Automated classification and visualization of fluorescent live cell microscopy images.

Robotic, high-throughput microscopy is a powerful tool for small molecule screening and classifying cell phenotype, proteomic and genomic data. An important hurdle in the field is the automated classification and visualization of results collected from a data set of tens of thousands of images. We present a method that approaches these problems from the perspective of flow cytometry with supporting open-source code. Image analysis software was created that allowed high-throughput microscopy data to be analysed in a similar manner as flow cytometry. Each cell on an image is considered an object and a series of gates similar to flow cytometry is used to classify and quantify the properties of cells including size and level of fluorescent intensity. This method is released with open-source software and code that demonstrates the method's implementation. Accuracy of the software was determined by measuring the levels of apoptosis in a primary murine myoblast cell line after exposure to staurosporine and comparing these results to flow cytometry.

Small molecules in stem cell self-renewal and differentiation.

The use of stem cells in regenerative medicine is a promising approach to the treatment of disease and injury. Natural and synthetic small molecules have been shown to be useful chemical tools for controlling and manipulating the fates of cells. Small molecules can target signaling transduction pathways (for example, tyrosine kinase receptors) and affect DNA replication, cell differentiation, tumor metastasis and apoptosis. Stem cells share many properties with cancer cells and these similarities can provide insights to control and direct cell behavior; small molecules are already standard chemotherapeutics in the treatment of cancer. Libraries of small molecules have been examined for anticancer behavior (especially apoptosis), and, more recently, for stem cell self-renewal and differentiation capabilities in potential approaches to regenerative medicine. Differentiation therapy for cancer is based on the idea that cancer cells are undifferentiated embryonic-like cells and proposes to promote the differentiation and hence block cell proliferation. For example, retinoids have a role in stem cell differentiation to several lineages and have also been used to promote differentiation of acute promyeloic leukemic cells. Small molecules are also important tools for understanding mechanistic and developmental processes. Strategies for generating functional small molecule libraries have been outlined previously. In this review, we will look at several small molecules that have been described in the recent literature as effectors of stem cell self-renewal or differentiation as associated with the Wnt, Hedgehog or NF-kappaB pathways.

Cyclooxygenase-2 inhibitors demonstrate anti-proliferative effects in oesophageal cancer cells by prostaglandin E(2)-independent mechanisms.

The incidence of oesophageal cancer (OC) has risen in recent decades, with survival rates remaining poor despite surgical treatment and adjuvant chemotherapy. Studies have reported cyclooxygenase-2 (COX-2) overexpression in OC and current evidence suggests NSAIDs have major potential for chemoprevention through COX-2 inhibition. However, several reports have questioned the specificity of these inhibitors, suggesting they may act through mechanisms other than COX-2. We evaluated the effects of specific COX-2 inhibitors, NS-398 and nimesulide, on cell lines of both histological types of OC. COX-2 protein expression varied in the cell lines and corresponded with levels of prostaglandin E(2) (PGE(2)) production. Following treatment with low concentrations of NS-398 (0.1 microM), PGE(2) production was reduced dramatically, indicating inhibition of COX-2 activity. Examination of cellular morphology, caspase-3 activity and mitochondrial membrane integrity found no major induction of apoptotic cell death at concentrations below 100 microM. Tumour cell proliferation was significantly reduced at high concentrations (50-100 microM) of both inhibitors over 6 days. Cellular responses were more evident in NS-398-treated adenocarcinoma cells. However, concentrations required to inhibit proliferation were up to 1000-fold higher than those needed to inhibit enzyme activity. Addition of exogenous PGE(2) to NS-398-treated adenocarcinoma cells failed to reverse the inhibitory effects, indicating PG and COX-2 independence. It remains possible that in vivo COX-2 is the primary target, as enzyme inhibition can be achieved at low concentrations, however, inhibition of proliferation is not the primary mechanism of their anti-tumour activity.

Long-term self-renewal of postnatal muscle-derived stem cells.

The ability to undergo self-renewal is a defining characteristic of stem cells. Self-replenishing activity sustains tissue homeostasis and regeneration. In addition, stem cell therapy strategies require a heightened understanding of the basis of the self-renewal process to enable researchers and clinicians to obtain sufficient numbers of undifferentiated stem cells for cell and gene therapy. Here, we used postnatal muscle-derived stem cells to test the basic biological assumption of unlimited stem cell replication. Muscle-derived stem cells (MDSCs) expanded for 300 population doublings (PDs) showed no indication of replicative senescence. MDSCs preserved their phenotype (ScaI+/CD34+/desmin(low)) for 200 PDs and were capable of serial transplantation into the skeletal muscle of mdx mice, which model Duchenne muscular dystrophy. MDSCs expanded to this level exhibited high skeletal muscle regeneration comparable with that exhibited by minimally expanded cells. Expansion beyond 200 PDs resulted in lower muscle regeneration, loss of CD34 expression, loss of myogenic activity, and increased growth on soft agar, suggestive of inevitable cell aging attributable to expansion and possible transformation of the MDSCs. Although these results raise questions as to whether cellular transformations derive from cell culturing or provide evidence of cancer stem cells, they establish the remarkable long-term self-renewal and regeneration capacity of postnatal MDSCs.

Modeling stem cell population growth: incorporating terms for proliferative heterogeneity.

Expansion of the undifferentiated stem cell phenotype is one of the most challenging aspects in stem cell research. Clinical protocols for stem cell therapeutics will require standardization of defined culture conditions. A first step in the development of predictable and reproducible, scalable bioreactor processes is the development of mathematical growth models. This paper provides practical models for describing cell growth in general, which are particularly well suited for examining stem cell populations. The nonexponential kinetics of stem cells derive from proliferative heterogeneity, which is biologically recognized as mitosis, quiescence, senescence, differentiation, or death. Here, we examined the assumptions of the Sherley model, which describes heterogeneous expansion in the absence of cell loss. We next incorporated terms into the model to account for A) cell loss or apoptosis and B) cell differentiation. We conclude that the basic assumptions of the model are valid and a high correlation between the modified equations and experimental data obtained using muscle-derived stem cells was observed. Finally, we demonstrate an improved estimation of the kinetic parameters. This study contributes to both the biological and mathematical understanding of stem cell dynamics. Further, it is expected that the models will prove useful in establishing standardization of cell culture conditions and scalable systems and will be required to develop clinical protocols for stem cell therapeutics.

Muscle-derived stem cells.

The existence of cells with stem cell-like abilities derived from various tissues can now be extended to include the skeletal muscle compartment. Although researchers have focused on the utilization of these cells with regard to their myogenic capacity, initially exploring more efficient cellular therapy treatments for muscular dystrophy, it is becoming increasingly apparent that such cells may one day be used in the treatment of non-myogenic disorders. Evidence regarding the existence and differentiation capacity of muscle-derived stem cells is discussed, along with current theories regarding their proposed position within the myogenic hierarchy.

Mechanisms of muscle stem cell expansion with cytokines.

Stem cell expansion and proliferation are important for cell transplantation and stem cell-mediated applications. While we have demonstrated that muscle stem cells can be obtained from adult skeletal muscle tissue, these cells represent only a small percentage of the muscle-derived cells and require in vitro expansion for successful stem cell-mediated therapies. In this study, we have examined the potential of several cytokines to stimulate stem cell growth by combining a non-exponential mathematical model with a unique cell culture system. The growth kinetics of two populations of muscle stem cells were characterized in culture medium supplemented with epidermal growth factor (EGF), fibroblast growth factor-2 (FGF-2), insulin-like growth factor-1 (IGF-1), FLT-3 ligand, hepatocyte growth factor, or stem cell factor (SCF). The division time (DT) and fraction of mitotically active cells were investigated as key parameters to further understand the mechanism of the expansion of the stem cell populations. Our results show that expansion of the freshly isolated, muscle-derived stem cells (MDSC) occurred by recruiting cells into the cell cycle in the presence of EGF, IGF-1, and SCF. However, expansion of the cultured stem cell clone, MC13, is attributed to a reduction of the length of the cell cycle in the presence of FGF-2, EGF, IGF-1, and SCF. Both MDSC and MC13 growth were inhibited in the presence of FLT-3 ligand by increasing the length of the cell cycle. Our results suggest that EGF, IGF-1, FGF-2, and SCF are important cytokines for stimulating the proliferation of MDSC. In addition, this study illustrates that expansion of stem cells occurs through different mechanisms, which consequently demonstrates the importance of monitoring several parameters of cell growth, such as DT and dividing fraction, following stimulation with growth factors.

Muscle-derived stem cells: characterization and potential for cell-mediated therapy.

Skeletal muscle may represent a convenient source of stem cells for cell-mediated gene therapy and tissue-engineering applications. A population of cells isolated from skeletal muscle exhibits both multipotentiality and self-renewal capabilities. Satellite cells, referred to by many as muscle stem cells, are myogenic precursors that are capable of regenerating muscle and demonstrating self-renewal properties; however, they are considered to be committed to the myogenic lineage. Muscle-derived stem cells, which may represent a predecessor of the satellite cell, are considered to be distinct. This article considers the evidence for the existence of muscle-derived stem cells as well as their potential embryonic origin. Comparison of muscle-derived stem cells to bone marrow and hematopoietic-derived stem cells illustrates similarities and distinctions among these various stem cells. Hematopoietic stem cell research provides lessons for the isolation of a defined phenotype as well as for the expansion of the stem cells in vitro. Recent investigations highlighting the potential of stem cell transplantation for the treatment of muscular dystrophies are discussed.

A rapid PCR based method to distinguish between Lactococcus and Enterococcus.

Phenotypic characterisation of Lactococcus and Enterococcus species remains unreliable as strains of both genera have been isolated which do not conform to the traditional criteria for separation of these genera. A bank of 131 isolates was phenotypically characterised by three methods: (a) traditional broth tests, (b) API Rapid ID 32 Strep and (c) BBL Crystal ID kits. Differences in genus designation between commercial kits were evident for 12 strains (9%), while 7 strains (5%) remained unidentified by either kit. Published 16S rRNA sequences were aligned and used to design genus-specific primers which, when used in separate PCR reactions, were capable of distinguishing all type strains of Lactococcus and Enterococcus. These primers did not react with known species of Streptococcus, Pediococcus, Lactobacillus, Leuconostoc or Tetragenococcus. Isolates which could not be identified by phenotype were assigned to either genus on the basis of the gene primers.