Periostin induces proliferation of differentiated cardiomyocytes and promotes cardiac repair

Modulation of cardiac fibrosis by Krüppel-like factor 6 through transcriptional control of thrombospondin 4 in cardiomyocytes

AIMS

Krüppel-like factors (KLFs) are a family of transcription factors which play important roles in the heart under pathological and developmental conditions. We previously identified and cloned Klf6 whose homozygous mutation in mice results in embryonic lethality suggesting a role in cardiovascular development. Effects of KLF6 on pathological regulation of the heart were investigated in the present study.

METHODS AND RESULTS

Mice heterozygous for Klf6 resulted in significantly diminished levels of cardiac fibrosis in response to angiotensin II infusion. Intriguingly, a similar phenotype was seen in cardiomyocyte-specific Klf6 knockout mice, but not in cardiac fibroblast-specific knockout mice. Microarray analysis revealed increased levels of the extracellular matrix factor, thrombospondin 4 (TSP4), in the Klf6-ablated heart. Mechanistically, KLF6 directly suppressed Tsp4 expression levels, and cardiac TSP4 regulated the activation of cardiac fibroblasts to regulate cardiac fibrosis.

CONCLUSION

Our present studies on the cardiac function of KLF6 show a new mechanism whereby cardiomyocytes regulate cardiac fibrosis through transcriptional control of the extracellular matrix factor, TSP4, which, in turn, modulates activation of cardiac fibroblasts.

Cardiac Repair and Regeneration: The Value of Cell Therapies

Ischaemic heart disease is the predominant contributor to cardiovascular morbidity and mortality; one million myocardial Infarctions occur per year in the USA, while more than five million patients suffer from chronic heart failure. Recently, heart failure has been singled out as an epidemic and is a staggering clinical and public health problem associated with significant mortality, morbidity and healthcare expenditures, particularly among those aged ≥65 years. Death rates have improved dramatically over the last four decades, but new approaches are nevertheless urgently needed for those patients who go on to develop ventricular dysfunction and chronic heart failure. Over the past decade, stem cell transplantation has emerged as a promising therapeutic strategy for acute or chronic ischaemic cardiomyopathy. Multiple candidate cell types have been used in preclinical animal models and in humans to repair or regenerate the injured heart, either directly or indirectly (through paracrine effects), including: embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), neonatal cardiomyocytes, skeletal myoblasts (SKMs), endothelial progenitor cells, bone marrow mononuclear cells (BMMNCs), mesenchymal stem cells (MSCs) and, most recently, cardiac stem cells (CSCs). Although no consensus has emerged yet, the ideal cell type for the treatment of heart disease should: (a) improve heart function; (b) create healthy and functional cardiac muscle and vasculature, integrated into the host tissue; (c) be amenable to delivery by minimally invasive clinical methods; (d) be available 'off the shelf' as a standardised reagent; (e) be tolerated by the immune system; (f) be safe oncologically, i.e. not create tumours; and (g) circumvent societal ethical concerns. At present, it is not clear whether such a 'perfect' stem cell exists; what is apparent, however, is that some cell types are more promising than others. In this brief review, we provide ongoing data on agreement and controversy arising from clinical trials and touch upon the future directions of cell therapy for heart disease.

Cardiac endothelium-myocyte interaction: clinical opportunities for new heart failure therapies regardless of ejection fraction

Heart failure (HF) is an important global health problem with great socioeconomic burden. Outcomes remain sub-optimal. Endothelium-cardiomyocyte interactions play essential roles in cardiovascular homeostasis, and deranged endothelium-related signalling pathways have been implicated in the pathophysiology of HF. In particular, disturbances in nitric oxide (NO)-mediated pathway and neuregulin-mediated pathway have been shown to contribute to the development of HF. These signalling pathways hold the potential as pathophysiological targets for new HF therapies, and may aid in patient selection for future HF trials.

Periostin Promotes Neural Stem Cell Proliferation and Differentiation following Hypoxic-Ischemic Injury

Neural stem cell (NSC) proliferation and differentiation are required to replace neurons damaged or lost after hypoxic-ischemic events and recover brain function. Periostin (POSTN), a novel matricellular protein, plays pivotal roles in the survival, migration, and regeneration of various cell types, but its function in NSCs of neonatal rodent brain is still unknown. The purpose of this study was to investigate the role of POSTN in NSCs following hypoxia-ischemia (HI). We found that POSTN mRNA levels significantly increased in differentiating NSCs. The proliferation and differentiation of NSCs in the hippocampus is compromised in POSTN knockout mice. Moreover, NSC proliferation and differentiation into neurons and astrocytes significantly increased in cultured NSCs treated with recombinant POSTN. Consistently, injection of POSTN into neonatal hypoxic-ischemic rat brains stimulated NSC proliferation and differentiation in the subventricular and subgranular zones after 7 and 14 days of brain injury. Lastly, POSTN treatment significantly improved the spatial learning deficits of rats subjected to HI. These results suggest that POSTN significantly enhances NSC proliferation and differentiation after HI, and provides new insights into therapeutic strategies for the treatment of hypoxic-ischemic encephalopathy.

ERBB2 triggers mammalian heart regeneration by promoting cardiomyocyte dedifferentiation and proliferation

The murine neonatal heart can regenerate after injury through cardiomyocyte (CM) proliferation, although this capacity markedly diminishes after the first week of life. Neuregulin-1 (NRG1) administration has been proposed as a strategy to promote cardiac regeneration. Here, using loss- and gain-of-function genetic tools, we explore the role of the NRG1 co-receptor ERBB2 in cardiac regeneration. NRG1-induced CM proliferation diminished one week after birth owing to a reduction in ERBB2 expression. CM-specific Erbb2 knockout revealed that ERBB2 is required for CM proliferation at embryonic/neonatal stages. Induction of a constitutively active ERBB2 (caERBB2) in neonatal, juvenile and adult CMs resulted in cardiomegaly, characterized by extensive CM hypertrophy, dedifferentiation and proliferation, differentially mediated by ERK, AKT and GSK3β/β-catenin signalling pathways. Transient induction of caERBB2 following myocardial infarction triggered CM dedifferentiation and proliferation followed by redifferentiation and regeneration. Thus, ERBB2 is both necessary for CM proliferation and sufficient to reactivate postnatal CM proliferative and regenerative potentials.

Label-free mass spectrometric analysis of the mdx-4cv diaphragm identifies the matricellular protein periostin as a potential factor involved in dystrophinopathy-related fibrosis

Proteomic profiling plays a decisive role in the identification of novel biomarkers of muscular dystrophy and the elucidation of new pathobiochemical mechanisms that underlie progressive muscle wasting. Building on the findings of recent comparative analyses of tissue samples and body fluids from dystrophic animals and patients afflicted with Duchenne muscular dystrophy, we have used here label-free MS to study the severely dystrophic diaphragm from the not extensively characterized mdx-4cv mouse. This animal model of progressive muscle wasting exhibits less dystrophin-positive revertant fibers than the conventional mdx mouse, making it ideal for the future monitoring of experimental therapies. The pathoproteomic signature of the mdx-4cv diaphragm included a significant increase in the fibrosis marker collagen and related extracellular matrix proteins (asporin, decorin, dermatopontin, prolargin) and cytoskeletal proteins (desmin, filamin, obscurin, plectin, spectrin, tubulin, vimentin, vinculin), as well as decreases in proteins of ion homeostasis (parvalbumin) and the contractile apparatus (myosin-binding protein). Importantly, one of the most substantially increased proteins was identified as periostin, a matricellular component and apparent marker of fibrosis and tissue damage. Immunoblotting confirmed a considerable increase of periostin in the dystrophin-deficient diaphragm from both mdx and mdx-4cv mice, suggesting an involvement of this matricellular protein in dystrophinopathy-related fibrosis.

Drug and cell delivery for cardiac regeneration

The spectrum of ischaemic cardiomyopathy, encompassing acute myocardial infarction to congestive heart failure is a significant clinical issue in the modern era. This group of diseases is an enormous source of morbidity and mortality and underlies significant healthcare costs worldwide. Cardiac regenerative therapy, whereby pro-regenerative cells, drugs or growth factors are administered to damaged and ischaemic myocardium has demonstrated significant potential, especially preclinically. While some of these strategies have demonstrated a measure of success in clinical trials, tangible clinical translation has been slow. To date, the majority of clinical studies and a significant number of preclinical studies have utilised relatively simple delivery methods for regenerative therapeutics, such as simple systemic administration or local injection in saline carrier vehicles. Here, we review cardiac regenerative strategies with a particular focus on advanced delivery concepts as a potential means to enhance treatment efficacy and tolerability and ultimately, clinical translation. These include (i) delivery of therapeutic agents in biomaterial carriers, (ii) nanoparticulate encapsulation, (iii) multimodal therapeutic strategies and (iv) localised, minimally invasive delivery via percutaneous transcatheter systems.

Origin of cardiomyocytes in the adult heart

This review article discusses the mechanisms of cardiomyogenesis in the adult heart. They include the re-entry of cardiomyocytes into the cell cycle; dedifferentiation of pre-existing cardiomyocytes, which assume an immature replicating cell phenotype; transdifferentiation of hematopoietic stem cells into cardiomyocytes; and cardiomyocytes derived from activation and lineage specification of resident cardiac stem cells. The recognition of the origin of cardiomyocytes is of critical importance for the development of strategies capable of enhancing the growth response of the myocardium; in fact, cell therapy for the decompensated heart has to be based on the acquisition of this fundamental biological knowledge.

Possible dual role of decorin in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is characterized by chronic inflammation, which leads to pathological remodeling of the extracellular matrix. Decorin, a small leucine-rich repeat proteoglycan, has been suggested to regulate inflammation and stabilize the extracellular matrix. Therefore, the present study investigated the role of decorin in the pathogenesis of AAA. Decorin was localized in the aortic adventitia under normal conditions in both mice and humans. AAA was induced in mice using CaCl2 treatment. Initially, decorin protein levels decreased, but as AAA progressed decorin levels increased in all layers. Local administration of exogenous decorin prevented the development of CaCl2-induced AAA. However, decorin was highly expressed in the degenerative lesions of human AAA walls, and this expression positively correlated with matrix metalloproteinase (MMP)-9 expression. In cell culture experiments, the addition of decorin inhibited secretion of MMP-9 in vascular smooth muscle cells, but had the opposite effect in macrophages. The results suggest that decorin plays a dual role in AAA. Adventitial decorin in normal aorta may protect against the development of AAA, but macrophages expressing decorin in AAA walls may facilitate the progression of AAA by up-regulating MMP-9 secretion.

Periostin accelerates bone healing mediated by human mesenchymal stem cell-embedded hydroxyapatite/tricalcium phosphate scaffold

BACKGROUND

Periostin, an extracellular matrix protein, is expressed in bone, more specifically, the periosteum and periodontal ligaments, and plays a key role in formation and metabolism of bone tissues. Human adipose tissue-derived mesenchymal stem cells (hASCs) have been reported to differentiate into osteoblasts and stimulate bone repair. However, the role of periostin in hASC-mediated bone healing has not been clarified. In the current study, we examined the effect of periostin on bone healing capacity of hASCs in a critical size calvarial defect model.

METHODS AND RESULTS

Recombinant periostin protein stimulated migration, adhesion, and proliferation of hASCs in vitro. Implantation of either hASCs or periostin resulted in slight, but not significant, stimulation of bone healing, whereas co-implantation of hASCs together with periostin further potentiated bone healing. In addition, the number of Ki67-positive proliferating cells was significantly increased in calvarial defects by co-implantation of both hASCs and periostin. Consistently, proliferation of administered hASCs was stimulated by co-implantation with periostin in vivo. In addition, co-delivery of hASCs with periostin resulted in markedly increased numbers of CD31-positive endothelial cells and α-SMA-positive arterioles in calvarial defects.

CONCLUSIONS

These results suggest that recombinant periostin potentiates hASC-mediated bone healing by stimulating proliferation of transplanted hASCs and angiogenesis in calvarial defects.

Programming and reprogramming a human heart cell

The latest discoveries and advanced knowledge in the fields of stem cell biology and developmental cardiology hold great promise for cardiac regenerative medicine, enabling researchers to design novel therapeutic tools and approaches to regenerate cardiac muscle for diseased hearts. However, progress in this arena has been hampered by a lack of reproducible and convincing evidence, which at best has yielded modest outcomes and is still far from clinical practice. To address current controversies and move cardiac regenerative therapeutics forward, it is crucial to gain a deeper understanding of the key cellular and molecular programs involved in human cardiogenesis and cardiac regeneration. In this review, we consider the fundamental principles that govern the "programming" and "reprogramming" of a human heart cell and discuss updated therapeutic strategies to regenerate a damaged heart.

Using exercise to measure and modify cardiac function

Exercise is the archetype of physiologic demands placed on the cardiovascular system. Acute responses provide an informative assessment of cardiovascular function and fitness, while repeated exercise promotes cardiovascular health and evokes important molecular, structural, and functional changes contributing to its effects in primary and secondary prevention. Here we examine the use of exercise in murine models, both as a phenotypic assay and as a provocative intervention. We first review the advantages and limitations of exercise testing for assessing cardiac function, then highlight the cardiac structural and cellular changes elicited by chronic exercise and key molecular pathways that mediate these effects.

Periostin expression contributes to cortical bone loss during unloading

Periostin (a product of Postn gene) is a matricellular protein which is increased in periosteal osteoblasts and osteocytes upon mechanical stimulation. We previously reported that periostin-deficient mice (Postn(-/-)) have low bone mass and a diminished response to physical activity due to a lack of sclerostin (a product of Sost gene) inhibition by mechanical loading. Here we hypothesized that periostin could play a central role in the control of bone loss during unloading induced by hindlimb suspension (HU). In Postn(+/+) mice (wildtype littermate), HU significantly decreased femur BMD, as well as trabecular BV/TV and thickness (Tb.Th). Cortical bone volume and thickness at the femoral midshaft, also significantly decreased. These changes were explained by an inhibition of endocortical and periosteal bone formation activity and correlated with a decrease of Postn expression and a consecutive increase in Sost early after HU. Whereas trabecular bone loss in Postn(-/-) mice was comparable to Postn(+/+) mice, HU did not significantly alter cortical bone microstructure and strength in Postn(-/-) mice. Bone formation remained unchanged in these mice, as Sost did not increase in the absence of periostin. In contrast, changes in Dkk1, Rankl and Opg expression in response to HU were similar to Postn(+/+) mice, indicating that changes in periostin expression were quite specifically related to changes in Sost. In conclusion, HU inhibits periostin expression, which in turn plays an important role in cortical bone loss through an increase in Sost. These results further indicate that periostin is an essential mediator of cortical bone response to mechanical forces (loading and unloading).

Matricellular protein periostin contributes to hepatic inflammation and fibrosis

Periostin actively contributes to tissue injury, fibrosis, atherosclerosis, and inflammatory diseases; however, its role in hepatic fibrosis is unclear. Herein, we revealed that periostin expression was significantly up-regulated in carbon tetrachloride- and bile duct ligation-induced mice with acute and chronic liver fibrosis. Deficiency in periostin abrogated the development of liver fibrosis in mice. Carbon tetrachloride treatment significantly increased α-smooth muscle actin, fibronectin, and collagen I levels in wild-type mice, which were unaffected in periostin-knockout mice. Periostin-deficient mice showed a significantly reduced area of collagen deposition and decreased levels of serum alanine aminotransferase and aspartate aminotransferase compared with wild-type mice after 2 weeks of carbon tetrachloride administration. Chemokine ligand 2, IL-6, IL-1β, tumor necrosis factor-α, and tissue inhibitor of metalloproteinases 1 mRNA levels were significantly lower in periostin-deficient mice than in wild-type mice after carbon tetrachloride treatment. Periostin colocalized with hepatic stellate cell-derived collagen I and α-smooth muscle actin in mouse acute and chronic fibrotic liver tissues. Transforming growth factor (TGF)-β1 markedly induced periostin expression in primary mouse hepatic stellate cells. Periostin-deficient mice showed significantly lower levels of TGF-β1 and TGF-β2 compared with wild-type mice after carbon tetrachloride treatment. High levels of periostin in patients with acute or chronic hepatitis correlated with TGF-β1 and TGF-β2 expression in serum from patients with hepatitis. Data indicate that periostin is a novel mediator of hepatic fibrosis development.

Macro advances in microRNAs and myocardial regeneration

PURPOSE OF REVIEW

Myocardial injury and disease often result in heart failure, a major cause of death worldwide. To achieve myocardial regeneration and foster development of efficient therapeutics for cardiac injury, it is essential to uncover molecular mechanisms that will promote myocardial regeneration. In this review, we examine the latest progress made in elucidation of the roles of small non-coding RNAs called microRNAs (miRs) in myocardial regeneration.

RECENT FINDINGS

Promising progress has been made in studying cardiac regeneration. Several miRs, which include miR-590, miR-199a, miR-17-92 cluster, miR-199a-214 cluster, miR-34a, and miR-15 family, have been recently shown to play an essential role in myocardial regeneration by regulating different processes during cardiac repair, including cell death, proliferation, and metabolism. For example, miR-590 promotes cardiac regeneration through activating cardiomyocyte proliferation, whereas miR-34a inhibits cardiac repair through inducing apoptosis.

SUMMARY

These recent findings shed new light on our understanding of myocardial regeneration and suggest potential novel therapeutic targets to treat cardiac disease.

Transcriptional reversion of cardiac myocyte fate during mammalian cardiac regeneration

RATIONALE

Neonatal mice have the capacity to regenerate their hearts in response to injury, but this potential is lost after the first week of life. The transcriptional changes that underpin mammalian cardiac regeneration have not been fully characterized at the molecular level.

OBJECTIVE

The objectives of our study were to determine whether myocytes revert the transcriptional phenotype to a less differentiated state during regeneration and to systematically interrogate the transcriptional data to identify and validate potential regulators of this process.

METHODS AND RESULTS

We derived a core transcriptional signature of injury-induced cardiac myocyte (CM) regeneration in mouse by comparing global transcriptional programs in a dynamic model of in vitro and in vivo CM differentiation, in vitro CM explant model, as well as a neonatal heart resection model. The regenerating mouse heart revealed a transcriptional reversion of CM differentiation processes, including reactivation of latent developmental programs similar to those observed during destabilization of a mature CM phenotype in the explant model. We identified potential upstream regulators of the core network, including interleukin 13, which induced CM cell cycle entry and STAT6/STAT3 signaling in vitro. We demonstrate that STAT3/periostin and STAT6 signaling are critical mediators of interleukin 13 signaling in CMs. These downstream signaling molecules are also modulated in the regenerating mouse heart.

CONCLUSIONS

Our work reveals new insights into the transcriptional regulation of mammalian cardiac regeneration and provides the founding circuitry for identifying potential regulators for stimulating heart regeneration.

How to make a cardiomyocyte

During development, cardiogenesis is orchestrated by a family of heart progenitors that build distinct regions of the heart. Each region contains diverse cell types that assemble to form the complex structures of the individual cardiac compartments. Cardiomyocytes are the main cell type found in the heart and ensure contraction of the chambers and efficient blood flow throughout the body. Injury to the cardiac muscle often leads to heart failure due to the loss of a large number of cardiomyocytes and its limited intrinsic capacity to regenerate the damaged tissue, making it one of the leading causes of morbidity and mortality worldwide. In this Primer we discuss how insights into the molecular and cellular framework underlying cardiac development can be used to guide the in vitro specification of cardiomyocytes, whether by directed differentiation of pluripotent stem cells or via direct lineage conversion. Additional strategies to generate cardiomyocytes in situ, such as reactivation of endogenous cardiac progenitors and induction of cardiomyocyte proliferation, will also be discussed.

Cardiac regeneration based on mechanisms of cardiomyocyte proliferation and differentiation

Cardiomyocyte proliferation and progenitor differentiation are endogenous mechanisms of myocardial development. Cardiomyocytes continue to proliferate in mammals for part of post-natal development. In adult mammals under homeostatic conditions, cardiomyocytes proliferate at an extremely low rate. Because the mechanisms of cardiomyocyte generation provide potential targets for stimulating myocardial regeneration, a deep understanding is required for developing such strategies. We will discuss approaches for examining cardiomyocyte regeneration, review the specific advantages, challenges, and controversies, and recommend approaches for interpretation of results. We will also draw parallels between developmental and regenerative principles of these mechanisms and how they could be targeted for treating heart failure.

Alpha-catenins control cardiomyocyte proliferation by regulating Yap activity

RATIONALE

Shortly after birth, muscle cells of the mammalian heart lose their ability to divide. Thus, they are unable to effectively replace dying cells in the injured heart. The recent discovery that the transcriptional coactivator Yes-associated protein (Yap) is necessary and sufficient for cardiomyocyte proliferation has gained considerable attention. However, the upstream regulators and signaling pathways that control Yap activity in the heart are poorly understood.

OBJECTIVE

To investigate the role of α-catenins in the heart using cardiac-specific αE- and αT-catenin double knockout mice.

METHODS AND RESULTS

We used 2 cardiac-specific Cre transgenes to delete both αE-catenin (Ctnna1) and αT-catenin (Ctnna3) genes either in the perinatal or in the adult heart. Perinatal depletion of α-catenins increased cardiomyocyte number in the postnatal heart. Increased nuclear Yap and the cell cycle regulator cyclin D1 accompanied cardiomyocyte proliferation in the α-catenin double knockout hearts. Fetal genes were increased in the α-catenin double knockout hearts indicating a less mature cardiac gene expression profile. Knockdown of α-catenins in neonatal rat cardiomyocytes also resulted in increased proliferation, which could be blocked by knockdown of Yap. Finally, inactivation of α-catenins in the adult heart using an inducible Cre led to increased nuclear Yap and cardiomyocyte proliferation and improved contractility after myocardial infarction.

CONCLUSIONS

These studies demonstrate that α-catenins are critical regulators of Yap, a transcriptional coactivator essential for cardiomyocyte proliferation. Furthermore, we provide proof of concept that inhibiting α-catenins might be a useful strategy to promote myocardial regeneration after injury.

Transcriptional response to cardiac injury in the zebrafish: systematic identification of genes with highly concordant activity across in vivo models

Background

Zebrafish is a clinically-relevant model of heart regeneration. Unlike mammals, it has a remarkable heart repair capacity after injury, and promises novel translational applications. Amputation and cryoinjury models are key research tools for understanding injury response and regeneration in vivo. An understanding of the transcriptional responses following injury is needed to identify key players of heart tissue repair, as well as potential targets for boosting this property in humans.

Results

We investigated amputation and cryoinjury in vivo models of heart damage in the zebrafish through unbiased, integrative analyses of independent molecular datasets. To detect genes with potential biological roles, we derived computational prediction models with microarray data from heart amputation experiments. We focused on a top-ranked set of genes highly activated in the early post-injury stage, whose activity was further verified in independent microarray datasets. Next, we performed independent validations of expression responses with qPCR in a cryoinjury model. Across in vivo models, the top candidates showed highly concordant responses at 1 and 3 days post-injury, which highlights the predictive power of our analysis strategies and the possible biological relevance of these genes. Top candidates are significantly involved in cell fate specification and differentiation, and include heart failure markers such as periostin, as well as potential new targets for heart regeneration. For example, ptgis and ca2 were overexpressed, while usp2a, a regulator of the p53 pathway, was down-regulated in our in vivo models. Interestingly, a high activity of ptgis and ca2 has been previously observed in failing hearts from rats and humans.

Conclusions

We identified genes with potential critical roles in the response to cardiac damage in the zebrafish. Their transcriptional activities are reproducible in different in vivo models of cardiac injury.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-852) contains supplementary material, which is available to authorized users.

Single intracoronary injection of encapsulated antagomir-92a promotes angiogenesis and prevents adverse infarct remodeling

Background

Small and large preclinical animal models have shown that antagomir‐92a‐based therapy reduces early postischemic loss of function, but its effect on postinfarction remodeling is not known. In addition, the reported remote miR‐92a inhibition in noncardiac organs prevents the translation of nonvectorized miR‐targeted therapy to the clinical setting. We investigated whether a single intracoronary administration of antagomir‐92a encapsulated in microspheres could prevent deleterious remodeling of myocardium 1 month after acute myocardial infarction AUTHOR: Should “acute” be added before “myocardial infarction” (since abbreviation is AMI)? Also check at first mention in main text (AMI) without adverse effects.

Methods and Results

In a percutaneous pig model of reperfused AMI, a single intracoronary administration of antagomir‐92a encapsulated in specific microspheres (9 μm poly‐d,‐lactide‐co‐glycolide [PLGA]) inhibited miR‐92a in a local, selective, and sustained manner (n=3 pigs euthanized 1, 3, and 10 days after treatment; 8×, 2×, and 5×‐fold inhibition at 1, 3, and 10 days). Downregulation of miR‐92a resulted in significant vessel growth (n=27 adult minipigs randomly allocated to blind receive encapsulated antagomir‐92a, encapsulated placebo, or saline [n=8, 9, 9]; P=0.001), reduced regional wall‐motion dysfunction (P=0.03), and prevented adverse remodeling in the infarct area 1 month after injury (P=0.03). Intracoronary injection of microspheres had no significant adverse effect in downstream myocardium in healthy pigs (n=2), and fluorescein isothiocyanate albumin‐PLGA microspheres were not found in myocardium outside the left anterior descending coronary artery territory (n=4) or in other organs (n=2).

Conclusions

Early single intracoronary administration of encapsulated antagomir‐92a in an adult pig model of reperfused AMI prevents left ventricular remodeling with no local or distant adverse effects, emerging as a promising therapeutic approach to translate to patients who suffer a large AMI.

Ageing related periostin expression increase from cardiac fibroblasts promotes cardiomyocytes senescent

Periostin, as an extracellular matrix (ECM) protein, plays a critical role in myocardial fibrosis and also might be involved in the heart inflammatory process since it is a downstream molecule of IL4 and IL13. Considering the possible important role of periostin in heart aging, this study explored periostin expression pattern in both rat and human, the effect of periostin expression on cardiomyocyte senescent and expression of three cytokines (IL13, IL4 and IL6) in different age groups of human. This study found heart aging is associated with increased expression of periostin from cardiac fibroblasts and serum inflammatory cytokines (IL13 and IL6). Excessive periostin expression contributed to cardiomyocyte senescent, which could be alleviated through blocking the Ang-II-TGF β1-MAPK/ERK pathway. Thus, periostin might play an important role in a vicious circle (aging-fibrosis-inflammation-aging) of heart through promoting myocardial fibrosis and cardiomyocyte senescent simultaneously. It is a potential aging marker that could be directly measured in serum.

Depolarization of Cellular Resting Membrane Potential Promotes Neonatal Cardiomyocyte Proliferation In Vitro

Cardiomyocytes (CMs) undergo a rapid transition from hyperplastic to hypertrophic growth soon after birth, which is a major challenge to the development of engineered cardiac tissue for pediatric patients. Resting membrane potential (V_mem) has been shown to play an important role in cell differentiation and proliferation during development. We hypothesized that depolarization of neonatal CMs would stimulate or maintain CM proliferation in vitro. To test our hypothesis, we isolated postnatal day 3 neonatal rat CMs and subjected them to sustained depolarization via the addition of potassium gluconate or Ouabain to the culture medium. Cell density and CM percentage measurements demonstrated an increase in mitotic CMs along with a ~2 fold increase in CM numbers with depolarization. In addition, depolarization led to an increase in cells in G2 and S phase, indicating increased proliferation, as measured by flow cytometry. Surprisingly depolarization of V_mem with either treatment led to inhibition of proliferation in cardiac fibroblasts. This effect is abrogated when the study was carried out on postnatal day 7 neonatal CMs, which are less proliferative, indicating that the likely mechanism of depolarization is the maintenance of the proliferating CM population. In summary, our findings suggest that depolarization maintains postnatal CM proliferation and may be a novel approach to encourage growth of engineered tissue and cardiac regeneration in pediatric patients.

Characterization of a novel periodontal ligament-specific periostin isoform

Periostin is a mesenchymal cell marker predominantly expressed in collagen-rich fibrous connective tissues, including heart valves, tendons, perichondrium, periosteum, and periodontal ligament (PDL). Knockdown of periostin expression in mice results in early-onset periodontitis and failure of cardiac healing after acute myocardial infarction, suggesting that periostin is essential for connective tissue homeostasis and regeneration. However, its role(s) in periodontal tissues has not yet been fully defined. In this study, we describe a novel human isoform of periostin (PDL-POSTN). Isoform-specific analysis by reverse-transcription polymerase chain-reaction (RT-PCR) revealed that PDL-POSTN was predominantly expressed in the PDL, with much lower expression in other tissues and organs. A PDL cell line transfected with PDL-POSTN showed enhanced alkaline phosphatase (ALPase) activity and calcified nodule formation, compared with cells transfected with the full-length periostin isoform. A neutralizing antibody against integrin-αv inhibited both ALPase activity and calcified nodule formation in cells transfected with PDL-POSTN. Furthermore, co-immunoprecipitation assays revealed that PDL-POSTN bound to integrin αvβ3 more strongly than the common isoform of periostin, resulting in strong activation of the integrin αvβ3-focal adhesion kinase (FAK) signaling pathway. These results suggest that PDL-POSTN positively regulates cytodifferentiation and mineralization in PDL cells through integrin αvβ3.

A neonatal blueprint for cardiac regeneration

Adult mammals undergo minimal regeneration following cardiac injury, which severely compromises cardiac function and contributes to the ongoing burden of heart failure. In contrast, the mammalian heart retains a transient capacity for cardiac regeneration during fetal and early neonatal life. Recent studies have established the importance of several evolutionarily conserved mechanisms for heart regeneration in lower vertebrates and neonatal mammals including induction of cardiomyocyte proliferation, epicardial cell activation, angiogenesis, extracellular matrix deposition and immune cell infiltration. In this review, we provide an up-to-date account of the molecular and cellular basis for cardiac regeneration in lower vertebrates and neonatal mammals. The historical context for these recent findings and their ramifications for the future development of cardiac regenerative therapies are also discussed.

Expressions and roles of periostin in otolaryngological diseases

Periostin is a 90-kDa member of the fasciclin-containing family; it functions as part of matricellular proteins, and its production by airway epithelial cells is induced by IL-4 and IL-13. Periostin is secreted by fibroblasts and upregulated in the airway epithelia of patients with bronchial asthma; it is considered to contribute to remodeling under this pathological condition. However, despite many studies in diverse research areas, our overall understanding of this intriguing molecule is still inadequate. Here, we integrate the available evidence on periostin expression and its roles in otolaryngological diseases, including allergic rhinitis, chronic rhinosinusitis with nasal polyps, aspirin-induced asthma, organized hematoma, eosinophilic otitis media, and IgG4-related disease. Periostin might be involved as an important structural mediator in pathological processes such as insult and injury, Th2-driven inflammation, extracellular matrix restructuring, fibrosclerosis, tumor angiogenesis, and tissue remodeling.

Comparative study of directional differentiation of human and mouse embryonic stem cells into cardiomyocytes

This comparative study investigates the method, efficiency, and anti-hypoxic ability of cardiomyocytes, directionally induced from human (h) and mouse (m) embryonic stem cells (ESCs). hESCs were induced into cardiomyocytes by suspension culture, without inducers, or adherent culture using the inducers activin A and BMP4. mESCs were induced into cardiomyocytes by hanging-drop method, without inducers or induced with vitamin C. All four methods successfully induced ESCs to differentiate into cardiomyocytes. There was a significant difference between groups with and without inducers. A significant difference was found between mESC and hESC groups with inducers. The average beating frequency of cardiomyocytes differentiated from hESC was lower than cardiomyocytes differentiated from mESC, while the average beating frequency of cardiomyocytes differentiated from the same cell line, despite different culture methods, did not differ. Beating cardiomyocytes of each group were positive for cTnT staining. Spontaneous action potentials of beating cardiomyocytes were detected by patch-clamp experiments in each group. Different apoptotic ratios were detected in beating cardiomyocytes in each group and the difference between cardiomyocytes induced from mESCs and hESCs was statistically significant. The differentiation efficiencies in the groups without inducers were significantly higher than those without inducers. The induction of mESCs was more simple and efficient compared with hESCs. Without the presence of other protective factors, the anti-hypoxic ability of cardiomyocytes induced from hESCs was stronger and the beating times were longer in vitro compared with mESCs.

Therapeutic angiogenesis in a murine model of limb ischemia by recombinant periostin and its fasciclin I domain

Periostin, an extracellular matrix protein, is expressed in injured tissues, such as the heart with myocardial infarction, and promotes angiogenesis and tissue repair. However, the molecular mechanism associated with periostin-stimulated angiogenesis and tissue repair is still unclear. In order to clarify the role of periostin in neovascularization, we examined the effect of periostin in angiogenic potentials of human endothelial colony forming cells (ECFCs) in vitro and in an ischemic limb animal model. Recombinant periostin protein stimulated the migration and tube formation of ECFCs. To identify the functional domains of periostin implicated in angiogenesis, five fragments of periostin, including four repeating FAS-1 domains and a carboxyl terminal domain, were expressed in Escherichia coli and purified to homogeneity. Of the five different domains, the first FAS-1 domain stimulated the migration and tube formation of human ECFCs as potent as the whole periostin. Chemotactic migration of ECFCs induced by the full length and the first FAS-1 domain of periostin was abrogated by blocking antibodies against β3 and β5 integrins. Intramuscular injection of the full length and the first FAS-1 domain of periostin into the ischemic hindlimb of mice attenuated severe limb loss and promoted blood perfusion and homing of intravenously administered ECFCs to the ischemic limb. These results suggest that the first FAS-1 domain is responsible for periostin-induced migration and angiogenesis and it can be used as a therapeutic tool for treatment of peripheral artery occlusive disease by stimulating homing of ECFCs.

Novel therapeutic strategies for cardioprotection

The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application.

Harnessing Hippo in the heart: Hippo/Yap signaling and applications to heart regeneration and rejuvenation

The adult mammalian heart exhibits limited regenerative capacity after myocardial injury, a shortcoming that is responsible for the current lack of definitive treatments for heart failure. A search for approaches that might enhance adult heart regeneration has led to interest in the Hippo/Yap signaling pathway, a recently discovered signaling pathway that regulates cell proliferation and organ growth. Here we provide a brief overview of the Hippo/Yap pathway and its known roles in the developing and adult heart. We discuss the implications of Hippo/Yap signaling for regulation of cardiomyocyte death and regeneration.

Signalling between microvascular endothelium and cardiomyocytes through neuregulin

Heterocellular communication in the heart is an important mechanism for matching circulatory demands with cardiac structure and function, and neuregulins (Nrgs) play an important role in transducing this signal between the hearts' vasculature and musculature. Here, we review the current knowledge regarding Nrgs, explaining their roles in transducing signals between the heart's microvasculature and cardiomyocytes. We highlight intriguing areas being investigated for developing new, Nrg-mediated strategies to heal the heart in acquired and congenital heart diseases, and note avenues for future research.

The cardiac stem cell compartment is indispensable for myocardial cell homeostasis, repair and regeneration in the adult

Resident cardiac stem cells in embryonic, neonatal and adult mammalian heart have been identified by different membrane markers and transcription factors. However, despite a flurry of publications no consensus has been reached on the identity and actual regenerative effects of the adult cardiac stem cells. Intensive research on the adult mammalian heart's capacity for self-renewal of its muscle cell mass has led to a consensus that new cardiomyocytes (CMs) are indeed formed throughout adult mammalian life albeit at a disputed frequency. The physiological significance of this renewal, the origin of the new CMs, and the rate of adult CM turnover are still highly debated. Myocyte replacement, particularly after injury, was originally attributed to differentiation of a stem cell compartment. More recently, it has been reported that CMs are mainly replaced by the division of pre-existing post-mitotic CMs. These latter results, if confirmed, would shift the target of regenerative therapy toward boosting mature CM cell-cycle re-entry. Despite this controversy, it is documented that the adult endogenous c-kit(pos) cardiac stem cells (c-kit(pos) eCSCs) participate in adaptations to myocardial stress, and, when transplanted into the myocardium, regenerate most cardiomyocytes and microvasculature lost in an infarct. Nevertheless, the in situ myogenic potential of adult c-kit(pos) cardiac cells has been questioned. To revisit the regenerative potential of c-kit(pos) eCSCs, we have recently employed experimental protocols of severe diffuse myocardial damage in combination with several genetic murine models and cell transplantation approaches showing that eCSCs are necessary and sufficient for CM regeneration, leading to complete cellular, anatomical, and functional myocardial recovery. Here we will review the available data on adult eCSC biology and their regenerative potential placing it in the context of the different claimed mechanisms of CM replacement. These data are in agreement with and have reinforced our view that most CMs are replaced by de novo CM formation through the activation, myogenic commitment and specification of the eCSC cohort.

Dynamic changes in myocardial matrix and relevance to disease: translational perspectives

The cardiac extracellular matrix (ECM) provides the architectural scaffold to support efficient contraction and relaxation of cardiomyocytes. The elegant design of the ECM facilitates optimal force transduction, electric transmission, intercellular communication, and metabolic exchange within the myocardial microenvironment. In the setting of increased wall stress, injury, or disease, the ECM can undergo a series of dynamic changes that lead to favorable chamber remodeling and functional adaptation. Over time, sustained matrix remodeling can impair diastolic and systolic function caused by excess deposition of interstitial fibrous tissue. These pathological alterations in ECM structure/function are considered central to the evolution of adverse cardiac remodeling and the development of heart failure. This review discusses the complex dynamics of the cardiac ECM in the setting of myocardial infarction, pressure overload, and volume overload. We also summarize the current status of ECM biomarkers that may have clinical value in prognosticating cardiac disease progression in patients. Finally, we discuss the most current status of drugs under evaluation for use in cardiac fibrosis.

Recent advances in heart regeneration

Although cardiac stem cells (CSCs) and tissue engineering are very promising for cardiac regenerative medicine, studies with model organisms for heart regeneration will provide alternative therapeutic targets and opportunities. Here, we present a review on heart regeneration, with a particular focus on the most recent work in mouse and zebrafish. We attempt to summarize the recent progresses and bottlenecks of CSCs and tissue engineering for heart regeneration; and emphasize what we have learned from mouse and zebrafish regenerative models on discovering crucial genetic and epigenetic factors for stimulating heart regeneration; and speculate the potential application of these regenerative factors for heart failure. A brief perspective highlights several important and promising research directions in this exciting field.

Astroglial-derived periostin promotes axonal regeneration after spinal cord injury

Traumatic spinal cord injury (SCI) results in a cascade of tissue responses leading to cell death, axonal degeneration, and glial scar formation, exacerbating the already hostile environment and further inhibiting axon regeneration. Overcoming these inhibitory cues and promoting axonal regeneration is one of the primary targets in developing a cure for SCI. Previously, we demonstrated that transplantation of bone morphogenetic protein (BMP)-induced astrocytes derived from embryonic glial-restricted precursors (GDAs(BMP)) promotes extensive axonal growth and motor function recovery in a rodent spinal cord injury model. Here, we identify periostin (POSTN), a secreted protein, as a key component of GDA(BMP)-induced axonal regeneration. POSTN is highly expressed by GDAs(BMP) and the perturbation of POSTN expression by shRNA diminished GDA(BMP)-induced neurite extension in vitro. We also found that recombinant POSTN is sufficient to overcome the inhibitory effect of scar-associated molecules and promote neurite extension in vitro by signaling through focal adhesion kinase and Akt. Furthermore, transplantation of POSTN-deficient GDAs(BMP) into the injured rat spinal cord resulted in compromised axonal regeneration, indicating that POSTN plays an essential role in GDA(BMP)-mediated axonal regeneration. This finding reveals not only one of the major mechanisms underlying GDA(BMP)-dependent recovery from SCI, but also the potential of POSTN as a therapeutic agent for traumatic injury of the CNS.

The role of periostin in tissue remodeling across health and disease

Periostin, also termed osteoblast-specific factor 2, is a matricellular protein with known functions in osteology, tissue repair, oncology, cardiovascular and respiratory systems, and in various inflammatory settings. However, most of the research to date has been conducted in divergent and circumscribed areas meaning that the overall understanding of this intriguing molecule remains fragmented. Here, we integrate the available evidence on periostin expression, its normal role in development, and whether it plays a similar function during pathologic repair, regeneration, and disease in order to bring together the different research fields in which periostin investigations are ongoing. In spite of the seemingly disparate roles of periostin in health and disease, tissue remodeling as a response to insult/injury is emerging as a common functional denominator of this matricellular molecule. Periostin is transiently upregulated during cell fate changes, either physiologic or pathologic. Combining observations from various conditions, a common pattern of events can be suggested, including periostin localization during development, insult and injury, epithelial-mesenchymal transition, extracellular matrix restructuring, and remodeling. We propose mesenchymal remodeling as an overarching role for the matricellular protein periostin, across physiology and disease. Periostin may be seen as an important structural mediator, balancing appropriate versus inappropriate tissue adaption in response to insult/injury.

The expression and immunohistochemical localization of periostin in odontogenic tumors of mixed epithelial/mesenchymal origin

OBJECTIVE

The object of this study was to determine the expression and localization of periostin in the major mixed odontogenic tumors and to correlate any differential staining of the mesenchymal components to the interrelationship of these tumors.

STUDY DESIGN

Five ameloblastic fibromas, 8 ameloblastic fibro-odontomas and 10 odontomas were assessed immunohistochemically for periostin staining. Because mesenchymal tissues were consistently present in all studied cases, these tissues were selected for statistical analysis of differential periostin staining.

RESULTS

Periostin was variably localized to the mesenchymal component of the tumors as well as to preameloblasts and ameloblasts. Analysis of the mesenchymal staining intensity was statistically significantly different between ameloblastic fibro-odontomas and odontomas (P < .001; Dunn multiple comparisons test).

CONCLUSIONS

Our results document periostin staining in human mixed odontogenic tumors. Statistical analysis of differential stromal staining supports the concept that the ameloblastic fibroma is a histogenetically distinct neoplasm as compared to ameloblastic fibro-odontoma and odontoma.

Periostin in allergic inflammation

Periostin, an extracellular matrix protein belonging to the fasciclin family, has been shown to play a critical role in the process of remodeling during tissue/organ development or repair. Periostin functions as a matricellular protein in cell activation by binding to their receptors on cell surface, thereby exerting its biological activities. After we found that periostin is a downstream molecule of interleukin (IL)-4 and IL-13, signature cytokines of type 2 immune responses, we showed that periostin is a component of subepithelial fibrosis in bronchial asthma, the first formal proof that periostin is involved in allergic inflammation. Subsequently, a great deal of evidence has accumulated demonstrating the significance of periostin in allergic inflammation. It is of note that in skin tissues, periostin is critical for amplification and persistence of allergic inflammation by communicating between fibroblasts and keratinocytes. Furthermore, periostin has been applied to development of novel diagnostics or therapeutic agents for allergic diseases. Serum periostin can reflect local production of periostin in inflamed lesions induced by Th2-type immune responses and also can predict the efficacy of Th2 antagonists against bronchial asthma. Blocking the interaction between periostin and its receptor, αv integrin, or down-regulating the periostin expression shows improvement of periostin-induced inflammation in mouse models or in in vitro systems. It is hoped that diagnostics or therapeutic agents targeting periostin will be of practical use in the near future.

Matricellular proteins and biomaterials

Biomaterials are essential to modern medicine as components of reconstructive implants, implantable sensors, and vehicles for localized drug delivery. Advances in biomaterials have led to progression from simply making implants that are nontoxic to making implants that are specifically designed to elicit particular functions within the host. The interaction of implants and the extracellular matrix during the foreign body response is a growing area of concern for the field of biomaterials, because it can lead to implant failure. Expression of matricellular proteins is modulated during the foreign body response and these proteins interact with biomaterials. The design of biomaterials to specifically alter the levels of matricellular proteins surrounding implants provides a new avenue for the design and fabrication of biomimetic biomaterials.

Mechanisms of exercise-induced cardiac growth

Exercise is a well-established intervention for the prevention and treatment of cardiovascular disease. Increase in cardiomyocyte size is likely to be the central mechanism of exercise-induced cardiac growth, but recent research also supports a role for the generation of new cardiomyocytes as a contributor to physiological cardiac growth. Other cardiac cell types also respond to exercise. For example, endothelial cells are important for the regulation of large vessels and expansion of microvasculature in meeting demands of the growing heart. Cardiac fibroblasts are known to generate and respond to important signals from their environment, but their role in exercise is less well defined. Therefore, cardiac growth relies on complex, finely regulated and interdependent signaling pathways as well as cross-talk among cardiac cell types.