MEDICAL JOURNALIST REPORT OF INNOVATIVE BIOLOGICS CLINICAL APPLICATIONS
OF FROZEN, LIQUID, LIVER GROWTH FACTORS
Defining Live Cell Liver Peptide Growth Factors
reprinted from "Triumph Over Hepatitis C" with permission
From the Department of Pathology and Laboratory Medicine at Brown University in Providence, Rhode Island, U.S.A., three investigating
pathologists, Drs. N. Fausto, A.D. Laird, and E.M. Webber, advise: "During liver regeneration quiescent hepatocytes [liver cells] undergo one or two rounds of replication and then return to a
nonproliferative state. Growth factors regulate this process by providing both stimulatory and inhibitory signals for cell proliferation.” (1)
The idea of intrinsic hepatic growth control
factors produced by animal and human liver cells has been stated in published reports, which date back as Iong as forty-six years ago. (2,3,4,5,6) Much of this early research was conducted on rats
and dogs, (7) but currently clinical investigations among both healthy human volunteers and really sick people have taken place.
Comprised of the tiniest of protein molecules which biochemists and
physiologists call peptides, these growth factors are of an exceedingly low molecular weight (30,000 Da) which yield two or more amino acids on hydrolysis. The Dalton with a symbol of D or Da, also
called an atomic mass unit is equivalent to 1.657 X 10 (24) gm. Peptide growth factors form by loss of water from the NH2and COOH molecular groups of adjacent amino acids and are additionally
referred to in biochemistry as di-, tri-, tetra-, etc. peptides, depending on the number of amino acids in the molecule. Thus peptides make up the constituent parts of proteins. Examples of those
several dozen peptides from the human liver and other organs which often give birth to growth factors are: hepatocyte growth factor (HGF), epidermal growth factor (EGF), transforming growth
factor-beta (TGF-beta), and dozens more. (7,8,9,10)
According to which of the various scientific disciplines are being queried, different names exist for peptide growth factors. Historically, for
instance, cell biologists have called members of their identified growth factor-type set of molecules "growth factors"; immunologists have named their growth factor-types
"interleukins," “lymphokines," or "cytokines"; while hematologists have used the growth factor-type descriptive term "colony stimulating factors" (CSF). However,
the present generally delineating nomenclature of "growth factors" has been and is now widely used throughout the world's scientific literature.
Thegrowth factor term is now used
consistently among almost every scientific and medical discipline because in almost every case it reflects the context of the original discovery or isolation of any peptide. Since essentially all
of these many molecules are multifunctional, it's not easy to conceive of unique new names for them that would be entirely satisfactory; almost all of them are “panregulins," that is they react as
universal regulators of the particular organ from which they derive. As you’ll learn below, for the animal and human body, actually, peptide growth factors are physiological symbols for the
transfer of signals or a kind of language of biological regulation. (11,12)
Peptides often promote cell growth, but they also can inhibit it; moreover, they regulate many critical cellular
functions, such as in the control of cell differentiation and other processes which have little to do with growth itself. All peptide growth factors actin sets. To understand their actions,
one must always consider the biological context in which they act.
Peptide growth factors provide an essential means for a cell to communicate with its immediate environment. They ensure
that there is proper local homeostatic balance between the numerous cells that comprise a tissue or organ. Since a cell must adjust its behavior to changes in its environment, the cell needs
mechanisms to provide this adaptation. Therefore the tissue cells either singularly or collectively use sets of peptide growth factors as signaling molecules to communicate with each other and to
alter their own behavior to respond appropriately to their biological context.
The most important peptide growth factors of the liver's hepatocytes have been identified as a collection of hormones
called somatomedins. These liver hormones are peptides which produce major effects on the growth of bone and muscle. Also they influence the metabolism of ingested minerals, including
calcium, phosphate, carbohydrate, and lipid. Somatomedins growth factors are indirectly stimulated to divide by the pituitary hormone somatotropin (also referred to as growth hormone by endocrinologists).
The peptide growth factors act by binding to functional receptors which transduce their signals, and the peptides themselves may be viewed as bifunctional molecules. The following are two
main responses or actions that peptide growth factors accomplish:
They possess an afferent function in that there is the conveying of information to cellular receptors, providing them with
information from outside the organism's cell, tissue, or organ.
They have an efferent function in that there is the inception of any latent biochemical activity of the receptor.