Novel heat shock protein 90 inhibitor improves cardiac recovery in a rodent model of donation after circulatory death.

OBJECTIVE: Organ donation after circulatory death (DCD) is a potential solution for the shortage of suitable organs for transplant. Heart transplantation using DCD donors is not frequently performed due to the potential myocardial damage following warm ischemia. Heat shock protein (HSP) 90 has recently been investigated as a novel target to reduce ischemia/reperfusion injury. The objective of this study is to evaluate an innovative HSP90 inhibitor (HSP90i) as a cardioprotective agent in a model of DCD heart. METHODS: A DCD protocol was initiated in anesthetized Lewis rats by discontinuation of ventilation and confirmation of circulatory death by invasive monitoring. Following 15 minutes of warm ischemia, cardioplegia was perfused for 5 minutes at physiological pressure. DCD hearts were mounted on a Langendorff ex vivo heart perfusion system for reconditioning and functional assessment (60 minutes). HSP90i (0.01 µmol/L) or vehicle was perfused in the cardioplegia and during the first 10 minutes of ex vivo heart perfusion reperfusion. Following assessment, pro-survival pathway signaling was evaluated by western blot or polymerase chain reaction. RESULTS: Treatment with HSP90i preserved left ventricular contractility (maximum + dP/dt, 2385 ± 249 vs 1745 ± 150 mm Hg/s), relaxation (minimum -dP/dt, -1437 ± 97 vs 1125 ± 85 mm Hg/s), and developed pressure (60.7 ± 5.6 vs 43.9 ± 4.0 mm Hg), when compared with control DCD hearts (All P = .001). Treatment abrogates ischemic injury as demonstrated by a significant reduction of infarct size (2,3,5-triphenyl-tetrazolium chloride staining) of 7 ± 3% versus 19 ± 4% (P = .03), troponin T release, and mRNA expression of Bax/Bcl-2 (P < .05). CONCLUSIONS: The cardioprotective effects of HSP90i when used following circulatory death might improve transplant organ availability by expanding the use of DCD hearts.

Pharmacological Preconditioning Improves the Viability and Proangiogenic Paracrine Function of Hydrogel-Encapsulated Mesenchymal Stromal Cells.

The efficacy of cell therapy is limited by low retention and survival of transplanted cells in the target tissues. In this work, we hypothesize that pharmacological preconditioning with celastrol, a natural potent antioxidant, could improve the viability and functions of mesenchymal stromal cells (MSC) encapsulated within an injectable scaffold. Bone marrow MSCs from rat (rMSC) and human (hMSC) origin were preconditioned for 1 hour with celastrol 1 µM or vehicle (DMSO 0.1% v/v), then encapsulated within a chitosan-based thermosensitive hydrogel. Cell viability was compared by alamarBlue and live/dead assay. Paracrine function was studied first by quantifying the proangiogenic growth factors released, followed by assessing scratched HUVEC culture wound closure velocity and proliferation of HUVEC when cocultured with encapsulated hMSC. In vivo, the proangiogenic activity was studied by evaluating the neovessel density around the subcutaneously injected hydrogel after one week in rats. Preconditioning strongly enhanced the viability of rMSC and hMSC compared to vehicle-treated cells, with 90% and 75% survival versus 36% and 58% survival, respectively, after 7 days in complete media and 80% versus 64% survival for hMSC after 4 days in low serum media (p < 0.05). Celastrol-treated cells increased quantities of proangiogenic cytokines compared to vehicle-pretreated cells, with a significant 3.0-fold and 1.8-fold increase of VEGFa and SDF-1α, respectively (p < 0.05). The enhanced paracrine function of preconditioned MSC was demonstrated by accelerated growth and wound closure velocity of injured HUVEC monolayer (p < 0.05) in vitro. Moreover, celastrol-treated cells, but not vehicle-treated cells, led to a significant increase of neovessel density in the peri-implant region after one week in vivo compared to the control (blank hydrogel). These results suggest that combining cell pretreatment with celastrol and encapsulation in hydrogel could potentiate MSC therapy for many diseases, benefiting particularly ischemic diseases.

Heat shock protein 90 inhibition and multi-target approach to maximize cardioprotection in ischaemic injury.

Despite several advances in medicine, ischaemic heart disease remains a major cause of morbidity and mortality. The unravelling of molecular mechanisms underlying disease pathophysiology has revealed targets for pharmacological interventions. However, transfer of these pharmcological possibilities to clinical use has been disappointing. Considering the complexity of ischaemic disease at the cellular and molecular levels, an equally multifaceted treatment approach may be envisioned. The pharmacological principle of 'one target, one key' may fall short in such contexts, and optimal treatment may involve one or many agents directed against complementary targets. Here, we introduce a 'multi-target approach to cardioprotection' and propose heat shock protein 90 (HSP90) as a target of interest. We report on a member of a distinct class of HSP90 inhibitor possessing pleiotropic activity, which we found to exhibit potent infarct-sparing effects.

Pre-clinical Model of Cardiac Donation after Circulatory Death.

Cardiac transplantation demand is on the rise; nevertheless, organ availability is limited due to a paucity of suitable donors. Organ donation after circulatory death (DCD) is a solution to address this limited availability, but due to a period of prolonged warm ischemia and the risk of tissue injury, its routine use in cardiac transplantation is seldom seen. In this manuscript we provide a detailed protocol closely mimicking current clinical practices in the context of DCD with continuous monitoring of heart function, allowing for the evaluation of novel cardioprotective strategies and interventions to decrease ischemia-reperfusion injury. In this model, the DCD protocol is initiated in anesthetized Lewis rats by stopping ventilation to induce circulatory death. When systolic blood pressure drops below 30 mmHg, the warm ischemic time is initiated. After a pre-set warm ischemic period, hearts are flushed with a normothermic cardioplegic solution, procured, and mounted onto a Langendorff ex vivo heart perfusion system. Following 10 min of initial reperfusion and stabilization, cardiac reconditioning is continuously evaluated for 60 min using intraventricular pressure monitoring. A heart injury is assessed by measuring cardiac troponin T and the infarct size is quantified by histological staining. The warm ischemic time can be modulated and tailored to develop the desired amount of structural and functional damage. This simple protocol allows for the evaluation of different cardioprotective conditioning strategies introduced at the moment of cardioplegia, initial reperfusion and/or during ex vivo perfusion. Findings obtained from this protocol can be reproduced in large models, facilitating clinical translation.

Celastrol-type HSP90 modulators allow for potent cardioprotective effects.

AIMS: Cardiac ischemic conditioning has been shown to decrease ischemic injury in experimental models and clinically. Activation of survival pathways leading to heat shock proteins (HSP) modulation is an important contributor to this effect. We have previously shown that celastrol, an HSP90 modulator, achieves cardioprotection through activation of cytoprotective HSP's and heme-oxygenase-1 (HO-1). This is the first comparative evaluation of several modulators of HSP90 activity for cardioprotection. Furthermore, basic celastrol structure-activity relationship was characterized in order to develop novel potent infarct sparing agents suitable for clinical development. MAIN METHODS: Combining in vitro cell culture using rat myocardial cell line exposed to ischemic and ischemia/reperfusion (I/R) stresses, and ex vivo Langendorff rat heart perfusion I/R model, we evaluated cardioprotective effects of various compounds. Selected signalling pathways were evaluated by western blot and reporter gene activation. KEY FINDINGS: From a variety of HSP90 modulator chemotypes, the celastrol family was most efficient in inducing cytoprotective HSP70 and HO-1 protein overexpression and cell survival in vitro. Celastrol and two synthetic analogs were protective against ischemia and prevented ischemia/reperfusion (I/R) injury when given as pre-treatment or at time of reperfusion, increasing viability and reducing mitochondrial permeability transition pore opening. Ex vivo experiments demonstrated that the two synthetic analogs show cardioprotective activity at lower concentrations compared to celastrol, with activation of multiple survival pathways. SIGNIFICANCE: Celastrol backbone is essential for cardioprotection through HSP90 activity modulation. These compounds hold promise as novel adjunct treatment to improve outcome in the clinical management of I/R injury.

Optimization of Mesenchymal Stem Cells to Increase Their Therapeutic Potential.

The heart which has limited renewal and regenerative capacity is a prime target for cellular therapy. Stem cell transplantation has emerged as a promising therapeutic strategy to improve healing of the ischemic heart, repopulate the injured myocardium, and restore cardiac function. However, clinical usefulness is impacted by the quality and quantity of delivered cells, the suboptimal manipulations prior to transplantation, and the general poor viability of the cells transferred particularly to an ischemic microenvironment. Focus is now on developing new ways to enhance stem cell renewal and survival capacity before transplant. This can be done by physical, chemical, pharmacological, or genetic manipulation of cells followed by accurate evaluation of conditioning methods by validated tests.This chapter covers the proper handling of mesenchymal stem cells (human and rat lines) and methodologies to evaluate efficacy and the translational potential of conditioning methods. Specifically, we will cover stem cell culture methods, preconditioning protocols, viability assessment in hypoxic and oxidative challenges as encountered in an ischemic microenvironment, and the proliferative capacity of cells.

Preconditioning of stem cells by oxytocin to improve their therapeutic potential.

Principal limitation of cell therapy is cell loss after transplantation because of the interplay between ischemia, inflammation, and apoptosis. We investigated the mechanism of preconditioning of mesenchymal stem cells (MSCs) with oxytocin (OT), which has been proposed as a novel strategy for enhancing therapeutic potential of these cells in ischemic heart. In this study, we demonstrate that rat MSCs express binding sites for OT receptor and OT receptor transcript and protein as detected by RT-PCR and immunofluorescence, respectively. In response to OT (10(-10) to 10(-6) M) treatment, MSCs respond with rapid calcium mobilization and up-regulation of the protective protein kinase B (PKB or Akt) and phospho-ERK1/2 proteins. In OT-stimulated cells, phospho-Akt accumulates intracellularly close to the mitochondrial marker cytochrome c oxidase subunit 4. Functional analyses reveal the involvement of Akt/ERK1/2 pathways in cell proliferation, migration, and protection against the cytotoxic and apoptotic effects of hypoxia and serum deprivation. In addition, OT preconditioning increases MSC glucose uptake. Genes with angiogenic, antiapoptotic, and cardiac antiremodeling properties, such as heat shock proteins (hsps) HSP27, HSP32, HSP70, vascular endothelial growth factor, thrombospondin, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, TIMP-3, and matrix metalloproteinase-2, were also up-regulated upon OT exposure. Moreover, coculture with OT-preconditioned MSC reduces apoptosis, as measured using terminal transferase dUTP nick end labeling assay in newborn rat cardiomyocytes exposed to hypoxia and reoxygenation. In conclusion, these results indicate that OT treatment evokes MSC protection through both intrinsic pathways and secretion of cytoprotective factors. Ex vivo cellular treatment with OT represents an attractive strategy aimed to maximize the biological and functional properties of effector cells.

Improved function and myocardial repair of infarcted heart by intracoronary injection of mesenchymal stem cell-derived growth factors.

Transplantation of mesenchymal stem cells (MSC) improves repair and function recovery following myocardial infarction (MI), but underlying mechanisms remain to be elucidated. We hypothesize that MSC could achieve protection by paracrine effects through released mediators rather than direct cardiac regeneration. We sought to characterize the effects of MSC-secreted growth factors on extent of early recovery from MI. Swine subjected to acute MI by temporary balloon occlusion of the left anterior descending coronary artery using percutaneous techniques received intracoronary injection of either concentrated MSC-derived growth factors or control medium. Animals were killed at 7 days to evaluate early effects. Treatment with MSC-derived factors significantly reduced cardiac troponin-T elevation and improved echocardiographic parameters, including fractional area shortening, stroke volume, cardiac output, and wall motion score index. Quantitative evaluation of fibrosis by Verhoff staining revealed a reduction of the fibrotic area in the infarcted zone. Similarly, Masson's trichrome staining revealed reduced myocardial damage as demonstrated by areas of relatively preserved myocardium in the infarcted area. TUNEL assay demonstrated less cardiomyocyte apoptosis. Protein array detected the presence of angiogenic (vascular endothelial growth factor, endothelin, and epiregulin), anti-apoptotic (Galectin-3, Smad-5, sRFP-1, and sRFP-4) and anti-remodeling factors. Reverse transcription polymerase chain reaction confirmed the expression of these factors. In summary, a single intracoronary injection of concentrated biologically active factors secreted by MSC could achieve early protection of ischemic myocardium and improve cardiac repair and contractility. MSC-derived growth factors injection (rather than MSC themselves) should be evaluated as a novel therapy to treat ischemic heart disease, avoiding many practical and technical issues of cell therapy.