K. Ozer et al., In vivo microscopic assessment of cremasteric microcirculation during hindlimb allograft rejection in rats, PLAS R SURG, 103(7), 1999, pp. 1949-1956
Experimental and clinical studies of vascular allogenic extremity transplan
tation have yielded disappointing results and have not been clinically usef
ul. with recent advances in transplantation immunology, considerable intere
st has focused on the understanding of leukocyte-endothelial interaction at
the microcirculatory level. The objective of this study was to characteriz
e the alterations in leukocyte-endothelial interaction in the early stages
of rat hindlimb allograft rejection. To study the changes at the microcircu
latory level, a new microsurgical model was developed; the cremaster muscle
was incorporated into the transplanted hindlimb. The purpose of this study
was to report on the microcirculatory changes during rat hindlimb allograf
t rejection.
A total of 24 transplantations were performed among the four experimental g
roups. In a control group, 12 rat hindlimb-cremaster grafts were transplant
ed between genetically identical animals, Lewis to Lewis. Microcirculatory
measurements of graft survival were taken at 24 hours (group 1A, n = 6) and
at 72 hours (group 1B, n = 6). In the rejection control group, 12 transpla
ntations were performed across a major histocompatibility barrier between L
ewis-Brown Norway and Lewis rats. Microcirculatory measurements were taken
at 24 (group 2A, n = 6) and 72 hours (group 2A, n = 6) as above. The follow
ing parameters were evaluated to discover the leukocyte-endothelial interac
tion: endothelial edema index and the number of rolling, adherent, and tran
smigrating leukocytes and lymphocytes in the postcapillary venule. Physical
signs of limb rejection, such as edema, erythema, scaling, plaque formatio
n on the skin, hair loss, and skin surface temperature, were monitored.
Microcirculatory signs of rejection included the following. There was a sig
nificant increase in the number of adherent leukocytes in allograft transpl
ants at both 24 hours (205 percent; 2.05 +/- 0.38) and 72 hours (431 percen
t; 9.11 +/- 3.41) when compared with isograft controls (1.00 +/- 0.89 at 24
hours; 2.11 +/- 0.34 at 72 hours) (p < 0.05), The activation of leukocyte
transmigration in creased more than 7-fold in muscle allografts at 24 hours
(0.55 +/- 0.25 versus 4.16 +/- 1.89) and more than 6-fold at 72 hours (0.7
2 +/- 0.38 versus 4.38 +/- 1.28) after transplantation (p < 0.05). Endothel
ial edema index, a measure of endothelial swelling and cellular deposit acc
umulation, increased more than 119 percent in the allograft group 72 hours
after transplantation (1.23 +/- 0.07 versus 1.46 +/- 0.09) (p < 0.05). The
first clinical signs of limb rejection were scaling of the skin or hair los
s; they were observed between the seventh and ninth postoperative days.
The composite rat hindlimb-cremaster model presented in this study introduc
es a new in vivo approach to monitor acute graft rejection using the intrav
ital microscopy system. This is a valuable model for defining the timing, s
equence, and correlation between immunologic events and clinical signs duri
ng the acute phase of allograft-rejection.