title: Myofibroblasts differentiate from fibroblasts when plated at low density.
abstract: Myofibroblasts, defined by their expression of smooth muscle alpha-actin, appear at corneal and dermal incisions and promote wound contraction. We report here that cultured fibroblasts differentiate into myofibroblasts by a cell density-dependent mechanism. Fibroblasts seeded at low density (5 cells per mm2) produced a cell culture population consisting of 70-80% myofibroblasts, 5-7 days after seeding. In contrast, fibroblasts seeded at high density (500 cells per mm2) produced cultures with only 5-10% myofibroblasts. When the myofibroblast-enriched cultures were subsequently passaged at high density, the smooth muscle alpha-actin phenotype was lost within 3 days. Furthermore, initially 60% of the low density-cultured cells incorporated BrdUrd compared to 30% of cells passaged at high density. Media from myofibroblast-enriched cultures had more latent and active transforming growth factor beta (TGF-beta) than did media from fibroblast-enriched cultures. Although there was a trend towards increased numbers of myofibroblasts after addition of exogenous TGF-beta, the results did not reach statistical significance. We conclude that myofibroblast differentiation can be induced in fibroblasts by plating at low density. We propose a cell density-dependent model of myofibroblast differentiation during wounding and healing in which at least two factors interact: loss of cell contact and the presence of TGF-beta.
authors.affiliation: Department of Ophthalmology, Mount Sinai School of Medicine of the City University of New York, NY 10029-6574, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Masur
authors.forename: H S
authors.initials: HS
authors.lastname: Dewal
authors.forename: T T
authors.initials: TT
authors.lastname: Dinh
authors.forename: I
authors.initials: I
authors.lastname: Erenburg
authors.forename: S
authors.initials: S
authors.lastname: Petridou
mesh_terms: D000199:Actins / Q000032:analysis / Q000096:biosynthesis; D000818:Animals; D015415:Biomarkers; D001973:Bromodeoxyuridine; D002135:Calcium-Binding Proteins / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology*; D046508:Culture Techniques / Q000379:methods; D005347:Fibroblasts / Q000166:cytology; D007150:Immunohistochemistry; D008840:Microfilament Proteins; D009124:Muscle Proteins / Q000032:analysis; D009130:Muscle, Smooth / Q000166:cytology*; D011817:Rabbits; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D000096985:Calponins
chemical_list: D000199:Actins; D015415:Biomarkers; D001973:Bromodeoxyuridine; D002135:Calcium-Binding Proteins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D016212:Transforming Growth Factor beta; D000096985:Calponins