Abstract
BackroundEmploying growth factor-induced partial reprogramming in vitro, peripheral human blood monocytes can acquire a state of plasticity along with expression of various markers of pluripotency. These so-called programmable cells of monocytic origin (PCMO) hold great promise in regenerative therapies. The aim of this translational study was to explore and exploit the functional properties of PCMO for allogeneic cell transplantation therapy in critical limb ischemia (CLI).MethodsUsing our previously described differentiation protocol, murine and human monocytes were differentiated into PCMO. We examined paracrine secretion of pro-angiogenic and tissue recovery-associated proteins under hypoxia and induction of angiogenesis by PCMO in vitro. Allogeneic cell transplantation of PCMO was performed in a hind limb ischemia mouse model in comparison to cell transplantation of native monocytes and a placebo group. Moreover, we analyzed retrospectively four healing attempts with PCMO in patients with peripheral artery disease (PAD; Rutherford classification, stage 5 and 6). Statistical analysis was performed by using one-way ANOVA, Tukey’s test or the Student’s t test, p < 0.05.ResultsCell culture experiments revealed good resilience of PCMO under hypoxia, enhanced paracrine release of pro-angiogenic and tissue recovery-associated proteins and induction of angiogenesis in vitro by PCMO. Animal experiments demonstrated significantly enhanced SO2 saturation, blood flow, neoangiogenesis and tissue recovery after treatment with PCMO compared to treatment with native monocytes and placebo. Finally, first therapeutic application of PCMO in humans demonstrated increased vascular collaterals and improved wound healing in patients with chronic CLI without exaggerated immune response, malignant processes or extended infection after 12 months. In all patients minor and/or major amputations of the lower extremity could be avoided.ConclusionsIn summary, PCMO improve angiogenesis and tissue recovery in chronic ischemic muscle and first clinical results promise to provide an effective and safe treatment of CLI.
Highlights
Critical limb ischemia (CLI) results from insufficient supply of blood due to arterial stenosis/ occlusion, vessel trauma or vasoconstriction because of catecholamine therapy and shock
programmable cells of monocytic origin (PCMO) release pro-angiogenic and tissue recoveryassociated proteins under hypoxia To evaluate whether transient ischemic conditions could influence the expression pattern of PCMO for proteins involved in angiogenesis and tissue recovery, cell lysates as well as cell culture media of PCMO were collected 24 h after hypoxia and normoxia, respectively
Human proteome profiling arrays (Fig. 2a) representing 55 proteins involved in angiogenesis and tissue regeneration were performed with the respective samples and showed a hypoxia-induced upregulation by more than 25% of 10/ 55 (18%) proteins in culture medium and 3/55 (6%) proteins within the PCMO cells
Summary
Critical limb ischemia (CLI) results from insufficient supply of blood due to arterial stenosis/ occlusion, vessel trauma or vasoconstriction because of catecholamine therapy and shock. In response to the significant need for new strategies to prevent tissue damage after CLI and consecutive major limb amputation, there have been numerous studies investigating different strategies in cell-based therapy for inducing neoangiogenesis in ischemic tissues. These previous studies mostly investigate the application of bone marrow-derived hematopoietic stem cells in ischemic tissue and include a wide range of embryonic stem cells, mesenchymal cells, skeletal myoblasts, and endothelial progenitor cells [6,7,8,9]. In most cases transplanted cells may not have been directly involved in forming vascular structures but possibly contribute to neoangiogenesis and vascular remodeling by paracrine mechanisms, which have not been investigated in detail so far [12, 14]
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