Up-regulation of thrombospondin-2 in Akt1-null mice contributes to compromised tissue repair due to abnormalities in fibroblast function.
Vascular remodeling is essential for tissue repair and is regulated by multiple factors, including thrombospondin-2 (TSP2) and hypoxia/VEGF-induced activation of Akt. In contrast to TSP2 knock-out (KO) mice, Akt1 KO mice have elevated TSP2 expression and delayed tissue repair. To investigate the contribution of increased TSP2 to Akt1 KO mice phenotypes, we generated Akt1/TSP2 double KO (DKO) mice. Full-thickness excisional wounds in DKO mice healed at an accelerated rate when compared with Akt1 KO mice. Isolated dermal Akt1 KO fibroblasts expressed increased TSP2 and displayed altered morphology and defects in migration and adhesion. These defects were rescued in DKO fibroblasts or after TSP2 knockdown. Conversely, the addition of exogenous TSP2 to WT cells induced cell morphology and migration rates that were similar to those of Akt1 KO cells. Akt1 KO fibroblasts displayed reduced adhesion to fibronectin with manganese stimulation when compared with WT and DKO cells, revealing an Akt1-dependent role for TSP2 in regulating integrin-mediated adhesions; however, this effect was not due to changes in β1 integrin surface expression or activation. Consistent with these results, Akt1 KO fibroblasts displayed reduced Rac1 activation that was dependent upon expression of TSP2 and could be rescued by a constitutively active Rac mutant. Our observations show that repression of TSP2 expression is a critical aspect of Akt1 function in tissue repair.
From the Departments of Pathology, the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520.
Tara
T
Bancroft
Cell Biology.
Mohamed
M
Bouaouina
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520.
Sophia
S
Roberts
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Pharmacology.
Monica
M
Lee
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Cell Biology, Pharmacology.
David A
DA
Calderwood
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Cardiology, and.
Martin
M
Schwartz
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Cardiology, and.
Michael
M
Simons
the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Pharmacology.
William C
WC
Sessa
From the Departments of Pathology, the Program of Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, Connecticut 06520 Biomedical Engineering and themis.kyriakides@yale.edu.
Themis R
TR
Kyriakides
D000818:Animals; D002465:Cell Movement; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D005816:Genetic Complementation Test; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D012867:Skin / Q000293:injuries / Q000378:metabolism* / Q000473:pathology; D019699:Thrombospondins / Q000172:deficiency / Q000235:genetics*; D014945:Wound Healing / Q000235:genetics; D014949:Wounds, Nonpenetrating / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D000099262:Thrombospondin 2
D019012:Integrin beta1; D009479:Neuropeptides; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D019699:Thrombospondins; D020830:rac1 GTP-Binding Protein; D000099262:Thrombospondin 2; C484602:Rac1 protein, mouse; C496315:Nos3 protein, mouse; C514862:Akt1 protein, mouse; C494922:Akt2 protein, mouse
Akt PKB; Angiogenesis; Fibroblast; TSP; Thrombospondin; Wound Healing