Heme oxygenase‐1 affects generation and spontaneous cardiac differentiation of induced pluripotent stem cells

Abstract

Cellular stress can influence efficiency of iPSCs generation and their differentiation. However, the role of intracellular cytoprotective factors in these processes is still not well known. Therefore, we investigated the effect of HO-1 (Hmox1) or Nrf2 (Nfe2l2), two major cytoprotective genes. Hmox1 fibroblasts demonstrated decreased reprogramming efficiency in comparison to Hmox1 cells. Reversely, pharmacological enhancement of HO-1 resulted in higher number of iPSCs colonies. Importantly, elevated level of both p53 and p53-regulated miR-34a and 14-3-3σ was observed in HO-1-deficient fibroblasts whereas downregulation of p53 in these cells markedly increased their reprogramming efficiency. In human fibroblasts HO-1 silencing also induced p53 expression and affected reprogramming outcome. Hmox1 and Hmox1 iPSCs similarly differentiated in vitro to cells originating from three germ layers, however, lower number of contracting cells was observed during this process in HO-1-deficient cells indicating attenuated cardiac differentiation. Importantly, silencing of Hmox1 in murine ESC using CRISPR/Cas-9 editing also impaired their spontaneous cardiac differentiation. Decreased reprogramming efficiency was also observed in Nrf2-lacking fibroblasts. Reversely, sulforaphane, a Nrf2 activator, increased the number of iPSCs colonies. However, both Nfe2l2 and Nfe2l2 iPSCs showed similar pluripotency and differentiation capacity. These results indicate that regulation of HO-1 expression can further optimize generation and cardiac differentiation of iPSCs. © 2018 IUBMB Life, 70(2):129-142, 2018.

Novel Interplay between p53 and HO-1 in Embryonic Stem Cells

“…Based on the evidence that HO-1 is involved in stem cells differentiation [ 37 , 58 , 59 , 60 ], we analyzed the HO-1 expression in ES cells during this process. First, we exploited ChIP Atlas data-mining platform [ 61 ] to investigate histone modifications and the binding of multiple transcriptional regulators to Hmox1 locus in undifferentiated ES cells and in ES cells subjected to differentiation protocols.…”

“…In addition, during ES cells differentiation both HO-1 [ 37 , 58 , 60 , 82 , 83 , 84 ] and p53 [ 24 , 76 , 82 , 85 ] play a relevant role. Using the Chip Atlas platform, we found that in undifferentiated ES cells Hmox1 is associated with negative transcriptional regulators.…”

“…Remarkably, NRF2 controls the self-renewal and pluripotency of human ES cells and is required for pluripotency reestablishment during induced pluripotent stem (iPS) cells generation [ 13 ]. Furthermore, it was found that HO-1 modulation affects both, the cellular reprograming efficiency and the capability of pluripotent stem cells to spontaneously differentiate to cardiac lineages [ 37 ]. Interestingly, it was suggested that HO-1 function during fibroblasts reprograming could be related to p53 downregulation [ 37 ].…”

“…Furthermore, it was found that HO-1 modulation affects both, the cellular reprograming efficiency and the capability of pluripotent stem cells to spontaneously differentiate to cardiac lineages [ 37 ]. Interestingly, it was suggested that HO-1 function during fibroblasts reprograming could be related to p53 downregulation [ 37 ]. This evidence highlights the existence of an interesting and complex connection between p53 and HO-1 in pluripotent stem cells that has not been fully described yet.…”

The pluripotency transcription factor OCT4 represses heme oxygenase‐1 gene expression

“…On the other hand, ES cells that do not express HO‐1 show higher levels of mesodermal and smooth muscle cell markers during embryoid‐body differentiation, suggesting that HO‐1 could be regulating the expression of specific genes [22]. Moreover, HO‐1 activity contributes to the differentiation and maturation of ES cells into cardiomyocytes [23] and HO‐1 knockout PS cells show impaired differentiation toward cardiac lineage [24]. On the contrary, it was suggested that HO‐1 protects ES cells against spontaneous differentiation [25], on the basis that OCT4 levels were lower in HO‐1 knockout iPS cells compared to wild type iPS and ES cells, and that the products of HO‐1 enzymatic activity, bilirubin, and CO, rescue the accelerated loss of OCT4.…”