Changqing Xie

Porous nanofibrous PLLA scaffolds for vascular tissue engineering

Tissue-engineered small-diameter vascular grafts are needed for patients requiring replacement of their injured coronary and below-the-knee vessels. Understanding the interactions between the scaffolds and implanted cells and therefore the phenotype control of smooth muscle cells (SMCs) is critical for constructing functional vascular grafts. In this study, the effect of nanofibrous (NF) poly-L-lactide (PLLA) scaffolds on phenotype control of human aortic smooth muscle cells (HASMCs) was investigated. A tubular NF PLLA scaffold for blood vessel regeneration was fabricated and cell seeding studies showed cell distribution throughout the scaffold. It was found that NF PLLA scaffolds preferentially supported contractile phenotype of HASMCs under the in vitro culture conditions, as evidenced by elevated gene expression level of SMCs contractile markers including smooth muscle myosin heavy chain, smoothelin and myocardin. In vivo subcutaneous implantation studies confirmed HASMCs differentiation in the implants. Taken together, the results showed promising application of the porous NF PLLA scaffolds for reconstruction of tissue-engineered vascular grafts.

miR-10a contributes to retinoid acid-induced smooth muscle cell differentiation.

MicroRNAs (miRs) have been reported to play a critical role in muscle differentiation and function. The purpose of this study is to determine the role of miRs during smooth muscle cell (SMC) differentiation from embryonic stem cells (ESCs). MicroRNA profiling showed that miR-10a expression is steadily increased during in vitro differentiation of mouse ESCs into SMCs. Loss-of-function approaches using miR-10a inhibitors uncovered that miR-10a is a critical mediator for SMC lineage determination in our retinoic acid-induced ESC/SMC differentiation system. In addition, we have documented for the first time that histone deacetylase 4 is a novel target of miR-10a and mediates miR-10a function during ESC/SMC differentiation. To determine the molecular mechanism through which retinoic acid induced miR-10a expression, a consensus NF-κB element was identified in the miR-10a gene promoter by bioinformatics analysis, and chromatin immunoprecipitation assay confirmed that NF-κB could bind to this element. Finally, inhibition of NF-κB nuclear translocation repressed miR-10a expression and decreased SMC differentiation from ESCs. Our data demonstrate for the first time that miR-10a is a novel regulator in SMC differentiation from ESCs. These studies suggest that miR-10a may play important roles in vascular biology and have implications for the diagnosis and treatment of vascular diseases.

Smooth Muscle Cell Differentiation In Vitro Models and Underlying Molecular Mechanisms

Development of in vitro models by which to study smooth muscle cell (SMC) differentiation has been hindered by some peculiarities intrinsic to these cells, namely their different embryological origins and their ability to undergo phenotypic modulation in cell culture. Although many in vitro models are available for studying SMC differentiation, careful consideration should be taken so that the model chosen fits the questions being posed. In this review, we summarize several well-established in vitro models available to study SMC differentiation from stem cells and outline novel mechanisms recently identified as underlying SMC differentiation programs.

Three-dimensional growth of iPS cell-derived smooth muscle cells on nanofibrous scaffolds

Induced pluripotent stem cells (iPSCs) have been considered as the major component for personalized regenerative medicine. However, the potential of iPSCs in constructing tissue-engineered (TE) blood vessels has not been exploited. In the present study, we generated mouse iPSCs with the combination of over-expression of 4 iPS factors and knock-down of p53 gene. The established iPSCs were then directed to differentiate into smooth muscle cells (SMCs) with the treatment of 10(-5) (M) all-trans retinoid acid (RA). The vehicle dimethyl sulfoxide (DMSO) treatment served as a spontaneous differentiation control. The differentiated cells were then cultured on three-dimensional (3D) macro-porous nanofibrous (NF) poly(L-lactide) (PLLA) scaffolds in vitro. Our data showed that the expression of SMC specific marker genes, including myocardin, smoothelin, SM22α and SMMHC, were higher for the group induced by RA than for the group treated by DMSO, while pluripotent marker gene expression was repressed by the RA-treatment. Upon subcutaneous implantation, the implanted cells maintained the SMC phenotype. In conclusion, the data suggest that iPSCs-derived SMCs can be an important cell source for personalized vascular tissue engineering applications.

Construction of Vascular Tissues with Macro-Porous Nano-Fibrous Scaffolds and Smooth Muscle Cells Enriched from Differentiated Embryonic Stem Cells

Vascular smooth muscle cells (SMCs) have been broadly used for constructing tissue-engineered blood vessels. However, the availability of mature SMCs from donors or patients is very limited. Derivation of SMCs by differentiating embryonic stem cells (ESCs) has been reported, but not widely utilized in vascular tissue engineering due to low induction efficiency and, hence, low SMC purity. To address these problems, SMCs were enriched from retinoic acid induced mouse ESCs with LacZ genetic labeling under the control of SM22α promoter as the positive sorting marker in the present study. The sorted SMCs were characterized and then cultured on three-dimensional macro-porous nano-fibrous scaffolds in vitro or implanted subcutaneously into nude mice after being seeded on the scaffolds. Our data showed that the LacZ staining, which reflected the corresponding SMC marker SM22α expression level, was efficient as a positive selection marker to dramatically enrich SMCs and eliminate other cell types. After the sorted cells were seeded into the three-dimensional nano-fibrous scaffolds, continuous retinoic acid treatment further enhanced the SMC marker gene expression level while inhibited pluripotent maker gene expression level during the in vitro culture. Meanwhile, after being implanted subcutaneously into nude mice, the implanted cells maintained the positive LacZ staining within the constructs and no teratoma formation was observed. In conclusion, our results demonstrated the potential of SMCs derived from ESCs as a promising cell source for therapeutic vascular tissue engineering and disease model applications.

MicroRNA and Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) exhibit extraordinary plasticity during postnatal development. Vascular injury initiates VSMC phenotypic switch from the contractile to proliferative phenotype, which plays a central role in vascular lesion formation and diverse vascular diseases. MicroRNAs (miRNAs) regulate gene expression posttranscriptionally by either degrading target mRNAs or repressing their translation. Emerging evidence has revealed miRNAs are critical regulators in VSMC differentiation from stem cells, phenotypic switch, and various vascular pathogenesis. Here, we review recent advances regarding functions of specific miRNAs in vasculature and discuss possible mechanisms by which miRNAs affect VSMC biology.

Smooth Muscle Cells for Vascular Engineering

In the first decade of this century, ever-increasing scientific and technological advances are revolutionizing our approaches to developing therapies that bring about the promise of personalized medicine and the possibility of regenerative interventions. Multidisciplinary research has led to a better understanding of four key areas of scientific and technological knowledge that are essential to the development of such innovative therapies for cardiovascular disease: (1) increased understanding of normal development and cell differentiation processes in vivo; (2) elucidating signaling pathways involved in these processes; (3) uncovering new technological approaches that can efficiently mimic these processes in vitro; and (4) most importantly, the identification and characterization of adequate sources of precursor cells that serve as the starting material for regenerative undertakings. See accompanying article on page 2938 A normal vasculature is crucial for maintaining homeostasis and providing the necessary nutrients to cells of the human body. Therefore, impairment to the integrity of blood vessels will lead to various complications. Cardiac and peripheral vascular diseases have been the major causes of morbidity and mortality in the Western world.1 Currently available therapies rely on the implantation of stents or grafts for reconstruction of blood conduits. However, the availability of suitable venous and arterial grafts for implantation is a challenge, and furthermore these therapies may not be sufficient for complete recovery of function and integrity of the injured vasculature.2 Thus, alternative vascular drains that have the ability to mechanically and biologically fulfill the properties of …