(7) CSB329 (Stem Cell Biology) - Lecture Seven Content

Definition of hematopoiesis

Developmental process through which all cellular components of the blood are derived from

What availability of a specific stem cell is hematopoiesis contingent on?

Availability of hemopoietic stem cells

What is the predominant location of prenatal hematopoiesis?

The predominant location of prenatal hematopoiesis is the yolk sac.

What are the three auxiliary locations of prenatal hematopoiesis?

The three auxiliary locations of prenatal hematopoiesis are the liver, spleen, and bone marrow

What is the predominant location of postnatal hematopoiesis?

Bone marrow

What two skeletal structures does postnatal hematopoiesis occur in?

The vertebral column and pelvis

What percentage of hematopoietic stem cells (HSCs) are quiescent?

90% (i.e., the majority) of hematopoietic stem cells are quiescent.

What are the two predominant functions of quiescence as it relates to hematopoietic stem cells (HSCs)?

The two predominant functions of quiescence is to preserve genome integrity and self-renewal properties long-term.

Three distinct differentiated cell morphologies derived from the common lymphoid progenitor

The B cell, the T cell, and the NK cell

Three distinct cell morphologies derived from the common myeloid progenitor

Erythrocytes, megakaryocyte, and the mast cell

Three distinct cell morphologies are derived from the granulocyte-monocyte progenitor

Neutrohils, osteoclasts, and eosinophils

Cell morphology derived from the common lymphoid progenitor and the common myeloid progenitor

Dendritic cell

Cell morphology derived from the common myeloid progenitor and the granulocyte-monocyte progenitor

The basophil

What are the two predominant cellular components of the hemopoietic stem cells niche?

The presence of osteoblasts, and of multipotent stromal cells (MSCs)

What are the five predominant acellular components of the hemopoietic stem cells niche?

Hypoxia, the presence of cytokines that support the proliferation of hemopoietic stem cells, calcium ions, extracellular matrix mechanics, and forces (i.e., shear)

Three primary cell morphologies multipotent stromal cells, previously known as mesenchymal stem cells can differentiate to

Bone, cartilage, and adipose tissue.

Function of osteoblasts (OBs)

Matrix secretion to regulate mineralization and the production of bone

Function of vascular endothelial cells

Facilitate the production of adhesion molecules, and chemokines (i.e., facilitate the movement of HSCs)

Why does hypoxia maintain the hemopoietic stem cell niche?

Concentration of oxygen regulate the enzymatic activity of prolyl hydroxylase (PHD). Reduced oxygen concentrations decreases the activity of prolyl hydroxylase (PHD)

Function of prolyl hydroxylase (PHD)

Catalyze proteasomal degradation of HIF-1(alpha)

Low oxygen concentration (i.e., hypoxia) [increases/decreases] the activity of prolyl hydroxylase, [stabilizing/destabilizing] HIF-1(alpha)

Decreases, and stabilizing

Describe the conditions in which proteasomal degradation of HIF-1(alpha) occurs. What molecule is bound to HIF-1(alpha) to signal proteasomal degradation?

Under condition of high oxygen concentrations (i.e., normoxia), HIF-1(alpha) is bound to ubiquitin, signalling for its proteasomal degradation.

Where in is HIF-1(alpha) translocated to in conditions of low oxygen concentrations. Describe the function of HIF-1(alpha)

The

The proximity to what structure determines the oxygen concentration available to the hemopoietic stem cell

The promixity to microvasculature determines the oxygen concentration available to the hemopoietic stem cell. The closer in promixity to microvasculature, the higher the oxygen concentration available.

What are the two secreted factors involved in the activation of signalling pathways that decrease the activity of prolyl hydroxylase (PHD), and increase HID-1(alpha) stability?

Thromopoietin and stem cell factor (SCF)

What conclusions were derived from the experiment preformed on the deficiency in HIF-1(alpha) mice in relation to quiescence and the population of hemapoietic stem cells?

Hemopoietic stem cells were unable to maintain a state of quiescence; therefore, the population depleted gradually with time.

Describe the procedure of competitive reconstitution assay performed on mice.

Admixture of equivalent concentration of hematopoietic stem cells from two distinct donors compete to repopulate the bone marrow of an irradiated recipient

What feature of hemopoietic stem cells distinguishes distinct donor populations from each other? Describe the method used to separate the donor populations in an admixture.

Hemopoietic lineages express distinct surface antigens. FACS (Fluorescent Antigens Cell Sorting) is used to separate indivudal hematopoietic cell populations from each other in an admixture.

Experimental function of the competitive reconstitution assay in relation to the function hematopoietic stem cell lineages.

The competitive reconstitution assay can experimentally determine if genetic deletions or other alterations influence hematopoietic stem cell renewal or differentiation (i.e., lymphoid or myeloid lineages)

Describe the procedure involving the competitive reconstitution assay in mice to determine if Piwi knockout influenced the function of hematopoietic lineages significantly in irradiated mice.

1. Source irradiated mouse population

2. Source bone marrow (i.e., hemopoietic stem cell) from Piwi Knockout and WT

3. Transplant admixture of Piwi Knockout and WT hemopoietic stem cell in irradiated mouse population

4. Observe in Piwi Knockout produces an effective or defective phenotype in hemopoietic stem cell, relative to the WT

What are the two major hematopoietic lineages produced by hematopoietic stem cells?

The common myeloid, and the common lymphoid

What is the cell located in the bone marrow that is incapable of differentiation into erythrocytes?

Multipotent stromal cell

Definition of human leukocyte antigens (HLA)

Class of polymorphic genes (genetic region where multiple allelic variants exist) that encode for the major histocompatibility complex (MHC)

Predominant function of the major histocompatibility complex (MHC)

The major histocompatibility complex enables the immune system to recognize and produce differential responses to “self” cellular components and “foreign” cellular components

Definition of graft-versus-host via ease (GvHD)

Disease specific to allogeneic hematopoietic stem cell transplantations where hematopoietic stem cells reconstitutes the recipient immune system (i.e., lymphoid lineage) which can produce a whole body inflammatory response (i.e., somatic cells)

What are the two primary distinctions between graft-versus-host disease (GvHD) and graft rejection

Graft-versus-host disease (GvHD) is an allogeneic hematopoietic stem cell specific condition while graft rejection describes transplantations that induce an immune response, and it reconstitutes the recipients immune system while graft rejections do not.

What comprises the innate immune system?

Natural killer cells (NKC)

What comprises the adaptive immune system?

T cells

Natural killer cells of the innate immune system and T cells of the adaptive immune system are able to recognize [blank] [blank] [blank] [blank] proteins

Self human leukocytes antigen

Describe the procedure involved in hematopoietic stem cell transplantations.

1. Source of blood or bone marrow from patient or immune-compatible donor

2. Separate hematopoietic stem cells in culture using antibodies

3. Transplant hematopoietic stem cells into irradiated patient (i.e., chemotherapy, radiation therapy)

Distinction between long term hematopoietic stem cells extracted from the umbilical cord, relative to hematopoietic stem cells extracted from the bone marrow.

Fewer in extracted from the umbilical cord relative to the bone marrow. The number is sufficient for a transplantation into children; however, insufficient to treat an adult patient

How do stem cells banks store stem cells?

Cryogenically

What are the three distinct stem cell repositories. Describe their distinctions.

Public repositories: donors void ownership of their donated cells; access to the general population (i.e., allogenic transplantations)

Private repositories: donors have ownership of their donated cells; often for personal use (i.e., autologous transplantations) or family (i.e., allogenic transplantations)

Biobanks: donors void ownership of their donated cells to the biobank; stored for research and development of new cellular therapies

How was the function of CCR5 (i.e., in relation to HIV inflection) discovered?

The function of CCR5 was discovered when a patient infected with HIV received a bone marrow transplantation that had a mutation influencing the expression (i.e., absence) of CCR5 receptors located on T cells.

How does the absence of CCR5 (i.e., mutation) influence an HIV infection?

HIV is unable to use CCR5 as a coreceptor

What is responsible for producing the immense variation observed in human leukocytes antigens (HLA)

Polymorphic genes

Where do somite mesodermal cells move to during embryogenesis? Describe the function of somite mesodermal cells.

Somite mesodermal cells move to the developing limb buds, producing the skeletal musculature of the developing fetus.

What is the distinct marker of muscle stem cells that comprise the limb skeletal muscle?

Satellite cell expressing Pax7

What is the distinct marker of muscle stem cells that comprise the limb skeletal muscle?

Satellite cell expressing Pax3 and Pax7

Where are

Definition of myogenesis

Process of developing bundling of elongated skeletal muscle fibers (i.e., myofibers)

What are the two distinct characteristics of myofibers?

Myofibers are multinucleated post-mitosis, and contractile (i.e., expression of genes comprising the contractile apparatus and transmembrane complexes)

Function of genes comprising the contractile apparatus and transmembrane complexes.

Structural integrity during muscle contraction.