Cell-based gene therapy for the prevention and treatment of cardiac dysfunction

A Novel Role for CAMKK1 in the Regulation of the Mesenchymal Stem Cell Secretome

Transplantation of adult stem cells into myocardial tissue after acute myocardial infarction (AMI), has been shown to improve tissue recovery and prevent progression to ischemic cardiomyopathy. Studies suggest that the effects of mesenchymal stem cells (MSC) are due to paracrine factors released by MSC, as the benefits of MSC can be achieved through delivery of conditioned media (CM) alone. We previously demonstrated that downregulation of Dab2 enhances MSC cardiac protein expression and improves cardiac function after AMI following MSC engraftment. In order to define the molecular mechanisms that regulate MSC secretome, we analyzed gene arrays in MSC following downregulation of Dab2 via TGFβ1 pretreatment or transfection with Dab2:siRNA or miR‐145. We identified 23 genes whose expressions were significantly changed in all three conditions. Among these genes, we have initially focused our validation and functional work on calcium/calmodulin‐dependent protein kinase kinase‐1 (CAMKK1). We quantified the effects of CAMKK1 overexpression in MSC following injection of CM after AMI. Injections of CM from MSC with CAMKK1 over‐expression correlated with an increase in vascular density (CAMKK1 CM: 2,794.95 ± 44.2 versus Control: 1,290.69 ± 2.8 vessels/mm²) and decreased scar formation (CAMKK1 CM 50% ± 3.2% versus Control: 28% ± 1.4%), as well as improved cardiac function. Direct overexpression of CAMKK1 in infarcted tissue using a CAMKK1‐encoding plasmid significantly improved ejection fraction (CAMKK1: 83.2% ± 5.4% versus saline: 51.7% ± 5.8%. Baseline: 91.3% ± 4.3%) and decreased infarct size after AMI. Our data identify a novel role for CAMKK1 as regulator of the MSC secretome and demonstrate that direct overexpression of CAMKK1 in infarcted cardiac tissue, results in therapeutic beneficial effects. Stem Cells Translational Medicine2017;6:1759–1766

SDF-1 Recruits Cardiac Stem Cell-Like Cells that Depolarize In Vivo

Prolongation or reestablishment of stem cell homing through the expression of SDF-1 in the myocardium has been shown to lead to homing of endothelial progenitor cells to the infarct zone with a subsequent increase in vascular density and cardiac function. While the increase in vascular density is important, there could clearly be other mechanisms involved. In a recent study we demonstrated that the infusion of mesenchymal stem cells (MSC) and MSC that were engineered to overexpress SDF-1 led to significant decreases in cardiac myocyte apoptosis and increases in vascular density and cardiac function compared to control. In that study there was no evidence of cardiac regeneration from either endogenous stem cells or the infused mesenchymal stem cells. In this study we performed further detailed immunohistochemistry on these tissues and demonstrate that the overexpression of SDF-1 in the newly infracted myocardium led to recruitment of small cardiac myosin-expressing cells that had proliferated within 2 weeks of acute MI. These cells did not differentiate into mature cardiac myocytes, at least by 5 weeks after acute MI. However, based on optical mapping studies, these cells appear capable of depolarizing. We observed greater optical action potential amplitude in the infarct border in those animals that received SDF-1 overexpressing MSC than observed in noninfarcted animals and those that received control MSC. Further immunohistochemistry revealed that these proliferated cardiac myosin-positive cells did not express connexin 43, but did express connexin 45. In summary, our study suggests that the prolongation of SDF-1 expression at the time of acute MI leads to the recruitment of endogenous cardiac myosin stem cells that may represent cardiac stem cells. These cells are capable of depolarizing and thus may contribute to increased contractile function even in the absence of maturation into a mature cardiac myocyte.

Mesenchymal stem cells can improve anal pressures after anal sphincter injury

OBJECTIVE

Fecal incontinence reduces the quality of life of many women but has no long-term cure. Research on mesenchymal stem cell (MSC)-based therapies has shown promising results. The primary aim of this study was to evaluate functional recovery after treatment with MSCs in two animal models of anal sphincter injury.

METHODS

Seventy virgin female rats received a sphincterotomy (SP) to model episiotomy, a pudendal nerve crush (PNC) to model the nerve injuries of childbirth, a sham SP, or a sham PNC. Anal sphincter pressures and electromyography (EMG) were recorded after injury but before treatment and 10 days after injury. Twenty-four hours after injury, each animal received either 0.2 ml saline or 2 million MSCs labelled with green fluorescing protein (GFP) suspended in 0.2 ml saline, either intravenously (IV) into the tail vein or intramuscularly (IM) into the anal sphincter.

RESULTS

MSCs delivered IV after SP resulted in a significant increase in resting anal sphincter pressure and peak pressure, as well as anal sphincter EMG amplitude and frequency 10 days after injury. MSCs delivered IM after SP resulted in a significant increase in resting anal sphincter pressure and anal sphincter EMG frequency but not amplitude. There was no improvement in anal sphincter pressure or EMG with in animals receiving MSCs after PNC. GFP-labelled cells were not found near the external anal sphincter in MSC-treated animals after SP.

CONCLUSION

MSC treatment resulted in significant improvement in anal pressures after SP but not after PNC, suggesting that MSCs could be utilized to facilitate recovery after anal sphincter injury.

Exposure to supernatants of macrophages that phagocytized dead mesenchymal stem cells improves hypoxic cardiomyocytes survival

OBJECTIVE

To observe the impact of supernatants from macrophages that phagocytized dead MSCs (pMΦ) on the survival of hypoxic cardiomyocytes.

METHODS

MSCs were isolated from bone marrow of mice and dead MSCs were harvested after 6h hypoxia. Macrophages were obtained from thioglycolate-elicited peritoneal cavity. Macrophages and dead MSCs were co-cultured for 2 days in the presence or absence of LPS (1 μg/ml). Cardiomyocytes obtained from neonatal mice were exposed to various medium including supernatants from pMΦ. MTT cell proliferation assay and mitochondria membrane potential were used to evaluate the viability of cardiomyocytes. Cytokines and chemokines (TNF-α, IFN-γ, IL-6, IL-12, PGE2, VEGF-α, Ang-1, KGF, IGF-1, PDGF-BB, and EPO) in culture medium of macrophages, MSCs and pMΦ were detected by ELISA and Real-Time-PCR.

RESULTS

phagocytic activity of macrophages to dMSC was significantly enhanced by LPS. PGE2, VEGF-α, Ang-1, KGF, IGF-1, PDGF-BB, and EPO levels were significantly increased in supernatants of pMΦ. Exposure to supernatants of pMΦ significantly improved viability and survival time of hypoxic cardiomyocytes.

CONCLUSION

Exposure to supernatants of pMΦ significantly improved viability and survival time of hypoxic cardiomyocytes, which might be linked to increased cytokines and chemokines secretion by pMΦ.

Transplantation of microencapsulated cells expressing VEGF improves angiogenesis in implanted xenogeneic acellular dermis on wound

BACKGROUND

Cell-based gene therapy using cells that express angiogenic factors is an alternative technique for therapeutic angiogenesis in transplantation of xenogeneic acellular dermis matrix (ADM). However, immune rejection is a substantial obstacle to implantation of genetically engineered allogeneic or xenogeneic cells.

OBJECTIVE

To evaluate application of microencapsulated cells that express vascular endothelial growth factor (VEGF) in xenogeneic ADM transplants to improve wound angiogenesis and healing.

MATERIALS AND METHODS

NIH3T3 cells were genetically modified to secrete VEGF and enveloped in semipermeable microcapsules. Microencapsulated VEGF-NIH3T3 cells were implanted in defects on the dorsa of guinea pigs with xenogeneic ADM and autologous split-thickness skin grafts. Cell structure and microencapsulation were observed at microscopy, and expression of VEGF was detected using an enzyme-linked immunosorbent assay (ELISA) and immunochemistry. Extent of angiogenesis in the ADM and the survival rate of the composite skin were evaluated after 2 weeks. In addition, expression of human VEGF and CD31 in the implanted acellular dermis was assessed, and microvessel density was calculated.

RESULTS

Microencapsulated VEGF-expressing NIH3T3 cells were prepared successfully, and demonstrated proliferation and viability, and expressed VEGF both in vitro and in vivo. Extent of angiogenesis and survival rate of the composite skin containing the microencapsulated VEGF-expressing cells were significantly greater than in controls. Microencapsulated VEGF-expressing NIH3T3 cells augmented early angiogenesis in ADM implanted on wound and improved healing.

CONCLUSION

Microencapsulated xenogeneic cell-based gene therapy may be a novel approach to therapeutic angiogenesis in transplantation of xenogeneic ADM skin.

Enhancing biological therapy through conditional regulation of protein stability

The ability to externally regulate the expression or function of a gene product has proven to be a powerful tool in the study of proteins and disease in vitro, and more recently in transgenic animal models. The transfer of these technologies to regulate a therapeutic, adoptively transferred gene product in a clinical setting may provide a means to exert additional control over a large variety of therapies for many diseases, leading to increased safety and effectiveness. This could be applied to any biological therapy, including gene therapy, viral therapies, cellular therapies (such as immune cell therapies, stem cell therapies and bone marrow transplant), some vaccines and even organ transplant. A variety of systems have been used in a basic research setting to conditionally regulate the function of a protein, including control of transcription and mRNA stability, and the use of protein inhibitors. However, most of these have disadvantages for medical use, where a simple, specific, tunable, reversible and broadly applicable means to regulate protein function is needed. Recent advances in controlling the stability or function of proteins through the interaction of small-molecule effectors and fusion domains on the protein have raised the possibility that direct and highly specific external control of therapeutic protein function in humans will be feasible.

Tracking the migration of cardially delivered therapeutic stem cells in vivo: state of the art

Cell-based therapy is a promising, novel therapeutic strategy for cardiovascular disease. The rapid transition of this approach from the benchside to clinical trials has left a gap in the understanding of the mechanisms of cell therapy. Monitoring of cell homing and the fate of cardially delivered stem cells is fundamental for clarification of the myocardial regenerative process. Noninvasive imaging techniques allow an in vivo evaluation of the survival, migration and differentiation of implanted stem cells over time, and by this means, can help to answer unresolved questions. The most promising in vivo tracking methods involve the direct, nonspecific labeling of cells including MRI, radionuclide imaging and the use of reporter-gene imaging. This review summarizes the most important results of animal and human studies in which the fate and biodistribution of cardially delivered stem cells are assessed through different in vivo tracking methods.

Cardiac renewing: interstitial Cajal-like cells nurse cardiomyocyte progenitors in epicardial stem cell niches

Recent studies suggested that various cell lineages exist within the subepicardium and we supposed that this area could host cardiac stem cell niches (CSCNs). Using transmission electron microscopy, we have found at least 10 types of cells coexisting in the subepicardium of normal adult mice: adipocytes, fibroblasts, Schwann cells and nerve fibres, isolated smooth muscle cells, mast cells, macrophages, lymphocytes, interstitial Cajal-like cells (ICLCs) and cardiomyocytes progenitors (CMPs). The latter cells, sited in the area of origin of coronary arteries and aorta, showed typical features of either very immature or developing cardiomyocytes. Some of these cells were connected to each other to form columns surrounded by a basal lamina and embedded in a cellular network made by ICLCs. Complex intercellular communication occurs between the ICLCs and CMPs through electron-dense nanostructures or through shed vesicles. We provide here for the first time the ultrastructural description of CSCN in the adult mice myocardium, mainly containing ICLCs and CMPs. The existence of resident CMPs in different developmental stages proves that cardiac renewing is a continuous process. We suggest that ICLCs might act as supporting nurse cells of the cardiac niches and may be responsible for activation, commitment and migration of the stem cells out of the niches. Briefly, not only resident cardiac stem cells but also ICLCs regulate myocyte turnover and contribute to both cardiac cellular homeostasis and endogenous repair/remodelling after injuries.

Pre-transplantation specification of stem cells to cardiac lineage for regeneration of cardiac tissue

Myocardial infarction (MI) is a lead cause of mortality in the Western world. Treatment of acute MI is focused on restoration of antegrade flow which inhibits further tissue loss, but does not restore function to damaged tissue. Chronic therapy for injured myocardial tissue involves medical therapy that attempts to minimize pathologic remodeling of the heart. End stage therapy for chronic heart failure (CHF) involves inotropic therapy to increase surviving cardiac myocyte function or mechanical augmentation of cardiac performance. Not until the point of heart transplantation, a limited resource at best, does therapy focus on the fundamental problem of needing to replace injured tissue with new contractile tissue. In this setting, the potential for stem cell therapy has garnered significant interest for its potential to regenerate or create new contractile cardiac tissue. While to date adult stem cell therapy in clinical trials has suggested potential benefit, there is waning belief that the approaches used to date lead to regeneration of cardiac tissue. As the literature has better defined the pathways involved in cardiac differentiation, preclinical studies have suggested that stem cell pretreatment to direct stem cell differentiation prior to stem cell transplantation may be a more efficacious strategy for inducing cardiac regeneration. Here we review the available literature on pre-transplantation conditioning of stem cells in an attempt to better understand stem cell behavior and their readiness in cell-based therapy for myocardial regeneration.

Update on therapeutic vascularization strategies

The ability to exploit angiogenesis and vascularization as a therapeutic strategy will be of enormous benefit to a wide range of medical and tissue-engineering applications. Angiogenic growth factor and cell-based therapies have thus far failed to produce a robust healing response in clinical trials for a variety of ischemic diseases, while engineered tissue substitutes are still size-limited by a lack of vascularization. The purpose of this review is to investigate current research advances in therapeutic vascularization strategies applied to ischemic disease states, tissue engineering and regenerative medicine. Recent advances are discussed that focus on better regulation of growth factor delivery and attempts to better mimic natural processes by delivering combinations of multiple growth factors, cells and bioactive materials in the right spatial and temporal setting. Some unconventional approaches and novel therapeutic targets that hold significant potential are also discussed.

Stem cells in the heart: what's the buzz all about? Part 2: Arrhythmic risks and clinical studies

New approaches for cardiac repair have been enabled by the discovery that the heart contains its own reservoir of stem cells. In Part 1 of this review, we discussed various cardiac stem cell populations, reviewed our own work on cardiosphere-derived cells from human hearts, and outlined large animal preclinical models testing the regenerative potential of cardiac stem cells. Here we continue with a discussion on other adult stem cell sources with clinical potential. We summarize the critical safety issues associated with stem cell therapy and present the possible proarrhythmic and antiarrhythmic effects of stem cell transplantation. We discuss the outcomes of clinical stem cell trials and identify the technical, ethical, and practical issues facing the clinical application of cardiac stem cells.

Exploitation of stem cell homing for gene delivery

Stem cells have been the focus of numerous investigations to treat diseases as far ranging as diabetes, chronic heart failure and multiple sclerosis over the past decade. The process of stem-cell-based repair of acute injury involves homing and engrafting of the stem cell of interest to the site of injury followed by either differentiation of the stem cell to indigenous end-organ cells or liberation of paracrine factors that lead to preservation and/or optimization of organ function. Recognition of the ability of stem cells to home to sites of acute injury suggests that, if appropriately defined and harnessed, stem cell homing could serve as a means of local drug delivery through the infusion of genetically engineering stem cells that secrete gene products of interest. The authors have recently demonstrated the use of this approach in preclinical studies of acute myocardial function. In addition, the use of engineered cells that home to appropriate niches have been used to correct genetic deficiency states (i.e., severe combined immunodeficiency, diabetes mellitus) in patients with otherwise chronic debilitating diseases. This review focuses on exploiting stem cell homing for gene transfer and on the state of the art and the challenges that face the field.

Transplantation of microencapsulated genetically modified xenogeneic cells augments angiogenesis and improves heart function

Cell-based gene therapy offers an alternative strategy for therapeutic angiogenesis for the management of myocardial infarction (MI). However, immune rejection poses a significant obstacle to the implantation of genetically engineered allogeneic or xenogeneic cells. In the present study, an ex vivo gene therapy approach utilizing cell microencapsulation was employed to deliver vascular endothelial growth factor (VEGF) to ischemic myocardium. Chinese hamster ovary (CHO) cells were genetically modified to secrete VEGF and enveloped into semipermeable microcapsules. In vitro assay indicated that the microencapsulated engineered CHO cells could secrete VEGF as high as 3852 pg ml(-1) per 48 h at day 8 after encapsulation. Then the microencapsulated CHO cells were implanted into the injured myocardium in a rat MI model, while engineered CHO cells, blank microcapsules and serum-free culture media were implanted as controls. The humoral immunity to xenogeneic CHO cells were evaluated and we found that the titer of anti-CHO antibodies was significantly lower in the microencapsulated CHO transplantation group than the group receiving unencapsulated CHO cells at two weeks after implantation. However, 1 week later, there was almost no difference between these groups. Histology and western blotting confirmed that the microencapsulated CHO cells maintained their original structure and VEGF secretion three weeks after implantation. The capillary density in the treatment region was also significantly higher in the microencapsulated CHO cell group than control groups, which was consistent with gross heart functional improvement. These data suggest that microencapsulated xenogeneic cell-based gene therapy might be a novel approach for therapeutic angiogenesis in ischemic heart disease.