Ravi K. Birla’s research while affiliated with Texas Children's Hospital and other places

In this study, we propose a new method for bioprinting 3D Spheroids to study complex congenital heart disease known as discrete subaortic stenosis (DSS). The bioprinter allows us to manipulate the extrusion pressure to change the size of the spheroids, and the alginate porosity increases in size over time. The spheroids are composed of human umbilical vein endothelial cells (HUVECs), and we demonstrated that pressure and time during the bioprinting process can modulate the diameter of the spheroids. In addition, we used Pluronic acid to maintain the shape and position of the spheroids. Characterization of HUVECs in the spheroids confirmed their uniform distribution and we demonstrated cell viability as a function of time. Compared to traditional 2D cell cultures, the 3D spheroids model provides more relevant physiological environments, making it valuable for drug testing and therapeutic applications.

Background Early clinical outcomes data for adjunctive systemic sirolimus therapy (SST) for moderate to severe pediatric pulmonary vein stenosis (PVS) are promising but limited. Objectives The authors aimed to characterize a cohort of patients treated with SST to determine if SST was associated with a reduction in frequency of PVS interventions. Methods Medical records of 45 patients with PVS treated with SST for ≥1 month from 2015 to 2022 were retrospectively reviewed. PVS intervention rates pre-SST and on-SST were compared using generalized Poisson mixed models, accounting for paired intervals within each patient. In addition to an unadjusted model, an adjusted model accounted for age at interval start, PVS type, sex, prematurity, and concurrent antiproliferative therapy. Mean number of PVS interventions per patient over time (mean cumulative function) were also compared for these intervals in an unpaired fashion. Kaplan-Meier estimates were used to quantify survival over time. Results Median per-patient PVS intervention rate (interventions/year) was 5 pre-SST and 1.7 on-SST, significantly lower on-SST in the unadjusted and adjusted models (P < 0.001, both). Patients accrued an increased cumulative number of interventions over time pre-SST compared to on-SST by mean cumulative function (P < 0.001). Median duration of SST was 1.7 years and median follow-up time from SST initiation was 2.7 years. There were 6 mortalities at a median of 1.1 years (range, 4.4 months-6.5 years) following SST initiation. Conclusions SST was associated with a reduction in frequency of PVS interventions. Prospective studies are warranted to determine potential causality, delineate patient- and vein-level outcomes, and determine optimal therapeutic duration.

Background: Pediatric pulmonary vein stenosis (PVS) is associated with substantial morbidity and mortality for the subset of patients with recurrent or progressive disease. The molecular mechanisms underlying the development and trajectory of PVS remain unclear. This study characterizes the transcriptome of clinical and phenotypic subtypes of PVS. Methods: Bulk RNA sequencing analysis was performed on human pulmonary vein tissue samples obtained from surgical interventions for pediatric patients with PVS. Transcriptomic profiles were compared for primary versus post-repair PVS as well as aggressive versus non-aggressive clinical phenotypes. Principal component analysis was performed, the differential gene expression quantified, and pathway analysis conducted based on gene ontology, KEGG and Reactome. Results: When comparing AggPPVS vs NonAggPPVS, differences were noted in the genes associated in extracellular matrix regulation and PIEZO1, a mechanosensitive receptor present in endothelial cells. In addition, there were notable changes in cardiac muscle contractility, calcium handling, respiratory and energy metabolism. These results point to a potential mechanism for aggressive PPVS phenotype, due to an overexpression of PIEOZ1 in response to elevated shear stress, subsequent activation of intracellular signaling pathways and leading to reduced contractility and intracellular calcium transients with cardiomyocytes. Conclusions: The result of this study suggests that aggressive PPVS phenotype is caused by an increase in PIEZO1 expression and subsequent changes in extracellular matrix production, heart muscle contractility and changes in calcium transients within cardiomyocytes. These results provide a potential target for therapeutic invention for primary PPVS by inhibiting the activity of PIEZO1. This could potentially reduce morbidity in this patient population.

BACKGROUND: In this study, we present a method to bioengineer functional Purkinje networks using recent advances in laser-based bioprinting. METHODS: A custom bioink as formulated using optimized concentrations of polyethylene glycol diacrylate (PEGDA), gelatin methacryloyl (GELMA), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), and tartrazine. A standard triangle language (STL) model of Purkinje networks was developed based on the mammalian Purkinje network mapped out using India ink staining. A commercial bioprinter, the Lumen X, from CellInk, was used to bioprint Purkinje networks. The biocompatibility of the bioprinted Purkinje networks was tested using iPSCs from healthy donors. Negative molds of the Purkinje networks were designed to simulate interaction between Purkinje cells and adjacent cardiomyocytes using different degrees of overlap between the two cell types. The negative molds were also shown to be biocompatible, based on the culture of iPSCs derived from healthy donors. RESULTS: We were able to successfully bioprint over 100 Purkinje networks and demonstrate biocompatibility with iPSCs for up to 7 days. Three different configurations of the negative molds were designed and fabricated and all three shown to be biocompatible with iPSCs for up to 7 days. A co-culture system was developed by placing the Purkinje networks in proximity to the negative molds for all three configurations designed. CONCLUSION: Our results demonstrate the ability to bioprint Purkinje networks and molds and provide an in vitro system to study the functional interaction between Purkinje cells and adjacent cardiomyocytes.

Macrophages are innate immune cells that are known for their extreme plasticity, enabling diverse phenotypes that lie on a continuum. In a simplified model, they switch between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes depending on surrounding microenvironmental cues, which have been implicated in disease outcomes. Although considerable research has been focused on macrophage response to biochemical cues and mechanical signals, there is a scarcity of knowledge surrounding their behavior in response to shear stress. In this study, we applied varying magnitudes of shear stress on human monocyte-derived macrophages (MDMs) using a cone-and-plate viscometer and evaluated changes in morphology, gene expression, protein expression, and cytokine secretion over time. MDMs exposed to shear stress exhibited a rounder morphology compared to statically-cultured controls. RT-qPCR results showed significant upregulation of TNF-α, and analysis of cytokine release revealed increased secretion of IL-8, IL-18, fractalkine, and other chemokines. The upregulation of pro-inflammatory factors was evident with both increasing magnitudes of shear and time. Taken together, these results indicate that prolonged shear exposure induced a pro-inflammatory phenotype in human MDMs. These findings have implications for medical technology development, such as in situ vascular graft design wherein macrophages are exposed to shear and have been shown to affect graft resorption, and in delineating disease pathophysiology, for example to further illuminate the role of macrophages in atherosclerosis where shear is directly related to disease outcome.

Background: Pediatric pulmonary vein stenosis (PVS) is often progressive and treatment-refractory, requiring multiple interventions. Hybrid pulmonary vein interventions (HPVIs), involving intraoperative balloon angioplasty or stent placement, leverage surgical access and customization to optimize patency while facilitating future transcatheter procedures. We review our experience with HPVI and explore potential applications of this collaborative approach. Methods: Retrospective chart review of all HPVI cases between 2009 to 2023. Results: Ten patients with primary (n = 5) or post-repair (n = 5) PVS underwent HPVI at median age of 12.7 months (range 6.6 months-9.5 years). Concurrent surgical PVS repair was performed in 7/10 cases. Hybrid pulmonary vein intervention was performed on 17 veins, 13 (76%) with prior surgical or transcatheter intervention(s). One patient underwent intraoperative balloon angioplasty of an existing stent. In total, 18 stents (9 bare metal [5-10 mm diameter], 9 drug eluting [3.5-5 mm diameter]) were placed in 16 veins. At first angiography (median 48 days [range 7 days-2.8 years] postoperatively), 8 of 16 (50%) HPVI-stented veins developed in-stent stenosis. Two patients died from progressive PVS early in the study, one prior to planned reintervention. Median time to first pulmonary vein reintervention was 86 days (10 days-2.8 years; 8/10 patients, 13/17 veins). At median survivor follow-up of 2.2 years (2.3 months-13.1 years), 1 of 11 surviving HPVI veins were completely occluded. Conclusions: Hybrid pulmonary vein intervention represents a viable adjunct to existing PVS therapies, with promising flexibility to address limitations of surgical and transcatheter modalities. Reintervention is anticipated, necessitating evaluation of long-term benefits and durability as utilization increases.

In this study, we propose a new method for bioprinting 3D Spheroids to study complex congenital heart disease known as discrete subaortic stenosis (DSS). The bioprinter allows us to manipulate the extrusion pressure to change the size of the spheroids, and the alginate porosity increases in size over time. The Spheroids is composed of human umbilical vein endothelial cells (HUVECs), and we demonstrated that pressure and time during the bio-printing process can modulate the diameter of the spheroids. In addition, we used Pluronic to maintain the shape and position of the spheroids. Characterization of HUVECs in the Spheroids confirmed their uniform distribution, making them a suitable model for understanding interactions between macrophages, endocardial endothelial cells (EECs), and DSS fibroblasts. The multiple cells typing in 3D spheroids extend the horizon to study the functional interactions between cells in promoting fibrosis and DSS pathology. Compared to traditional 2D cell cultures, the 3D spheroids model provide more relevant physiological environments, making it valuable for drug testing and therapeutic applications.

The aim of this study was to investigate the survival, distribution and reaction of different cell types on a monolayer disk, as well as their behavior under bioreactor treatment. Specifically, porcine EEC and porcine fibroblasts (PCF) were labeled with GFT and Texas Red, respectively, to track their viability and distribution. The experiments involved monitoring the cells using various microscopy techniques and comparing the results with controls. These findings have important implications for understanding cell behavior and potential applications for Discrete Subaortic Stenosis. This paper aims to discuss the implications of the findings in the context of existing literature and future research directions.