Age-dependent cellular reactions of the human immune system of humanized NOD scid gamma mice on LPS stimulus

Abstract

Despite sepsis being a life-threatening disease, targeted drugs that improve the therapy of affected patients are still lacking. Infants and adults differ in the maturity level of their immune system and this results in distinct reactions to Gram-negative bacteria. To study reactions of human immune cells in vivo, we used NOD scid gamma mice transplanted with human CD34 stem cells to engraft a functional human immune system. Human cells undergo differentiation and maturation in these mice after transplantation and, accordingly, animals were divided into two groups: 8-13 wk and 15-22 wk after transplantation. Endotoxemia was induced by injecting LPS. Six h later, mice were euthanized. In both groups, LPS stimulation induced a decrease of CD14 monocytes in peripheral blood, an up-regulation of activation markers on different cell subsets such as myeloid dendritic cells, and a release of the human cytokines TNF-α, IL-6 and IL-10. However, significant differences were detected with regard to the amounts of released cytokines, and 8-13-wk-old mice produced more IL-6, while PTX3 was mainly released by 15-22-wk-old animals. Thus, here we provide a potential model for preclinical research of sepsis in infants and adults.

Potential Pitfalls of the Humanized Mice in Modeling Sepsis

“…Bone marrow suppression closely resembling the natural history of sepsis was seen as well [ 77 ]. The critical role of HMGB1, TLR4, and Notch in sepsis and apoptosis was also demonstrated using humanized mice [ 67 , 76 – 78 ]. However, the degree to which these processes replicate the complexity of the septic response is difficult to assess fully.…”

“…However, the degree to which these processes replicate the complexity of the septic response is difficult to assess fully. For example, IL-15, a critical cytokine for the development of sepsis-related apoptosis, can be studied in humanized mice only after modification of the model still resulting in production of age-dependent IL-15 [ 32 , 39 , 78 ]. Introduction of several human cytokines improved cell recovery but introduced artificially skewed populations [ 37 ].…”

“…Possible measurements include host's age, grafting time, or the age of the grafted human immune system. This important question has some biological underpinnings since the production of cytokines in response to pathogens has been reported as a variable dependent on the amount of time after grafting [ 78 ]. Since sepsis disproportionally affects the lower and upper extremes of age, younger mice are still reconstituting their immune system while older ones are at higher risk of immune system disorders; humanized mice may not be the most suitable model in age-related studies of sepsis [ 2 , 6 , 32 , 83 ].…”

Human immune cells infiltrate the lesioned spinal cord and impair recovery after spinal cord injury in humanized mice

“…107 108Collectively, these data illustrate that hNSG mice do not develop a mature human immune system until 3-4 months 109 post-engraftment with human UCB CD34 + stem cells. This is an important biological variable that is not well-110documented in the literature but if ignored, could dramatically affect experimental outcome (Audigé et al, 2017; 111 Ishikawa et al, 2005;Lang et al, 2013;Rodewohl et al, 2017;Tanaka et al, 2012). 112 113Human immune cells respond to ex vivo and in vivo immune stimulation 114 115To determine whether human immune cells in hNSG mice are functional at 4-6 months post-engraftment, human 116 splenocytes were isolated, purified (see Fig.…”

“…documented in the literature but if ignored, could dramatically affect experimental outcome (Audigé et al, 2017; 111 Ishikawa et al, 2005;Lang et al, 2013;Rodewohl et al, 2017;Tanaka et al, 2012). 112 113…”