Science, asked by rishi1803, 1 year ago

is stem cell treatment really promising? research paper plz answer fast...​

Answers

Answered by venky14800
0

Which stem cell? Yes, stem cell treatment is promising. In one case — hematopoietic stem cells (HSCs) — it has been very successful. When considering other stem cells, it is still “promising”.

For many stem cells, good results have been obtained in animal studies, but results in human clinical studies have been disappointing

Below is a summary of the common stem cells that have either been tested in the clinic or proposed as a major treatment option for a wide range of illnesses and/or injuries, but have limited clinical trials. There is discussion about the characteristics of the stem cells that have contributed to the disappointing translation to the clinic.

1. Hematopoietic stem cells (HSCs): these have transferred very well to the clinic and are routinely used as adjunct therapy in leukemia by regenerating the hematopoietic system. HSCs isolated from umbilical cord blood are also translating well to the clinic.

2. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs): These cells are pluripotent and can potentially differentiate into all the cell types in the body. They are what people most often think of when they hear the words “stem cells”. They cannot be used undifferentiated in humans, because they form teratomas when implanted as stem cells. Therefore, ESCs and iPSCs have to be differentiated in a culture dish to the phenotype desired. This limits their utility in the clinic to elective cases where only 1 phenotype is needed, i.e. retinal cells for macular degeneration. ESCs also have the potential problem of immunorejection. iPSCs have the problem of being generated by the transduction of genes, therefore there are safety concerns that the transduction will turn on oncogenes. Another obstacle that has come to light is that ESCs and iPSCs differentiate to the fetal form of cells. These are often not able to function in an adult. Currently researchers are trying to “age” the differentiated cells in vitro.

3. Neural stem cells (NSCs): This stem cells can become the 3 cell types of the central nervous system: neurons, astrocytes, oligodendrocytes. They have the potential to treat traumatic brain injury, Parkinson’s, epilepsy, etc. The problem with moving NSCs to the clinic is obtaining sufficient quantity of the cells. NSCs are isolated from the brain, and there are insufficient quantities of human brain available. It is possible, in animal studies, to take the brains of a large number of donor animals, isolate the NSCs, and then use those NSCs to treat a small number of test animals. That procedure, obviously, is not possible with humans. Taking a large enough biopsy of a person’s brain to obtain NSCs simply is not possible without injury to the donor, and obtaining the brains of recently deceased individuals to isolate NSCs is not feasible. At least one company is trying to immortalize the NSCs so that they have an unlimited proliferation potential, but that raises safety concerns.

4. Mesenchymal stem cells (MSCs): This is the stem cell that people thought could be translated to the clinic and has had problems. MSCs differentiate in vitro to at least 4 cells types: chondrocytes, osteoblasts, adipocytes, and skeletal myocytes. The initial animal trials showed promising results for regeneration. However, there were methodological problems associated with those initial animal trials:

a. All the initial in vivo animal work was done in young animals. These animals correspond to 12-18 year old humans. These young animals, and young humans, regenerate well. The human studies were conducted, of course, on individuals > 30 years old, who do not heal easily.

b. The initial studies did not track the MSCs and therefore did not know if the regenerated tissue came from the donor MSCs or host cells.

c. Many of the initial animal studies did not show regeneration. The initial Caplan paper on MSCs regenerating a cartilage defect in young rabbits, for instance, stated regeneration in the Abstract but in the body of the paper animals treated with MSCs did no better than the controls without MSCs.

d. Animal studies used small numbers of cells – 1-5 million cells. In small animals, this was a sufficient number of cells. However, humans are much larger, and 1-5 million cells were not adequate; they needed hundreds of millions of cells.  

e. The animal studies used, of course, MSCs isolated from that animal. None of the studies demonstrated differentiation of human MSCs in vivo.

5. Unrestricted somatic stem cells (USSCs) and Multipotent Adult Progenitor Cells (MAPCs): Both of these adult stem cells have published studies showing regeneration in animal models. However, those studies suffer from the same methodological flaws as noted for MSCs. Clinical trials have shown no effect. However, most of the trials are attempting to deliver the stem cells intravenously, and it is probable that very few of the cells reach the site of injury (studies show ~ 90% are trapped in the lungs).

Similar questions