Oo. Olutoye et al., COLLAGEN INDUCES CYTOKINE RELEASE BY FETAL PLATELETS - IMPLICATIONS IN SCARLESS HEALING, Journal of pediatric surgery, 32(6), 1997, pp. 827-830
In previous studies the authors demonstrated that unlike adult platele
ts, fetal platelets respond poorly to collagen. When platelets make co
ntact with the exposed collagen at the site of injury, the result is a
ctivation, aggregation, and degranulation with the release of cytokine
s and growth factors. This sequence of events is well characterized in
adult wounds, which heal with an acute inflammatory response and dens
e scar formation. In sharp contrast, fetal dermal wounds heal without
an acute inflammatory response and minimal scar formation. Therefore,
the aim of this study was to test the hypothesis that collagen, abunda
nt at the site of dermal injury, is a poor inducer of cytokine release
by fetal platelets. This could explain, in part, the minimal inflamma
tion accompanying fetal dermal wound healing. Platelet suspensions fro
m six fetal Yorkshire swine at day 80 of gestation (term, 114 days) we
re exposed to either arachidonic acid, 0.5 mg/mL, collagen, 0.19 mg/mL
, or saline. The release into plasma of transforming growth factor-bet
a (TGF-beta 1), and platelet-derived growth factor (PDGF)-AB effected
by these agents was determined by enzyme-linked immunosorbent assays.
Transmission electron microscopy (TEM) was used to correlate the bioch
emical findings with ultrastructural changes and showed that arachidon
ate-treated platelets were aggregated and devoid of granules. In contr
ast, collagen-treated platelets had undergone conformational changes b
ut showed only a moderate change in the quantity and homogeneity of th
eir secretory granules compared with saline-treated controls. There wa
s a significant increase in TGF-beta 1 release into plasma after treat
ment with collagen (6.64 +/- 0.36 ng/mL) and arachidonate (7.64 +/- 0.
77 ng/mL) compared with saline (4.74 +/- 0.36 ng/mL), P <.05. Likewise
, PDGF-AB release was significantly higher after collagen (0.22 +/- 0.
02 ng/mL) and arachidonate treatment (0.44 +/- 0.04 ng/mL) compared wi
th saline (0.09 +/- 0.02 ng/ml), P <.05. The authors conclude that fet
al platelets actually do release cytokines in response to contact with
collagen despite poor aggregation. Therefore, impaired aggregation to
collagen cannot solely explain the minimal inflammation after fetal w
ounding. Copyright (C) 1997 by W.B. Saunders Company.