Evidence against a role for platelet-derived molecules in liver regeneration after partial hepatectomy in humans

Abstract

Background and Aim: Blood platelets have been shown to stimulate liver regeneration after partial hepatectomy in animal models and humans, but the molecular mechanisms involved are unclear. It has been proposed that growth factors and angiogenic molecules stored within platelets drive platelet-mediated liver regeneration, but little direct evidence in support of this mechanism is available. Methods: We assessed levels of relevant platelet-derived proteins (vascular endothelial growth factor, hepatocyte growth factor, fibroblast growth factor, platelet-derived growth factor, thrombospondin, and endostatin) in platelet-rich and platelet-poor plasma taken at various perioperative time points from patients undergoing a (extended) right partial hepatectomy (n = 17) or a pylorus-preserving pancreatico-duodenectomy (n = 10). In addition, we collected intraoperative samples from the efferent and afferent liver veins prior to and after completion of liver resection. Twenty-four healthy controls were included to establish reference ranges for the various tests. Results and Conclusions: Although we demonstrate perioperative changes in platelet and plasma levels of the proteins assessed, the changes observed in patients undergoing partial hepatectomy largely mirror the changes observed in patients undergoing a pylorus-preserving pancreatico-duodenectomy. In addition, no change in the growth factor levels in platelet-rich plasma between afferent and efferent liver veins was observed. Thus, the absence of an intra- or postoperative consumption of platelet-derived proteins in patients undergoing partial hepatectomy argues against a role of release of these molecules in stimulation of liver regeneration. Relevance for patients: In depth knowledge of the mechanism underlying platelet-mediated liver regeneration may facilitate development of targeted therapeutic interventions for patients with failing liver regeneration, which for example may occur following a partial hepatectomy. Although the prevailing dogma is that platelet stimulate liver regeneration by release of growth factors stored within platelets, data in this manuscript argue against this mechanism and suggest other pathways to be responsible.

Keywords: growth factors; liver regeneration; liver resection; pancreatico-duodenectomy; platelet; pylorus-preserving.

Figure 1.. Circulating platelet count prior to and after partial liver resection or PPPD. *P < 0.05. Pre-OP, pre-operative, End-OP, end of surgery; POD, post-operative day.

Figure 2.. Levels of growth factors and angiogenic molecules in afferent and efferent veins prior to and just after anatomical transection in patients undergoing partial hepatectomy.

Levels of (A) VEGF, (B) HGF, (C) bFGF, (D) PDGF, (E) TSP1, (F) endostatin, and (G) the platelet count in PRP were measured prior to (pre) and just after (post) parynchymal transection in samples taken from the portal vein (PV) or hepatic vein (HV) during partial hepatectomy.

Figure 3.. Levels of growth factors and angiogenic molecules in PRP taken at various perioperative time points from patients undergoing partial liver resection or PPPD. Levels of (A) VEGF, (B) HGF, (C) bFGF, (D) PDGF, (E) TSPl and (F) endostatin were measured in lysates of PRP in samples taken from healthy controls (white boxes), patients undergoing partial hepatectomy (dark grey boxes), and patients undergoing PPPD (light gray boxes). *P < 0.05, **P < 0.01, ***P < 0.001, versus pre-op (Friedman’s test). ⁺P < 0.05, partial hepatectomy versus PPPD (Mann-Whitney’s U test). Pre-OP, pre-operative, End-OP, end of surgery; POD, post-operative day.

Figure 4.. Levels of growth factors and angiogenic molecules in PPP taken at various perioperative time points from patients undergoing partial liver resection or PPPD. Plasma levels of (A) VEGF, (B) HGF, (C) bFGF, (D) PDGF, (E) TSPl and (F) endostatin in samples taken from healthy controls (white boxes), patients undergoing partial hepatectomy (dark grey boxes), and patients undergoing PPPD (light gray boxes).. *P < 0.05, **P < 0.01, ***p < 0.001, versus pre-op (Friedman’s test). ⁺P < 0.05, ⁺⁺P < 0.01, hemihepatectomy versus PPPD (Mann-Whitney’s U test). Pre-OP, pre-operative, End-OP, end of surgery; POD, post-operative day.

Figure 5.. Levels of growth factors and angiogenic molecules in platelets taken at various perioperative time points from patients undergoing partial liver resection or PPPD. Calculated intraplatelet levels of (A) VEGF, (B) HGF, (C) bFGF, (D) PDGF, (E) TSPl and (F) endostatin in samples taken from healthy controls (white boxes), patients undergoing partial hepatectomy (dark grey boxes), and patients undergoing PPPD (light gray boxes).. *P < 0.05, **P < 0.01, ***p < 0.001, versus pre-op (Friedman’s test). ⁺P < 0.05, hemihepatectomy versus PPPD (Mann-Whitney’s U test). Pre-OP, pre-operative, End-OP, end of surgery; POD, post-operative day.