Impact of cardiac surgery on heart failure serum factor mediated suppression of cord blood mesenchymal stem cells

Objective: The regenerative capacity of autologuous stem cells from heart failure (HF) patients is limited by age and disease. We sought to investigate the behaviour of neonatal cord blood mesenchymal stem cells (CB-MSC) in the presence of serum factors from patients with severe HF. The impact of cardiac surgery on the molecular composition of HF serum and its effect on CB-MSC response was studied.

Methods: Human serum was prepared from blood collected from 21 patients with advanced HF (LVEF< 35%, cardiac surgery indication), before and after surgery. Serum obtained from healthy volunteers served as controls. CB-MSC isolated from healthy donors were seeded in DMEM-LG supplemented with 10% FCS. Following cell attachment, FCS was replaced by 10% protein-normalized HF or control serum. CB-MSC morphology, tri-lineage mesodermal differentiation potential, surface marker expression (FACS), colony forming unit ability (CFU-F), proliferation (BrdU), metabolic activity (MTS), and expression of proteins associated with apoptosis, cell cycle and stress response (Western Blot) were examined in response to pre- or post-surgery HF or control serum. Inflammatory serum cytokines were quantified (ELISA).

Results: Pro-inflammatory cytokines (Il-6, TNF-a) were significantly elevated in HF serum obtained during the pre-operative period (p < 0.01 vs. control serum). CB-MSC treated with pre-surgery HF serum maintained their morphology, surface marker expression and differentiation potential. In the CFU-F assay, however, number and size of cell clusters formed were significantly reduced. Growth kinetics were significantly impaired on day one and three, but approached control serum levels on day five of HF serum treatment, despite simultaneously upregulated expression of cell cycle inhibitors (p21, p27) and apoptosis markers (pp53, Caspase 3). HF serum led to a marked increase in JNK and p38 MAP kinase expression. Compared to pre-surgery HF serum, the effect of post-surgery HF serum on CB-MSC response was similar, with no significant difference detectable. There was no difference in cytokine concentrations between pre- and post operative serum samples.

Conclusions: Heart disease impairs the proliferative capacity of juvenile stem cells from healthy donors and does not favor their clinical use. Cardiac surgery does not enhance this effect. The extent to which HF-related stem cell impairment is transient and might be overcome in the long run needs to be determined.