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MOTOGENIC AND BIOSYNTHETIC RESPONSE OF ADULT SKIN FIBROBLASTS TO TGF‐β ISOFORMS (−1, −2 AND −3) DETERMINED BY ‘TISSUE RESPONSE UNIT’: ROLE OF CELL DENSITY AND SUBSTRATUM
Author(s) -
Ellis I.R,
Banyard J.,
Schor S.L
Publication year - 1999
Publication title -
cell biology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 77
eISSN - 1095-8355
pISSN - 1065-6995
DOI - 10.1006/cbir.1999.0423
Subject(s) - gene isoform , cell migration , fibroblast , microbiology and biotechnology , transforming growth factor , cell , chemistry , in vitro , cell growth , cell culture , biology , biophysics , biochemistry , gene , genetics
We have recently demonstrated that the three principal mammalian isoforms of transforming growth factor β (TGF‐β) exert distinct effects upon: (1) the migration of confluent adult fibroblasts into 3D gels of native type I collagen fibres (i.e. TGF‐β−1 and −2 had no apparent motogenic activity, whilst TGF‐β−3 induced a dose‐dependent stimulation of cell migration); and (2) the synthesis of hyaluronan (HA) by these cells is also affected by the TGF‐β isoforms in a manner which parallels their effect on cell migration. The objective of the present study is to elucidate the manner in which this differential activity of the TGF‐β−1, −2 and −3 may be modulated by experimental parameters. Data presented in this communication indicate that cytokine bioactivity is determined by a combination of cell density and the nature of the macromolecular substratum. Thus, we now report that all three TGF‐β isoforms inhibit the migration of subconfluent cells in the collagen gel assay. Our data confirm that the migration of confluent cells is stimulated by TGF‐β−3 and further indicate that this motogenic activity is completely abrogated by either TGF‐β−1 or −2 when these are co‐incubated with TGF‐β−3. In contrast to these results obtained using a native type I collagen substratum, all three isoforms stimulated adult fibroblast migration in the transmembrane assay (in which cells are adherent to a 2‐D porous polycarbonate substratum). The precise effect of TGF‐β isoforms on HA synthesis was also affected by cell density and the nature of the substratum in a manner which paralleled their diverse effects on cell migration (i.e. stimulation, inhibition or no effect). Streptomyces hyaluronidase completely neutralized the TGF‐β−3‐induced stimulation of confluent fibroblast migration, thus suggesting a mechanistic link between the cytokine‐induced cell migration and HA synthesis under these conditions. Taken together, these data indicate that: (1) the bioactivity of TGF‐β−1, −2 and −3 are determined by cell density, the macromolecular substratum and the presence of other cytokines; and (2) it is therefore necessary to define cytokine bioactivity within the context of a larger ‘tissue response unit’ which more fully defines the activity state of the target cell and its microenvironment.