Understanding Stem Book 1 Pdf Free Download

[Otilia Mojarro]

Thesite is secure.

The ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Stem cells and their differentiated progeny offer great hope for treating disease by providing an unlimited source of cells for repairing or replacing damaged tissue. Initial studies suggested that, unlike 'normal' transplants, specific characteristics of stem cells enabled them to avoid immune attack. However, recent findings have revealed that the immunogenicity of stem cells may have been underestimated. Here, we review the current understanding of the mechanisms of immune recognition associated with stem cell immunogenicity, and discuss the relevance of reprogramming and differentiation strategies used to generate cells or tissue from stem cells for implantation in eliciting an immune response. We examine the effectiveness of current strategies for minimising immune attack in light of our experience in the transplantation field and, in this context, outline important challenges moving forward.

Stem cells are found in bone marrow, in the bloodstream and in umbilical cord blood. In the bloodstream, they are called peripheral blood stem cells (PBSCs). Stem cells from any of these sources can be used in transplants.

With a stem cell transplant, a doctor gives you healthy replacement cells that help you fight infection and disease. Doctors most often use stem cell transplants to treat blood disorders and blood cancers that:

New cells are added to your bloodstream with an IV. The cells collect in your bone marrow, where they produce new blood cells. Because conditioning leaves your immune system weak, you will need two to three weeks of monitoring.

Our transplant nurse navigator will be your first contact. This health care professional will provide information and resources, and help you understand the process. The navigator will also be your advocate and guide.

How it works: Your care team draws blood and uses a machine to separate out stem cells. The stem cells are frozen. After the conditioning process, the cells are transplanted using an IV drip.

What is it? We use cells from a donor. Sometimes your own cells are too diseased to collect and reuse. Donor cells are more aggressive in killing any diseased cells left after conditioning. The risk is that they may aggressively target your healthy cells as well, a complication called graft-versus-host disease.

How it works: After the conditioning process, we transplant healthy donor cells using an IV drip. The donor cells help your body rebuild your immune system. A donor can be a relative or someone else whose marrow matches yours.

Infection: Chemotherapy and radiation therapy weaken your immune system. You are at high risk of infection for up to six weeks until your new cells make healthy blood cells. Your care team will keep you in a safe environment with protection against airborne germs. You will receive safety instructions for going home.

Low platelets: Your platelets will be low for three or more weeks. We will take great care to help you avoid injury or bleeding. Some patients may need a blood transfusion to replace platelets.

Infertility: The chemotherapy and radiation therapy used before transplants typically result in infertility. OHSU fertility experts can offer options before your treatment begins to preserve your ability to have children.

Transplants are difficult. They require weeks in or near the hospital, away from work and regular activities. Our cancer social workers and other experts can provide support to you and your family before, during and after treatment.

OHSU has participated in Be The Match: The National Marrow Donor Program since 1996. This program helps people find a lifesaving marrow or PBSC donor. Donors must meet medical guidelines and should expect to spend 20 to 30 hours over four to six weeks to donate.

Everyone inherits a set of HLA markers from their parents. These markers, on the surface of almost all of your cells, tell your body which cells belong to you. The more matching markers you and a donor have, the better your chances of a successful transplant.

Recent studies have associated the transcription factors, Oct4, Sox2 and Nanog as parts of a self-regulating network which is responsible for maintaining embryonic stem cell properties: self renewal and pluripotency. In addition, mutual antagonism between two of these and other master regulators have been shown to regulate lineage determination. In particular, an excess of Cdx2 over Oct4 determines the trophectoderm lineage whereas an excess of Gata-6 over Nanog determines differentiation into the endoderm lineage. Also, under/over-expression studies of the master regulator Oct4 have revealed that some self-renewal/pluripotency as well as differentiation genes are expressed in a biphasic manner with respect to the concentration of Oct4.

The computational model provides a mechanistic understanding of how different lineages arise from the dynamics of the underlying regulatory network. It provides a framework to explore strategies of reprogramming a cell from a differentiated state to a stem cell state through directed perturbations. Such an approach is highly relevant to regenerative medicine since it allows for a rapid search over the host of possibilities for reprogramming to a stem cell state.

Copyright: 2008 Chickarmane et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This research was in part supported by the Swedish Foundation for Strategic Research through a Senior Individual Grant and the National Science Foundation-FIBR Award EF-0330786. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Recent breakthroughs in reprogramming differentiated cells into embryonic stem cells [1], [2], [3], [4], [5], have made major inroads into stem cell biology. What emerges is a relatively small core of master regulators that are required for successful reprogramming of a differentiated cell into a cell exhibiting stem cell like properties. This set of transcription factors (TF) has previously been established as candidates to regulate both pluripotency and differentiation of embryonic stem cells [6], [7], [8], [9], [10].

The fact that there appears to be only a hand full of master regulators argues for a computational approach. A model based upon regulatory mechanisms inferred from ChIP-on-chip and microarray data can quantify functionality of the genetic network. This would also provide a platform for reprogramming studies, by allowing us to enumerate the possibilities of over/under-expression of key TFs. The motivation for this model comes from a recent review [9], in which lineage determination, i.e. how pluripotency and self-renewal versus the two differentiation lineages, trophectoderm and endoderm, arise as a result of the system finding different stable states. These are given by combinations of certain TF concentrations, resulting from the dynamics of the interaction network, which contains several positive and negative feedback loops. At the core of the network reside Oct4, Sox2 and Nanog, which form a self-organized core of the TFs maintaining pluripotency and self-renewal [6], [7], [8]. A computational model of the dynamics of this core network has revealed that it functions as a bistable switch, which in the on state, corresponds to all these TFs being expressed and the downstream differentiation target genes being shut off [11].

In this work we develop a dynamical model of lineage determination based upon a minimal circuit, as discussed in [9], which contains the Oct4/Sox2/Nanog core as well its interaction with a few other key genes. The model dynamics both suggests the mechanisms of interaction as gleaned from data, as well as point to reprogramming strategies.

In [11] a dynamical model was developed for the core embryonic stem cell network which comprises Oct4, Sox2 and Nanog. It was found that cooperative interactions between these TFs give rise to a bistable switch-like behavior. One key prediction of the resulting dynamics is that over-expression of Nanog can maintain pluripotency of the cell even in the absence of the external factor(s) inducing Oct4 and Sox2. This result is consistent with experiments for mouse embryonic stem cells [8]. In [12], the authors discussed the mutual antagonism between Cdx2 and Oct4 which determines the trophectoderm versus stem cell fate. The heterodimer Cdx2-Oct4 binds to both Cdx2 and Oct4 acting as a repressor. Since Cdx2 and Oct4 are both autoregulatory, the latter through the Oct4/Sox2 complex, an excess of Cdx2 will give rise to the trophectoderm lineage, and similarly an excess of Oct4 defines the stem cell lineage. Therefore, with respect to an external signal which regulates the Oct4, low values of this signal would correspond to the trophectoderm state. On the other hand, the mutual antagonism between Gata-6 and Nanog decides between endoderm and stem cell fates [13]. An excess of Gata-6 leads to the endoderm fate. The master regulator Oct4 also receives negative feedback from Gcnf [17], [18], which itself is activated by both Gata-6 and Cdx2 [9]. This negative feedback ensures that once differentiated, the pluripotency genes are shut off. The assembled network interactions are displayed in Figure 1. The red dotted line, indicates that Oct4 positively induces Gata-6, and is a hypothesis, which arises due to a dynamical consideration of the model as will be discussed below. What is known from ChIP-on-chip experiments is that Gata-6 is a target of both Nanog and Oct4 [6], [19].

3a8082e126