Department of Surgery, Experimental Surgery, Charité -Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
Berlin Institute of Health at Charité -Universitätsmedizin Berlin, BIH Academy, Clinician Scientist Program, Berlin, Germany.
PLoS One. 2024 Apr 18;19(4):e0297497. doi: 10.1371/journal.pone.0297497. eCollection 2024.
Considering the expected increase in the elderly population and the growing emphasis on aging-related biomedical research, the demand for aged laboratory animals has surged, challenging established husbandry practices. Our objective was to establish a cost-effective method for environmental enrichment, utilizing the liver as a representative organ to assess potential metabolic changes in response to differing enrichment levels.
We conducted a six-month study involving 24 male Sprague Dawley rats, randomly assigned to four environmental enrichment groups. Two groups were housed in standard cages, while the others were placed in modified rabbit cages. Half of the groups received weekly playtime in an activity focused rat housing unit. We evaluated hormone levels, playtime behavior, and subjective handling experience. Additionally, liver tissue proteomic analysis was performed.
Initial corticosterone levels and those after 3 and 6 months showed no significant differences. Yet, testosterone levels were lower in the control group by the end of the study (p = 0.007). We observed 1871 distinct proteins in liver tissue, with 77% being common across groups. In gene ontology analysis, no specific pathways were overexpressed. In semiquantitative analysis, we observed differences in proteins associated in lipid metabolism such as Apolipoprotein A-I and Acyl-CoA 6-desaturase, which were lower in the control group (p = 0.024 and p = 0.009). Rats in the intervention groups with weekly playtime displayed the least amount of reported distress during inspection or upon room entry and were less prone to accepting treats. Removing animals from their enclosure was most effortless for those in the large cage group. Over time, there was a decrease in conflicts among rats that interacted only twice weekly during playpen time.
In summary, refining husbandry practices for aging rats is both simple and budget-friendly, with no apparent adverse effects on stress levels, animal development, or relevant metabolic changes in the liver.
考虑到老年人口的预期增长和对与衰老相关的生物医学研究的重视，对老年实验动物的需求猛增，这对既定的饲养实践提出了挑战。我们的目标是建立一种经济有效的环境丰富化方法，利用肝脏作为代表性器官来评估不同丰富度水平下潜在的代谢变化。
我们进行了一项为期六个月的研究，涉及 24 只雄性 Sprague Dawley 大鼠，随机分为四组环境丰富化组。两组饲养在标准笼中，另外两组饲养在改良的兔笼中。一半的组每周在活动集中的大鼠饲养单元中玩耍。我们评估了激素水平、玩耍行为和主观处理经验。此外，还进行了肝脏组织蛋白质组学分析。
初始皮质酮水平以及 3 个月和 6 个月后的水平没有显著差异。然而，研究结束时对照组的睾酮水平较低（p=0.007）。我们在肝脏组织中观察到 1871 种不同的蛋白质，其中 77%在各组中是共同的。在基因本体分析中，没有特定的途径被过度表达。在半定量分析中，我们观察到与脂质代谢相关的蛋白质存在差异，如载脂蛋白 A-I 和酰基辅酶 A 6-去饱和酶，对照组中这些蛋白质的水平较低（p=0.024 和 p=0.009）。每周有玩耍时间的干预组的大鼠在检查或进入房间时表现出的不适最少，并且不太愿意接受食物。从大笼组的动物中取出动物最为容易。随着时间的推移，在玩耍时间内每周只互动两次的大鼠之间的冲突减少了。
总之，改进老龄大鼠的饲养实践既简单又经济实惠，对压力水平、动物发育或肝脏中相关的代谢变化没有明显的不利影响。
