Objectives To evaluate the role that intravesical P2X2/3 purinergic receptors (P2X2/3Rs) play in early and advanced neurogenic lower urinary tract (LUT) dysfunction after contusion spinal cord injury (SCI) in female rats. Materials and Methods Female Sprague‐Dawley rats received a thoracic Th8/Th9 spinal cord contusion with either force of 100 kDy (cN); moderate) or 150 kDy (cN; severe); Sham rats had no injury. Evaluations on urethane‐anesthetised rats were conducted at either 2 or 4 weeks after SCI. LUT electrical signals and changes in bladder pressure were simultaneously recorded using cystometry and a set of custom‐made flexible microelectrodes, before and after intravesical application of the P2X2/3R antagonist AF‐353 (10 μM), to determine the contribution of P2X2/3R‐mediated LUT modulation. Results Severe SCI significantly increased bladder contraction frequency, and reduced both bladder pressure amplitude and intraluminal‐pressure high‐frequency oscillations (IPHFO). Intravesical P2X2/3R inhibition did not modify bladder pressure or IPHFO in the Sham and moderate‐SCI rats, although did increase the intercontractile interval (ICI). At 2 weeks after SCI, the Sham and moderate‐SCI rats had significant LUT electromyographic activity during voiding, with a noticeable reduction in LUT electrical signals seen at 4 weeks after SCI. Intravesical inhibition of P2X2/3R increased the ICI in the Sham and moderate‐SCI rats at both time‐points, but had no effect on rats with severe SCI. The external urethral sphincter (EUS) showed strong and P2X2/3R‐independent electrical signals in the Sham and moderate‐SCI rats in the early SCI stage. At 4 weeks after SCI, the responsiveness of the EUS was significantly attenuated, independently of SCI intensity. Conclusions This study shows that electrophysiological properties of the LUT are progressively impaired depending on SCI intensity and that intravesical P2X2/3R inhibition can attenuate electrical activity in the neurogenic LUT at early, but not at semi‐chronic SCI. This translational study should be useful for planning clinical evaluations.

The purpose of this study was to develop, assess, and validate a custom 32-channel system to analyze the electrical properties of 3-D artificial heart muscle (3D-AHM). In this study, neonatal rat cardiac cells were cultured in a fibrin gel to drive the formation of 3D-AHM. Once the tissues were fully formed, the customized electrocardiogram (EKG) sensing system was used to obtain the different electrophysiological characteristics of the muscle constructs. Additionally, this system was used to evaluate the electrical properties of native rat hearts, for comparison to the fabricated tissues and native values found in the literature. Histological evaluation showed extensive cellularization and cardiac tissue formation. EKG data analysis yielded time delays between the signals ranging from 0 to 7 ms. Optical maps exhibited slight trends in impulse propagation throughout the fabricated tissue. Conduction velocities were calculated longitudinally at 277.81 cm/s, transversely at 300.79 cm/s, and diagonally at 285.68 cm/s for 3D-AHM. The QRS complex exhibited an R-wave amplitude of 438.42 ± 36.96 μV and an average duration of 317.5 ± 16.5 ms for the tissue constructs. The data collected in this study provide a clearer picture about the intrinsic properties of the 3D-AHM while proving our system's efficacy for EKG data procurement. To achieve a viable and permanent solution, the bioengineered heart muscle must physiologically resemble native heart tissue as well as mimic its electrical properties for proper contractile function. This study allows us to monitor such properties and assess the necessary changes that will improve construct development and function.

There is a chronic shortage of donor hearts. The ability to fabricate complete bioartificial hearts (BAHs) may be an alternative solution. The current study describes a method to support the fabrication and culture of BAHs. Rat hearts were isolated and subjected to a detergent based decellularization protocol to remove all cellular components, leaving behind an intact extracellular matrix. Primary cardiac cells were isolated from neonatal rat hearts, and direct cell transplantation was used to populate the acellular scaffolds. Bioartificial hearts were maintained in a custom fabrication gravity fed perfusion culture system to support media delivery. The functional performance of BAHs was assessed based on left ventricle pressure and on electrocardiogram. Furthermore, BAHs were sectioned and stained for the whole heart cardiac tissue distribution and for cardiac molecules, such as α-actinin, cardiac troponin I, collagen type I, connexin 43, von Willebrand factor, and ki67. Bioartificial hearts replicated a partial subset of properties of natural rat hearts. The current study provided a method for fabrication of a BAH and revealed challenges toward BAH fabrication with functional performance metrics of natural mammalian hearts.

Purpose The purpose of this study was to develop enabling bioreactor technologies using a novel voice coil actuator system for investigating the effects of periodic strain on cardiac patches fabricated with rat cardiomyocytes. Methods The bioengineered muscle constructs used in this study were formed by culturing rat neonatal primary cardiac cells on a fibrin gel. The physical design of the bioreactor was initially conceived using Solidworks to test clearances and perform structural strain analysis. Once the software design phase was completed the bioreactor was assembled using a combination of commercially available, custom machined, and 3-D printed parts. We utilized the bioreactor to evaluate the effect of a 4-hour stretch protocol on the contractile properties of the tissue after which immunohistological assessment of the tissue was also performed. Results An increase in contractile force was observed after the strain protocol of 10% stretch at 1Hz, with no significant increase observed in the control group. Additionally, an increase in cardiac myofibril alignment, connexin 43 expression, and collagen type I distribution were noted. Conclusion In this study we demonstrated the effectiveness of a new bioreactor design to improve contractility of engineered cardiac muscle tissue.