The paracrine effect: pivotal mechanism in cell-based cardiac repair

Transplantation of MITO cells, mitochondria activated cardiac progenitor cells, to the ischemic myocardium of mouse enhances the therapeutic effect

Given the potential for myocardial stem cell transplantation as a promising treatment for heart failure, numerous clinical trials have been conducted and its usefulness has been clearly confirmed. However, the low rate of engraftment of transplanted cells has become a clinical problem, and this needs to be improved in the case of transplanting cells to the heart. To address this issue, we report on attempts to prepare mitochondria-activated stem cells (MITO cells) for use in transplantation. MITO cells, which is cardiac progenitor cells (CPCs) activated by the mitochondrial delivery of resveratrol with an anti-oxidant and mitochondrial activation effects were successfully prepared using a mitochondrial targeting nanocarrier (MITO-Porter). The purpose of this study was to validate the therapeutic effect of cell transplantation by the MITO cells using a mouse model of myocardial ischemia–reperfusion. Mouse CPCs were used as transplanted cells. The transplantation of CPCs and MITO cells were conducted after myocardial ischemia–reperfusion, and the therapeutic effect was determined. The MITO cells transplanted group showed increase in postoperative weight gain, improve cardiac function and inhibition of fibrosis compared to the non-transplanted group and the CPC group. The transplantation of MITO cells to the ischemic myocardium showed a stronger transplantation effect compared to conventional CPC transplantation.

Mesenchymal stem cell mediates cardiac repair through autocrine, paracrine and endocrine axes

In the past decade, despite key advances in therapeutic strategies following myocardial infarction, none can directly address the loss of cardiomyocytes following ischemic injury. Cardiac cell-based therapy is at the cornerstone of regenerative medicine that has shown potential for tissue repair. Mesenchymal stem cells (MSC) represent a strong candidate to heal the infarcted myocardium. While differentiation potential has been described as a possible avenue for MSC-based repair, their secreted mediators are responsible for the majority of the ascribed prohealing effects. MSC can either promote their own survival and proliferation through autocrine effect or secrete trophic factors that will act on adjacent cells through a paracrine effect. Prior studies have also documented beneficial effects even when MSCs were remotely delivered, much akin to an endocrine mechanism. This review aims to distinguish the paracrine activity of MSCs from an endocrine-like effect, where remotely transplanted cells can promote healing of the injured myocardium.

Verification of mesenchymal stem cell injection therapy for interstitial cystitis in a rat model

Objective

Interstitial cystitis (IC) is a chronic intractable disease. Recently, the potential application of stem cell (SC) therapy was suggested for IC management. This study aimed to establish an optimal SC source and verify the efficacy and safety of SC injection therapy in an IC rat model.

Design

After IC animal model induction, urine-derived stem cells (USCs), adipose tissue-derived stem cells (ADSCs), bone marrow-derived stem cells (BMSCs) and amniotic fluid-derived stem cells (AFSCs) were injected into the bladder submucosa. The following parameters were analysed: 1) functional improvement of bladder via cystometry, 2) histological changes and 3) inflammatory gene expression and regenerative potential of damaged bladder tissues. Additionally, an optimal method for SC introduction in terms of effective bladder regeneration was analysed.

Results

Intercontraction interval was significantly increased and inflammatory reactions and fibrotic changes were decreased in all of the SC-injected groups than in the control group. PCR analysis revealed that inflammatory gene expression significantly decreased in the USC-treated group than in the other groups. To confirm the optimal SC injection route in the IC rat model, group was divided according to the following criteria: 1) direction of SC injection into the bladder submucosa, 2) injection via tail vein, 3) transurethral instillation. In each analysis, the groups in which SCs were injected into the bladder submucosa showed significantly longer intercontraction interval, better morphologic regeneration and inhibition of bladder inflammatory reaction compared with the other groups.

Conclusion

Regardless of the cell source, human tissue-derived mesenchymal SCs regenerated damaged bladder tissue, promoted functional recovery and inhibited inflammatory cell accumulation in an IC rat model; particularly, USC had the highest inhibitory effect on inflammation. Additionally, direct USC injection into the bladder submucosa was expected to have the best therapeutic effect, which will be an important factor for clinical applications in the future.

Longitudinal intravital imaging of transplanted mesenchymal stem cells elucidates their functional integration and therapeutic potency in an animal model of interstitial cystitis/bladder pain syndrome

Rationale: Mesenchymal stem cell (MSC) therapy may be a novel approach to improve interstitial cystitis/bladder pain syndrome (IC/BPS), an intractable disease characterized by severe pelvic pain and urinary frequency. Unfortunately, the properties of transplanted stem cells have not been directly analyzed in vivo, which hampers elucidation of the therapeutic mechanisms of these cells and optimization of transplantation protocols. Here, we monitored the behaviors of multipotent stem cells (M-MSCs) derived from human embryonic stem cells (hESCs) in real time using a novel combination of in vivo confocal endoscopic and microscopic imaging and demonstrated their improved therapeutic potency in a chronic IC/BPS animal model.

Methods: Ten-week-old female Sprague-Dawley rats were instilled with 10 mg of protamine sulfate followed by 750 μg of lipopolysaccharide weekly for 5 weeks. The sham group was instilled with phosphate-buffered saline (PBS). Thereafter, the indicated dose (0.1, 0.25, 0.5, and 1×10⁶ cells) of M-MSCs or PBS was injected once into the outer layer of the bladder. The distribution, perivascular integration, and therapeutic effects of M-MSCs were monitored by in vivo endoscopic and confocal microscopic imaging, awake cystometry, and histological and gene expression analyses.

Results: A novel combination of longitudinal intravital confocal fluorescence imaging and microcystoscopy in living animals, together with immunofluorescence analysis of bladder tissues, demonstrated that transplanted M-MSCs engrafted following differentiation into multiple cell types and gradually integrated into a perivascular-like structure until 30 days after transplantation. The beneficial effects of transplanted M-MSCs on bladder voiding function and the pathological characteristics of the bladder were efficient and long-lasting due to the stable engraftment of these cells.

Conclusion: This longitudinal bioimaging study of transplanted hESC-derived M-MSCs in living animals reveals their long-term functional integration, which underlies the improved therapeutic effects of these cells on IC/BPS.

Comparison of Non-Coding RNAs in Exosomes and Functional Efficacy of Human Embryonic Stem Cell- versus Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Both human embryonic stem cell-derived cardiomyocytes (ESC-CMs) and human induced pluripotent stem cell-derived CMs (iPSC-CMs) can serve as unlimited cell sources for cardiac regenerative therapy. However, the functional equivalency between human ESC-CMs and iPSC-CMs for cardiac regenerative therapy has not been demonstrated. Here, we performed a head-to-head comparison of ESC-CMs and iPSC-CMs in their ability to restore cardiac function in a rat myocardial infarction (MI) model as well as their exosomal secretome. Human ESCs and iPSCs were differentiated into CMs using small molecule inhibitors. Fluorescence-activated cell sorting analysis confirmed ∼85% and ∼83% of CMs differentiated from ESCs and iPSCs, respectively, were positive for cardiac troponin T. At a single-cell level, both cell types displayed similar calcium handling and electrophysiological properties, with gene expression comparable with the human fetal heart marked by striated sarcomeres. Sub-acute transplantation of ESC-CMs and iPSC-CMs into nude rats post-MI improved cardiac function, which was associated with increased expression of angiogenic genes in vitro following hypoxia. Profiling of exosomal microRNAs (miRs) and long non-coding RNAs (lncRNAs) revealed that both groups contain an identical repertoire of miRs and lncRNAs, including some that are known to be cardioprotective. We demonstrate that both ESC-CMs and iPSC-CMs can facilitate comparable cardiac repair. This is advantageous because, unlike allogeneic ESC-CMs used in therapy, autologous iPSC-CMs could potentially avoid immune rejection when used for cardiac cell transplantation in the future. Stem Cells 2017;35:2138-2149.

Stem Cell Therapy for Myocardial Infarction 2001-2013 Revisited

Stem cell therapy for ischemic heart disease was an emerging concept in the early 2000s. First hopes were largely overshadowed by rather inconsistent results in human trials conducted in the middle of the decade. We aimed at investigating how the field of stem cell research expanded worldwide over the years using scientometric methods. We performed a PubMed inquiry and screened a total of 2609 publications dealing with stem cell therapy for myocardial infarction in the years 2001-2013. Density equalizing maps were used to visualize important centres of stem cell research worldwide. This systematic bibliometric study revealed an increasing research interest in the field of stem cell research in the context of ischemic heart disease over the last decade. Though some of the large human trials failed to show significant effects of stem cell therapy, especially basic science represents an ever growing field that evolved promising new concepts over the last couple of years. The scientific principle of protective paracrine mediators released from transplanted stem cells seems to bear great potential for future cell-free therapeutic use. However, further mechanistic insights are needed before transition from bench to bedside should be attempted, taking the lessons learned from previous studies into account.

Stem Cell Therapy for Interstitial Cystitis/Bladder Pain Syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a disease characterized by pelvic pain, usually with urinary frequency. These symptoms make patients suffer from a poor quality of life. However, there is still a lack of consensus on the pathophysiology and curable treatment of IC/BPS. We have reviewed several candidates for the pathophysiology of this disease and also treatments that have been used. Although several oral medications, bladder instillation therapies, fulguration for Hunner's lesion, and hydrodistention have been tried as IC/BPS treatments, their outcomes have not been satisfactory. As the application of stem cell therapy is expanding into the urologic field, innovative strategies have been tested with animal models of IC/BPS and have shown promising therapeutic effects for reversing the symptoms of this disorder. Although several concerns about stem cell sources and their safety should be addressed before initiating human clinical trials, we introduce stem cell therapy as a valuable future treatment approach for IC/BPS.

Alginate biomaterial for the treatment of myocardial infarction: Progress, translational strategies, and clinical outlook: From ocean algae to patient bedside

Alginate biomaterial is widely utilized for tissue engineering and regeneration due to its biocompatibility, non-thrombogenic nature, mild and physical gelation process, and the resemblance of its hydrogel matrix texture and stiffness to that of the extracellular matrix. In this review, we describe the versatile biomedical applications of alginate, from its use as a supporting cardiac implant in patients after acute myocardial infarction (MI) to its employment as a vehicle for stem cell delivery and for the controlled delivery and presentation of multiple combinations of bioactive molecules and regenerative factors into the heart. Preclinical and first-in-man clinical trials are described in details, showing the therapeutic potential of injectable acellular alginate implants to inhibit the damaging processes after MI, leading to myocardial repair and tissue reconstruction.

The Therapeutic Effects of Human Mesenchymal Stem Cells Primed with Sphingosine-1 Phosphate on Pulmonary Artery Hypertension

Stem cell (SC) therapy has become a potential treatment modality for pulmonary artery hypertension (PAH), but the efficacy of human SC and priming effects have not yet been established. The mobilization and homing of hematopoietic stem cells (HSCs) are modulated by priming factors that include a bioactive lipid, sphingosine-1-phosphate (S1P), which stimulates CXCR4 receptor kinase signaling. Here, we show that priming human mesenchymal stem cells (MSCs) with S1P enhances their therapeutic efficacy in PAH. Human MSCs, similar to HSCs, showed stronger chemoattraction to S1P in transwell assays. Concomitantly, MSCs treated with 0.2 μM S1P showed increased phosphorylation of both MAPKp42/44 and AKT protein compared with nonprimed MSCs. Furthermore, S1P-primed MSCs potentiated colony forming unit-fibroblast, anti-inflammatory, and angiogenic activities of MSCs in culture. In a PAH animal model induced by subcutaneously injected monocrotaline, administration of human cord blood-derived MSCs (hCB-MSCs) or S1P-primed cells significantly attenuated the elevated right ventricular systolic pressure. Notably, S1P-primed CB-MSCs, but not unprimed hCB-MSCs, also elicited a significant reduction in the right ventricular weight ratio and pulmonary vascular wall thickness. S1P-primed MSCs enhanced the expression of several genes responsible for stem cell trafficking and angiogenesis, increasing the density of blood vessels in the damaged lungs. Thus, this study demonstrates that human MSCs have potential utility for the treatment of PAH, and that S1P priming increases the effects of SC therapy by enhancing cardiac and vascular remodeling. By optimizing this protocol in future studies, SC therapy might form a basis for clinical trials to treat human PAH.

Adipose-derived stem cells from both visceral and subcutaneous fat deposits significantly improve contractile function of infarcted rat hearts

Adipose-derived stem cells (ASCs) from subcutaneous and visceral adipose tissues have been studied individually. No studies have compared their abilities in treatment of heart failure. This study was designed to evaluate whether ASCs from the two sources could provide a long-term improvement of cardiac function in infarcted hearts. Rat subcutaneous and visceral adipose tissues were excised for isolation of ASCs. Morphology, yield, proliferation, surface markers, differentiation, and cytokine secretion of the subcutaneous ASCs (S-ASCs) and visceral ASCs (V-ASCs) were analyzed. Then a rat model of myocardial infarction (MI) was established by a coronary occlusion. Seven days after occlusion, S-ASCs (n = 22), V-ASCs (n = 22), and Dulbecco's modified Eagle medium (DMEM, n = 20) were injected into the infarct rim, respectively. Cardiac function was then monitored with MRI for up to 6 months. The hearts were then removed for histological assessments. The yield of V-ASCs per gram of the visceral adipose depot was significantly greater than that of S-ASCs in 1 g of the subcutaneous adipose depot. On the other hand, the S-ASCs showed a greater proliferation rate and colony-forming unit relative to the V-ASCs. In addition, the infarcted hearts treated with either S-ASCs or V-ASCs showed a significantly greater left ventricular ejection fraction (LVEF) than those treated with DMEM at 4 weeks and 6 months following the cell/DMEM transplantation. Moreover, the infarct sizes of both S-ASC- and V-ASC-treated hearts were significantly smaller than that in the DMEM-treated hearts. MRI showed the implanted ASCs at the end of 6 months of recovery. Despite the differences in cell yield, proliferation, and colony formation capacity, both S-ASCs and V-ASCs provide a long-lasting improvement of cardiac contractile function in infarcted hearts. We conclude that the subcutaneous and visceral adipose tissues are equally effective cell sources for cell therapy of heart failure.

Stem cell factor gene transfer improves cardiac function after myocardial infarction in swine

BACKGROUND

Stem cell factor (SCF), a ligand of the c-kit receptor, is a critical cytokine, which contributes to cell migration, proliferation, and survival. It has been shown that SCF expression increases after myocardial infarction (MI) and may be involved in cardiac repair. The aim of this study was to determine whether gene transfer of membrane-bound human SCF improves cardiac function in a large animal model of MI.

METHODS AND RESULTS

A transmural MI was created by implanting an embolic coil in the left anterior descending artery in Yorkshire pigs. One week after the MI, the pigs received direct intramyocardial injections of either a recombinant adenovirus encoding for SCF (Ad.SCF, n=9) or β-gal (Ad.β-gal, n=6) into the infarct border area. At 3 months post-MI, ejection fraction increased by 12% relative to baseline after Ad.SCF therapy, whereas it decreased by 4.2% (P=0.004) in pigs treated with Ad.β-gal. Preload-recruitable stroke work was significantly higher in pigs after SCF treatment (Ad.SCF, 55.5±11.6 mm Hg versus Ad.β-gal, 31.6±12.6 mm Hg, P=0.005), indicating enhanced cardiac function. Histological analyses confirmed the recruitment of c-kit(+) cells as well as a reduced degree of apoptosis 1 week after Ad.SCF injection. In addition, increased capillary density compared with pigs treated with Ad.β-gal was found at 3 months and suggests an angiogenic role of SCF.

CONCLUSIONS

Local overexpression of SCF post-MI induces the recruitment of c-kit(+) cells at the infarct border area acutely. In the chronic stages, SCF gene transfer was associated with improved cardiac function in a preclinical model of ischemic cardiomyopathy.

Re-activated adult epicardial progenitor cells are a heterogeneous population molecularly distinct from their embryonic counterparts

Cardiovascular disease remains the major cause of mortality, and cardiac cell therapy has recently emerged as a paradigm for heart repair. The epicardium is a layer of mesothelial cells covering the heart that during development contributes to different cardiovascular lineages, including cardiomyocytes, but which becomes quiescent after birth. We previously revealed that the peptide thymosin beta 4 (Tβ4) can reactivate adult epicardium-derived cells (EPDCs) after myocardial infarction (MI), to proliferate, and differentiate into cardiovascular derivatives. The aim of this study was to provide a lineage characterization of the adult EPDCs relative to the embryonic epicardial lineage and to determine prospective cell fate biases within the activated adult population during cardiovascular repair. Wt1(GFPCre/+) mice were primed with Tβ4 and MI induced by ligation of the left anterior descending coronary artery. Adult WT1(+) GFP(+) EPDCs were fluorescence-activated cell sorted (FACS) at 2, 4, and 7 days after MI. Embryonic WT1(+) GFP(+) EPDCs were isolated from embryonic hearts (E12.5) by FACS, and sorted cells were characterized by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) and immunostaining. Adult WT1(+) GFP(+) EPDCs were highly heterogeneous, expressing cardiac progenitor and mesenchymal stem markers. Based on the expression of stem cell antigen-1 (Sca-1), CD44, and CD90, we identified different subpopulations of EPDCs of varying cardiovascular potential, according to marker gene profiles, with a molecular phenotype distinct from the source embryonic epicardial cells at E12.5. Thus, adult WT1(+) GFP(+) cells are a heterogeneous population that when activated can restore an embryonic gene programme, but do not revert entirely to adopt an embryonic phenotype. Potential biases in cardiovascular cell fate suggest that discrete subpopulations of EPDCs might be clinically relevant for regenerative therapy.

Heart regeneration, stem cells, and cytokines

The human heart has limited regenerative capacity, which makes the reparative response after the cardiac infarction quite challenging. During the last decade, stem cells have become promising candidates for heart repair, owing to their potent differentiation capacity and paracrine cytokine secretion. Among the different types of stem cells, mesenchymal stem cells have high proliferative potential and secrete numerous cytokines, growth factors, and microRNAs. The paracrine cytokines play important roles in cardiac regeneration, neovascularization, anti-apoptosis, and anti-remodeling mechanisms, among others. This review summarizes the cytokines secreted by stem cells and their relative signaling pathways, which represent key mechanisms for heart regeneration and may serve as a promising future therapeutic strategy for myocardial infarction patients.

The paracrine effects of mesenchymal stem cells stimulate the regeneration capacity of endogenous stem cells in the repair of a bladder-outlet-obstruction-induced overactive bladder

Overactive bladder (OAB), which is characterized by the sudden and uncomfortable need to urinate with or without urinary leakage, is a challenging urological condition. The insufficient efficacy of current pharmacotherapies that uses antimuscarinic agents has increased the demand for novel long-term/stable therapeutic strategies. Here, we report the superior therapeutic efficacy of using mesenchymal stem cells (MSCs) for the treatment of OAB and a novel therapeutic mechanism that activates endogenous Oct4(+) primitive stem cells. We induced OAB using bladder-outlet-obstruction (BOO) in a rat model and either administered a single transplantation of human adipose-derived MSCs or daily intravenous injections of solifenacin, an antimuscarinic agent, for 2 weeks. Within 2 weeks, both the MSC- and solifenacin-treated groups similarly demonstrated relief from BOO-induced detrusor overactivity, hypertrophic smooth muscle, and neurological injuries. In contrast with the solifenacin-treated groups, a single transplantation of MSCs improved most OAB parameters to normal levels within 4 weeks. Although the transplanted human MSCs were hardly engrafted into the damaged bladders, the bladder tissues transplanted with MSCs increased rat sequence-specific transcription of Oct4, Sox2, and Stella, which are surrogate markers for primitive pluripotent stem cells. In addition, MSCs enhanced the expression of several genes, responsible for stem cell trafficking, including SDF-1/CXCR4, HGF/cMet, PDGF/PDGFR, and VEGF/VEGFR signaling axis. These changes in gene expression were not observed in the solifenacin-treated group. Therefore, we suggest the novel mechanisms for the paracrine effect of MSCs as unleashing/mobilizing primitive endogenous stem cells, which could not only explain the long-term/stable therapeutic efficacy of MSCs, but also provide promising new therapies for the treatment of OAB.

Treatment of experimental esophagogastric myotomy with bone marrow mesenchymal stem cells in a rat model

BACKGROUND

Over the last 15 years, many studies demonstrated the myogenic regenerative potential of bone marrow mesenchymal stem cells (BM-MSC), making them an attractive tool for the regeneration of damaged tissues. In this study, we have developed an animal model of esophagogastric myotomy (MY) aimed at determining the role of autologous MSC in the regeneration of the lower esophageal sphincter (LES) after surgery.

METHODS

Syngeneic BM-MSC were locally injected at the site of MY. Histological and functional analysis were performed to evaluate muscle regeneration, contractive capacity, and the presence of green fluorescent protein-positive BM-MSC (BM-MSC-GFP(+) ) in the damaged area at different time points from implantation.

KEY RESULTS

Treatment with syngeneic BM-MSC improved muscle regeneration and increased contractile function of damaged LES. Transplanted BM-MSC-GFP(+) remained on site up to 30 days post injection. Immunohistochemical analysis demonstrated that MSC maintain their phenotype and no differentiation toward smooth or striated muscle was shown at any time point.

CONCLUSIONS & INFERENCES

Our data support the use of autologous BM-MSC to both improve sphincter regeneration of LES and to control the gastro-esophageal reflux after MY.

Efficacy of epicardially delivered adipose stroma cell sheets in dilated cardiomyopathy

AIMS

Few studies have assessed the effects of cell therapy in non-ischaemic cardiomyopathies which, however, contribute to a large number of cardiac failures. Assuming that such conditions are best suited for a global delivery of cells, we assessed the effects of epicardially delivered adipose tissue-derived stroma cell (ADSC) sheets in a mouse model of dilated cardiomyopathy based on cardiac-specific and tamoxifen-inducible invalidation of serum response factor.

METHODS AND RESULTS

Three weeks after tamoxifen administration, the function of the left ventricle (LV) was assessed by echocardiography. Twenty-nine mice were then allocated to control (n = 9, non-transgenic), sham (n = 10, transgenic non-treated), and treated (n = 10, transgenic) groups. In the treated group, 3 × 10(6) allogeneic ADSCs were cultured for 2 days onto temperature-responsive polymers and the generated sheets were then transplanted over the surface of the heart. In 10 additional mice, the sheet was made of green fluorescent protein (GFP)-labelled ADSCs to track cell fate. Function, engraftment, and fibrosis were blindly assessed after 3 weeks. In the non-treated group, fractional shortening declined compared with baseline, whereas the sheet application resulted in its stabilization. This correlated with a lesser degree of LV remodelling, as LV end-diastolic and end-systolic diameters did not differ from baseline values. Many GFP(+) cells were identified in the epicardial graft and in the myocardium. Treated animals also displayed a reduced expression of the stress-induced atrial natriuretic factor and beta-myosin heavy chain genes. These protective effects were also accompanied by a reduction of myocardial fibrosis.

CONCLUSION

These results strongly suggest the functional relevance of epicardially delivered cell-seeded biomaterials to non-ischaemic heart failure.

The acellular myocardial flap: a novel extracellular matrix scaffold enriched with patent microvascular networks and biocompatible cell niches

There is a great need for acellular, fully vascularized, and biocompatible myocardial scaffolds that provide agreeable biological, nutritional, and biomechanical niches for reseeded cells for in vitro and in vivo applications. We generated myocardial flap scaffolds comprising porcine left-anterior ventricular myocardium and its associated coronary arteries and veins and investigated the combinatorial effects of sodium dodecyl sulfate (SDS) and sodium hydroxide (NaOH) perfusion on both the myocardial extracellular matrix (ECM) and the vascular ECM. Results showed that all scaffolds displayed a fully intact and patent vasculature, with arterial burst pressures indistinguishable from native coronary arteries and perfusion to the level of capillaries. Scaffolds were free of cellular proteins and retained collagen and elastin ECM components, exhibited excellent mechanical properties, and were cytocompatible toward relevant seeded cells. SDS perfusion preserved collagen IV, laminin, and fibronectin well, but only reduced DNA content by 33%; however, this was further improved by post-SDS nuclease treatments. By comparison, NaOH was very effective in removing cells and eliminated more than 95% of tissue DNA, but also significantly reduced levels of laminin and fibronectin. Such constructs can be readily trimmed to match the size of the infarct and might be able to functionally integrate within host myocardium and be nourished by direct anastomotic connection with the host's own vasculature; they might also be useful as physiologically accurate models for in vitro studies of cardiac physiology and pathology.

Allogeneic amniotic membrane-derived mesenchymal stromal cell transplantation in a porcine model of chronic myocardial ischemia

Introduction. Amniotic membrane contains a multipotential stem cell population and is expected to possess the machinery to regulate immunological reactions. We investigated the safety and efficacy of allogeneic amniotic membrane-derived mesenchymal stromal cell (AMSC) transplantation in a porcine model of chronic myocardial ischemia as a preclinical trial.

Methods. Porcine AMSCs were isolated from amniotic membranes obtained by cesarean section just before delivery and were cultured to increase their numbers before transplantation. Chronic myocardial ischemia was induced by implantation of an ameroid constrictor around the left circumflex coronary artery. Four weeks after ischemia induction, nine swine were assigned to undergo either allogeneic AMSC transplantation or normal saline injection. Functional analysis was performed by echocardiography, and histological examinations were carried out by immunohistochemistry 4 weeks after AMSC transplantation.

Results. Echocardiography demonstrated that left ventricular ejection fraction was significantly improved and left ventricular dilatation was well attenuated 4 weeks after AMSC transplantation. Histological assessment showed a significant reduction in percentage of fibrosis in the AMSC transplantation group. Injected allogeneic green fluorescent protein (GFP)-expressing AMSCs were identified in the immunocompetent host heart without the use of any immunosuppressants 4 weeks after transplantation. Immunohistochemistry revealed that GFP colocalized with cardiac troponin T and cardiac troponin I.

Conclusions. We have demonstrated that allogeneic AMSC transplantation produced histological and functional improvement in the impaired myocardium in a porcine model of chronic myocardial ischemia. The transplanted allogeneic AMSCs survived without the use of any immunosuppressants and gained cardiac phenotype through either their transdifferentiation or cell fusion.

Factors secreted by mesenchymal stem cells and endothelial progenitor cells have complementary effects on angiogenesis in vitro

Stem cell-based therapy for myocardial regeneration has reported several functional improvements that are attributed mostly to the paracrine effects stimulating angiogenesis and cell survival. This study was conducted to comparatively evaluate the potential of factors secreted by mesenchymal stem cells (MSCs) in normoxic and hypoxic conditions to promote tissue repair by sustaining endothelial cell (EC) adhesion and proliferation and conferring protection against apoptosis. To this aim, a conditioned medium (CM) was generated from MSCs after 24-h incubation in a serum-free normal or hypoxic environment. MSCs exhibited resistance to hypoxia, which induced increased secretion of vascular endothelial growth factor (VEGF) and decreased levels of other cytokines, including stromal-derived factor-1 (SDF). The CM derived from normal (nMSC-CM) and hypoxic cells (hypMSC-CM) induced similar protective effects on H9c2 cells in hypoxia. Minor differences were noticed in the potential of normal versus hypoxic CM to promote angiogenesis, which were likely connected to SDFα and VEGF levels: the nMSC-CM was more effective in stimulating EC migration, whereas the hypMSC-CM had an enhanced effect on EC adhesion. However, the factors secreted by MSCs in normoxic or hypoxic conditions supported adhesion, but not proliferation, of ECs in vitro, as revealed by impedance-based dynamic assessments. Surprisingly, factors secreted by other stem/progenitor cells, such as endothelial progenitor cells (EPCs), had complementary effects to the MSC-CM. Thus, the EPC-CM, in either a normal or hypoxic environment, supported EC proliferation, but did not sustain EC adhesion. Combined use of the MSC-CM and EPC-CM promoted both EC adhesion and proliferation, suggesting that the local angiogenesis at the site of ischemic injury might be better stimulated by simultaneous releasing of factors secreted by multiple stem/progenitor cell populations.

Secreted proteins as a fundamental source for biomarker discovery

The proteins secreted by various cells (the secretomes) are a potential rich source of biomarkers as they reflect various states of the cells at real time and at given conditions. To have accessible, sufficient and reliable protein markers is desirable as they mark various stages of disease development and their presence/absence can be used for diagnosis, prognosis, risk stratification and therapeutic monitoring. As direct analysis of blood/plasma, a common and noninvasive patient screening method, can be difficult for candidate protein biomarker identification, the alternative/complementary approaches are required, one of them is the analysis of secretomes in cell conditioned media in vitro. As the proteins secreted by cells as a response to various stimuli are most likely secreted into blood/plasma, the identification and pre-selection of candidate protein biomarkers from cell secretomes with subsequent validation of their presence at higher levels in serum/plasma is a promising approach. In this review, we discuss the proteins secreted by three progenitor cell types (smooth muscle, endothelial and cardiac progenitor cells) and two adult cell types (neonatal rat ventrical myocytes and smooth muscle cells) which can be relevant to cardiovascular research and which have been recently published in the literature. We found, at least for secretome studies included in this review, that secretomes of progenitor and adult cells overlap by 48% but the secretomes are very distinct among progenitor cell themselves as well as between adult cells. In addition, we compared secreted proteins to protein identifications listed in the Human Plasma PeptideAtlas and in two reports with cardiovascular-related proteins and we performed the extensive literature search to find if any of these secreted proteins were identified in a biomarker study. As expected, many proteins have been identified as biomarkers in cancer but 18 proteins (out of 62) have been tested as biomarkers in cardiovascular diseases as well.

Bioengineering the infarcted heart by applying bio-inspired materials

Induction of cardiac muscle regeneration following myocardial infarction (MI) represents a major challenge in cardiovascular therapy, as the current clinical approaches are limited in their ability to regenerate a new muscle tissue and to replace infarcted myocardium. Here, we describe the conception of two strategies based on bio-inspired materials, aimed at myocardial repair after MI. In the first strategy, alginate biomaterial was designed with affinity-binding moieties, enabling the binding of heparin-binding proteins and their controlled presentation and release. The combined features of this unique alginate hydrogel, as a temporary extracellular matrix replacement and a depot for bio-molecules such as insulin-like growth factor-1 and hepatocyte growth factor, led to improvements in cardiac structure and function, as demonstrated by the biomaterial's abilities to thicken the scar and prevent left-ventricular remodeling and dilatation. Endogenous regeneration occurring at the infarct as manifested by the enhanced angiogenesis, cardiomyocyte proliferation, and appearance of cardiac-related stem cells is likely to have contributed to this. In the second strategy, phosphatidylserine (PS)-presenting liposomes were developed to mimic apoptotic cells bodies, specifically their capability of immunomodulating activated macrophages into anti-inflammatory state. In a rat model of acute MI, targeting of PS-presenting liposomes to infarct macrophages after injection via the femoral vein was demonstrated by magnetic resonance imaging. The treatment promoted angiogenesis, the preservation of small scars, and prevention of ventricular dilatation and remodeling. Collectively, the two bio-inspired material-based strategies presented herein represent unique and clinical accessible approaches for myocardial infarct repair.

Human endothelial stem/progenitor cells, angiogenic factors and vascular repair

Neovascularization or new blood vessel formation is of utmost importance not only for tissue and organ development and for tissue repair and regeneration, but also for pathological processes, such as tumour development. Despite this, the endothelial lineage, its origin, and the regulation of endothelial development and function either intrinsically from stem cells or extrinsically by proangiogenic supporting cells and other elements within local and specific microenvironmental niches are still not fully understood. There can be no doubt that for most tissues and organs, revascularization represents the holy grail for tissue repair, with autologous endothelial stem/progenitor cells, their proangiogenic counterparts and the products of these cells all being attractive targets for therapeutic intervention. Historically, a great deal of controversy has surrounded the identification and origin of cells and factors that contribute to revascularization, the use of such cells or their products as biomarkers to predict and monitor tissue damage and repair or tumour progression and therapeutic responses, and indeed their efficacy in revascularizing and repairing damaged tissues. Here, we will review the role of endothelial progenitor cells and of supporting proangiogenic cells and their products, principally in humans, as diagnostic and therapeutic agents for wound repair and tissue regeneration.