Cellular re- and de-programming by microenvironmental memory: why short TGF-β1 pulses can have long effects

Abstract

BackgroundFibrosis poses a substantial setback in regenerative medicine. Histopathologically, fibrosis is an excessive accumulation of collagen affected by myofibroblasts and this can occur in any tissue that is exposed to chronic injury or insult. Transforming growth factor (TGF)-β1, a crucial mediator of fibrosis, drives differentiation of fibroblasts into myofibroblasts. These cells exhibit α-smooth muscle actin (α-SMA) and synthesize high amounts of collagen I, the major extracellular matrix (ECM) component of fibrosis. While hormones stimulate cells in a pulsatile manner, little is known about cellular response kinetics upon growth factor impact. We therefore studied the effects of short TGF-β1 pulses in terms of the induction and maintenance of the myofibroblast phenotype.ResultsTwenty-four hours after a single 30 min TGF-β1 pulse, transcription of fibrogenic genes was upregulated, but subsided 7 days later. In parallel, collagen I secretion rate and α-SMA presence were elevated for 7 days. A second pulse 24 h later extended the duration of effects to 14 days. We could not establish epigenetic changes on fibrogenic target genes to explain the long-lasting effects. However, ECM deposited under singly pulsed TGF-β1 was able to induce myofibroblast features in previously untreated fibroblasts. Dependent on the age of the ECM (1 day versus 7 days’ formation time), this property was diminished. Vice versa, myofibroblasts were cultured on fibroblast ECM and cells observed to express reduced (in comparison with myofibroblasts) levels of collagen I.ConclusionsWe demonstrated that short TGF-β1 pulses can exert long-lasting effects on fibroblasts by changing their microenvironment, thus leaving an imprint and creating a reciprocal feed-back loop. Therefore, the ECM might act as mid-term memory for pathobiochemical events. We would expect this microenvironmental memory to be dependent on matrix turnover and, as such, to be erasable. Our findings contribute to the current understanding of fibroblast induction and maintenance, and have bearing on the development of antifibrotic drugs.

Simultaneous Delivery of Highly Diverse Bioactive Compounds from Blend Electrospun Fibers for Skin Wound Healing

“…15 While a 12 h release profile is relatively quick, long-term stimulation of cells with growth factors may not be necessary. As shown in Tan et al, 16 transforming growth factor-β1 was as effective in inducing myofibroblast transformation of fibroblasts as a 4 day stimulation due to an autocrine stimulation of transforming growth factor-β1 by fibroblasts after short pulses of external stimulation. Short term burst release may also be better as a long term stimulation of mitogenic factors such as that during inflammation have been linked to malignant transformation in cells.…”

Adverse outcome pathway development from protein alkylation to liver fibrosis

“…Czaja et al (1989) did prove that treatment of cultured hepatic cells with TGF-β1 increased type I pro-collagen mRNA levels 13-fold due to posttranscriptional gene regulation. Tan et al (2013) discovered that short TGF-β1 pulses can exert long-lasting effects on fibroblasts. Accumulated CD11b1 macrophages are critical for activating HSCs (via expression of TGF-β1) (Chu et al 2013)KE 4 to KE 5Biological plausibility is highIt is general accepted knowledge that activated HSCs are the primary collagen producing cell, the key cellular mediators of liver fibrosis (Benyon and Arthur 2001; Lee and Friedman 2011; Li et al 2008; Milani et al 1994)Empirical support is moderateAnalytical methods in vitro focus on measurement of pro-collagen secreted into culture medium or measurement of α-smooth muscle actin (α-SMA) expression, a marker of fibroblast activation (Brenner 2009; Rockey et al 1992).…”

“…Furthermore, at the gene expression level, HSCs activated in in vitro conditions do not fully reproduce the changes observed in vivo (De Minicis et al 2007). However, Czaja et al (1989) did prove that treatment of cultured hepatic cells with TGF-β1 increased type I pro-collagen mRNA levels 13-fold due to posttranscriptional gene regulation and in Tan et al (2013), it was shown that short TGF-β1 pulses can exert long-lasting effects on fibroblasts.…”

Self-Assembly of Prevascular Tissues from Endothelial and Fibroblast Cells Under Scaffold-Free, Nonadherent Conditions

“…14 The maintenance of normal vascular patterns in TGFb1-treated tissues was also unexpected, as TGFb1 is known to affect fibroblasts' ability to synthesize type I collagen and is also a known fibroblast mitogen. 13 Evidence of increased average ultimate tensile strength and Young's modulus upon treatment with the 5 ng/mL dose of TGFb1 (Fig. 10) suggests that TGFb1-treatment is a means to increase tissue strength without sacrificing vascular network patterning.…”

“…We investigated whether factors known to affect neovascularization in vivo could enhance tissue strength and rapid fabrication without disrupting network patterning. To this end we generated toroids under nonadherent conditions using high-density 1:4 EC:fibroblast cell suspension in which media was supplemented with either VEGF, 11,12 TGFb1, 13 or RA. 14 The time course for these experiments was 3 days and each culture received fresh media and supplemental factors daily.…”