Gene Transfer in Cosmetics

Gene transfer; the words can trigger emotional reactions! And yet, nothing is more frequent or more usual than gene transfer. Indeed, from the tiny paramecium to the largest whale, the reproduction of sexuated organisms occurs via gene transfer. And when it comes to our basic understanding of biology, we know that DNA is the blueprint of heredity because of an experiment in which the DNA of a pathogenic pneumococcus was transferred to a non-pathogenic pneumococcus and transformed it into a pathogenic one.¹ More recently, gene transfer became the basis of some of the new technologies used to achieve cost-effective, large-scale, safe and efficient vaccination against the virus that causes COVID-19.

Foreign RNA encapsulated in liposomes can be transferred into target cells and translated into proteins.² DNA can be made to penetrate cells when encapsulated into liposomes³ and liposomes are currently used to deliver active ingredients to the skin, such as the antioxidant vitamin E, the DNA repair enzyme T4 endo V and the coenzyme NAD.

Why don’t we use liposomes to transfer DNA to our skin cells and improve our skin? Let’s review a couple of examples. A disease called Xeroderma pigmentosum is the consequence of a mutation in a gene participating in DNA repair. People with this disease develop skin cancer. If we could replace the defective gene in all of their keratinocytes with the correct one, they (the keratinocytes) would be cured. This might be an endeavor for the medical sciences. For what concerns skin care, we know that filaggrin is at the origin of the Natural Moisturizing Factor. The production of filaggrin decreases with age, because the transcription of the filaggrin gene decreases with age. One of the consequences of decreased filaggrin production is dry and itchy skin. If the DNA sequence that controls the rate of transcription of the filaggrin gene could be replaced, one could maintain the transcription rate of young skin and we would live to a mature age without dry and itchy skin.

Gene Transfer in Skin

Some may ask why don’t we apply liposomes with the good copy of a gene on the skin when we have a problem with that gene?  Simply put, that is a very bad idea!

It is as bad an idea as randomly inserting a printed page in a bundle of pages with a misprinted one and hope that with this insertion, the book will be corrected.

Ah, somebody might interject…isn’t it true that experiments with cultured cells did show that gene cloning is possible because the cellular machinery puts the foreign DNA in the right place in the genome?

Yes, I would say, but…laboratory experiments are performed with millions of cells (each one being the equivalent of one bundle of printed pages) and the experimenter can adjust the culture conditions so that survival will be possible only for the cells that accommodate the foreign gene in the right place, and all the other cells will be eliminated.

The epidermis, on which the hypothetical gene-loaded liposomes will be applied, has one million basal keratinocytes per square centimeter, let alone the microorganisms of the microbiome. The foreign gene vehiculated by the liposomes can randomly enter some of the keratinocytes and some of the microorganisms. It will be randomly inserted, if at all, in their genomes, thus affecting in unknown ways the growth of keratinocytes and microorganisms. What would be the point of having a few keratinocytes, if any, with the correct gene, while all the others remain unchanged? What is the risk of having the correct gene inserted in the wrong spot, such as for instance, in the middle of a gene that controls the rate of growth and producing a cell that grows out of control?

Gene-Editing Technology

To insert the foreign gene in the right spot in the genome, and to eliminate the original, deficient gene, one needs to put in the liposomes all of the machinery to correct and replace a gene, the so-called CRISPR-Cas9.⁴ This means that one should synthetize a short piece of RNA complementary to a DNA sequence located in close proximity of the DNA stretch to be corrected or replaced. One should, of course, make sure that the sequence of this piece of RNA finds a complementary sequence only in the target gene and nowhere else in the genome. Then this RNA will bind to genomic DNA with that complementary sequence and the protein Cas9 will cut the DNA—like a pair of scissors—at a spot close by, and ideally nowhere else.

Once the DNA is cut, the cell’s repair mechanisms work to introduce changes to the genome and to join the resulting modified extremities of the “cut.” These changes will be random, and only a few changes will result in correcting the defective gene. This is to say that the enzymes of the cell do a work that is not under the control of the experimenter. A “selection” process is then needed to separate the cells with the “cured” gene from all the others: hardly a possibility in a human tissue in vivo.

When the liposomes, in addition to the RNA and the Cas9 protein, also contain a piece of DNA with the correct sequence of the gene to be modified, the genomic DNA that has been cut can be “repaired” by incorporating that piece of DNA where the cut has occurred.

A Concluding Caveat

Unfortunately, this does not guarantee that all the keratinocytes in the epidermis will correct their defective gene. In addition, there is no guarantee against “off target” effects, where the DNA of the keratinocyte is cut at sites other than the intended target. This can lead to the introduction of unintended mutations. Furthermore, even when the system cuts on target, there is a chance of not getting a precise edit, thus resulting in the vandalic addition of disorder and destruction in an already defective gene.

How to avoid this “genome vandalism” is the object of deep considerations in the academic arena, and this deep consideration is strong evidence that the times are not ripe for envisioning the application of a therapeutic gene transfer technology in cosmetics. 

References

1. Avery OT, Mc Leod CM,  Mc Charty M. (1944) Studies on the chemical nature of the substance inducing transformation of pneumococcal types. Induction of transformation by a desoxyribonucleic acid fraction isolated from Pneumococcus type III. J. Exptl Med 79 : 137-158
2. Ostro MJ, Giacomoni D, Lavelle D, Paxton W, Dray S (1978) Evidence for translation of rabbit globin mRNA after liposome mediated insertion into a human cell line. Nature 274: 921-923
3. Straubinger R.M., Papahadjopoulos D. (1982) Liposome-Mediated DNA Transfer. In: Shay J.W. (eds) Techniques in Somatic Cell Genetics. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-4271-7_28
4. Doudna, J.A. and Charpentier, E. (2014) The New Frontier of Genome Engineering with CRISPR-Cas9. Science, 346: (6213):1258096. doi: 10.1126/science.1258096. PMID: 25430774.

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Paolo Giacomoni, PhD
Insight Analysis Consulting
paologiac@gmail.com
516-769-6904
 
Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as executive director of research at Estée Lauder and was head of the department of biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents.