Bone loss in adult offspring induced by low-dose exposure to teratogens

Abstract

Maternal malnutrition during pregnancy was shown by numerous studies to result in the birth of offspring exhibiting altered bone characteristics, which are indicative of bone loss. We hypothesized that not only maternal malnutrition but also some developmental toxicants (teratogens) given at a dose inducing neither structural anomalies nor growth retardation can detrimentally affect skeletal health in adult offspring. To check this hypothesis, pregnant mice were exposed to a single injection of 5-aza-2-deoxycytidine (5-AZA) (a teratogen capable of inducing phocomelia of the hind limbs) at a sub-threshold teratogenic dose. Micro-computed tomography scanning revealed that femora of 5-month-old male offspring exposed in uterus to 5-AZA had trabecular microarchitecture indicative of bone loss. Furthermore, exposure to 5-AZA increased the susceptibility of offspring to postnatal chronic mild stress, which has been shown to induce bone loss in mice. While exploring possible mechanisms underlying this phenomenon, we observed that the expression of some microRNAs, which have been demonstrated as regulators of key osteoblastogenic genes, was altered in hind limb buds of embryos exposed to 5-AZA. Furthermore, the expression of receptor activator of nuclear factor kappa B ligand (RANKL) in femoral stromal/osteoblastic cells of 5-month-old offspring of 5-AZA-treated females was found to be increased. Collectively, this study implies for the first time that single low-dose exposure to a teratogen can induce bone loss in adult offspring, possibly via alteration of embryonic microRNAs and RANKL expression.

Intrauterine stress induces bone loss in adult offspring of C3H/HeJ mice having high bone mass phenotype but not C57BL/6J mice with low bone mass phenotype

“…The results demonstrating the adverse effect of 5-AZA on femora of 6-mo-old C3H offspring are indirectly supported by those obtained in our previous study in ICR mice exposed to 5-AZA [7]. Indeed, the bone phenotype of adult ICR mice much more resembles that of C3H than C57 mice and changes observed in femora of 5-mo-old ICR male offspring are similar to those observed in C3H male offspring [7,15].…”

“…We also observed that exposure to 5-AZA increased the susceptibility of offspring to postnatal chronic mild stress, which has been shown to induce bone loss in mice [13]. Of note, the analysis of the relevant literature indicates that 5-AZA at a dose used in this study does not affect maternal homeostasis [7], thus no indirect effect on the embryo is expected.…”

“…Moreover, the exposure time of 5-AZA approximately matched the very beginning of osteoblastogenesis [13]. Finally, we [7] showed that 5-month-old offspring of ICR mice exposed to a single injection of 5-AZA at a sub-threshold teratogenic dose on day 10 of pregnancy exhibited femoral trabecular microarchitecture indicative of bone loss. We also observed that exposure to 5-AZA increased the susceptibility of offspring to postnatal chronic mild stress, which has been shown to induce bone loss in mice [13].…”

“…The choice of C57 and C3H mouse strains is based on data demonstrating that bones of C3H and C57 mice have similar external size but differ significantly in such traits as adult peak bone density, trabecular thickness, cortical bone density and cortical thickness [7,8], as well as biomechanical properties. Importantly, these two strains have been suggested for almost two decades as a model system to study genetics of osteoporosis [9], where C3H represents a model of high bone mass phenotype, and C57 represents a model of low bone mass phenotype.…”

“…The main objective of this work was to reveal whether offspring of mice exhibiting high (C3H) and low (C57) bone mass phenotypes differ with respect to their susceptibility to 5-AZA-induced antenatal insult resulting in bone loss in adult life, as shown by us [7]. To this end, we evaluated the structure and BMD of the femur and 3rd lumbar vertebra of 3-and 6-month-old (before and after the peak bone mass age, correspondingly) male and female offspring using micro-computed tomography (μCT).…”