Cultured tumor cells produce chemotactic factors specific for endothelial cells: a possible mechanism for tumor-induced angiogenesis.

The production of stimulants of endothelial cell motility by cultured tumor cells was studied. Spontaneously transformed murine fibroblasts in culture produced activity that stimulated migration of endothelial cells, while this kind of activity was not detected in media from cultures of the normal counterparts of the transformed cells. Furthermore, a line of murine tumor cells (HB4), known to induce vasoformative sarcomas in vivo, was found to produce in culture a strong chemoattractant specific for endothelial cells. Since the tumor-derived material also caused vessel ingrowth when implanted in the rabbit eye, these results suggest that the angiogenesis observed during tumor growth may involve chemoattractants for endothelial cells produced by tumor cells.

Platelet-derived growth factor is a chemoattractant for vascular smooth muscle cells.

In previous experiments (Grotendorst et al, 1981), we showed that platelet-derived growth factor promotes the migration of smooth muscle cells in vitro. Using a "checkerboard" analysis, we now establish that platelet-derived growth factor (PDGF) acts as a true chemoattractant for cultured aortic smooth muscle cells. Other growth factors such as epidermal growth factor, fibroblast growth factor, and insulin are not chemoattractants. The chemotactic response occurs before the initiation of DNA synthesis and is not affected by inhibition of DNA synthesis. Chemotaxis occurs at levels of PDGF lower than required for mitogenesis. RNA and protein synthesis are required for the chemotactic response. As found previously in bacteria and leucocytes, we find that methylation reactions are required for the chemotactic response. The possibility is discussed that PDGF acts in vivo at sites of vascular injury to attract smooth muscle cells from the medial layer to the luminal surface, and is involved in the early stages of the formation of atherosclerotic plaques.

Fibronectin promotes rat Schwann cell growth and motility.

Techniques are now available for culturing well characterized and purified Schwann cells. Therefore, we investigated the role of fibronectin in the adhesion, growth, and migration of cultured rat Schwann cells. Double-immunolabeling shows that, in primary cultures of rat sciatic nerve, Schwann cells (90%) rarely express fibronectin, whereas fibroblasts (10%) exhibit a granular cytoplasmic and fibrillar surface-associated fibronectin. Secondary cultures of purified Schwann cells do not express fibronectin. Exogenous fibronectin has a small effect on promoting the adhesion of Schwann cells to the substrate and does not significantly affect cell morphology, but it produced a surface fibrillar network on fibronectin on the secondary Schwann cells. Tritiated thymidine autoradiography revealed that addition of fibronectin to the medium, even at low concentrations, markedly stimulates Schwann cell proliferation, in both primary and secondary cultures. In addition, when cell migration was measured in a Boyden chamber assay, fibronectin was found to moderately, but clearly, stimulate directed migration or chemotaxis.

The cell binding fragment of fibronectin is chemotactic for fibroblasts.

The fibroblast chemoattractant property of fibronectin is retained in the proteolytically produced 160 kilodalton peptide that contains the heparin binding and cell binding domains of the molecule, while the 40 kilodalton collagen binding peptide is inactive. Further degradation of the 160 kilodalton peptide leads to destruction of chemoattractant activity. An analysis of the migration of fibroblasts in varied gradients of the 160 K peptide shows that the effect is chemotactic, i.e. directed migration of cells towards a higher concentration of the peptide.

Attachment of smooth muscle cells to collagen and their migration toward platelet-derived growth factor.

Smooth muscle cells use fibronectin to bind to type I and type III collagens but bind to type V collagen by a trypsin-resistant intrinsic glycoconjugate. The binding site on type V collagen is located in the alpha A chain. By using collagen-coated filters in a modified Boyden chamber assay for chemotaxis, it was observed that the platelet-derived growth factor was chemotactic for smooth muscle cells but that several other growth factors were inactive. We suggest that the migration of smooth muscle cells from the media to the intima of a blood vessel, which leads to the formation of an atherosclerotic plaque, may be the result of a chemotactic migration of cells responsive to the platelet-derived growth factor.

The main neutral protease of rat skin is a mast cell enzyme. Immunohistochemical localization of the enzyme in rat skin with the peroxidase-antiperoxidase (PAP) complex method.

The highly sensitive PAP immunoperoxidase method was used to localize the main neutral protease of rat skin. The use of the neutral detergent, Triton X-100, in the reagent and washing solutions was observed to effectively decrease the nonspecific staining. The specific staining was localized to the mast cell granules.

Rat skin main neutral protease: immunohistochemical localization.

Specific antiserum against the purified rat skin main neutral protease was used in double layer immunofluorescent method to localize the enzyme in normal rat skin. The specific immunofluorescence was seen in dermal cells that were identified as mast cells on basis of their metachromatic granules. Enzyme histochemical staining with naphthol AS-D chloroacetate localized to the same cells that exhibited specific immunofluorescence. The granules of isolated rat mast cells also gave a specific reaction with the immunohistochemical technique. The results provide further evidence for the suggestion that rat skin main neutral protease is identical with the rat mast cell "chymase."

A rat skin acid esteroprotease hydrolyzing benzoylarginine ethylester: purification and properties.

A benzoylarginine ethylester hydrolyzing enzyme from rat skin has been purified 54-fold by chromatography on arginine methylester-CH-Sepharose and Sephadex G-200 prior to isoelectrofocusing. The molecular weight of the enzyme is approximately 125,000. The enzyme hydrolyzes bensoylarginine ethylester, acetyltyrosine ethylester, benzoylarginine methylester, benzoyllysine methylester, and benzoylalanine methylester. Casein is slightly hydrolyzed at an optimum pH of 6.5. The enzyme is inhibited by diisopropylfluorophosphate, and p-chloromercuribenzoic acid. KC1 enhances the extraction of the enzyme, increased its activity, and is essential for its stability.