No description available.

RTEL1 (Regulator of telomere length1) DNA helicase has been demonstrated to be vital for the maintenance of telomere length and genomic stability. However, its biological role during development is unknown. Our recent finding that RTEL1 is selectively expressed in several types of adult stem cells, suggests that RTEL1 could play an essential role in the maintenance of these cells. Depending on the function of RTEL1 in the maintenance of genomic stability, we hypothesize that RTEL1 could be required for protecting adult stem cells from genomic instability, whose dysfunction may not only impair tissue homeostasis/regeneration, but also could transform these cells to form tumors. In this study, we have used mouse intestinal stem/progenitor cells model to address this hypothesis. With a transgenic lineage tracing assay, we demonstrated that RTEL1-expressing cells in intestinal crypts can self renew and differentiate to the progeny cells required for intestinal homeostasis. Using a conditional knockout approach, we also showed that loss of RTEL1 function could induce genomic instability in intestinal stem/progenitor cells, which significantly affected the survival of intestinal stem cells and intestinal regeneration. Finally, in this study, we also observed intestinal hyperplasia in our RTEL1 conditional knockout mice, indicating that loss of RTEL1 function may initiate intestinal tumorigenesis. All of these findings strongly support that RTEL1 could be one the key molecules necessary for the maintenance of intestinal stem/progenitor cells and this function could be important for preventing intestinal tumorigenesis.

Human embryonic stem cells (hESCs) replicate in vitro by the process of self-renewal, whilst maintaining their pluripotency. Understanding the pathways involved in the regulation of this process will assist in developing fully-defined conditions for the robust proliferation of hESCs necessary for therapeutic applications.

No description available.

In this work, I investigated the influence of different surfaces on stem cell proliferation and osteogenetic differentiation. Surface properties of biomaterials are important factors that influence cell fate such as cell adhesion, viability, proliferation and differentiation. Herein, mesenchymal stem cells (MSCs) were cultured on composite electrospun nanofibrous membranes with varied surface wettability for designed periods and cell morphologies, proliferation and viability were characterized via analysis methods such as Infrared attenuated total reflectance Spectroscopy (IR-ATR), scanning electron microscopy (SEM) and MTT cell proliferation assay. The expression of genes associated with osteogenesis, including bone sialoprotein (BSP), alkaline phosphatase (ALP), osteopontin (OPN) and osteocalcin (OCN) were measured by real-time RT-PCR on different time points. Through western blot analysis, ERK1/2 pathway was found to be responsible for the differentiation of MSCs on nanofibrous membranes with different wettability.

There is emerging evidence to suggest that cardiac myofibroblasts (CMyfbs) participating in cardiac fibrosis represent a heterogeneous population in origin. We hypothesized that bone marrow derived mesenchymal stem cells (MSCs) readily adopt a myofibroblastic phenotype in culture. We assessed and compared human primary MSCs and human CMyfbs with respect to their phenotypic and functional characteristics by examining their gene expression profile, ability to contract collagen gels, and ability to synthesize collagen. We also examined the role of non-muscle myosin II (NMMII) in modulating the myofibroblast function using siRNA and blebbistatin to inhibit NMMII activity. The data revealed that MSCs adopt a myofibroblastic phenotype in culture and demonstrate the capability to contract collagen gels and synthesize collagen similar to human CMyfbs. Inhibition of NMMII activity with blebbistatin completely inhibits gel contractility without affecting cell viability. Thus, MSCs exhibit similar physiological and functional characteristics as CMyfbs, and may contribute to cardiac fibrosis.

No description available.

We have studied the factors that are important for producing functional retinal neurons from adult derived retinal stem and progenitor cells (RPCs) investigating the role of substrate stiffness or soluble factors in 2D and 3D culture on the differentiation and survival of RPCs. RPCs were cultured on agarose scaffolds modified with the adhesive peptides of varying stiffness. We observed that cell survival in the 0.75% matrix was greater in 3D than in 2D by a factor of 50% irrespective of the time in culture. We observed the presence of photoreceptors exclusively in 0.75% agarose, while the stiffer matrices (1.75%) led to retinal ganglion cell and glial cell differentiation with no significant difference in the differentiation profiles when cells were cultured in 2D vs. 3D. These data indicate that substrate stiffness, more than growth factors, has a significant impact on both the survival and differentiation profile of retinal precursor cells.

Recent evidence suggests that “mesenchymal stem cells” (MSCs) are resident in the perivascular compartment of connective tissues. However, since the definition of a stem cell assumes that these progenitors have clonal self-renewal and multi-lineage differentiation potential, the term “MSC” has been criticised, as it has been impossible to isolate definitive clonally derived “MSCs.” To test for this most basic definition of a stem cell, here it is shown that human umbilical cord perivascular cells (HUCPVCs) are capable of multilineage differentiation in vitro and, more importantly, in vivo, displaying the ability to differentiate into functionally synthetic cells that direct and contribute to rapid connective tissue healing by producing bone, cartilage and fibrous stroma in a mouse injury model. Uniquely, these cells can be enriched to >1:3 clonogenic frequency in early passage culture, making it possible to isolate clones and daughter sub-clones from mixed gender suspensions, determined to be definitively single-cell-derived by Y-chromosome fluorescent in situ hybridization (FISH) analysis. Each clone was assayed for multi-lineage differentiation capacity into the five mesenchymal lineages: myogenic, adipogenic, chondrogenic, osteogenic and fibroblastic (stroma). The observation that daughter sub-clones possess equal or lesser differentiative potential to their respective parent clones demonstrated the two intrinsic properties of stem cells in vitro: clonal self-renewal and multi-lineage differentiation. This evidence provides a new hierarchical structure of robust MSCs self-renewing to produce more restricted progenitors that gradually lose differentiation potential until a state of complete restriction to the fibroblast is reached. The methods described herein combined with recognition of this lineage hierarchy provides a significant advance to the understanding of MSC biology, and will enable interrogation of the properties of robust self-renewal and differentiation of MSCs in serially transplanted living recipients.

We have studied the factors that are important for producing functional retinal neurons from adult derived retinal stem and progenitor cells (RPCs) investigating the role of substrate stiffness or soluble factors in 2D and 3D culture on the differentiation and survival of RPCs. RPCs were cultured on agarose scaffolds modified with the adhesive peptides of varying stiffness. We observed that cell survival in the 0.75% matrix was greater in 3D than in 2D by a factor of 50% irrespective of the time in culture. We observed the presence of photoreceptors exclusively in 0.75% agarose, while the stiffer matrices (1.75%) led to retinal ganglion cell and glial cell differentiation with no significant difference in the differentiation profiles when cells were cultured in 2D vs. 3D. These data indicate that substrate stiffness, more than growth factors, has a significant impact on both the survival and differentiation profile of retinal precursor cells.