Biological response of nonhuman primates to controlled levels of acute blood loss

Abstract

IntroductionThe global shortage of human blood for medical use has prompted the development of alternative blood sources. Nonhuman primates (NHPs) are commonly used owing to their physiological similarities to humans. The objective of the current study was to establish a controlled-blood-loss model in NHPs to explore their clinical and biological responses.MethodsBlood was sequentially withdrawn from 10 cynomolgus monkeys (10, 14, 18, 22, and 25% of the total blood volume); their vital signs were monitored, and blood parameters were serially analyzed. Humoral mediators in the blood were measured using flow cytometry and enzyme-linked immunosorbent assays.ResultsIn NHPs subjects to 25% blood loss and presenting with related clinical symptoms, the systolic blood pressure ratio on day 0 after bleeding was significantly lower than that of the animals from the other groups (median: 0.65 vs. 0.88, P = 0.0444). Red blood cell counts from day 0–14 and hematocrit levels from day 0–7 were markedly decreased relative to the baseline (P < 0.01). These parameters showed a direct correlation with the extent of blood loss. The levels of creatine phosphokinase, aspartate aminotransferase, and alanine aminotransferase exhibited increases in response to blood loss and had a stronger correlation with the hemoglobin ratio than the volume of blood loss. The levels of C3a and C4a, as well as interleukin (IL)-1α and IL-15, displayed a strong correlation, with no apparent association with blood loss.ConclusionThe findings of the present study showed that only NHPs with 25% blood loss exhibited clinical decompensation and significant systolic blood pressure reduction without fatalities, suggesting that this level of blood loss is suitable for evaluating blood transfusion efficacy or other treatments in NHP models. In addition, the ratio of hemoglobin may serve as a more dependable marker for predicting clinical status than the actual volume of blood loss. Thus, our study could serve as a basis for future xenotransfusion research and to predict biological responses to massive blood loss in humans where controlled experiments cannot be ethically performed.

Investigation of the efficacy and safety of wild- type and triple-gene knockout pig RBC transfusions in nonhuman primates

“…In our previous NHP blood-loss model study ( 14 ), we observed a significant increase in WBCs, including neutrophils, regardless of transfusion, likely owing to stress and compensatory mechanisms. The pRBC preparations used leukocyte-depletion filters, resulting in leukocyte counts below measurable limits ( Table 1 ).…”

“…From all the NHPs, 25% of the total blood volume was removed, and the same amount of WT- or TKO-pRBCs (n=4 per group; male 2, female 2), or saline (n=2; male 1, female 1) as a control was administered to each NHP. The data and leftover samples of the two NHPs with 25% blood withdrawal in our previous study ( 14 ) were included in the control group (n=4). Vital signs and general symptoms were observed daily for three weeks from the day of blood withdrawal/transfusion (D0).…”

“…Two months later, the second transfusion with pRBCs was conducted in three NHPs (1 WT group and 2 TKO group) following the same protocol. The data and samples of two NHPs from a previous study ( 14 ) were included in the control group.…”

“…Statistical analyses were performed using MedCalc software (version 22.0; Ostend, Belgium). For comparison between groups, the data were transformed into ratios or differences (Δ) based on the results at the D0pre and plotted against each time point ( 14 ). The area under the curve (AUC) was compared using one-way analysis of variance.…”

“…Previously, we investigated the compatibility of pRBCs from several genetically modified pigs with human sera in vitro and found that triple knockout (TKO)-pRBCs with/without further modifications are comparable to O-type hRBCs ( 13 ), where TKO pigs are devoid of expressing major xenoantigens: galactose-α-1,3-galactose (αGal), N -glycolylneuraminic acid, and Sd(a) on the surface of pig cells. Next, to assess the feasibility of xenotransfusion in vivo , we established a controlled blood loss model in NHPs, in which 25% withdrawal of the total blood volume was appropriate for observing significant hematological changes without consequent lethality of the animal ( 14 ). In this study, we investigated the therapeutic impact and adverse reactions of wild-type (WT)- or TKO-pRBC transfusions in NHPs with 25% blood volume loss.…”