When it comes to analyzing the genetic material inside human cells, we are not entirely humans. Instead, every individual is made from as many as 145 genes that constitute bacteria, viruses, and other single-celled microorganisms. Human/nonhuman chimera studies based on stem-cell research include transferring human stem cells into animal bodies. The transfer takes place at several stages of growth. These studies aim to propose localized human biological and cellular features into lab animals. The investigations help advance stem cell science, developmental biology, and various fields of biomedicine. Human/nonhuman chimera analysis has survived without controversies for decades. Some examples are rat models of human cancer and their immune systems. Read on to learn more about chimera investigations.
Protocols explain chimeras to be a single organism including two or more genomes. It constitutes cells, DNA, tissues, or body parts from two or more species. When the tissue is taken from two different individuals, it creates an interspecific chimera. Chimeras do not form through sexual reproduction like hybrids. For instance, Mules are considered a hybrid of a male donkey and a female horse. Instead, human-to-human chimeras transpire naturally. Mothers bear cells from prior fetuses in their blood. When double impregnation and fusion happen, a child could be born with double genomes. However, the birth of that individual is a vision. Most people certified as chimera are unaware of their dual genetic identity. Human to human images can also be done. For example, kidney transplantation individuals have two genomes. Patients who have Leukemia receive donor blood cell transplants making them chimeric, as they carry the genetic codes of two people.
Cross-species chimerism is popular in both experimentation and healing treatments. Many animals are now able to carry human cells. In several studies, they can take human organs as well. For instance, cows discharge human protein in milk, sheep develop human heart tissue and liver, pigs have human blood, and mice brains constitute human neurons. Scientists routinely also put human neoplasm cells into animal forms. The scenario is reversed in humans as well. Some people are implanted with pig or cattle-based heart valves.
In an innovative experiment, scientists were successful in creating the first human-monkey chimera. The goal behind the study was not to develop cross-species mutants. They did not want to capitalize on physical attributes or features like X-Men. The main goal was to understand what happens in the first trimester of human pregnancy right after embryo fertilization. Unfortunately, there are pretty limited studies or research on the topic. The only data on early embryogenesis involves different animal forms such as mice, rats, and worms. Producing an embryo of the human-monkey chimera was done to pave the path for more advanced knowledge of what cell types can be generated. Additionally, the study has the potential to deal with the lack of human organs available for transplantation.
In 2017, a controversial project created a lot of hype by devising a human-pig hybrid. This biomedical progress was a long-term dream and predicament for researchers. This project is the hope to approach the severe shortage of human donor organs. An international team of researchers created a Chimera from human and pig species. Firstly, the organization collected stem cells from rodents and inserted them inside pig blastocysts. Unfortunately, this experiment was a failure, as the gestation period of rats and pigs are different. However, pigs have a distinguished resemblance to humans. The gestation period in pigs is more extended, but the organs are shaped similarly. The task was still complicated for the team. The timing to introduce the humans’ cells into pigs was crucial, as this might kill them. Once the researchers could get the time-period correct, the embryos were left inside for 3–4 weeks. After removal and analysis of the embryos, the team successfully generated 186 later-stage alive chimeric embryos.
Growing tissues or organs of one species in another one
There are two methods to form a chimera. Firstly, by introducing the organs of one species into another. However, this method is a risky one as the host immune system might reject the new organ. Secondly, raising the animal’s cells into another species at the embryonic level. This procedure allows the embryos to develop together as a hybrid. Nevertheless, the technique is considered excellent for solving many vexing biological concerns that usually occur with lab-grown organs.
Can it solve donor shortages?
Recent technological advancements in stem cell research would guarantee that every organ is the right genetic match for the recipient. It would also solve the current dire demand for organ donors and consequent lifetime immunosuppression. Furthermore, human/nonhuman stem cells or tissues can also be utilized for drug screening tests or toxicology studies. Finally, the development would allow surgeons to perform surgeries on unimpaired human organs before working on subjects. In addition, experts can also study the characteristics of early human evolution efficiently.
The discovery of stem cells producing any body tissue appeared to be an infinite scientific development. However, the task of growing different tissues and cells together is a daunting one. Nevertheless, cells should be able to persevere in Petri dishes. As for making sure that the organs develop into suitable shapes, researchers have to utilize scaffolds. Moreover, the evolutionary gaps among species can distort the delivery of growth signaling pathways. Hence, the merger of the two species is quite risky.