Hypoxia and inflammatory factor preconditioning enhances the immunosuppressive properties of human umbilical cord mesenchymal stem cells

Abstract

BACKGROUND Mesenchymal stem cells (MSCs) have great potential for the treatment of various immune diseases due to their unique immunomodulatory properties. However, MSCs exposed to the harsh inflammatory environment of damaged tissue after intravenous transplantation cannot exert their biological effects, and therefore, their therapeutic efficacy is reduced. In this challenging context, an in vitro preconditioning method is necessary for the development of MSC-based therapies with increased immunomodulatory capacity and transplantation efficacy. AIM To determine whether hypoxia and inflammatory factor preconditioning increases the immunosuppressive properties of MSCs without affecting their biological characteristics. METHODS Umbilical cord MSCs (UC-MSCs) were pretreated with hypoxia (2% O2) exposure and inflammatory factors (interleukin-1β, tumor necrosis factor-α, interferon-γ) for 24 h. Flow cytometry, polymerase chain reaction, enzyme-linked immunosorbent assay and other experimental methods were used to evaluate the biological characteristics of pretreated UC-MSCs and to determine whether pretreatment affected the immunosuppressive ability of UC-MSCs in coculture with immune cells. RESULTS Pretreatment with hypoxia and inflammatory factors caused UC-MSCs to be elongated but did not affect their viability, proliferation or size. In addition, pretreatment significantly decreased the expression of coagulation-related tissue factors but did not affect the expression of other surface markers. Similarly, mitochondrial function and integrity were retained. Although pretreatment promoted UC-MSC apoptosis and senescence, it increased the expression of genes and proteins related to immune regulation. Pretreatment increased peripheral blood mononuclear cell and natural killer (NK) cell proliferation rates and inhibited NK cell-induced toxicity to varying degrees. CONCLUSION In summary, hypoxia and inflammatory factor preconditioning led to higher immunosuppressive effects of MSCs without damaging their biological characteristics.

Searching for the optimal precondition procedure for mesenchymal stem/stromal cell treatment: Facts and perspectives

“…Generally, the study by Li et al [ 1 ] was important not only because they made great progress in discovering the optimal preconditioning procedure for UC-MSCs but also because they raised an essential safety concern for further discussion and investigation. Furthermore, detailed horizontal comparisons of the optimal time, oxygen level and cytokine supplementation is necessary to reach a unanimous conclusion.…”

“…In their recent study entitled “Hypoxia and inflammatory factor preconditioning enhances the immunosuppressive properties of human umbilical cord mesenchymal stem cells” published in this journal, Li et al [ 1 ] pretreated UC-MSCs with a novel combination of hypoxia (2% O 2 ) and inflammatory factors for 24 hours (Figure 1 ). The authors discovered that the immunosuppressive ability of UC-MSCs was enhanced after pretreatment.…”

“…In this article, we comment on an article written by Li et al [ 1 ] published in the recent issue of World Journal of Stem Cells . High hopes have been given to mesenchymal stem cells (MSCs) as an optimal cell source for stem cell therapies because of their prominent availability, validated regeneration ability and safety[ 2 ].…”

Multiple pretreatments can effectively improve the functionality of mesenchymal stem cells

“…Tumor necrosis factor-α preconditioning can improve the therapeutic efficacy of MSCs in atherosclerosis[ 36 ]. In the study of “Hypoxia and inflammatory factor preconditioning enhances the immunosuppressive properties of human umbilical cord MSCs”, the researchers pretreated UC-MSCs with hypoxia (2% O 2 ) exposure and inflammatory factors (interleukin-1β, tumor necrosis factor-α, IFN-γ)[ 37 ]. After 24 h of exposure, they found that the pretreatment caused UC-MSCs to become elongated without affecting viability, proliferation, or size.…”

Priming mesenchymal stem cells to develop “super stem cells”

“…Unlike the strategies mentioned above, Li et al [ 29 ] in this issue report a preconditioning protocol that employs a combinatorial approach of culturing UC-MSCs in a pro-inflammatory milieu including a cocktail of IL-1β, tumor necrosis factor-α (TNF-α), and INF-γ, under hypoxia (2% O 2 ) for 24 h. The authors report improving the preconditioned cells’ immunoregulation-related gene and protein profiles, thus enhancing their immunoregulatory properties compared to the naïve (non-preconditioned) UC-MSCs. More importantly, the preconditioned UC-MSCs’ immunoregulatory properties were accentuated without conceding their biological characteristics, i.e., surface marker expression, proliferation, mitochondrial integrity, etc.…”