Mechanisms of recovery from mechanical injury of renal tubular epithelial cells

Abstract

The mechanism(s) whereby a denuded renal tubular epithelial cell surface becomes reestablished remains unknown. We therefore measured the rate of renewal of mechanical wounds made in confluent monolayers of two established renal tubular epithelial cell lines. We found that wounds of MDCK cells heal at a faster rate than wounds of LLC-PK1 cells. The magnitude of wound healing did not differ when cells grown on plastic were compared with cells grown on fibronectin, laminin, or collagen. Irradiation (4,000 rads) of MDCK and LLC-PK1 cells significantly reduced indexes of proliferation (5-bromo-2'-deoxyuridine and thymidine uptake) without affecting wound healing. Serum and epidermal growth factor (EGF) enhance whereas transforming growth factor-beta 1 (TGF-beta 1) impairs wound healing. Hepatocyte growth factor (HGF) stimulates wound healing at low concentrations and inhibits healing at high concentrations in MDCK cells while not affecting healing of LLC-PK1 cell wounds at any concentration. Several interleukins (IL-1, IL-2, IL-3, and IL-6) did not affect wound healing in either cell type. Healing of LLC-PK1 but not MDCK cells was impaired by exposure to a peptide containing a RGD sequence. Conversely, healing of MDCK but not LLC-PK1 cells was impaired by the REDV tetrapeptide. Healing of both LLC-PK1 and MDCK was impaired by heparin but not by the LDVPS peptide. These results demonstrate that mechanical wounds of LLC-PK1 and MDCK cells heal, at least in part, by migration. Healing is regulated by serum and growth factors including EGF, HGF, and TGF-beta 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple rows of cells behind an epithelial wound edge extend cryptic lamellipodia to collectively drive cell-sheet movement

“…In addition, serum is not required for wound closure in MDCK cell monolayers, which occurs at the same rate after serum deprivation as with serum (Altan and Fenteany, 2004). These findings are in agreement with a previous report showing that inhibition of MDCK cell proliferation by irradiation with ultraviolet light does not affect wound closure (Sponsel et al, 1994) and are consistent with previous observations (Fenteany et al, 2000). Because some cells are irrevocably damaged and die even with careful mechanical wounding and generation of small wounds, the role of proliferation is probably to restore the initial cell density and morphology, controlled homeostatically by an unknown mechanism in epithelia.…”

“…Soluble factors, either passively released from damaged cells or actively secreted by intact cells, may be involved, as may factors associated with extracellular matrix deposited by cells. Exogenously supplied epidermal growth factor and low concentrations of hepatocyte growth factor/ scatter factor are each capable of accelerating wound closure in MDCK cell monolayers (Sponsel et al, 1994), as are certain nucleotides discussed further below (Kartha and Toback, 1992;Sponsel et al, 1995). However, it has not been determined whether MDCK cells normally actively produce autocrine factors that stimulate closure after wounding, which appears the case for transforming growth factor-β (TGF-β) in bronchial epithelial wound repair (Howat et al, 2002).…”

“…However, it has not been determined whether MDCK cells normally actively produce autocrine factors that stimulate closure after wounding, which appears the case for transforming growth factor-β (TGF-β) in bronchial epithelial wound repair (Howat et al, 2002). In MDCK cell monolayers, exogenously supplied TGF-β1 impairs wound closure (Sponsel et al, 1994). We have hitherto seen little or no effect of either the potent and selective epidermal growth factor receptor tyrosine kinase inhibitor PD 153035 (AG 1517) or a function-blocking anti-pan-TGF-β antibody on wound closure (data not shown).…”

Induction of tissue inhibitor of metalloproteinases-3 is a delayed early cellular response to hepatocyte growth factor

“…Later induction events correlate with HGF-induced epithelial and endothelial cell migration and morphogenesis, including increased production of transcription factor ETS1 (Fafeur et al, 1997), urokinase-type plasminogen activator (u-PA), and its receptor (Pepper et al, 1992), and the zinc ®nger protein slug (Savagner et al, 1997). The HGFstimulated proliferation and migration of keratinocytes that is thought to occur during wound healing Gohda et al, 1994;Watanabe et al, 1994;Nusrat et al, 1994;Sponsel et al, 1994), is accompanied by the induction of collagenase (matrix metalloproteinase 1; MMP-1; Dunsmore et al, 1996;Fafeur et al, 1997) and stromelysin-1 (MMP-3; Dunsmore et al, 1996). These induction events may be coordinated with the HGF-stimulated induction of plasminogen activator inhibitor-1, resulting in appropriate spatial and temporal inhibition of matrix proteolysis (Pepper et al, 1992;Wojta et al, 1994).…”

Emergence of collective modes and tri-dimensional structures from epithelial confinement

“…Growth factors such as hepatocyte growth factor (HGF) are known to promote motility and to favour individual versus collective behaviours 25 . In the present situation, oscillations were suppressed by HGF at a concentration too low to induce scattering or enhanced proliferation in the first 12 h ( Supplementary Fig.…”