Evidence for recipient derived fibroblast recruitment and activation during the development of chronic cardiac allograft rejection.
BACKGROUND
Allograft fibrosis is a prominent feature of chronic rejection. Although intragraft fibroblasts contribute to this process, their origin and exact role remain poorly understood.


METHODS
Using a rat model of chronic rejection, LEW to F344, cardiac fibroblasts were isolated at the point of rejection and examined in a collagen gel contraction assay to measure fibroblast activation. The allograft microenvironment was examined using immunohistochemistry for fibrogenic markers (transforming growth factor [TGF]-beta, platelet-derived growth factor [PDGF], tissue plasminogen activator [TPA], plasminogen activator inhibitor [PAI]-1, matrix metalloproteinase [MMP]-2, and tissue inhibitor of matrix metalloproteinase [TIMP]-2). The origin of intragraft fibroblasts was studied using female to male allografts followed by polymerase chain reaction [PCR] and in situ hybridization for the male sry gene.


RESULTS
The cardiac fibroblasts isolated from allografts with chronic rejection exhibited higher gel contractibility (50.9% +/- 6.1% and 68.2% +/- 3.8% at 4 and 24 hr) compared with naive cardiac fibroblasts (30.7% +/- 3.5% and 55.3% +/- 6.6% at 4 and 24 hr; P<0.05 and <0.05, respectively). Immunostaining for TGF-beta, PDGF, TPA, PAI-1, MMP-2 and TIMP-2 was observed in all allografts at the time of rejection. In situ hybridization demonstrated the presence of sry positive cells in female allografts rejected by male recipients. Sixty-five percent of fibroblast colonies (55 of 85) isolated from female heart allografts expressed the male sry gene.


CONCLUSIONS
Cardiac fibroblasts are activated and exist in a profibrogenic microenvironment in allografts undergoing chronic rejection. A substantial proportion of intragraft fibroblasts are recruited from allograft recipients in this experimental model of chronic cardiac allograft rejection.
Wu
Gordon D
GD
Department of Cardiothoracic Surgery, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA. gdw@.usc.edu.
Tuan
Tai-Lan
TL
Bowdish
Michael E
ME
Jin
Yang-Sun
YS
Starnes
Vaughn A
VA
Cramer
Donald V
DV
Barr
Mark L
ML
D000818:Animals; D002908:Chronic Disease; D005260:Female; D005347:Fibroblasts / Q000502:physiology*; D006084:Graft Rejection / Q000473:pathology*; D016027:Heart Transplantation; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000032:analysis; D017395:Plasminogen Activator Inhibitor 1 / Q000032:analysis; D010982:Platelet-Derived Growth Factor / Q000032:analysis; D016133:Polymerase Chain Reaction; D051381:Rats; D011916:Rats, Inbred F344; D011917:Rats, Inbred Lew; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000032:analysis; D010959:Tissue Plasminogen Activator / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000032:analysis; D014184:Transplantation, Homologous
D017395:Plasminogen Activator Inhibitor 1; D010982:Platelet-Derived Growth Factor; D016212:Transforming Growth Factor beta; D019716:Tissue Inhibitor of Metalloproteinase-2; D010959:Tissue Plasminogen Activator; D020778:Matrix Metalloproteinase 2