasound frequency from the above study was chosen based on the 1 MHz waveform primarily being absorbed in tissues at depths of 3 to 5 cm, which is similar to the depth of a hernia repair mesh location in the abdominal wall. 9,10 With in vitro cellular studies providing more information about how electrical stimulation and electric fields can promote proliferation and migration in specific cell types, it is important to understand the effect electric fields have in more complex environments through computational modeling. For example, Sun et al used COMSOL Multiphysics to model the optimal electrode configuration with a 30 mV input electric potential in a wound created in the skin, to understand the impact the electrical configuration has on the produced electric field and power density outputs on the skin layers.…”

“…The current study uses COMSOL Multiphysics software to observe the effect of anatomical placement of an electrically active hernia repair mesh with varying levels of electrical potential on the electric field generated in the abdominal wall tissue layers. The input parameters for this model are based on the ultrasound frequency and reported electric potential outputs from the in vitro study by Drapal and Mosier et al 9 This study aims to further understand how an electrically active hernia repair mesh could be used in clinical practice and provide insight on optimal placement locations for optimal tissue healing.…”

“…The range of voltages applied was chosen to incorporate voltage levels from previously published studies focusing on electrical stimulation for soft tissue healing applications. 9,11 These voltages are also applicable to potential piezoelectric voltage outputs. A frequency domain study was used with an input frequency of 1 MHz, as this is a clinically relevant ultrasound frequency that could be used for stimulating electrical signals in the electrically active hernia repair mesh with deep tissue injuries at depths between 3 and 5 cm.…”

“…Rouabhia et al saw increased dermal fibroblast viability and increased fibroblast growth factor 2 (FGF2) in cultures exposed to 50 and 200 mV/mm direct current (DC) for 2, 4, and 6 h. 6 Drapal and Mosier et al showed cellular viability and integration density of NIH 3T3 mouse fibroblasts when exposed to AC stimulation at approximately 12 mV and 100 nA/cm 2 current density for 10 min twice daily for either 2, 5, or 7 days. 9 Their ES was driven by a 1 MHz therapeutic ultrasound wave which mechanically loaded a piezoelectric component connected to the cellular experimental setup. The ultrasound frequency from the above study was chosen based on the 1 MHz waveform primarily being absorbed in tissues at depths of 3 to 5 cm, which is similar to the depth of a hernia repair mesh location in the abdominal wall.…”