Regional Institute of Pharmaceutical Science and Technology (RIPSAT), Abhoynagar, Agartala, 799005, Tripura, India.
Rheumatoid arthritis (RA) is a chronic inflammatory illness that primarily involves the joints but can also have systemic repercussions, affecting numerous organs and systems throughout the body. It is classified as an autoimmune disease, in which the immune system mistakenly targets healthy joint tissues, causing inflammation, pain, and eventual damage to the joints. Traditional therapeutic approaches for rheumatoid arthritis (RA) have predominantly aimed at symptom management and the application of disease-modifying antirheumatic drugs (DMARDs). However, these approaches frequently exhibit limited effectiveness and can lead to substantial side effects. In response to these challenges, innovative gene therapy strategies have emerged, providing a promising new frontier for targeted molecular intervention in the treatment of RA. The possible advantages of these therapeutic modalities consist of lower systemic toxicity, enhanced targeting of pathological pathways, and the opportunity for long-term remission through genetic modifications. The integration of gene therapy into the management of rheumatoid arthritis (RA) holds promise for improved patient outcomes and a shift towards more personalized healthcare. This article reviews recent innovations in gene therapy strategies aimed at modulating immune responses and fostering tissue regeneration in affected joints.
Rheumatoid arthritis (RA) is a common and complex autoimmune disorder in which the immune system erroneously targets the body's own tissues, particularly affecting the joints. This condition is characterized by chronic inflammation that progressively damages synovial joints, leading to pain, swelling, and the destruction of cartilage and bone. Over time, this can result in reduced mobility and significant joint damage, including deformities [1]. This irregular immune response is mediated by several pro-inflammatory agents, notably tumor necrosis factor-alpha (TNF-?), interleukin-1 (IL-1), and interleukin-6 (IL-6), which contribute to the ongoing process of inflammation. Approximately 1% of individuals worldwide are diagnosed with rheumatoid arthritis (RA), creating notable challenges for both patients and healthcare systems on a global scale. [2]. The consequences of untreated or poorly managed chronic inflammation can be profound, leading to significant physical disabilities, a compromised quality of life, and systemic complications that may involve essential organs like the heart and lungs. This ongoing inflammatory process elevates the risk of cardiovascular diseases, including atherosclerosis, which can culminate in heart attacks or strokes. Furthermore, rheumatoid arthritis (RA) is associated with an increased risk of pericarditis, an inflammation of the heart's outer membrane. Individuals with rheumatoid arthritis (RA) may experience respiratory problems, which can include pleuritis, an inflammatory condition affecting the lung lining, interstitial lung disease that results in lung tissue scarring, or the appearance of nodules within the lungs. These issues can contribute to symptoms such as shortness of breath and a long-lasting cough. Traditional therapies for rheumatoid arthritis (RA), such as nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, Disease-Modifying Anti-Rheumatic Drugs (DMARDs), and biologic agents, have led to significant improvements in patient outcomes over the past few decades. These treatments are designed to target the immune system's excessive inflammatory response, thereby reducing symptoms and decelerating disease progression. However, they are not without their limitations. The pharmacological treatments available for rheumatoid arthritis (RA) are recognized for their therapeutic benefits; however, they also come with a spectrum of potential side effects. Corticosteroids, for instance, are known to cause weight gain, osteoporosis, and an increased risk of infections [3]. In a similar vein, disease-modifying antirheumatic drugs (DMARDs) and biologics can weaken the immune system, thus heightening the risk of infectious diseases [4]. Many individuals do not exhibit an adequate response to these treatment modalities, while others may face adverse reactions or require lifelong pharmacological intervention to keep the disease in check. Furthermore, the current therapeutic approaches typically focus on symptom management rather than addressing the underlying etiological factors of rheumatoid arthritis (RA), which can lead to recurrent flare-ups and disease progression. In response to these challenges, there is a rising interest in the development of treatments that are not only more precise and durable but also hold the potential for curative outcomes. Gene therapy has emerged as one of the most promising methodologies in recent years. This approach is groundbreaking in the field of medicine, as it targets diseases at the genetic and molecular levels by modifying the genetic material found within a patient's cells [5]. Traditional treatments typically work by suppressing immune function or controlling inflammation; however, gene therapy has the unique capability to directly amend the molecular dysfunctions that trigger autoimmune responses in rheumatoid arthritis (RA). This article aims to investigate the most recent advancements in gene therapy for rheumatoid arthritis (RA), focusing on the diverse methodologies being developed, their underlying mechanisms, and the obstacles that researchers encounter in the quest to make these therapies broadly accessible.
Pathogenesis Of Rheumatoid Arthritis
The pathogenesis of rheumatoid arthritis (RA) is a complex phenomenon that results from the interplay of various elements, including genetic factors, environmental influences, immune responses, and hormonal changes.
Hormonal influences: The modulation of immune responses and inflammation is significantly influenced by hormones. Specifically, sex hormones such as estrogen and testosterone have been linked to the initiation and progression of rheumatoid arthritis (RA). Epidemiological data reveal a higher prevalence of RA in women compared to men, particularly during their reproductive years. Estrogen exhibits both protective and detrimental effects on RA. In premenopausal women, increased estrogen levels may result in a decreased incidence of RA, while postmenopausal women tend to show heightened disease activity, potentially associated with diminished estrogen levels [12]. In contrast, testosterone is thought to possess anti-inflammatory properties. Studies indicate that men with diminished testosterone levels may experience an elevated risk of developing rheumatoid arthritis (RA), which points to a potential protective role of this hormone in relation to the disease [13].
Figure 1. Pathogenesis of rheumatoid arthritis
Steps In Gene Therapy For Rheumatoid Arthritis
Gene therapy aimed at rheumatoid arthritis (RA) seeks to modify the immune response of patients by delivering genetic material into their cells. This approach is designed to alter or inhibit the pathological processes responsible for inflammation and joint deterioration. The primary objective is to address RA at a molecular level, which may diminish the reliance on traditional pharmacological treatments and target the underlying mechanisms of the disease. Here's a detailed explanation of how to introduce a gene in gene therapy for RA:
1. Recognize the therapeutic gene
The initial phase of gene therapy for rheumatoid arthritis (RA) involves the careful selection of the therapeutic gene to be administered. The selected genes generally focus on the following objectives:
• Reducing inflammation: This includes genes that encode for anti-inflammatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-?).
• Inhibiting pro-inflammatory signals: This encompasses genes that hinder the expression or activity of tumor necrosis factor-alpha (TNF-?), interleukin-1 (IL-1), or interleukin-6 (IL-6), which are critical inflammatory mediators in RA.
• Protecting or regenerating joint tissues: This involves genes that facilitate cartilage repair or offer protection against further deterioration of joint structures.
2. Selection of an appropriate delivery vector
The next step is selecting a suitable vector to deliver the gene into the patient's cells. There are two major types of vectors: viral and non-viral.
a. Viral vectors: The utilization of viral vectors is prevalent due to their high efficacy in gene delivery to cells. Notable examples of viral vectors include:
• Adeno-associated viruses (AAV): These vectors are non-pathogenic and are extensively used in gene therapy, offering long-lasting gene expression with a reduced risk of immune reactions [14].
• Lentiviruses: A type of retrovirus that can integrate therapeutic genes into both dividing and non-dividing cells, thus providing enduring gene expression [15].
• Adenoviruses: Capable of carrying large quantities of genetic material, these vectors yield strong expression but typically result in short-lived gene expression since they do not integrate into the host's genome [14].
b. non-viral vectors:
3. Choose the method of delivery
Gene therapy can be executed through two key methods: ex vivo, taking place outside the body, or in vivo, which involves direct application within the body.
a. Ex vivo gene therapy: This approach involves the extraction of cells from the patient, such as immune cells or synovial fibroblasts, which are then modified externally before being reintroduced into the patient. The process consists of the following steps:
• Cell Isolation: Cells are collected from the synovial tissue or immune system of the patient, including T-cells or dendritic cells.
• Gene Modification: A therapeutic gene is introduced into the cells using a chosen vector, typically a viral one, in a laboratory environment.
• Cell Reintroduction: The modified cells are subsequently injected back into the patient, often directly into the affected joints through intra-articular injection.
This approach enhances the ability to determine which cells will receive the therapeutic gene, ensuring that only those selected cells undergo genetic modification.
b. In vivo gene therapy: This approach entails the direct administration of the gene therapy vector into the patient's body, specifically aimed at the inflamed joints. The procedure consists of:
• Intra-articular Injection: The therapeutic gene is directly injected into the affected joint, ensuring localized delivery to the area requiring treatment.
• Intravenous Delivery: In certain instances, the vector is introduced into the systemic circulation. Targeting peptides or molecules may facilitate the vector's navigation to the inflamed joints. Nonetheless, systemic delivery presents challenges in restricting the gene's effects solely to the joints, avoiding impact on healthy tissues.
4. Integration and expression of therapeutic gene
After the therapeutic gene is introduced into the target cells, it is essential for the gene to be internalized and subsequently expressed. This process can occur through two primary mechanisms:
• Viral Integration: Utilizing viral vectors such as lentiviruses allows for the incorporation of the therapeutic gene into the host's genome, facilitating long-lasting or even permanent gene expression. This method ensures that the gene is consistently synthesized by the cells within the joint, potentially yielding a durable therapeutic outcome.
• Transient Expression: In contrast, non-integrating vectors, including adenoviruses or various non-viral techniques, typically result in short-lived gene expression. Consequently, these approaches may require more frequent administration to sustain the desired therapeutic effects.
Figure 2. Diagram of ex vivo and in vivo gene therapy
Mechanisms Of Action In Gene Therapy For Rheumatoid Arthritis
Gene therapy for rheumatoid arthritis (RA) represents an innovative strategy aimed at altering the fundamental biological processes that contribute to the disease. By specifically addressing the genetic and molecular pathways involved in the autoimmune and inflammatory responses, this therapeutic approach holds promise for modifying disease progression, facilitating tissue regeneration, and potentially attaining sustained remission. The following outlines the key mechanisms through which gene therapy operates in the treatment of RA:
1. Inhibition of pro-inflammatory cytokines
A significant aspect of rheumatoid arthritis (RA) is the increased generation of pro-inflammatory cytokines, which are vital in instigating inflammation and joint damage. Gene therapy can be utilized to selectively target these cytokines, thereby alleviating the inflammatory response.
a. Blocking TNF-?, IL-1 and IL-6: Tumor necrosis factor-alpha (TNF-?), interleukin-1 (IL-1), and interleukin-6 (IL-6) play pivotal roles in the pathophysiology of rheumatoid arthritis (RA). These cytokines perpetuate a chronic inflammatory response that ultimately results in tissue damage. Gene therapy presents a novel strategy for delivering therapeutic genes that encode for inhibitors of these cytokines, such as soluble TNF receptors or IL-1 receptor antagonists, directly to the affected joints. By targeting the source of cytokine activity, these inhibitors can effectively diminish inflammation and prevent further joint degradation. For instance, a gene therapy method could utilize a viral vector to introduce the gene for an IL-1 receptor antagonist (IL-1Ra) into joint tissues. Upon expression, this gene would lead to the production of the IL-1Ra protein, which competes with IL-1 for receptor binding, thereby inhibiting the inflammatory response [17].
b. Anti-inflammatory protein expression: Gene therapy can also promote the expression of proteins that counteract inflammation, such as interleukin-10 (IL-10) or transforming growth factor-beta (TGF-?), which help modulate the immune system and suppress excessive inflammation.
2. Immune system reprogramming
Gene therapy can serve to enhance the expression of proteins that counteract inflammatory responses, including interleukin-10 (IL-10) and transforming growth factor-beta (TGF-?). These proteins are vital for the modulation of immune system functions and the control of excessive inflammation.
a. Modulation of T cells: T cells are integral to the pathophysiology of rheumatoid arthritis (RA) as they activate various immune cells that contribute to inflammatory processes. Gene therapy presents a potential strategy to alter T cell behavior, rendering them less aggressive or capable of dampening immune responses. For instance, gene therapy can facilitate the introduction of genes that promote the development of regulatory T cells (Tregs), which inherently modulate immune responses and foster tolerance to self-antigens. This mechanism can mitigate the hyperactive immune response that leads to the destruction of joint tissues. Additionally, chimeric antigen receptor (CAR)-T cell therapy, which has shown promise in oncological applications, is currently being investigated for its efficacy in treating autoimmune disorders such as RA [18]. This approach focuses on the genetic alteration of T cells to enable them to express receptors that directly target and neutralize immune cells involved in the disease process of rheumatoid arthritis.
b. Antigen-specific immune modulation: Gene therapy can be engineered to enhance the immune system's tolerance towards particular antigens (proteins) that provoke autoimmune responses. By modifying the recognition mechanisms of immune cells concerning these antigens, it becomes feasible to prevent the immune system from targeting healthy tissues while preserving its overall functionality.
3. Cartilage and bone regeneration
The impact of rheumatoid arthritis (RA) is characterized by substantial harm to the cartilage and bone in the joints that are affected. Gene therapy, while primarily aimed at controlling inflammation, also holds the potential for the regeneration of these damaged tissues.
a. Stimulating chondrocyte (cartilage cell) production: The utilization of gene therapy can enable the introduction of genes that foster the production of chondrocytes, the cells responsible for cartilage synthesis. This method can activate the body's natural repair processes, potentially reversing joint damage. A pertinent example is the delivery of genes for growth factors such as transforming growth factor-beta (TGF-?) or bone morphogenetic proteins (BMPs), which can enhance the repair and regeneration of damaged cartilage and bone. These proteins are known to stimulate the proliferation of chondrocytes and the production of the extracellular matrix, thereby facilitating the restoration of cartilage [19].
b. Bone regeneration and osteoblast activation: Rheumatoid arthritis (RA) not only results in cartilage deterioration but also contributes to bone erosion, primarily due to the overactive osteoclasts that resorb bone tissue. Gene therapy has the potential to rectify this imbalance by enhancing osteoblast activity, which is crucial for bone formation, while simultaneously suppressing osteoclasts. This therapeutic intervention may involve the administration of genes that inhibit osteoclast activity or promote osteoblast activation, thus providing a promising approach to repair the bone erosion that occurs in chronic RA.
4. Gene editing to correct genetic defects
Innovations in gene-editing methodologies, especially CRISPR-Cas9, have made it feasible to specifically target and amend the genetic defects associated with the development of rheumatoid arthritis (RA).
a. CRISPR-Cas9 method in RA treatment: CRISPR-Cas9 is a revolutionary gene-editing technology that has garnered significant attention in the field of molecular biology and genetics since its discovery. If a genetic mutation is identified that increases the likelihood of an autoimmune response, CRISPR can be used to modify or correct this mutation, thereby reducing the risk of developing or exacerbating RA. CRISPR-Cas9 is a revolutionary genome editing technology that enables scientists to modify an organism’s DNA with high precision. The name CRISPR stands for “clustered regularly interspaced short palindromic repeats,” and Cas9 refers to “CRISPR-associated protein 9”. CRISPR refers to segments of DNA that contain short, repetitive base sequences. These sequences are part of an adaptive immune system used by bacteria to recognize and cut viral DNA. While Cas9 is an enzyme that cuts DNA at specific sites. It is guided by RNA molecules that match the DNA sequence to be edited. CRISPR-Cas9 utilizes a guide RNA to direct Cas9 to specific genomic locations where it creates double-strand breaks that are subsequently repaired by cellular mechanisms, enabling precise genetic modifications. It allows for precise modifications to DNA, enabling researchers to add, delete or alter genetic material at specific locations within the genome [20]. This technology has broad applications across various fields, including medicine, agriculture, and biological research.
Figure 3. Systemic diagram of CRISPR-Cas9 method for RA
b. Silencing disease-related genes: A further approach involves the use of gene silencing strategies, specifically RNA interference (RNAi), to inhibit the expression of genes that are involved in the inflammatory response. By interfering with messenger RNA (mRNA), RNAi can effectively block the production of harmful proteins that arise from these genetic instructions.
Challenges And Risks Associated With Rheumatoid Arthritis
Despite the exciting potential of gene therapy, several challenges must be addressed before it can become a standard treatment for rheumatoid arthritis:
CONCLUSION
The application of gene therapy is an exciting and developing frontier in the treatment landscape of rheumatoid arthritis. Although challenges persist, the ability to directly engage with the genetic and molecular causes of the disease holds substantial promise for future therapies. Gene therapy presents a transformative approach that goes beyond the mere management of symptoms, as it targets the underlying causes of diseases by reprogramming immune responses and mitigating inflammation at the molecular level. As advancements in research continue, gene therapy has the potential to play a pivotal role in personalized medicine for rheumatoid arthritis (RA), allowing for the customization of treatments based on the individual genetic profiles and disease trajectories of patients. In the coming years innovations in gene editing technologies, improved methods of delivery, and a more thorough understanding of the genetic underpinnings of rheumatoid arthritis (RA) may bring us closer to a future characterized by more effective treatments and the possibility of a cure for the condition.
REFERENCES
Chumi Sarma, Vivek Jyoti Das*, Rubli Sarma, Innovative Gene Therapy Approaches For Treatment Of Rheumatoid Arthritis, Int. J. of Pharm. Sci., 2024, Vol 2, Issue 10, 1843-1852. https://doi.org/10.5281/zenodo.14017689
10.5281/zenodo.14017689
