Elsevier

Life Sciences

Volume 152, 1 May 2016, Pages 244-248
Life Sciences

Review article
Men and mice: Relating their ages

https://doi.org/10.1016/j.lfs.2015.10.025Get rights and content

Abstract

Since the late 18th century, the murine model has been widely used in biomedical research (about 59% of total animals used) as it is compact, cost-effective, and easily available, conserving almost 99% of human genes and physiologically resembling humans. Despite the similarities, mice have a diminutive lifespan compared to humans. In this study, we found that one human year is equivalent to nine mice days, although this is not the case when comparing the lifespan of mice versus humans taking the entire life at the same time without considering each phase separately. Therefore, the precise correlation of age at every point in their lifespan must be determined. Determining the age relation between mice and humans is necessary for setting up experimental murine models more analogous in age to humans. Thus, more accuracy can be obtained in the research outcome for humans of a specific age group, although current outcomes are based on mice of an approximate age. To fill this gap between approximation and accuracy, this review article is the first to establish a precise relation between mice age and human age, following our previous article, which explained the relation in ages of laboratory rats with humans in detail.

Introduction

Most studies in the field of life science (almost 59% of the experimental studies [1]) use experimental murine models (Mus musculus) for investigating the implications on human health and body (Fig. 1). In terms of their maximum lifespan, mice (4 years) and humans (120 years) differ significantly, although murine models have been widely used to analyse human body functioning and its modulation (see Ref. [2]). In two pioneering studies, Sir L. Demeritus (published in 2005 and 2006) documented their similarities and differences in diverse metabolic processes, describing the molecular process of ageing in detail (see Refs. [2], [3]), but not the precise correlation of their ages in different phases of their lifespan.

Despite the large differences in their lifespan, humans and mice show similar patterns in disease pathogenesis as well as organ and systemic physiology. Their cells contain similar molecular structures that regulate the functioning of cells, differentiation. Moreover, the molecular mechanism of ageing in mice is similar to that in humans (see Ref. [3]). For instance, mice acquire mutations in the spectrum of proto-oncogenes and tumour suppressor genes, similar to those affected in human cancers (see Ref. [4]). Almost 99% of mouse genes resemble the human genome, thus making the murine model an ideal candidate for studying the functions of human genes in health as well as in the regulation of multifactorial diseases such as cancer, cardiovascular diseases, diabetes and arthritis (Table 1). Acute promyelocytic leukaemia (APL), although previously untreatable, is currently treated in humans after successful experimentation in murine models. Although certain larger mammals can better simulate human genotypic and phenotypic features, they can be expensive and difficult to maintain or handle [5].

Mice provide analogous experimental conditions and comparable results to humans. Findings of general experiments with mice, pharmaceutical trials for newly designed drugs in murine models, or studies on different developmental phases of mice are intended to be applied on human health and life. In all such cases, using mice of an approximate age rather than precisely correlated age or phase with humans limits the accuracy of experiments and their implications for human physiology. It is imperative that researchers consider the phase and age of animals used in experiments in relation to human physiology, which was explained in detail in our previous review work on the relation between the age of rats and humans (see Ref. [6]). Thus, the aim of this comprehensive review is to precisely analyse the relation between mice age and human age in various life stages to bridge the gap between the approximation and accuracy of future research in the biomedical field.

Section snippets

Age determination of laboratory mice: common methods

Various methods have been used to correlate the ages of small mammals with human age, for example, by determining the weight of eye lens (see Refs. [7], [8], [9], [10], [11] and [12]), epiphyseal closure (see Refs. [13], [14]), tooth wear (TW) pattern [15], and body weight correlation [15]. As these methods provide a relative age that does not exactly coincide with the exact age, more than one method is required for a closer approximation of the age of the experimental animal. To relate the

Relation between mice age and human age

Currently, biomedical studies achieve the highest accuracy and specificity due to the advances in technology. Therefore, in experiments with mice representing humans, the mice age must be precisely determined in relation to human age, in terms of both the lifespan and individual life stages. In the following section, we present human age in relation to different developmental stages of mice.

Conclusions

This article reveals the wide variations in the developmental durations and phases of mice versus humans, although murine models are essential in biomedical science to study human physiology and its modulations. The relative ages of mice differ depending on the life stage. Therefore, it is imperative that researchers know the precise correlation between mice age and human age at a specific life stage of the mice under their studies.

Conflict of interest

The authors declare that there are no conflicts of interest.

Funding source

None.

References (27)

  • R.A. Taft et al.

    Know thy mouse

    Trends Genet.

    (2006)
  • K. Flurkey et al.

    The mouse in aging research

  • Report of European Union

    The Statistics on the Number of Animals Used for Experimental and Other Scientific Purposes

    (2010)
  • L. Demeritus

    Of mice and men

    EMBO Rep.

    (2005)
  • L. Demeritus

    Aging in mouse and human systems: a comparative study

    Ann. N. Y. Acad. Sci.

    (2006)
  • A. Balmain et al.

    Carcinogenesis in mouse and human cells: parallels and paradoxes

    Carcinogenesis

    (2000)
  • European Commission workshop

    Are mice relevant models for human disease?

    (2010)
  • P. Sengupta

    The laboratory rat: relating its age with humans

    Int. J. Prev. Med.

    (2013)
  • A.R. Hardy et al.

    Estimation of age in the Norway rat (Rattus norvegicus) from the weight of the eyelens

    J. Appl. Ecol.

    (1983)
  • F.P. Rowe et al.

    Relationship between eye lens weight and age in the wild house mouse (Mus musculus)

    J. Appl. Ecol.

    (1985)
  • R.C. Augusteyn

    Growth of eye lens: 1. Weight accumulation in multiple species

    Mol. Vis.

    (2014)
  • E.C. Birney et al.

    Eye lens proteins as criteria of age in cotton rats

    J. Wild Lif. Manag.

    (1975)
  • D.R. Lord

    The lens as an indicator of age in cotton-tail rabbits

    J. Wildl. Manag.

    (1959)
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