Introduction:
Although the He Jiankui team's generation of the first genetically modified human babies in the world has generated significant media controversy, this advancement heralds a new era of bioengineering with great opportunity for plastic surgeons in translation. Using genome editing to remove the CCR5 gene, this team has created HIV-resistant people, at least theoretically, though with unknowable long-term health effects. At the center of this revolutionary development is the Clustered Regular CRISPR (CRISPR for interspaced short palindromic repeats). It allows for accurate and effective genomic editing in a commonly available method. In a world where prevention. It is becoming a very common practice to treat more than simply visible ailments actual possibility; in cases where wound healing has improved, elimination of congenital disorders and abnormalities, the use of tissue reprogramming and immunotherapy redundant vascularized composite allotransplantation are manifesting in the real world.
What Is Crispr/Cas System in Plastic Surgery?
The CRISPR/Cas system, made up of CRISPR and CRISPR-associated DNA nucleases (Cas), has long been involved in prokaryotic adaptive immune responses.
Single-guide RNA, specifically targeting complementary DNA sequences, enters the cell directly or through viral vectors. The complex is then joined by the DNA nuclease Cas, which causes a double-stranded DNA break.
The DNA is then properly rewritten either by homologous repair, which allows for exact alterations in sequence and, as a result, precise gene modifications, or through nonhomologous repair, which prevents accurate rewriting and allows for the disabling of genes. With further development of the CRISPR system, RNA transcribed from the DNA backbone is targeted and modified by Cas13, changing the gene's phenotypic and expression without affecting the DNA.
Roh et al. simply list some of the most important applications of CRISPR technology in contemporary translational medicine and cosmetic surgery. These include using zebrafish models to discover pathways involved in craniofacial development, such as the TWIST homolog in craniosynostosis, and restoring normal dystrophin genes in mouse models of Duchenne muscular dystrophy. Additionally, Roh et al. show how important genes that encode modulatory growth factors are fundamental to wound healing and the diseases that accompany it and it has been demonstrated that improving wound healing through genetic editing of targets including HGF and HIF-1.
What Are the Future Clinical Applications of Gene Therapy?
Tissue engineering similarly focuses on generating biologic substitutes with tissue-level activity, as has been shown with viral delivery of genes intended to repair, inactivate, or enhance host gene activity. The application of tissue engineering to skin transplantation, tendon repair, and the creation of vital regeneration substrates like cartilage, bone, adipose tissue, and blood vessels has advanced the profession of plastic surgery. The core of reconstructive flaps is the segmentation and transplantation of tissue with a preserved blood supply to fill deficiencies. There is an increasing emphasis on methods to improve flap blood supply and viability due to the risk of compromise of arterial and venous perfusion, particularly in patients with vasculopathy, diabetes, or those undergoing corticosteroid medication.
Transverse Rectus Abdominis Myocutaneous (TRAM) flaps, in particular, have been the focus of methods to increase blood supply due to the unfavorable occurrence of myonecrosis with flap surgeries. With the injection of VEGF into rat muscle flaps, increased angiogenesis was seen. This growth factor is crucial for neovascularization because it promotes angiogenesis and vascular permeability. When compared to simple DNA injection, the electroporation method of introducing VEGF into flaps considerably boosts gene expression. VEGF gene therapy has several advantages over VEGF protein treatment, including the ability to produce human VEGF rather than recombinant bacterial VEGF, longer-lasting VEGF production by transfected cells, and VEGF activity limited to a specific area of cells that receive the vector. In rat models, unipedicle TRAM flap necrosis is decreased by intradermal injection of VEGF by electroporation. 39 Future research is required to more fully characterize the safety profile of this gene therapy treatment and improve the gene transfer method.
What Are the Gene Therapy Applications in Plastic Surgery?
Gene therapy has made it possible to advance reconstructive methods for bone production, nerve regeneration, wound and tissue healing, establishing cranial sutures, and treating cancer. Numerous cytokines, such as Fibroblast growth factors (FGFs), transforming growth factors (TGFs), and bone morphogenetic proteins (BMPs), are involved in the regulation of bone growth. Viral vectors, especially adenoviral vectors, which may transfect osseous tissue and infect osteoblasts, periosteal cells, endosteal cells, and soft tissues surrounding the injection site, can be employed to promote bone regeneration. Viral gene delivery can encourage the production of bone ossicles and a thickening of the growth plate. Adenoviral vectors can also introduce BMP-2 to encourage the production of thick trabecular bone; mice transfected with BMP-2-carrying adenoviral vectors show this effect.
Retroviral and nonviral methods have also shown promise as bone-forming and adenoviral vectors. Like adenoviral vectors, retroviral vectors expressing BMP-2 can enhance bone growth and BMP expression after sustained retroviral transfection. Gene-activated matrix, a nonviral delivery method, has been demonstrated to enhance bone regeneration following human parathyroid hormone (hPTH) and BMP-4 gene transfer.
What Are the Gene Transfer Methods and Delivery Mechanisms?
The transferred gene product is expressed at physiological or therapeutic levels following the transport of a gene and its regulating components into the nucleus of the recipient cell. While the expression of a therapeutic gene is more temporary and does not require host cell genome integration, the expression of a defective gene necessitates maintaining the transplanted gene in the cell nucleus for replication and numerous rounds of cellular division. Depending on the target cells and tissues, several gene delivery vectors are used, which aid in the uptake of genes across the host cell membrane. Each vector confirms distinct benefits and can be categorized as viral or nonviral systems.
Viral Vector: Because they are more effective at transducing signals in vivo than nonviral vectors, viral vectors are commonly chosen over nonviral vectors. 3 A genetically modified virus called a viral vector contains therapeutic genes in deleted areas. 4 Infecting viruses enable replication of therapeutic genes combined with retained viral genetic material by infecting host cells and utilizing host cell machinery for genome replication. Adenoviruses, retroviruses, adeno-associated viruses (AAV), and herpes simplex viruses (HSV) are the viruses most frequently utilized in gene therapy.
Adenoviral vectors: Adenoviral vectors can infect both proliferating and nondividing cells and have a wide range of infectivity. Large DNA (more than 30 kb) can be accepted by high capacity or "gutless" adenoviral vectors, enabling high levels of expression of genes of interest.
Retroviral Vectors: Moloney Murine Leukemia Virus (MoMLV), lentiviruses (HIV and other immunodeficiency viruses), spumavirus, and avian C-type retroviruses (oncoretroviruses) are examples of retroviral vectors. The viral genes gag (encoding viral core proteins), pol (encoding reverse transcriptase and integrase), and env (encoding viral envelope glycoprotein) are replaced with exogenous DNA to produce retroviral vectors.
Human Parvoviruses: Human parvoviruses, known as adeno-associated viral vectors, were first discovered as a contaminant in adenovirus preparations and need a helper virus to result in a productive infection.
Herpes Simplex Virus: The herpes simplex virus is a DNA infection with a special ability to remain dormant for extended periods without integrating into the genome of the host cell. HSV is a noteworthy viral vector since it can transfer up to 30 kb of foreign DNA and infect various cell and tissue types. Ten HSV vectors have shown promise in treating cancer, neurological disorders, and pain in animal models.
Non-Viral Vector: Liposomal formulations, proteins, polymers, and physical delivery methods are examples of nonviral vectors. However, because of nonviral vector DNA's interaction with blood plasma proteins, unwanted cells, and other factors, these vectors have poor in vivo transfection efficacy.
Nonviral vectors' conferred gene expression is not maintained because they do not integrate into the host DNA. Physical delivery methods like electroporation generate cytoplasmic membrane holes using electrical pulses. The combination of electroporation with ultrasound-guided plasmid deployment is known as electrosonoporation, and it has shown promise in mouse models.
Conclusion:
Over the past ten years, gene therapy's uses in plastic and reconstructive surgery have grown steadily. Through continued research and development of gene delivery and editing, the surgical community can realize newer methods to reconstructive treatments such as cleft palate repair, wound healing, flap biology and transplantation, and restoration of shape and function following tumor excision.
