Effects of Gravity, Microgravity or Microgravity Simulation on Early Mammalian Development

Abstract

Plant and animal life forms evolved mechanisms for sensing and responding to gravity on Earth where homeostatic needs require responses. The lack of gravity, such as in the International Space Station (ISS), causes acute, intra-generational changes in the quality of life. These include maintaining calcium levels in bone, maintaining muscle tone, and disturbances in the vestibular apparatus in the ears. These problems decrease work efficiency and quality of life of humans not only during microgravity exposures but also after return to higher gravity on Earth or destinations such as Mars or the Moon. It has been hypothesized that lack of gravity during mammalian development may cause prenatal, postnatal and transgenerational effects that conflict with the environment, especially if the developing organism and its progeny are returned, or introduced de novo, into the varied gravity environments mentioned above. Although chicken and frog pregastrulation development, and plant root development, have profound effects due to orientation of cues by gravity-sensing mechanisms and responses, mammalian development is not typically characterized as gravity-sensing. Although no effects of microgravity simulation (MGS) on mouse fertilization were observed in two reports, negative effects of MGS on early mammalian development after fertilization and before gastrulation are presented in four reports that vary with the modality of MGS. This review will analyze the positive and negative mammalian early developmental outcomes, and enzymatic and epigenetic mechanisms known to mediate developmental responses to simulated microgravity on Earth and microgravity during spaceflight experiments. We will update experimental techniques that have already been developed or need to be developed for zero gravity molecular, cellular, and developmental biology experiments.

Comparison of Microgravity Analogs to Spaceflight in Studies of Plant Growth and Development

“…The experiments to date suggest that while these devices may be useful tools in some cases, there are great differences observed between plants that grow and develop on these devices and plants that are grown in weightlessness during spaceflight. In fact, rotation on certain types of clinostats may have deleterious effects in some biological systems (Hensel and Sievers, 1980; Kozeko et al, 2018; Ruden et al, 2018).…”

Potential Impact of Space Environments on Developmental and Maturational Programs Which Evolved to Meet the Boundary Conditions of Earth: Will Maturing Humans Be Able to Establish a Functional Biologic System Set Point under Non-Earth Conditions?

“…4) Assess the epigenetic changes associated with pre-clinical models. Some characterization has been done with fish and other models [12], but work with rodents is more limited. However, pregnant rats were sent to the ISS and the offspring born in space [27].…”

“…First of all, given the variation between individual humans in gaining the ability to function up-right and exert vestibular control, and be mobile in the 1g environment with regard to timing post-birth, the critical events are likely not "fixed" in time, but may be dependent on several maturational pathways converging (neuromuscular control; visual acuity distinguishing self from the environment; actual muscle, tendon, and bone strength and their neural integration; cardiovascular competence required for walking upright; others). Secondly, the variation in timing does not appear to be detrimental to survival, but microgravity or microgravity simulation may influence developmental programs which could impact later events [reviewed in [12]]. Thirdly, the variations may be due to otherwise "silent" mutations (as long as one stays within the 1 g environment) within the central systems involved, or in some peripheral ancillary systems.…”

The Application of Mechanical Stimulations in Tendon Tissue Engineering

“…Mechanical stimulus has a huge impact on life activities, which is evident in gene expression, cell life activities, functions of living systems, and individual growth and development. With the redistribution of body fluids and the reduction of skeletal load under weightless conditions, bone loss and increased calcium secretion occur to the bones, which seriously affect the function of the musculoskeletal system [ 1 , 2 ]. In the context of induced differentiation of stem cells, different types of mechanical stimulations may play different roles.…”