growth factors

(noun)

Naturally occurring substances that stimulate cell growth, proliferation, healing, and cellular differentiation.

Related Terms

Examples of growth factors in the following topics:

  • Growth Factors

    • A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation.
    • A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation such as granulocyte macrophage colony-stimulating factor (GM-CSF), a growth factor which stimulates the production of white blood cells.
    • Growth factors are typically cytokines or hormones, but not all cytokines and hormones are growth factors.
    • Confusingly cytokine and growth factor are sometimes used interchangeably.
    • As with cytokines some are involved with growth, such as growth hormone produced by the anterior pituitary gland and may be classed as growth factors, but others are not.

  • Bone Remodeling

    • Numerous bone-derived growth factors have been isolated and classified via bone cultures.
    • These factors include insulin-like growth factors I and II, transforming growth factor beta, fibroblast growth factor, platelet-derived growth factor, and bone morphogenetic proteins.
    • Platelet-derived growth factor has been found to enhance bone collagen degradation.
    • Evidence suggests that bone cells produce growth factors for extracellular storage in the bone matrix.
    • Essentially, bone growth factors may act as potential determinants of local bone formation.

  • Medical Uses of Hematopoietic Growth Factors

    • Hemopoetic growth factors regulate the growth, differentiation, and proliferation of progenitor cells in the blood and bone marrow.
    • Hemopoetic growth factors show promise in improving the lives of those suffering from kidney disease or recovering from chemotherapy.
    • Hemopoietic growth factors regulate the differentiation and proliferation of particular progenitor cells.
    • Trials of a modified recombinant form, megakaryocyte growth and differentiation factor (MGDF), were stopped when healthy volunteers developed autoantibodies to endogenous thrombopoietin and then developed thrombocytopenia themselves.
    • GCSF is a glycoprotein growth factor that stimulates the bone marrow and is used therapeutically in certain cancer patients to accelerate recovery from neutropenia after chemotherapy.

  • Platelets

    • Platelets secrete many factors involved in coagulation and wound healing.
    • They also release wound healing-associated growth factors including platelet-derived growth factor (PDGF), which directs cell movement; TGF beta, which stimulates the deposition of extracellular matrix tissue into a wound during healing; and vascular endothelial growth factor (VEGF), which stimulates angiogenesis, or the regrowth of blood vessels.
    • These growth factors play a significant role in the repair and regeneration of connective tissues.
    • Local application of these platelet-produced healing-associated factors in increased concentrations has been used as an adjunct to wound healing for several decades.
    • Thrombosis also occurs when blood is allowed to pool, which causes clotting factors and platelets to form a blood clot even in the absence of an injury.

  • Aging and the Endocrine System

    • Three hormone axes are affected by aging: growth hormone/insulin-like growth factor I, cortisol/dehydroepiandrosterone, and testoterone/estradiol.
    • Three of the most important hormone axes in the endocrine system that are affected by aging include growth hormone (GH)/insulin-like growth factor I (IGF-I), cortisol/dehydroepiandrosterone (DHEA), and testosterone/estradiol.
    • Nuclear factor kappa B, which is a transcription factor, inhibits the activation induced apoptotic response (programmed cell death) that becomes more prevalent with aging.
    • GCs inhibit this transcription factor which in turn decreases inhibition of apoptosis.
    • Evaluate the effects of the hormonal axes affected by aging [growth hormone (GH)/insulin-like growth factor I (IGF-I), cortisol/dehydroepiandrosterone (DHEA), and testosterone/estradiol]

  • Platelet Plug Formation

    • During an injury, subendothelial collagen from the extracellular matrix beneath the endothelial cells is exposed on the epithelium as the normal epithelial cells are damaged and removed, which releases von Willebrand Factor (VWF).
    • The released chemicals include ADP, VWF, thromboxane A2, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), serotonin, and coagulation factors.
    • The other factors released during platelet activation perform other important functions.
    • PDGF and VEGF are involved in angiogenesis, the growth of new blood vessels and cell cycle proliferation (division) following injury.
    • The coagulation factors include factor V and VIII, which are involved in the coagulation cascade that converts fibrinogen into fibrin mesh after platelet plug formation.

  • Angiogenesis and Disease

    • Angiogenesis, the growth of new blood vessels from existing vessels, contributes to both normal tissue growth and tumorigenesis in cancer.
    • Tumors induce blood vessel growth (angiogenesis) by secreting various growth factors (e.g., VEGF).
    • Growth factors such as bFGF and VEGF can induce capillary growth into the tumor, which some researchers suspect supply the required nutrients that allow for tumor expansion .
    • Diverse chemoattractant factors promote the recruitment and infiltration of bone marrow cells to the tumor microenvironment where they suppress the antitumor immunity or promote tumor angiogenesis and vasculogenesis
    • Angiogenesis becomes clearly evident during dysplasia and is critical for further growth.

  • Capacity of Different Tissues for Repair

    • Growth is governed by factors secreted from Schwann cells.
    • Growth factors are not expressed or re-expressed.
    • Glial scars rapidly form, and the glia actually produce factors that inhibit remyelination and axon repair.
    • The axons themselves also lose the potential for growth with age.
    • The remodeling phase takes three to five years depending on factors such as age or general condition.

  • Hormonal Abnormalities and Height

    • Abnormal production of growth hormone due to tumors on the pituitary or other genetic causes can cause pathological changes in growth.
    • However, if these are not factors, then growth hormone deficiency may be the cause.
    • Growth hormone deficiency (GHD) is a medical condition in which the body produces insufficient growth hormone.
    • Growth hormone, also called somatotropin, is a polypeptide hormone which stimulates growth and cell reproduction.
    • Growth hormone deficiency has no single definite cause.

  • Regeneration of Nerve Fibers

    • The growth of the sprouts are governed by chemotactic factors secreted from Schwann cells (neurolemmocytes).
    • Also, macrophages and Schwann cells release neurotrophic factors that enhance re-growth.
    • Glial scars rapidly form and the glia actually produce factors that inhibit remyelination and axon repair.
    • The axons themselves also lose the potential for growth with age.
    • All these factors contribute to the formation of what is known as a glial scar, which axons cannot grow across.