Repair phenotype in corneal fibroblasts is controlled by an interleukin-1 alpha autocrine feedback loop.
OBJECTIVE
To explore the role of autocrine interleukin-1 alpha (IL-1 alpha) as a central regulator of the repair phenotype in corneal fibroblasts.


METHODS
Disruption of the actin cytoskeleton with cytochalasin B (CB), which mimics changes in shape that occur in repair tissues, was used to stimulate repair gene expression in early-passage fibroblasts. Changes in expression of IL-1 alpha, IL-8, collagenase, and ENA-78 were determined by Northern blot analysis, radioimmunoassay, and an enzyme-amplified sensitivity immunoassay (EASIA). Expression of repair genes was also examined in repair fibroblasts, isolated from healing, penetrating keratectomy wounds in rabbits.


RESULTS
Blocking IL-1 alpha activity prevented both constitutive and stimulated increases in synthesis of IL-8 and collagenase in early-passage cultures of corneal fibroblasts, demonstrating the role of IL-1 alpha as a necessary intermediate for expression of these genes. Evidence is also presented that the IL-1 alpha autocrine controls expression of an IL-8 related factor, ENA-78. Unlike early-passage fibroblasts, fibroblasts freshly isolated from the uninjured cornea did not express IL-1 alpha. However, fibroblasts freshly isolated from remodeling corneal repair tissue 3 weeks after injury were found to express substantial levels of IL-1 alpha, regulated through an autocrine feedback loop. Neutralization experiments demonstrated that the IL-1 alpha autocrine is largely responsible for controlling both collagenase and IL-8 synthesis in repair fibroblasts, as it is in early-passage fibroblasts.


CONCLUSIONS
These findings provide evidence that activation of an autocrine IL-1 alpha feedback loop is an important mechanism by which fibroblasts adopt a repair phenotype during remodeling of the cornea.
West-Mays
J A
JA
Vision Research Laboratories, New England Medical Center, Boston, MA 02111, USA.
Sadow
P M
PM
Tobin
T W
TW
Strissel
K J
KJ
Cintron
C
C
Fini
M E
ME
D000818:Animals; D015152:Blotting, Northern; D054365:Chemokine CXCL5; D019743:Chemokines, CXC; D017364:Collagenases / Q000378:metabolism; D003315:Cornea / Q000502:physiology*; D065306:Corneal Injuries; D015807:Eye Injuries, Penetrating / Q000503:physiopathology; D005246:Feedback; D005347:Fibroblasts / Q000502:physiology*; D007124:Immunoenzyme Techniques; D007375:Interleukin-1 / Q000494:pharmacology / Q000502:physiology*; D016209:Interleukin-8 / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D010641:Phenotype; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D011863:Radioimmunoassay; D014945:Wound Healing / Q000502:physiology*
C486263:CXCL5 protein, human; D054365:Chemokine CXCL5; D019743:Chemokines, CXC; D007375:Interleukin-1; D016209:Interleukin-8; D012333:RNA, Messenger; D017364:Collagenases