Scaffolds from Self-Assembling Tetrapeptides Support 3D Spreading, Osteogenic Differentiation, and Angiogenesis of Mesenchymal Stem Cells

The apparent rise of bone disorders demands advanced treatment protocols involving tissue engineering. Here, we describe self-assembling tetrapeptide scaffolds for the growth and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The rationally designed peptides are synthetic amphiphilic self-assembling peptides composed of four amino acids that are nontoxic. These tetrapeptides can quickly solidify to nanofibrous hydrogels that resemble the extracellular matrix and provide a three-dimensional (3D) environment for cells with suitable mechanical properties. Furthermore, we can easily tune the stiffness of these peptide hydrogels by just increasing the peptide concentration, thus providing a wide range of peptide hydrogels with different stiffnesses for 3D cell culture applications. Since successful bone regeneration requires both osteogenesis and vascularization, our scaffold was found to be able to promote angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro. The results presented suggest that ultrashort peptide hydrogels are promising candidates for applications in bone tissue engineering.

Preconditioning of Human Skeletal Myoblast with Stromal Cell-derived Factor-1α Promotes Cytoprotective Effects against Oxidative and Anoxic Stress

BACKGROUND AND OBJECTIVES

The incidence of human autologous transplanted skeletal myoblast (SkM) cell death in ischemic myocardium was higher in the first few days after cell therapy. We proposed that human SkM treated by human stromal cell-derived factor (SDF-1α) protein or tranfected by SDF-1α, precondition them against oxidative or anoxic injury.

METHODS AND RESULTS

The purification of human SkM (80∼90%) culture was assessed for desmin and CXCR4 expression using immunostaining and flow cytometry respectively. Cells were transfected to overexpress SDF-1α or treated with rSDF-1α (10∼200 ng/ml, 1∼4 h) were either exposed to anoxia or treated with 100μM H2O2 for different time periods (1∼6 h anoxia) (1∼3 h H2O2). Optimized conditions for transfection of SDF-1α gene into human SkM were achieved, using FuGene(TM)6/phSDF-1α(3：2 v/w, 4 h transfection) with 125μ M ZnCl2 (p＜ 0.001), up to 7 days post-transfection as compared with transfected SkM without ZnCl2 and non-transfected control cells. Transfection efficiency was assessed by immunostaining, ELISA, western blots and PCR. LDH analysis showed significant decrease in release of LDH after exposure to 6 h anoxia or 100μ M H2O2 for 2 h as compared with the normal un-treated or un-transfected SkM (p＜ 0.001). In western blots assay, SDF-1α over-expressing human SkM or treated with rSDF-1α induced marked expression of total Akt (1.2-fold) and phospho-Akt (2.7-fold), Bcl2 (1.6-fold) and VEGF (5.8-fold) after exposure to 6 h anoxia as compared with human SkM controls.

CONCLUSIONS

The preconditioning of donor transplanted human SkM with SDF-1α increased cell survival and promoted cytoprotective effect against oxidative or anoxic injury that may be an innovative approach for clinical application.

Age related changes of the extracellular matrix and stem cell maintenance

Aging is characterized by reduced tissue and organ function, regenerative capacity, and accompanied by a decrease in tissue resident stem cell numbers and a loss of potency. The impact of aging on stem cell populations differs between tissues and depends on a number of non cell-intrinsic factors, including systemic changes associated with immune system alterations, as well as senescence related changes of the local cytoarchitecture. The latter has been studied in the context of environmental niche properties required for stem cell maintenance. Here, we will discuss the impact of the extracellular matrix (ECM) on stem cell maintenance, its changes during aging and its significance for stem cell therapy. We provide an overview on ECM components and examples of age associated remodeling of the cytoarchitecture. The interaction of stem cells with the ECM will be described and the importance of an intact and hospitable ECM for stem cell maintenance, differentiation and stem cell initiated tissue repair outlined. It is concluded that a remodeled ECM due to age related inflammation, fibrosis or oxidative stress provides an inadequate environment for endogenous regeneration or stem cell therapies. Means to provide adequate ECM for stem cell therapies and endogenous regeneration and the potential of antioxidants to prevent ECM damage and promote its repair and subsequently support regeneration are discussed.

Myocardial regeneration in heart failure: integrated development of biological therapeutic approaches

Heart failure currently constitutes one of the greatest health problems in the Western world. Its incidence, far from diminishing or even remaining stable, is actually still increasing in association with the aging of the population and its lifestyle. A better knowledge of physiopathological mechanisms has allowed for the development of new therapeutic focal points and lines of research. Nevertheless, its treatment is complex and encompasses a multidisciplinary approach. Patients in an advanced stage still have a very high mortality rate in spite of receiving optimum medical care. The development of new therapeutic techniques that afford a better prognosis has therefore been essential. Of these, and leaving aside surgical treatments, myocardial regeneration by means of cellular therapy, new concepts in tissue engineering and their results, and the applications of new advances in the field of immunomodulation have all recently experienced development. In this article, the aim is to bring the latest concepts in the physiopathology and humoral response of cardiac failure up to date as well as doing the same with the therapeutic approaches in this area.

A 3D aligned microfibrous myocardial tissue construct cultured under transient perfusion

The goal of this study was to design and develop a myocardial patch to use in the repair of myocardial infarctions or to slow down tissue damage and improve long-term heart function. The basic 3D construct design involved two biodegradable macroporous tubes, to allow transport of growth media to the cells within the construct, and cell seeded, aligned fiber mats wrapped around them. The microfibrous mat housed mesenchymal stem cells (MSCs) from human umbilical cord matrix (Wharton's Jelly) aligned in parallel to each other in a similar way to cell organization in native myocardium. Aligned micron-sized fiber mats were obtained by electrospinning a polyester blend (PHBV (5% HV), P(L-D,L)LA (70:30) and poly(glycerol sebacate) (PGS)). The micron-sized electrospun parallel fibers were effective in Wharton's Jelly (WJ) MSCs alignment and the cells were able to retract the mat. The 3D construct was cultured in a microbioreactor by perfusing the growth media transiently through the macroporous tubing for two weeks and examined by fluorescence microscopy for cell distribution and preservation of alignment. The fluorescence images of thin sections of 3D constructs from static and perfused cultures confirmed enhanced cell viability, uniform cell distribution and alignment due to nutrient provision from inside the 3D structure.

Development of bioartificial myocardium using stem cells and nanobiotechnology templates

Cell-based regenerative therapy is undergoing experimental and clinical trials in cardiology, in order to limit the consequences of decreased contractile function and compliance of damaged ventricles following myocardial infarction. Over 1000 patients have been treated worldwide with cell-based procedures for myocardial regeneration. Cellular cardiomyoplasty seems to reduce the size and fibrosis of infarct scars, limit adverse postischemic remodelling, and improve diastolic function. The development of a bioartificial myocardium is a new challenge; in this approach, tissue-engineered procedures are associated with cell therapy. Organ decellularization for bioscaffolds fabrication is a new investigated concept. Nanomaterials are emerging as the main candidates to ensure the achievement of a proper instructive cellular niche with good drug release/administration properties. Investigating the electrophysiological properties of bioartificial myocardium is the challenging objective of future research, associating a multielectrode network to provide electrical stimulation could improve the coupling of grafted cells and scaffolds with host cardiomyocytes. In summary, until now stem cell transplantation has not achieved clear hemodynamic benefits for myocardial diseases. Supported by relevant scientific background, the development of myocardial tissue engineering may constitute a new avenue and hope for the treatment of myocardial diseases.

A G-CSF functionalized scaffold for stem cells seeding: a differentiating device for cardiac purposes

Myocardial infarction and its consequences represent one of the most demanding challenges in cell therapy and regenerative medicine. Transfer of skeletal myoblasts into decompensated hearts has been performed through intramyocardial injection. However, the achievements of both cardiomyocyte differentiation and precise integration of the injected cells into the myocardial wall, in order to augment synchronized contractility and avoid potentially life-threatening alterations in the electrical conduction of the heart, still remain a major target to be pursued. Recently, granulocytes colony-stimulating factor (G-CSF) fuelled the interest of researchers for its direct effect on cardiomyocytes, inhibiting both apoptosis and remodelling in the failing heart and protecting from ventricular arrhythmias through the up-regulation of connexin 43 (Cx43). We propose a tissue engineering approach concerning the fabrication of an electrospun cardiac graft functionalized with G-CSF, in order to provide the correct signalling sequence to orientate myoblast differentiation and exert important systemic and local effects, positively modulating the infarction microenvironment. Poly-(L-lactide) electrospun scaffolds were seeded with C2C12 murine skeletal myoblast for 48 hrs. Biological assays demonstrated the induction of Cx43 expression along with morphostructural changes resulting in cell elongation and appearance of cellular junctions resembling the usual cardiomyocyte arrangement at the ultrastructural level. The possibility of fabricating extracellular matrix-mimicking scaffolds able to promote myoblast pre-commitment towards myocardiocyte lineage and mitigate the hazardous environment of the damaged myocardium represents an interesting strategy in cardiac tissue engineering.