Blood Diseases: Haematopoiesis

Blood Diseases: Haematopoiesis

• Haematopoiesis involves cells from bone marrow and peripheral blood.
• Peripheral blood: Complex tissue with diverse molecules and cells.
  • Contains red blood cells (including platelets) and white blood cells.
  • White blood cells can be further classified into subtypes.
• Peripheral blood analysis uses blood smears with May-Grunwald Giemsa staining.
  • Allows identification of different cell types based on morphology.
  • Blood smear analysis can help determine if cells are normal or pathological, indicating a blood disease.
• Bone marrow: Primary site of post-natal haematopoiesis in humans under normal conditions.
  • Contains progenitors, precursors, stem cells, and mature blood cells.
• White blood cells can exit blood vessels and migrate into tissues, crucial for inflammation, phagocytosis, and immunity.
• Red blood cells are anucleate, biconcave, contain haemoglobin, and transport oxygen and carbon dioxide.
• Platelets are small, anucleate cells with molecules essential for haemostasis.

Bone Marrow Compartments

• Three compartments that are closely related and dependent.
  • Anatomical structure (location of bone marrow).
  • Haematopoietic stem cells (HSC).
  • Stroma.
• Bone: Container for stroma cells, molecules, and haematopoietic stem cells.
  • Bone matrix (trabeculae) forms cavities for different cells

Bone Marrow Structure

• Made of cavities compartmentalised by bone trabeculae that contain:
  • Fat cells.
  • Progenitors and hematopoietic precursors.
  • Stromal cells containing a complex vascular system.
• Vascular system structures:
  • Medullary and cortical arterioles.
  • Sinus network.
  • Central sinus permeable to mature blood cells due to migration pores.
• Haematopoietic niche present composed of bone matrix and cells and playing a role in:
  • Maintaining HSC in quiescence
  • Releasing blood cell precursors.
• Cells are not evenly distributed, which allows recognition of two niche subtypes:
  • Osteoblastic: Functional complex linking bone matrix and HSC, maintaining quiescence. HSC are beside the endosteal layer near osteoblasts.
  • Vascular: Located in the medullary area composed of primarily vessels. Contains haematopoietic progenitors receiving differentiation signals toward haematological lineages known as commitment.

Stroma

• Stroma: Microenvironment with HSCs and other cells, providing structural support that allows cell placement, and differentiation signals.
• Cellular component: Including myofibroblasts, adipocytes, macrophages, lymphocytes, and endothelial cells.
  • Produces growth factors (cytokines) that regulate HSC differentiation.
• Macromolecular component: Generates a structural network vital for stroma and haematopoietic cells.
• Haematopoiesis control depends on:
  • HSC's self-sustaining and differentiating intrinsic program.
  • External factors like the mesenchymal stromal cells, the immune system, and glycoproteins.
• Glycoproteins: Growth factors, colony stimulating factors, and interleukins interact in the regulation of cells.
• In conditions of high blood cells need, such as acute haemorrhage, the body initiates the haematopoiesis process. In normal states it is guaranteed.

Haematopoietic Stem Cells (HSC)

• HSC: Undifferentiated, totipotent cells producing all blood cell types.
• Difficult to identify, spotted indirectly, laying in the osteoblastic niche
• Have unlimited proliferative potential, ensuring a stable HSC pool throughout life.
• Can produce all blood cells (differentiation)
• Can proliferate via asymmetrical division (self-renewal).
• HSC pool is maintained
• Two proposed models:
  • Stochastic: HSC division produces one differentiated cell and one HSC, regenerating the pool.
  • Microenvironmental induction: An environment is key after the first HSC differentiation in cells, for further differentiation and regeneration to HSC phenotype in the osteoblastic niche.

Key Concepts

• Haematopoiesis: Dynamic process of blood cell formation and maturation.
• Proliferation during haematopoiesis ensures the maintenance of (HSC) pool.
• Differentiation leads to mature blood cells and is regulated by internal and external signalling, like the haematopoietic niche.
• Totipotent HSCs differentiate into peripheral blood cells and remain stable, presenting unlimited mitotic ability.
• Commitment: The process leading to hematopoietic progenitors formed from HSCs.
• Progenitors differentiate into lymphoid (lymphoblasts) and myeloid (erythroblasts, granuloblasts, monoblasts, megakaryoblasts) lineages.
• Constant renewal: Occurs to produce blood cells hourly, producing 10 billion red and 1 billion white blood cells.
• Requirements under stress like blood loss or infections could increase 10+ times or more

Cancer/Leukemic Stem Cells

• HSCs have cancer/leukemic stem cell counterparts (cancer stem cells: solid tumors, leukemia initiating cells or LIC: blood tumors) which have characteristics largely mirror to normal hematopoietic stem cells:
  • They are quiescent.
  • They can self renew through proliferation
  • Rate is not as high as normal stem cells
  • They can differentiate, but become leukemic cells
• First Theory: Only a subset of extensive proliferation in cancer cells, they are the cancer stem cells, responsible for the unregression of tumors when with chemotherapy or radiotherapy
• Liquid tumor cell study and can be performed through:
  • In vitro colony forming assay: Where cells incubated to count amount of cells produced into clones then called tumor cells
  • In vivo transplantation assays: immune deficient animal has leukemic cell transplanted and tested if it recreates tumors that means containing tumor stem cells, for staminal neoplastic cell isolation
• Stem cell transplants could fail or have the potential of being too small. As well, the cell stem cells’ terminal phase of life can have self-renewal capacity problems to generate new pool of tumor cells
• Tumoral cells can produce more “mature” cancer cells to generate pool of cells which is highly heterogenous.
• Chemoresistance, diseases’ recurrence and mets are all mainly caused by these cells, which chemotherapy and radiation act on when cycling
• Stem cells avoid the action because they are quiescent and those can regenerate pool after, or invade when those grow in size/treatment free
• New cancer stem cell targeting through immunotherapies, combinations, and tumor nonproliferating factors
• Full tumor elimination: Rarely necessary for tending on a therapy of reducing the tumor for immune system treatment

Haematological Tumors

• Origin can be from mature blood and immune system cells, or from immature precursors or progenitors
• Clonal diseases term also apply to solid tumors
• Develop abnormal features through the accumulation of genetic (DNA alterations) and epigenetic events (transcription regulation modifications) that production of abnormal protein, responsible for phenotype alteration
• Possibility of evading: Immunologic control ( lymphocytes unable to recognize irregular antigens from neoplastic cells).
• Leukemia evolution: Multitep that gains through tumor development, that is heterogeneous for leukemia through mutation patients that may have accumulate
• Mutations within those clonal cells that have some common alteration, although some subclones give particular irregular, that are not able to be found in other tumor cells
• Each with a malignant phenotype needs: A number of events including cell cooperation
• The cell abnormalities are needed to have express neoplastic phenotype
• The abnormalities provide either survival ( for cell proliferation) or acquisition in genomic instability
• Age related Clonal Haematopoiesis means either age relationship or undetermined potential. It has small clones in bone marrow of healthy individual
• DNA peripherials (NGS) reveals mutations in cells, of healthy people
• Occur on genes involving hematologic malignancies, but remain untumoral until acquiring the leukemia mutations
• Risk factor: Higher risk development of blood diseases
• Can also involve high proliferative tissue

Abnormality clone generations

• Involve higher possibilities in acquiring new mutations on high proliferation rates
• Growing older causes reparation difficulty, errors during DNA development
• Lower ability immune system in control development
• Alters one of those genes because of related causes due to aging process may develop relations to tunmor phenotype
• Could involve either germline or somatic
• Typically involved in hemotologic malignancy (DNT3A, TP53, JAK2, etc)
• Cells are to acquire also other mutations, as well as have pre-AML

Gene relations

• germline: predispose cancer.
• Hereditary is acquired from the uterus.
• All the body the patient bears germline even being only determined in the target tissue, so they are cause for familial tumors
• Somatic: the late mutation can be found just in neoplasmic cell and causes them the sporadic tumors, is classifiable in the early time phase (onset) of transformation/mutation or with late mutation being more related to full phenotype/tumoral, with major difference regarding the time transformation
• Oncogenes alteration, expresses high in some levels/abnormally (when should be silent )
• Oncosuppressors: the downregulation/inactivactivation reduce/absent protein transcription, has loss function. or has haploinsufficiency
• Genes affected genetic/epigenetic: karyotype (visible at chromosomal level,translocations/deletion/inversions/insertions/gaines/amplificatios) or molecular (few nucleidies sequence at level DNA/ just few nucleidies -referable as gene mutations/lots of there , distinguish missense mutation that is modified proteins.) Proto-oncogene can develop
• Proto-oncogene mutation: point mutation coding that hyperactive protein has more amplification (gene presented in mor ethen ) and recombination translocation
• In gene translocations: fusion active causes high protein
• Onco:deletions by losing or modification the function for hyperactivation/suppressor

Classification

• Methylation in DNA/histone/covalent
• Post translational modification,relaxation of chromatin

(WHO) Classifications

• Allows to diagnose with base diagnostic, through integration multiples, needs of recognizing by integrate multiples techniques -Morphology/Histopathology/Antigens and the immunophenotype -Classificatons stay upgraded

• Classified acute/chronic for progress of disease

• Class based on lesion/affected cells where immature cells become a higher number in peripheric tissue/blood or if lesion localized / lymph nodes.

• Genetic : Integrate genetic diagnosis, genetic entity, integrate -cytogenetic(study of karyotype) first/ molecular cytogenetic second/ molecular bio sequencing to express and assign -use algorithmic diagnosis to each, also classify according strats/prognosis/therapeutics.

AML ( Acute Mycloid Leukemia)

• Stem cell afflicts, differentiation decrease due increase of not differenced (blasts) cells in marrow(over %, parameters due change

• Tumors arise from from tranformation myleid cell, increases for adults with agening elders, most frequents form in leukemia in elders Congenitals from baby's from months: genetic events make full tumor phenotype : related maturation arrest, with accumulation of cells not grown in full that can invade.

• Multiple tool investigation must perform/based quantitative analysis in Micropscope, colors, immunophenotype recognizing surface, cytogenetics karyotiype etc and genotype based gene fusions.

• Latest classification(2017) states to consider the subtype for what that changes if need effect/ or not subtypes in patient -Based genetic lesions: fusions/rearrangments with/without alterations the subtypes.