Basic fibroblast growth factor regulates extracellular matrix and contractile protein expression independent of proliferation in vascular smooth muscle cells

Modified method for effective primary vascular smooth muscle progenitor cell culture from peripheral blood

In previous studies, vascular smooth muscle progenitor cells (vSMPCs) isolated from peripheral blood mononuclear cells (PBMCs) were cultured using medium containing platelet-derived growth factor-BB (PDGF-BB) for 4 weeks. However, this method requires long culture periods of up to 4 weeks and yields low cell counts. Therefore, we proposed the modified method to improve the cell yield and purity and to reduce the cell culture period. PBMCs were isolated from human peripheral blood and cultured by the conventional method using medium containing PDGF-BB alone or the modified method using medium containing PDGF-BB, basic fibroblast growth factor (bFGF), and insulin-transferrin-selenium ITS for 4 weeks. The purity of vSMPCs was analyzed for the expression of a- smooth muscle actin (SMA) by flow cytometry and significantly higher in the modified method than conventional methods at the 1st and 2nd weeks. Also, mRNA expression of a-SMA by real-time PCR was significantly higher in the modified method than conventional method at the 2 weeks. The yield of vSMPCs by trypan blue exclusion assay was significantly higher in the modified method than conventional method at the 1st, 2nd and 3rd weeks. The primary culture using the modified method with PDGF-BB, bFGF, and ITS not only improved cell purity and yield, but also shortened the culture period, compared to the conventional culture method for vSMPCs. The modified method will be a time-saving and useful tool in various studies related to vascular pathology.

Syndecan-1 regulates vascular smooth muscle cell phenotype

OBJECTIVE

We examined the role of syndecan-1 in modulating the phenotype of vascular smooth muscle cells in the context of endogenous inflammatory factors and altered microenvironments that occur in disease or injury-induced vascular remodeling.

METHODS AND RESULTS

Vascular smooth muscle cells (vSMCs) display a continuum of phenotypes that can be altered during vascular remodeling. While the syndecans have emerged as powerful and complex regulators of cell function, their role in controlling vSMC phenotype is unknown. Here, we isolated vSMCs from wild type (WT) and syndecan-1 knockout (S1KO) mice. Gene expression and western blotting studies indicated decreased levels of α-smooth muscle actin (α-SMA), calponin, and other vSMC-specific differentiation markers in S1KO relative to WT cells. The spread area of the S1KO cells was found to be greater than WT cells, with a corresponding increase in focal adhesion formation, Src phosphorylation, and alterations in actin cytoskeletal arrangement. In addition, S1KO led to increased S6RP phosphorylation and decreased AKT and PKC-α phosphorylation. To examine whether these changes were present in vivo, isolated aortae from aged WT and S1KO mice were stained for calponin. Consistent with our in-vitro findings, the WT mice aortae stained higher for calponin relative to S1KO. When exposed to the inflammatory cytokine TNF-α, WT vSMCs had an 80% reduction in syndecan-1 expression. Further, with TNF-α, S1KO vSMCs produced increased pro-inflammatory cytokines relative to WT. Finally, inhibition of interactions between syndecan-1 and integrins αvβ3 and αvβ5 using the inhibitory peptide synstatin appeared to have similar effects on vSMCs as knocking out syndecan-1, with decreased expression of vSMC differentiation markers and increased expression of inflammatory cytokines, receptors, and osteopontin.

CONCLUSIONS

Taken together, our results support that syndecan-1 promotes vSMC differentiation and quiescence. Thus, the presence of syndecan-1 would have a protective effect against vSMC dedifferentiation and this activity is linked to interactions with integrins αvβ3 and αvβ5.

Effects of cyclic strain and growth factors on vascular smooth muscle cell responses

Under physiological and pathological conditions, vascular smooth muscle cells (SMC) are exposed to different biochemical factors and biomechanical forces. Previous studies pertaining to SMC responses have not investigated the effects of both factors on SMCs. Thus, in our research we investigated the combined effects of growth factors like Bfgf (basic fibroblast growth factor), TGF-β (transforming growth factor β) and PDGF (platelet-derived growth factor) along with physiological cyclic strain on SMC responses. Physiological cyclic strain (10% strain) significantly reduced SMC proliferation compared to static controls while addition of growth factors bFGF, TGF-β or PDGF-AB had a positive influence on SMC growth compared to strain alone. Microarray analysis of SMCs exposed to these growth factors and cyclic strain showed that several bioactive genes (vascular endothelial growth factor, epidermal growth factor receptor, etc.) were altered upon exposure. Further work involving biochemical and pathological cyclic strain stimulation will help us better understand the role of cyclic strain and growth factors in vascular functions and development of vascular disorders.

Striated myogenesis and peristalsis in the fetal murine esophagus occur without cell migration or interstitial cells of Cajal

Esophageal striated myogenesis progresses differently from appendicular myogenesis, but the mechanism underlying this process is incompletely understood. Early theories of transdifferentiation of smooth muscle into striated muscle are not supported by transgenic fate-mapping experiments; however, the origin of esophageal striated muscle remains unknown. To better define the process of striated myogenesis, we examined myogenesis in murine fetal cultured esophageal whole-organ explants. Embryonic day 14.5 (E14.5) esophagi maintained a functional contractile phenotype for up to 7 days in culture. Striated myogenesis, as evidenced by myogenin expression, proceeded in a craniocaudal direction along the length of the esophagus. Esophageal length did not change during this process. Complete, but not partial, mechanical disruption of the rostral esophagus inhibited myogenesis distally. Addition of fibroblast growth factor-2 (FGF-2) to the culture media failed to inhibit striated myogenesis, but attenuated smooth muscle actin expression and reduced peristaltic activity. Inhibition of c-kit failed to inhibit peristalsis. These results suggest that striated myogenic precursors are resident along the entire length of the esophagus by day 14.5 and do not migrate along the esophagus after E14.5. Induction of myogenesis craniocaudally appears to require physical continuity of the esophagus and is not inhibited by FGF-2. Finally, peristalsis in E14.5 esophagi appears not to be regulated by interstitial cells of Cajal.

Omega-3 fatty acids enhance ligament fibroblast collagen formation in association with changes in interleukin-6 production

Altering dietary ratios of n-3 and n-6 polyunsaturated fatty acids (PUFA) represents an effective nonpharmaceutical means to improve systemic inflammatory conditions. An effect of PUFA on cartilage and bone formation has been demonstrated, and the purpose of this study was to determine the potential of PUFA modulation to improve ligament healing. The effects of n-3 and n-6 PUFA on the in vitro healing response of medial collateral ligament (MCL) fibroblasts were investigated by studying the cellular coverage of an in vitro wound and the production of collagen, PGE2, IL-1, IL-6, and TNF. Cells were exposed to a bovine serum albumin (BSA) control or either eicosapentaenoic acid (EPA, 20:5n-3) or arachidonic acid (AA, 20:4n-6) in the form of soaps loaded onto BSA for 4 days and wounded on Day 5. AA and EPA improved the healing of an in vitro wound over 72 hr. EPA increased collagen synthesis and the overall percentage of collagen produced, but AA reduced collagen production and total protein. PGE2 production was increased in the AA-treated group and decreased in the EPA-treated group, but was not affected by wounding. IL-1 was not produced at the time point evaluated, but TNF and IL-6 were both produced, and their levels varied relative to the PUFA or wounding treatment. There was a significant linear correlation (r2 = 0.57, P = 0.0045) between IL-6 level and collagen production. These results demonstrate that n-3 PUFA (represented by EPA in this study) positively affect the healing characteristics of MCL cells and therefore may represent a possible noninvasive treatment to improve ligament healing. Additionally, these results show that MCL fibroblasts produce PGE2, IL-6, and TNF and that IL-6 production is related to MCL collagen synthesis.

Heparin/endothelial cell growth supplement regulates matrix gene expression and prolongs life span of vascular smooth muscle cells through modulation of interleukin-1

Vascular smooth muscle cells produce and respond to interleukin-1, a cytokine which modifies inflammation-associated vascular activities including the synthesis of extracellular matrix proteins. We have established vascular smooth muscle cells culture conditions in which heparin, in the presence of endothelial cell growth supplement, promotes cell proliferation and inhibits interleukin-1 and matrix protein expression. To test whether interleukin-1 mediates growth and matrix modulation by heparin/endothelial cell growth supplement, vascular smooth muscle cells were transfected with an Epstein-Barr virus-derived expression vector designed to express interleukin-1 antisense transcripts. RNase protection and ELISA assays demonstrated a complete block of interleukin-1 transcription and protein synthesis. Northern blot analysis also showed that interleukin-1 antisense decreased the expression of matrix genes such as type I collagen, fibronectin, and decorin similar to downregulation after heparin/endothelial cell growth supplement treatment. In contrast, the expression of versican was not affected, indicating a selective suppression of matrix proteins. In addition, interleukin-1 antisense significantly prolonged the life span of vascular smooth muscle cells in culture. Our data suggest that heparin/endothelial cell growth supplement induces matrix remodeling and controls growth and senescence of vascular smooth muscle cells through down-regulation of interleukin-1.