Accelerated cellular senescence as underlying mechanism for functionally impaired bone marrow-derived progenitor...

Bone marrow (BM)-derived progenitor cells are functionally impaired in patients with ischemic heart disease (IHD), thereby hampering the outcome of autologous stem cell therapy. In search for underlying mechanisms for this BM dysfunction, accelerated cellular senescence was explored.

We analysed telomere length of BM-derived mononuclear cells (MNC) by MMqPCR in patients with coronary artery disease (n = 12), ischemic heart failure (HF; n = 9), non-ischemic HF (n = 7) and controls (n = 10), and related it to their myeloid differentiation capacity. Expressions of senescence-associated genes p53, p21^Cip1 and p16^lnk4A; and telomere maintenance genes TERT, TRF1/2, Sirt1 in BM-MNC were evaluated using qPCR. Pro-inflammatory cytokine levels (TNFα, IFNy, IL-6) in BM were measured by MSD.

BM-MNC telomere length was shortened in patients with IHD, irrespective of associated cardiomyopathy, and shortened further with increasing angiographic lesions. This telomere shortening was associated with reduced myeloid differentiation capacity of BM-MNC, suggesting accelerated senescence as underlying cause for progenitor cell dysfunction in IHD. Both p16^lnk4A and p21^Cip1 were activated in IHD and inversely related to myeloid differentiation capacity of BM-MNC; hence, the BM-MNC functional impairment worsens with increasing senescence. While BM-MNC telomere attrition was not related with alterations in TERT, TRF1/2 and Sirt1 expression, IFNy levels were associated with p21^Cip1/p16^lnk4A upregulation, suggesting a link between inflammation and cellular senescence. Still, the trigger for telomere shortening in IHD needs to be elucidated.

Accelerated replicative senescence is associated with a functional impairment of BM-derived progenitor cells in IHD and could be targeted to improve efficacy of stem cell therapy.