Interstitial fluid flow induces myofibroblast differentiation and collagen alignment in vitro

Abstract

The differentiation of fibroblasts to contractile myofibroblasts, which is characterized by de novo expression of α-smooth muscle actin (α-SMA), is crucial for wound healing and a hallmark of tissue scarring and fibrosis. These processes often follow inflammatory events, particularly in soft tissues such as skin, lung and liver. Although inflammatory cells and damaged epithelium can release transforming growth factor β1 (TGF-β1), which largely mediates myofibroblast differentiation, the biophysical environment of inflammation and tissue regeneration, namely increased interstitial flow owing to vessel hyperpermeability and/or angiogenesis, may also play a role. We demonstrate that low levels of interstitial (3D) flow induce fibroblast-to-myofibroblast differentiation as well as collagen alignment and fibroblast proliferation, all in the absence of exogenous mediators. These effects were associated with TGF-β1 induction, and could be eliminated with TGF-β1 blocking antibodies. Furthermore, α1β1 integrin was seen to play an important role in the specific response to flow, as its inhibition prevented fibroblast differentiation and subsequent collagen alignment but did not block their ability to contract the gel in a separate floating gel assay. This study suggests that the biophysical environment that often precedes fibrosis, such as swelling, increased microvascular permeability and increased lymphatic drainage – all which involve interstitial fluid flow – may itself play an important role in fibrogenesis.

Interstitial Fibrosis Restricts Osmotic Water Transport in Encapsulating Peritoneal Sclerosis

“…29 The effect of interstitial collagen accumulation on water flow has been demonstrated in vitro both in normal interstitia from various organs 29 and in conditions of fibrosis. 30 Reduced osmotic conductance by the fractional volume occupied by collagen fibrils results from three mechanisms: (1) exclusion of glycosaminoglycans from the intrafibrillar space, thereby increasing their extrafibrillar concentration; (2) reduction of the mean hydraulic radius in the interstitium, leading to a reduced area for flow; and (3) tortuosity, which increases the path length for flow. 29 Our results show that increased collagen deposition and concentration in the peritoneal interstitium restricts water transport in vivo, leading to UF failure and loss of free-water transport in patients with EPS.…”

Immunomodulatory Roles of Lymphatic Vessels in Cancer Progression

“…VEGF-C also induces TGFb secretion by LECs (J. Munson and M. Swartz, unpublished data), which can promote regulatory T-cell education and drives fibroblast-to-myofibroblast transformation and stromal stiffening. Finally, increased interstitial flow in the tumor stroma due to high pressure gradients at the tumor margin also promotes TGFb activation, myofibroblast transformation, and stromal stiffening (44), and promote fibroblast-led tumor-cell invasion (45). Drawings are courtesy of Katie Hubbell, University College London, UK.…”

Intermittent Pneumatic Compression Enhances Formation of Edema Tissue Fluid Channels in Lymphedema of Lower Limbs

“…It was found in rats that interstitial fluid flow induces collagen alignment. 15 In other studies, interstitial fluid channels formed before lymphatic endothelial cell organization and could direct lymphangiogenesis. 16 Uzarski et al found that interstitial fluid and edema resolution readily occur across the scar-free regenerating skin in the absence of VEGFR-3 signaling and lymphangiogenesis.…”