Do creams with “plant stem cells” help to fade scars?
This question really has two parts.
First, let’s talk about the appearance of scars. Your skin, the epidermal layer of your body, changes significantly over time. The connective tissue underlying the skin is made up of proteins such as elastin and fibrillin, that as you age, becomes less able to “snap back”, and is the result of slowly evolving microscopic damage to these connective tissues, resulting in the appearance of wrinkles and other signs of aging. Deep damage to the connective tissue can result in sudden changes which, along with defects in how the damage heals, causes the appearance of persistent wrinkles, clefts, or other features which aren’t there from the time a person is born or even as they age.
Creams of all kinds help to reduce the appearance of wrinkles, fine lines, scars, and other skin damage and defects because they tend to do a couple of things:
- they “moisturize”. Most moisturizers enhance the appearance of “moistness” by adding fatty or shiny substances to the skin which often results in a smoother appearance
- they “swell”. ingredients like alpha hydroxy acids irritate the skin and cause swelling of the underlying tissues. This swelling minimizes the appearance of wrinkles and lines on the skin
- they “peel”. by causing the outer layers of skin to peel off, the underlying skin is usually softer and has less superficial damage.
So, the first part to this answer is for the question, “do skin creams help to fade scars”, for which the answer is a qualified yes: the appearance of scars is diminished by any number of creams with any of thousands of ingredients.
The second part to this question would be to the question, “what incremental benefit do plant stem cells offer to help fade scars”, to which the answer is “no one knows”.
A recent review discusses “what is a plant stem cell”:
The phenomenon of callus creation from differentiated adult plant cells was described for the first time in 1902 by the Austrian botanist, Gottlieb Haberlandt . He suggested that the individual plant cell is able to regenerate the entire plant. This itself was demonstrated in 1958 by cloning a carrot from in vitro cultivated carrot cells . Since then, many articles have been published dedicated to regeneration of the entire plant from the cultivated cells and/or tissues. The callus creation process is one stage of somatic embryogenesis (i.e., formation of a zygote without fertilization) and the plant cells are subjected to dedifferentiation to again become stem cells capable of producing a new tissue or even an entire organ. The WUS protein is responsible for turning somatic cells back into stem cells. Research shows that cytokines are responsible for the production of stems from a callus, while auxins are responsible for the production of roots . (from Plant stem cells in cosmetics: current trends and future directions, Future Sci OA. 2017 Nov; 3(4): FSO226. doi: 10.4155/fsoa-2017–0026)
But there’s an important “gotcha”
In fact, almost all cosmetic companies advertising to contain stem cells in their products actually contain stem cell extracts and not the live stem cells.
If you read the linked article, most of the companies are basing their research on in-vitro studies of live cells being studied next to “plant stem cells”, and for these results, it’s clear that the production of growth-hormones such as cytokines and auxins along with a host of other signalling molecules by the plant stem cells has some kind of effect, although without proper blinded studies and careful controls it’s uncertain whether some of the results are due to actual science or “hopeful reading” of the produced data.
But most importantly, there is a popular conception that stem-cells themselves are a kind of “fountain of youth”: that in the human body, particularly with regard to embryonic stem cells derived from fetal tissue, there are multipotent or totipotent stem cells that can grow up to become any type of replacement cell. There are people who will see the word “stem cell”, and immediately form a positive connection with stories about embryonic development, youthful healing and growth, and stories of miracle cures, irrespective of the fact that “stem cells” are very fragile and only survive in a lab either frozen at -80 or under very specialized cell culture conditions. There is no possible way a stem cell could survive unfrozen in the typical matrix of a skin cream.
If, and this is a big if, there is a signalling molecule that helps to reverse the signs of aging, one might reasonably expect it to be present in stem cells, and it’s not entirely insane to think that such a molecule might be found in plant stem cells. But, let’s talk about Indole-3-acetic acid, the major signalling molecule found in plant stem cells. This is a known factor which is present in meristem formation in plants, and is present in a high enough concentration to be isolatable and measurable. It is also a probable mutagen:
IAA is listed in its MSDS as mutagenic to mammalian somatic cells, and possibly carcinogenic based on animal data. It may cause adverse reproductive effects (fetotoxicity) and birth defects based on animal data. No human data as of 2008. It is listed as a potential skin, eye, and respiratory irritant, and users are warned not to ingest it. Protocols for ingestion, inhalation, and skin/eye exposure are standard for moderately poisonous compounds and include thorough rinsing in the case of skin and eyes, fresh air in the case of inhalation, and immediately contacting a physician in all cases to determine the best course of action and not to induce vomiting when of ingested. The NFPA 704 health hazard rating for IAA is 2, which denotes a risk of temporary incapacitation with intense or prolonged, but not chronic exposure, and a possibility of residual injury. 
IAA produces microcephaly in rats during the early stage of cerebral cortex development. IAA decreased the locomotor activities of rat embryos/fetuses; treatment with IAA and analog 1(methyl)-IAA resulted in apoptosis of neuroepithelial cell and significantly decreased brain sizes relative to body weight in embryonic rats. 
So while there is circumstantial evidence under extremely controlled situations that plant stem cells might reduce the signs of aging, there’s also a much greater and larger body of evidence that a specific (and natural) plant hormone found in plant stem cells is a potential mutagen and might cause cancer or other diseases.
We know (it’s a fact) that there’s a fine line between the biology of fetal development and the biology of cancer and tumors are extremely closely related and intertwined. We know that signalling molecules responsible for fetal development (e.g. VEGF) are commandeered by cancer in the development of tumors. We know that experimentally, enzymes that lengthen telomeres are found in both youthful cells and cancer cells. Uncontrolled growth and immortality are the two major reasons why cancer and tumors are so deadly and problematic, and there’s good reason to believe that when cells gain the ability to grow uncontrolled and become immortal they become problems, not solutions.
The presence of plant stem cells in skin creams has all the hallmarks of an earlier deadly craze: Radium Cures. A “miracle substance” which has “many of the properties ordinary people see as indicating vitality or good health” is then “widely applied”, while many years later “the truth comes out” and such substances are not only “not healthy” but “actively harmful”. Yes, that last clause hasn’t “yet” come to pass, but really, why do you want to be the experimental test subject?
Personally, I think if you purchase skin creams with “stem cells” or “stem cell extract” and apply it to your skin, you’re a fool. You have no reasonable basis to believe that this will “help reduce or fade scars” beyond the way ordinary skin creams might, and might be exposing yourself unnecessarily to substances which might be harmful to you.
question originally answered on Quora at https://www.quora.com/Do-creams-with-plant-stem-cells-help-to-fade-scars-There-are-a-lot-of-plant-stem-cell-creams-on-market-Some-of-them-are-expensive-Do-they-actually-work-on-scar-treatment/answer/Matt-Harbowy?srid=hoC6
see also: do copper proteins like GHK-Cu help reduce scars? https://www.quora.com/Does-copper-peptides-GHK-Cu-products-help-to-fade-scars-Copper-peptides-for-topical-application-sometimes-recommended-for-scars-wrinkles-treatment-Is-it-really-effective-for-minimizing-scarring-or-it-is-just-marketing-hype/answer/Matt-Harbowy?srid=hoC6
matt harbowy is a scientist, activist, and data management expert. He is one of the founders of the non-profit Counter Culture Labs, working to bring fairness and egalitarian ideals to people interested in learning about science and biotechnology. He is also a top writer on the question and answer site, Quora.