Fibroblast growth factor-2-toxin induced cytotoxicity: differential sensitivity of co-cultured vascular smooth muscle cells and endothelial cells

Co-culture models of endothelial cells, macrophages, and vascular smooth muscle cells for the study of the natural history of atherosclerosis

BACKGROUND

This work aims to present a fast, affordable, and reproducible three-cell co-culture system that could represent the different cellular mechanisms of atherosclerosis, extending from atherogenesis to pathological intimal thickening.

METHODS AND RESULTS

We built four culture models: (i) Culture model #1 (representing normal arterial intima), where human coronary artery endothelial cells were added on top of Matrigel-coated collagen type I matrix, (ii) Culture model #2 (representing atherogenesis), which demonstrated the subendothelial accumulation and oxidative modification of low-density lipoproteins (LDL), (iii) Culture model #3 (representing intimal xanthomas), which demonstrated the monocyte adhesion to the endothelial cell monolayer, transmigration into the subendothelial space, and transformation to lipid-laden macrophages, (iv) Culture model #4 (representing pathological intimal thickening), which incorporated multiple layers of human coronary artery smooth muscle cells within the matrix. Coupling this model with different shear stress conditions revealed the effect of low shear stress on the oxidative modification of LDL and the upregulation of pro-inflammatory molecules and matrix-degrading enzymes. Using electron microscopy, immunofluorescence confocal microscopy, protein and mRNA quantification assays, we showed that the behaviors exhibited by the endothelial cells, macrophages and vascular smooth muscle cells in these models were very similar to those exhibited by these cell types in nascent and intermediate atherosclerotic plaques in humans. The preparation time of the cultures was 24 hours.

CONCLUSION

We present three-cell co-culture models of human atherosclerosis. These models have the potential to allow cost- and time-effective investigations of the mechanobiology of atherosclerosis and new anti-atherosclerotic drug therapies.

Complimentary endothelial cell/smooth muscle cell co-culture systems with alternate smooth muscle cell phenotypes

Development of in vitro models of native and injured vasculature is crucial for better understanding altered wound healing in disease, device implantation, or tissue engineering. Conditions were optimized using polyethyleneteraphalate transwell filters for human aortic endothelial cell (HAEC)/smooth muscle cell (HASMC) co-cultures with divergent HASMC phenotypes ('more or less secretory') while maintaining quiescent HAECs. Resulting HASMC phenotype was studied at 48 and 72 h following co-culture initiation, and compared to serum and growth factor starved monocultured 'forced contractile' HASMCs. Forced contractile HASMCs demonstrated organized alpha-smooth muscle actin filaments, minimal interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) secretion, and low intracellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and tissue factor expression. Organization of alpha-smooth muscle actin was lost in 'more secretory' HASMCs in co-culture with HAECs, and IL-8 and MCP-1 secretion, as well as ICAM-1, VCAM-1, and tissue factor expression were significantly upregulated at both time points. Alternately, 'less secretory' HASMCs in co-culture with HAECs showed similar characteristics to forced contractile HASMCs at the 48 h time point, while by the 72 h time point they behaved similarly to 'more secretory' HASMCs. These co-culture systems could be useful in better understanding vascular healing, however there remain time constraint considerations for maintaining culture integrity/cell phenotype.

Immunotoxins containing recombinant anti-CTLA-4 single-chain fragment variable antibodies and saporin: in vitro results and in vivo effects in an acute rejection model

Immunotoxins containing recombinant human-derived single-chain fragment variable (scFv) reagents (83 and 40) against CTLA-4 (CD152) linked to saporin, a ribosome-inactivating protein, were prepared and tested on CD3/CD28-activated T lymphocytes, MLRs, CTLA-4-positive cell lines, and hemopoietic precursors. Immunotoxins induced apoptosis in activated T lymphocytes and were able to specifically inhibit MLR between T lymphocytes and dendritic cells. The 83-saporin immunotoxin also inhibited the T cell activation in an MLR between T lymphocytes and an EBV-positive lymphoblastoid B cell line. Toxicity tests on hemopoietic precursors showed little or no effects in inhibiting colonies' growth. As the 83 scFv Ab was reactive also with activated mouse T lymphocytes, 83-saporin was tested in a model of tumor rejection consisting of C57BL/6 mice bearing a murine H.end endothelioma cell line, derived from DBA/2 mice. The lymphoid infiltration due to the presence of the tumor was reduced to a high extent, demonstrating that the immunotoxin was actually available and active in vivo. Thus, taking the results altogether, this study might represent a new breakthrough for immunotherapy, showing the possibility of targeting CTLA-4 to kill activated T cells, using conjugates containing scFv Abs and type 1 ribosome-inactivating protein.

Angiogenic mechanisms of endothelialization of cardiovascular implants: a review of recent investigative strategies

Both cardiovascular implants and therapeutic interventions on native arteries fail due to biologic responses occurring at the blood/prosthesis/arterial wall and tissue/prosthesis/arterial wall interfaces, resulting in the failure modes of thrombosis and myointimal hyperplasia. Systemic pharmacologic approaches including use of anti-coagulant and anti-platelet agents have significant untoward side effects and have not resulted in a dramatic impact on failure modes in many applications, including small diameter vascular grafts. Local delivery of therapeutic agents via surface attachment with defined release kinetics may alter thrombogenicity and/or myointimal hyperplasia. Therapeutic agents may include a spectrum of biologic agents from peptides to endothelial cells. Efficient attachment and release of these agents in biologically active form is dependent upon improved methods of surface modification. The intended action of the biologic agent may similarly be impacted by the surface and bulk characteristics of the underlying biomaterial. It is often assumed, without concrete data. that surface re-endothelialization may have a beneficial impact on both thrombogenicity and myointimal hyperplasia. New clinical data on endothelial cell seeding has been supportive. Spontaneous re-endothelialization may be stimulated via an induced directed angiogenesis resulting in trans-interstitial capillarization and surface endothelialization. Recent advances in therapeutic angiogenesis have suggested the power of angiogenic factors to induce neovascularization of ischemic tissue beds. These concepts have been used to surface modify prosthetic devices with either VEGF or FGF and both in vitro and animal data suggest a potent stimulation of surface re-endothelialization. Neither of these growth factors is likely to be ideal. VEGF is relatively endothelial cell specific but is a relatively weak endothelial cell mitogen. FGF-1 and FGF-2 are more potent mitogens but are less cell specific. Recent work has led to the generation of mutant growth factors via site-induced mutagenesis and results of several such FGF mutants on endothelial cell and smooth muscle cell proliferative response have been studied. The use of 'designer growth factors' on cardiovascular implants and on manipulated native vessels may have a significant positive impact on re-endothelialization and thereby on the failure modes of thrombosis and myointimal hyperplasia.

Irradiated versus nonirradiated endothelial cells: effect on proliferation of vascular smooth muscle cells

PURPOSE

Endovascular radiation therapy is a promising strategy for the prevention of restenosis. Radiation prevents proliferation of vascular smooth muscle cells, thereby reducing the incidence of restenosis, but may also affect the remaining endothelial cells. For this reason, a comparison was made between irradiated and nonirradiated endothelial cells and their effects on the proliferation of vascular smooth muscle cells in a coculture system was evaluated.

MATERIALS AND METHODS

A coculture system was used, in which both endothelial cells and vascular smooth muscle cells were grown on opposite sides of a semipermeable membrane. After a period of growth arrest, the proliferation of vascular smooth muscle cells was measured during four subsequent days.

RESULTS

The presence of endothelial cells stimulated the proliferation of vascular smooth muscle cells during the first days of analysis but had an inhibitory effect during the subsequent days (P <.5). gamma-irradiation of endothelial cells resulted in a complete blockage of the proliferation of these cells. However, irradiated endothelial cells affected the proliferation of vascular smooth muscle cells in coculture in a fashion comparable to nonirradiated endothelial cells (P >.5).

CONCLUSION

The results suggest that, in endovascular radiation therapy, irradiation of endothelial cells does not change their effects on the proliferative behavior of vascular smooth muscle cells.

Heterotypic smooth muscle cell/endothelial cell interactions differ between species

BACKGROUND

In vitro coculture models have been used to study heterotypic cell-cell interactions. This study was performed to determine if species of cell origin affects heterotypic smooth muscle cell (SMC) endothelial cell (EC) interactions in coculture.

METHODS

To study the effect of ECs on SMC proliferation, ECs were cultured on porous Dacron membranes. SMCs were added opposite the ECs or on bare membranes on Day 3, and after 4 days, cells were harvested for cell counts. To study the effect of SMCs on EC proliferation, ECs at a density of 5 x 10(5) cells/membrane were added to bare membranes or on membranes opposite SMCs plated 2 days earlier. After 48 h, cells were harvested for cell counts. (N = 3/condition, experiments repeated x2.) Cells of human and bovine aortic origin were used.

RESULTS

The effect of coculture on cell growth differed between species. The effect of heterotypic interactions between human cocultured cells was coinhibitory on the rate of growth as compared to the growth of cells cultured alone. Growth of cocultured ECs was 55.2 +/- 8.7% less than that of ECs cultured alone while growth of cocultured SMCs was 27.2 +/- 6.0% less than growth of SMCs cultured alone. This contrasted with the bovine EC stimulation of SMC proliferation, with 66.8 +/- 5.0% greater growth of cocultured SMCs compared to SMCs cultured alone, and failure of bovine SMCs to decrease EC proliferation.

CONCLUSIONS

Since significant differences in cell-material interactions occur in vivo between species, the finding that in vitro heterotypic cell-cell interactions are species dependent is not surprising. This fundamental difference in cell behavior stresses the potential importance of using human cells in studies evaluating cell-cell and cell-material interactions in vitro.