Researchers have engineered mice that menstruate

Is this not a case of animal cruelty in the name of science? Just thinking out loud! Where are the animal activists when you need them! However, I suppose this kind of research is very useful.

Notice here also the apparent deliberate confusion of female animals and any animals! When ideology trumps science? I bet, these researchers did not engineer male animals to menstruate.

"Efforts to study the female reproductive system have long been set back by societal stigma—but also by the problematic fact that most laboratory animals don’t menstruate. Now, researchers have engineered mice that get a period in response to certain drugs.

Among the handful of animals that menstruate—which include large primates, four bat species, and the elephant shrew—the inner lining of the uterus, or endometrium, thickens before the release of an egg from the ovary. The layer then breaks down and is shed if no viable embryo appears.

In the new work, a team of researchers engineered the endometrium of standard lab mice to react to signals that drive menstruation in other animals. They equipped the cells with a receptor protein that, when activated by a drug, amplifies their sensitivity to calcium, a trigger of decidualization which prepares the endometrium for embryo implantation. When the researchers raised those animals’ progesterone levels and stimulated the receptors, the mice produced a 3–4 day period about 3 days later, with hallmarks of human menstruation including an enlarged uterus and expanded endometrial blood vessels. ..."

From the abstract:

"During menstruation, an inner layer of the endometrium is selectively shed, while an outer, progenitor-containing layer is preserved to support repeated regeneration. Progress in understanding this compartmentalization has been hindered by the lack of suitable animal models, as mice and rats do not menstruate.

Here, we present transgenic mouse models that recapitulate the key anatomical, functional, and transcriptional features of human menstruation through targeted chemogenetic activation of premenstrual differentiation.

Using single-cell spatial transcriptomics, we define a new paradigm for spatially regulated fibroblast differentiation that drives pre-menstrual endometrial layering and ultimately determines the extent of tissue shedding.

Our results revise a century-old view of endometrial shedding and regeneration and establish new transgenic mice as powerful tools to advance menstruation research."

ScienceAdviser

Induction of menstruation in mice reveals the regulation of menstrual shedding (open access)

About 2.8 million procedures are performed per year on lab animals in the UK alone in the name of medical progress

Just try to extrapolate this number to global scale! Unfortunately, this horrible fact is rarely reported!

Where are the so called animal rights activists when you need them?

It is long beyond high time to find alternatives! Maybe iPSC, organoids etc.!

"... Global data on animals in research are incomplete, but there are signs that the number of scientific procedures performed on live animals is falling in some countries. According to UK government data for example, 2.76 million such procedures were performed in the country in 2022. This is the lowest number since 2002, and markedly lower than the 4.14-million peak in 2015.
What, then, are the alternatives? Induced pluripotent stem cells — which have been ‘reprogrammed’ so that they can turn into any cell type — offer a way to generate human cells from skin or blood samples. Organoids, 3D cultures that can comprise multiple cell types, take such Petri-dish systems to the next level. ..."

Nature briefing

Animal research is not always king: researchers should explore the alternatives Technological advances can reduce the numbers of laboratory animals used in studies — but they need to be carefully validated.

The Challenges of Studying Elderly Lab Animals

Sometimes science can be amusing! Aesop's fables come to mind!

A Prayer For Animals Used In Experimentation

"... Villeda studies how proteins and other molecules found in blood can influence aging in the brain. His research relies on mice that are 24 months old, roughly equivalent to a 60- to 70-year-old human, and thus far older than the vast majority of mice used in biological research. Indeed, animal care technicians were so unused to taking care of older animals that Villeda had to educate them about the physical and behavioral changes to expect, from sensitive skin and a more disheveled appearance to increased aggression. “These animals are going to lose hair,” says Villeda, an investigator with the Simons Collaboration on Plasticity and the Aging Brain. “It’s normal aging. This is fine.”
Researchers who are new to studying aging often confront new challenges when they begin working with animals nearing the end of their lives. Be they worms, mice or humans, these animals are in some stage of physical decline. They may be losing their hearing and eyesight or dealing with muscle loss and arthritis, problems that may cause animals to struggle with tasks used to assess their cognitive abilities. Or they may not live long enough to be included in the experiment at all. Everything from behavior to gene expression is more variable than it would be in a group of younger animals. And because aging proceeds differently in different individuals, it’s usually impossible to predict which animals will develop problems that will interfere with a planned study. ..."

The Challenges of Studying Elderly Animals Physical and cognitive decline, along with highly variable behavior and physiological factors, complicates studies of aging.

Tinkering with Gut Microbes Boosts Brain Plasticity in Mice

Recommendable!

"... Now, a study published January 11 in Cell Reports finds that the environment could act indirectly: living in enriched environments changes the animals’ gut microbiota, which appears to modulate plasticity. ...
To assess plasticity, the team used monocular deprivation, where the input to one eye is blocked by sewing it shut so that neurons in the visual cortex are driven to shift to responding to the other eye. In mice raised in enriched cages, this shift can be observed after several days of deprivation, while the neurons of mice raised in standard housing never make the shift. 
In a first step, the researchers analyzed the spectrum of bacteria present in the guts of mice raised in standard cages and in enriched cages. Although both groups of mice ate the same diet, the microbiota composition in their gut began to differ as the mice grew up, and had diverged substantially by 90 days after birth. "

From the abstract:

"Exposing animals to an enriched environment (EE) has dramatic effects on brain structure, function, and plasticity. ... revealing that gut microbiota signals are crucial for EE-driven plasticity. Developmental analysis reveals striking differences in intestinal bacteria composition between EE and standard rearing (ST) mice, as well as enhanced levels of short-chain fatty acids (SCFA) in EE mice. Depleting the microbiota of EE mice with antibiotics strongly decreases SCFA and prevents activation of adult ocular dominance plasticity, spine dynamics, and microglia rearrangement. SCFA treatment in ST mice mimics EE induction of ocular dominance plasticity and microglial remodeling. Remarkably, transferring the microbiota of EE mice to ST recipients activates adult ocular dominance plasticity. Thus, experience-dependent changes in gut microbiota regulate brain plasticity."

Here is A Prayer For Animals Used In Experimentation

Tinkering with Gut Microbes Boosts Brain Plasticity in Mice | The Scientist Magazine® Intestinal bacteria contribute to the effect of stimulating environments on the brain’s ability to adapt, a study concludes.

The gut microbiota of environmentally enriched mice regulates visual cortical plasticity (open access)

How the Food & Drug Administration Can Reduce Animal Testing

Federal bureaucracies are like molasses or worse! Members of the U.S. Congress are not much better! The issue addressed in this article has been known for several decades!

A Prayer For Animals Used In Experimentation

"... If the FDA prioritizes science, health, and ethics over political considerations, it should support the development of sophisticated in vitro and computational approaches to curtail animal testing ...

The number of annually required animal tests is staggering. Over 110 million mice and rats are killed every year in the name of science in the U.S., as are other animals, including monkeys, rabbits, pigs, guinea pigs, cats, and dogs.

And the benefits are not always apparent. When the KHA [Kefauver–Harris Amendments (KHA) to the Federal Food, Drug and Cosmetic Act] was passed [in 1962], it was the scientific standard of its time. Sixty years later, scientists have learned that the results of animal tests are not necessarily useful or predictive in humans. Approximately 90 percent of early-phase clinical trials fail after extensive animal testing has already been conducted. Despite this, the FDA requires animal tests to be performed for almost every IND [Investigational New Drug] it reviews, regardless of utility. ...
Animal tests are often unnecessary. Aside from the many animal species and breeds involved, the variety of metabolic pathways and drug metabolites in animals leads to variation in efficacy, toxicity, disease latency, and dosing schedules. Often, the results are only loosely relevant to human beings. For example: isotretinoin, also known as Accutane, causes birth defects in rabbits, monkeys, and humans, but not in mice or rats. ..."

How the FDA Can Reduce Animal Testing | City Journal The agency should support sophisticated in vitro and computational approaches that can curtail—and potentially even replace—the practice.

How many mice and rats are used in U.S. labs? Controversial study says more than 100 million

Human progress and its victims! You may want to keep this in mind! I have previously blogged e.g. here about this subject.

"The most numerous mammals in U.S. research are also the most invisible. Mice and rats comprise the vast majority of lab mammals, yet no one knows exactly—or even approximately—how many are used in scientific experiments every year. Now, for the first time, someone has attempted to calculate this number using data from U.S. labs, and it’s big: More than 111 million mice and rats are used annually in U.S. biomedical research, according to a new study. That represents more than 99% of all lab animals. ...
The figures are troubling ... because mice and rats are not covered by the federal Animal Welfare Act (AWA), which enforces the humane treatment of research animals. ..."

How many mice and rats are used in U.S. labs? Controversial study says more than 100 million | Science | AAAS