Purification of polypeptide growth factors from milk

Bovine Colostrum: Its Constituents and Uses

Colostrum is the milk produced during the first few days after birth and contains high levels of immunoglobulins, antimicrobial peptides, and growth factors. Colostrum is important for supporting the growth, development, and immunologic defence of neonates. Colostrum is naturally packaged in a combination that helps prevent its destruction and maintain bioactivity until it reaches more distal gut regions and enables synergistic responses between protective and reparative agents present within it. Bovine colostrum been used for hundreds of years as a traditional or complementary therapy for a wide variety of ailments and in veterinary practice. Partly due to concerns about the side effects of standard Western medicines, there is interest in the use of natural-based products of which colostrum is a prime example. Numerous preclinical and clinical studies have demonstrated therapeutic benefits of bovine colostrum for a wide range of indications, including maintenance of wellbeing, treatment of medical conditions and for animal husbandry. Articles within this Special Issue of Nutrients cover the effects and use bovine colostrum and in this introductory article, we describe the main constituents, quality control and an overview of the use of bovine colostrum in health and disease.

Quantitative evaluation of endothelial progenitors and cardiac valve endothelial cells: proliferation and differentiation on poly-glycolic acid/poly-4-hydroxybutyrate scaffold in response to vascular endothelial growth factor and transforming growth factor beta1

Three-dimensional scaffolds made of bioabsorbable polymeric constituents are currently being tested for use in tissue engineering of various tissues. A composite scaffold of poly-glycolic acid (PGA) non-woven mesh dip-coated in a 1% solution of poly-4-hydroxybutyrate (P4HB) was shown to be suitable as a scaffold for creation of tissue-engineered trileaflet pulmonic valve replacements in sheep [Hoerstrup, S.P., et al., Circulation 102(Suppl. 3), III44, 2000]. However, little is known about how cells seeded on PGA/P4HB respond in vitro to soluble factors supplied in the culture medium. To optimize tissue development in vitro, before implantation, we set out to develop quantitative biochemical assays to measure how cells seeded on PGA/P4HB respond to growth and differentiation factors. Herein we show that ovine aortic valvular endothelial cells and circulating endothelial progenitor cells (EPCs) seeded onto PGA/P4HB proliferate in response to vascular endothelial growth factor and transdifferentiate to a mesenchymal phenotype in response to transforming growth factor beta(1). Transdifferentiation from an endothelial to mesenchymal phenotype is a critical step during embryonic development of cardiac valves. Our results demonstrate that valvular endothelial cells and EPCs isolated from peripheral blood can recapitulate critical developmental steps on PGA/P4HB. These results demonstrate that PGA/P4HB provides a conducive environment for cellular proliferation, differentiation, and tissue development.

NFATc1 mediates vascular endothelial growth factor-induced proliferation of human pulmonary valve endothelial cells

Mice deficient for the transcription factor NFATc1 fail to form pulmonary and aortic valves, a defect reminiscent of some types of congenital human heart disease. We examined the mechanisms by which NFATc1 is activated and translocated to the nucleus in human pulmonary valve endothelial cells to gain a better understanding of its potential role(s) in post-natal valvular repair as well as valve development. Herein we demonstrate that activation of NFATc1 in human pulmonary valve endothelial cells is specific to vascular endothelial growth factor (VEGF) signaling through VEGF receptor 2. VEGF-induced NFATc1 nuclear translocation was inhibited by either cyclosporin A or a calcineurin-specific peptide inhibitor; these findings suggest that VEGF stimulates NFATc1 nuclear import in human pulmonary valve endothelial cells by a calcineurin-dependent mechanism. Importantly, both cyclosporin A and the calcineurin-specific peptide inhibitor reduced VEGF-induced human pulmonary valve endothelial cell proliferation, indicating a functional role for NFATc1 in endothelial growth. In contrast, VEGF-induced proliferation of human dermal microvascular and human umbilical vein endothelial cells was not sensitive to cyclosporin A. Finally, NFATc1 was detected in the endothelium of human pulmonary valve leaflets by immunohistochemistry. These results suggest VEGF-induced NFATc1 activation may be an important mechanism in cardiac valve maintenance and function by enhancing endothelial proliferation.

Characterization of receptors of insect cytokine, growth-blocking peptide, in human keratinocyte and insect Sf9 cells

Insect cytokine, growth-blocking peptide (GBP), enhances cell proliferation of human keratinocyte cells with a potency almost equivalent to that of human epidermal growth factor (EGF). GBP consists of 25 amino acid residues containing a core region that shows a striking similarity to the C-terminal beta-loop domain of EGF and disordered N and C termini. The present study demonstrates that, although GBP lacks the N-terminal half-portion of EGF molecule, at least five amino acids of the disordered N-terminal six-amino acid region are indispensable for affecting the cell growth activity of GBP. Upon stimulating mitogenesis in keratinocyte cells, GBP directly binds and activates their EGF receptors. GBP also effects proliferative activity on insect Sf9 cells through the binding and activation of the specific receptor, which consists of a heterodimeric complex: a binding subunit (60 kDa) and a tyrosine phosphorylation subunit (58 kDa). These results indicate that GBP enhances cell proliferation of human keratinocyte and insect Sf9 cells through the activation of EGF and GBP receptors, respectively.

Colostrum and milk-derived peptide growth factors for the treatment of gastrointestinal disorders

Colostrum is the specific first diet of mammalian neonates and is rich in immunoglobulins, antimicrobial peptides, and growth factors. In this article we review some of these constituents of human and bovine colostrum in comparison with those of mature milk. Recent studies suggest that colostral fractions, or individual peptides present in colostrum, might be useful for the treatment of a wide variety of gastrointestinal conditions, including inflammatory bowel disease, nonsteroidal antiinflammatory drug-induced gut injury, and chemotherapy-induced mucositis. We therefore discuss the therapeutic possibilities of using whole colostrum, or individual peptides present in colostrum, for the treatment of various gastrointestinal diseases and the relative merits of the 2 approaches.

Construction of an efficient Bacillus subtilis system for extracellular production of heterologous proteins

An efficient expression/secretion vector, designated pM2Veg, was constructed for extracellular production of heterologous proteins in Bacillus subtilis. To construct pM2Veg, a synthetic cassette, the Veg cassette carrying: (1) the strong vegetative vegI promoter from B. subtilis, (2) the Escherichia coli lac operator, (3) the B. subtilis consensus ribosome-binding site, (4) the Staphylococcal protein A leader sequence, (5) a cloning region for insertion of foreign genes, (6) translational stop codons in all three reading frames, and (7) the gnt transcriptional terminator, was cloned into a derivative of the stable pRB373 B. subtilis/E. coli shuttle plasmid, the pM2 vector. The application of pM2Veg to effect secretory production of heterologous proteins was illustrated using two widely different proteins: the endoglucanase (Eng) encoded by the cenA gene of Cellulomonas fimi and human epidermal growth factor (hEGF). Levels of Eng and hEGF measured in culture supernatant samples of B. subtilis transformants harboring recombinant constructs formed between pM2Veg and the cenA and hEGF genes were 8.3 U ml-1 and 7.0 mg l-1, respectively. The Eng activity is more than four times higher than the yield from the best cenA recombinant construct previously reported, and the hEGF data represents the first successful expression of the factor in B. subtilis.

Determination of transforming growth factor-beta 1 (TGF-beta 1) and insulin-like growth factor (IGF-1) in bovine colostrum samples

The major growth factors in bovine colostrum are transforming growth factor-beta s (TGF-beta 1 and TGF-beta 2) and insulin-like growth factors (IGF-1 and IGF-2). Recently, TGF-beta 2 content of bovine colostrum was measured using a TGF-beta 2 specific ELISA (1) and now we have validated ELISAs for for bovine TGF-beta 1 and IGF-1. The concentrations of IGF-1 and TGF-beta 1 in the first milking after calving were 248-1850 ng/ml and 12.4-42.6 ng/ml, respectively, and they declined in correlation with total protein concentration to 27.0-101 ng/ml (IGF-1) and 0.80-3.49 ng/ml(TGF-beta 1) by the fifth milkings. The amount of TGF-beta 1 was on average 5.3 +/- 1.4% of that of TGF-beta 2 and there is a high correlation (r = 0.966) between the concentrations of these growth factors in the same samples. No free TGF-beta 1 form of could be detected.

Studies on the growth-stimulatory activity of pigeon milk--comparison and synergistic effects with serum

Pigeon milk, a nutritive secretion from the crop of breeding pigeons, was tested (on v/v basis) for growth factor activity either separately or in combination with other growth supplements. Synthesis of DNA in confluent monolayers of quiescent Chinese hamster ovary cells was enhanced by the homogenates of pigeon milk in the presence of both fetal bovine serum and bovine serum albumin, although the response with fetal bovine serum was greater than that with bovine serum albumin. The in vitro growth stimulation by pigeon milk was also reflected in the increase in cell number. Specific activity of pigeon milk growth factor, measured against both Chinese hamster ovary cells and mouse embryo fibroblasts, was found to be higher than that of fetal calf serum, fetal bovine serum, and goat, horse, pig and human serum. The growth-stimulatory property of pigeon milk did not change in the first 5 days of its secretion.

Bovine colostrum fraction as a serum substitute for the cultivation of mouse hybridomas

Fractions of bovine colostrum were prepared and their ability to support the growth of mouse-mouse hybridomas in culture was tested. Whey was prepared from defatted colostrum by removal of casein using acid precipitation. An ultrafiltrate was obtained from cleared whey by filtration through membranes with a nominal molecular mass cut-off of 100,000 Da. Colostrum ultrafiltrate contained 1.16 milligrams protein, 0.24 milligrams immunoglobulin G (IgG) and less than 0.24 EU (endotoxin unit)/ml endotoxins. The effect of defatted colostrum, whey and ultrafiltrate as serum substitutes was examined by cultivation of hybridoma cells in minimal essential medium containing different concentrations of the supplements. Under optimal conditions in ultrafiltrate-supplemented medium, the maximal cell concentration was 35-40% of that obtained using 10% foetal bovine serum, and IgG production per cell was equal to that achieved using serum. In 1% defatted colostrum the maximum hybridoma concentration was about 30% of that in 10% serum, but at higher concentrations hybridoma growth was significantly reduced. The growth-promoting activity of whey was low. The results show that bovine colostrum ultrafiltrate provides a very attractive alternative to serum for production of monoclonal antibodies.

Neuroendocrine peptides in milk

Milk, which is a mammal-specific biologic fluid, contains several neuroendocrine peptides at concentrations higher than those found in plasma. These neuroendocrine peptides can be synthesized or processed in the mammary gland or excreted into milk through various pathways. In addition, certain milk proteins, notably casein, can be enzymatically processed to release "exorphins," peptides with opioid activities. In suckling mammals, hormones and neuropeptides are absorbed through the gastrointestinal tract and appear intact in the plasma. This absorption is age dependent and could have physiologic significance in neonatal development.

Identification of a unique biological tumor marker in human breast cyst fluid and breast cancer tissue

Breast cyst fluid from 35 women was stratified into risk groups based on personal and family history of breast cancer. Mitogenic activity in breast cyst fluid of women at highest risk to develop breast cancer was significantly higher than the activity in the lowest-risk group. There was a direct dose-dependent relationship between mitogenic activity and increased risk of developing breast cancer. Size-exclusion chromatography showed that breast cyst fluid from women at highest risk contained two peaks of growth factor activity: less than 6 kilodaltons (kd), identified as human EGF (epidermal growth factor), and 6 to 18 kd. Moderate-risk group samples demonstrated only the single less than 6 kd peak, whereas the lowest-risk group had insignificant growth-promoting activity. Breast cancer tissue analyzed in a similar manner revealed a predominant 6- to 14-kd peak of mitogenic activity demonstrating the same acid- and heat-stability found in breast cyst fluid.