Changes of development from childhood to late adulthood in rats tracked by urinary proteome

To date, studies of development have mainly focused on the embryonic stage and a short time thereafter. There has been little research on the whole life of an individual from childhood to aging and death. For the first time, we used noninvasive urinary proteome technology to track changes in several important developmental time points in a group of rats, covering 10 time points from childhood, adolescence, young adulthood, middle adulthood, and near-death in old age. Similar to previous studies on pu-berty, proteins were detected and they are involved in sexual or reproductive maturation, mature spermatozoa in seminiferous tubules (first seen), gonadal hormones, decline of estradiol, brain growth, and central nervous system myelination, and our differential protein enrich-ment pathways also included reproductive system devel-opment, tube development, response to hormone, response to estradiol, brain development, and neuron development. Similar to previous studies in young adults, proteins were detected and they are involved in muscu-loskeletal maturity, peak bone mass, development of the immune system, and growth and physical development, and our differential proteins enrichment pathways also included skeletal system development, bone regeneration, system development, immune system processes, myeloid leukocyte differentiation, and developmental growth. Urine is considered one of the most valuable biofluids for the discovery of disease biomarkers because urine collection is noninvasive and easy. More importantly, unlike blood, urine is not subject to homeostatic control, and it accumulates small, sensitive, and early changes associated with systemic changes, some of which may be used as biomarkers (1). Urine proteomics has already been applied to various clinical studies (2, 3), including studies on lung cancer (4-7), breast cancer (8, 9), bladder cancer (10-12), gastric cancer (13), genitourinary cancer (14), and knee osteoarthritis (15). More-over, urine-filtered plasma proteins originate from distal or-gans, including the brain, etc. not only the kidney (16-18). Most modern developmental biology research has focused on individuals during pregnancy and a short time before reaching adulthood and has generally focused on a certain organ or system (19, 20). There have also been some studies on elderly individuals (21), but they only involved a certain organ, and individuals of different ages were different, potentially hindering comparability. This study is the first time that the urinary proteome was used to track the whole development of a group of rats from childhood to old age. Urinary proteome can also reflect the overall changes in the body.