Serum from pregnant donors induces human beta cell proliferation and insulin secretion

Pancreatic beta cells are among the slowest replicating cells in the human body. Human beta cells usually do not increase in number with exceptions being during the neonatal period, in cases of obesity, and during pregnancy. This project explored maternal serum for stimulatory potential on human beta cell proliferation and insulin output. Gravid, full-term women who were scheduled to undergo cesarean delivery were recruited for this study. A human beta cell line was cultured in media supplemented with serum from pregnant and non-pregnant donors and assessed for differences in proliferation and insulin secretion. A subset of pregnant donor sera induced significant increases in beta cell proliferation and insulin secretion. Pooled serum from pregnant donors also increased proliferation in primary human beta cells but not primary human hepatocytes indicating a cell-type specific effect. This study suggests stimulatory factors in human serum during pregnancy could provide a novel approach for human beta cell expansion.


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Glucose metabolism changes during pregnancy to support the growing fetus' needs for glucose 50 through passive transport dependent on a concentration gradient between fetal and maternal 51 circulations. In the later stages of pregnancy, the placenta secretes hormones to increase 52 maternal insulin resistance and hepatic glucose production, raising the maternal glucose, 53 supporting the gradient [1]. To prevent excessive nutrient delivery to the fetus and prevent 54 maternal hyperglycemia, pregnancy is also associated with an increase in beta cell mass [1,2].

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This increase in beta cell mass during human pregnancy has been investigated by two autopsy 56 series [3,4]. However, the dominant mechanism (replication, neogenesis or both) for increased 57 beta cell mass during pregnancy in humans remains uncertain [1,4,5].

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In rodents, pregnancy-associated beta cell expansion depends on secreted placental lactogens 60 that signal through the prolactin receptor [2]. At the end of pregnancy, the beta cell population 61 contracts back to its pre-pregnancy size. However, loss of prolactin associated signaling 62 pathways in the mouse islet does not completely block the proliferative response to pregnancy.

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Studies of lactogens on human beta cell proliferation have generated inconclusive results [6,7].

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Therefore, other signals almost certainly contribute to beta cell proliferation in pregnancy [5]. and prenatal ultrasound examination confirmed that there were no anatomical abnormalities of 75 the fetuses. All participants underwent glucose tolerance testing from 24-28 weeks and were 76 confirmed to have normal glucose tolerance, gestational or pre-gestational diabetes.

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The EndoC-H1 human beta cell line was cultured consistent with conditions described by 95 Tsonkova et al [11]. The EndoC-H1 was cultured in DMEM low glucose (1g/L), 2% Albumin 96 from bovine serum fraction V, 50 µM 2-mercaptoethanol, 10 mM nicotinamide, 5.5 μg/ml 97 transferrin, 6.7 ng/ml sodium selenite and Penicillin (100 units/ml) / Streptomycin (100 g/ml) 98 and maintained in sub confluent densities. EndoC-H1 cells were seeded at 2 x 10 5 cells per 99 . CC-BY 4.0 International license available under a was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made

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. CC-BY 4.0 International license available under a was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made  We measured a donor-dependent effect of supplementing the cell culture medium with 10% 161 maternal serum on EndoC-βH1 beta cell proliferation by EdU incorporation, and on insulin 162 secretion by ELISA (Figure 1). There were no significant differences in the degree of 163 proliferation for EndoC-βH1 beta cells cultured with 10% maternal serum, 10% non-pregnant 164 serum, or serum-free control medium when samples were analyzed by treatment group 165 (p=0.78) ( Figure 1A). There was, however, a distinct group of maternal "responders" (n=4; 166 donors #5-8), which induced a higher degree of proliferation relative to control medium. When 167 analyzed as responders and non-responders, the proliferation induced by these four donors was 168 statistically significant (p=0.003). (Figure 1B and Supplementary Figure 1). Responders were 169 selected as having a mean more than 1 standard deviation higher than the mean of the 170 standard cell culture medium control group.

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. CC-BY 4.0 International license available under a was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made       Table 1 and Supplementary Tables 1 and 2). No other applicable 249 resources were generated during the current study.     was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made

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