The impact of heart valve and partial heart transplant models on the development of banking methods for tissues and organs: A concise review

Cryopreserved human heart valves fill a crucial role in the treatment for congenital cardiac anomalies, since the use of alternative mechanical and xenogeneic tissue valves have historically been limited in babies. Heart valve models have been used since 1998 to better understand the impact of cryopreservation variables on the heart valve tissue components with the ultimate goals of improving cryopreserved tissue outcomes and potentially extrapolating results with tissues to organs. Cryopreservation traditionally relies on conventional freezing, employing cryoprotective agents, and slow cooling to sub-zero centigrade temperatures; but it is plagued by the formation of ice crystals and cell damage upon thawing. Researchers have identified ice-free vitrification procedures and developed a new rapid warming method termed nanowarming. Nanowarming is an emerging method that utilizes targeted application of energy at the nanoscale level to rapidly rewarm vitrified tissues, such as heart valves, uniformly for transplantation. Vitrification and nanowarming methods hold great promise for surgery, enabling the storage and transplantation of tissues for various applications, including tissue repair and replacement. These innovations have the potential to revolutionize complex tissue and organ transplantation, including partial heart transplantation. Banking these grafts addresses organ scarcity by extending preservation duration while preserving biological activity with maintenance of structural fidelity. While ice-free vitrification and nanowarming show remarkable potential, they are still in early development. Further interdisciplinary research must be dedicated to exploring the remaining challenges that include scalability, optimizing cryoprotectant solutions, and ensuring long-term viability upon rewarming in vitro and in vivo.

The future of partial heart transplantation

Heart valve replacement in children is an unsolved problem in congenital cardiac surgery because state-of-the-art heart valve implants do not grow. This leads to serial repeat operations to replace outgrown heart valve implants. Partial heart transplantation is a new transplant that helps alleviate this problem by delivering growing heart valve implants. In the future, partial heart transplantation has the potential to complement conventional heart transplantation for treating children with congenital cardiac disease primarily affecting the heart valves.

Outcomes in Primary Repair of Truncus Arteriosus with Significant Truncal Valve Insufficiency: A Systematic Review and Meta-analysis

Data regarding the effect of significant TVI on outcomes after truncus arteriosus (TA) repair are limited. The aim of this meta-analysis was to summarize outcomes among patients aged ≤ 24 months undergoing TA repair with at least moderate TVI. A systematic literature search was conducted in PubMed, Scopus, and CINAHL Complete from database inception through June 1, 2022. Studies reporting outcomes of TA repair in patients with moderate or greater TVI were included. Studies reporting outcomes only for patients aged > 24 months were excluded. The primary outcome was overall mortality, and secondary outcomes included early mortality and truncal valve reoperation. Random-effects models were used to estimate pooled effects. Assessment for bias was performed using funnel plots and Egger's tests. Twenty-two single-center observational studies were included for analysis, representing 1,172 patients. Of these, 232 (19.8%) had moderate or greater TVI. Meta-analysis demonstrated a pooled overall mortality of 28.0% after TA repair among patients with significant TVI with a relative risk of 1.70 (95% CI [1.27-2.28], p < 0.001) compared to patients without TVI. Significant TVI was also significantly associated with an increased risk for early mortality (RR 2.04; 95% CI [1.36-3.06], p < 0.001) and truncal valve reoperation (RR 3.90; 95% CI [1.40-10.90], p = 0.010). Moderate or greater TVI before TA repair is associated with an increased risk for mortality and truncal valve reoperation. Management of TVI in patients remains a challenging clinical problem. Further investigation is needed to assess the risk of concomitant truncal valve surgery with TA repair in this population.

Building Interest in Cardiothoracic Surgery at an Osteopathic Medical School: Results of an Institutional Study and a Guide for Medical Schools

Objective A previous study at this institution revealed a connection between interest group involvement and specialty interest while identifying the negative perceptions of cardiothoracic (CT) surgery. This study aimed to build interest and ameliorate the negative perceptions of CT surgery by exposing pre-clinical students to the field through engaging events. Methods Students at a US osteopathic institution who attended CT surgery committee events were invited to complete an online survey after each event. Associations between the number of events attended and ranked responses to survey questions were assessed by two-tailed Spearman correlations. Statistical comparisons in ranked responses between the events attended and the survey questions were assessed by a two-way analysis of variance (ANOVA). Pre-clinical students actively enrolled at the institution during the 2022-2023 academic year were eligible for inclusion. Results There were 83 surveys completed over seven events. There was a significant association between the number of events a student attended and their perception of CT surgeon's work/life balance with a correlation coefficient of .258 (P=0.019) and whether CT surgeons have time for their families with a correlation coefficient of .235 (P=0.035). Residents and medical student events as well as wet lab events increased interest the most and helped students feel equipped to apply for CT surgery. Conclusions While negative perceptions associated with CT surgery exist, these may be ameliorated with more exposure to the field. Unique events that expose pre-clinical students to multiple facets of CT surgery, including physicians and trainees in the field, as well as offering hands-on activities, may increase interest in the field and further pursuit of the field during clinical years.

Ischemia-Reperfusion Injury in Porcine Aortic Valvular Endothelial and Interstitial Cells

Ischemia-reperfusion injury (IRI) in the myocardium has been thoroughly researched, especially in acute coronary syndrome and heart transplantation. However, our understanding of IRI implications on cardiac valves is still developing. This knowledge gap becomes even more pronounced given the advent of partial heart transplantation, a procedure designed to implant isolated human heart valves in young patients. This study aims to investigate the effects of IRI on aortic valvular endothelial cells (VECs), valvular interstitial cells (VICs), and whole leaflet cultures (no separation of VECs and VICs). We employed two conditions: hypoxic cold storage reperfusion (HCSR) and normothermia (NT). Key markers, secreted protein acidic and cysteine rich (SPARC) (osteonectin), and inducible nitric oxide synthase (iNOS2) were evaluated. In the isolated cells under HCSR, VICs manifested a significant 15-fold elevation in SPARC expression compared to NT (p = 0.0016). Conversely, whole leaflet cultures exhibited a 1-fold increment in SPARC expression in NT over HCSR (p = 0.0011). iNOS2 expression in VECs presented a marginal rise in HCSR, whereas, in whole leaflet settings, there was a 1-fold ascent in NT compared to HCSR (p = 0.0003). Minor escalations in the adhesion molecules intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM), E-selection, and P-selection were detected in HCSR for whole leaflet cultures, albeit without statistical significance. Additionally, under HCSR, VICs released a markedly higher quantity of IL-6 and IL-8, with respective p-values of 0.0033 and <0.0001. Interestingly, the IL-6 levels in VECs remained consistent across both HCSR and NT conditions. These insights lay the groundwork for understanding graft IRI following partial heart transplantation and hint at the interdependent dynamic of VECs and VICs in valvular tissue.

Adult With Unrepaired Single-Ventricle Defect

This case report discusses the diagnosis of double-inlet left ventricle in a male adult patient in his 50s who presented with New York Heart Association class III heart failure.

Assessing interest in cardiothoracic surgery at an osteopathic medical school: Results of an institutional survey

Objective

Cardiothoracic surgery is a surgical subspecialty that attracts few medical students. As integrated surgical residency programs continue to grow in number, there is increased interest in what factors influence specialty selection during undergraduate medical education. Previous institutional studies have studied allopathic medical schools affiliated with academic institutions. This study aimed to assess the interest and perception of cardiothoracic surgery at an osteopathic institution.

Methods

Active medical students at a US osteopathic institution were invited to complete an original online survey. Means and 95% confidence intervals were calculated and graphed for questions using Likert scale responses. Comparison of mean responses for preclinical versus clinical students was assessed by a Kruskal-Wallis nonparametric analysis of variance.

Results

There were 166 surveys (22%) completed, and interest in cardiothoracic surgery was indicated by 7.8% of respondents. Work/life balance, personality of cardiothoracic surgeons, and lack of family time were negative factors associated with cardiothoracic surgery. Clinical exposure, shadowing, mentorship, and significant personal/life events before medical school were strong factors in establishing students' interest in cardiothoracic surgery. Preclinical students noted exposure to cardiothoracic surgery would further increase their interest when compared with clinical students (μ = 3.39 vs μ = 2.69, P = .008).

Conclusions

All factors that established interest in cardiothoracic surgery occurred before students entered medical school. Although there are negative perceptions associated with cardiothoracic surgery, these may be ameliorated with more exposure to the field. Further research is needed to explore how early exposure in preclinical years of medical school affects students' perceptions and ultimate interest in cardiothoracic surgery.

Reducing Maternal Mortality Rates in Alabama Through Patient Education: A Scoping Review

Maternal mortality continues to rise in the United States and disproportionately affects those in Alabama. Lack of patient education on warning signs is a preventable cause of maternal mortality. This article aims to systematically quantify existing research investigating the effect of patient education on maternal outcomes. The inclusion criteria required an article to be (a) original research, (b) conducted within the United States, (c) in English, and (d) published between January 2012 and September 2022. PubMed® and Embase® databases were searched using key words and filters. Rayyan®, a systematic review research tool, was utilized to assess articles in a blinded two-person review process. A blinded third researcher resolved conflicts. A total of 3,139 articles were compiled; 3,115 articles did not meet inclusion criteria, and 24 articles were retrieved after an abstract review. Ultimately, 11 articles were included after a full-text review. None of these articles were specific to Alabama. However, they did contain evidence for patient education improving maternal mortality. More research is required in Alabama to demonstrate the effect of educating patients on maternal mortality. These articles contain evidence for education as a tool to improve maternal outcomes.

Intranasally administered extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells quickly incorporate into neurons and microglia in 5xFAD mice

Introduction

Extracellular vesicles (EVs) released by human-induced pluripotent stem cell (hiPSC)-derived neural stem cells (NSCs) have robust antiinflammatory and neurogenic properties due to therapeutic miRNAs and proteins in their cargo. Hence, hiPSC-NSC-EVs are potentially an excellent biologic for treating neurodegenerative disorders, including Alzheimer's disease (AD).

Methods

This study investigated whether intranasally (IN) administered hiPSC-NSC-EVs would quickly target various neural cell types in the forebrain, midbrain, and hindbrain regions of 3-month-old 5xFAD mice, a model of β-amyloidosis and familial AD. We administered a single dose of 25 × 10⁹ hiPSC-NSC-EVs labeled with PKH26, and different cohorts of naïve and 5xFAD mice receiving EVs were euthanized at 45 min or 6 h post-administration.

Results

At 45 min post-administration, EVs were found in virtually all subregions of the forebrain, midbrain, and hindbrain of naïve and 5xFAD mice, with predominant targeting and internalization into neurons, interneurons, and microglia, including plaque-associated microglia in 5xFAD mice. EVs also came in contact with the plasma membranes of astrocytic processes and the soma of oligodendrocytes in white matter regions. Evaluation of CD63/CD81 expression with the neuronal marker confirmed that PKH26 + particles found within neurons were IN administered hiPSC-NSC-EVs. At 6 h post-administration, EVs persisted in all cell types in both groups, with the distribution mostly matching what was observed at 45 min post-administration. Area fraction (AF) analysis revealed that, in both naïve and 5xFAD mice, higher fractions of EVs incorporate into forebrain regions at both time points. However, at 45 min post-IN administration, AFs of EVs within cell layers in forebrain regions and within microglia in midbrain and hindbrain regions were lower in 5xFAD mice than naïve mice, implying that amyloidosis reduces EV penetrance.

Discussion

Collectively, the results provide novel evidence that IN administration of therapeutic hiPSC-NSC-EVs is an efficient avenue for directing such EVs into neurons and glia in all brain regions in the early stage of amyloidosis. As pathological changes in AD are observed in multiple brain areas, the ability to deliver therapeutic EVs into various neural cells in virtually every brain region in the early stage of amyloidosis is attractive for promoting neuroprotective and antiinflammatory effects.

Immunogenicity of Homologous Heart Valves: Mechanisms and Future Considerations

Pediatric valvar heart disease continues to be a topic of interest due to the common and severe clinical manifestations. Problems with heart valve replacement, including lack of adaptive valve growth and accelerated structural valve degeneration, mandate morbid reoperations to serially replace valve implants. Homologous or homograft heart valves are a compelling option for valve replacement in the pediatric population but are susceptible to structural valve degeneration. The immunogenicity of homologous heart valves is not fully understood, and mechanisms explaining how implanted heart valves are attacked are unclear. It has been demonstrated that preservation methods determine homograft cell viability and there may be a direct correlation between increased cellular viability and a higher immune response. This consists of an early increase in human leukocyte antigen (HLA)-class I and II antibodies over days to months posthomograft implantation, followed by the sustained increase in HLA-class II antibodies for years after implantation. Cytotoxic T lymphocytes and T-helper lymphocytes specific to both HLA classes can infiltrate tissue almost immediately after implantation. Furthermore, increased HLA-class II mismatches result in an increased cell-mediated response and an accelerated rate of structural valve degeneration especially in younger patients. Further long-term clinical studies should be completed investigating the immunological mechanisms of heart valve rejection and their relation to structural valve degeneration as well as testing of immunosuppressant therapies to determine the needed immunosuppression for homologous heart valve implantation.

Partial heart transplantation can ameliorate donor organ utilization

BACKGROUND

The treatment of babies with unrepairable heart valve dysfunction remains an unsolved problem because there are no growing heart valve implants. However, orthotopic heart transplants are known to grow with recipients.

AIM

Partial heart transplantation is a new approach to delivering growing heart valve implants, which involves transplantation of the part of the heart containing the valves only. In this review, we discuss the benefits of this procedure in children with unrepairable valve dysfunction.

CONCLUSION

Partial heart transplantation can be performed using donor hearts with poor ventricular function and slow progression to donation after cardiac death. This should ameliorate donor heart utilization and avoid both primary orthotopic heart transplantation in children with unrepairable heart valve dysfunction and progression of these children to end-stage heart failure.