Nucleic acid-based therapeutics to restore joint homeostasis in age-related and post-traumatic arthritis

Abstract

Osteoarthritis, a complex genetic disease, involves disrupted joint homeostasis driven by catabolic and inflammatory processes. Traditional therapies offer limited success. This review explores nucleic acid-based therapeutics—siRNA, miRNA, and mRNA—as a promising strategy for restoring balance by modulating gene expression. Nanoplatforms enable precise delivery of these molecules, offering potential for disease-modifying interventions. Emphasis is placed on advancing RNA therapies tailored to the disease stage for effective disease management.

Introduction

Osteoarthritis (OA) can be defined as a whole-joint disorder that alters the anatomy and physiology of the synovial joints. It is characterized by the degeneration of articular cartilage and menisci, inflammation of the synovial membrane (synovitis), thickening (sclerosis) of subchondral bone, and the formation of osteophytes¹. The gross and clinical manifestations of the disease include joint space narrowing and persistent joint pain, whereas at the biochemical and molecular levels, the disease is marked by a disruption in homeostasis, wherein catabolic and degenerative processes outweigh anabolic and reparative mechanisms². Typically, OA can be categorized into two major types: age-related primary OA, predominantly found in the elderly population, where normal wear and tear accumulates over a lifetime due to continuous joint loading; and post-traumatic OA, which manifests as degenerative changes within joints, primarily affecting young and active individuals who encounter intra-articular injuries^3–5. The etiology of OA involves a complex interplay of intrinsic and extrinsic factors, including age, obesity, sex, genetics, and injuries, which collectively contribute to its initiation and progression. However, a comprehensive understanding of OA pathogenesis remains elusive, and effective treatment options thus remain limited.

Currently, knee OA diagnosis relies on radiographic assessment (other than clinical presentation and history), which evaluates cartilage loss by measuring the space between the articulating surfaces of the proximal tibia and distal femur⁶. In cases where surgery is contraindicated, corticosteroids are often prescribed to alleviate short-term pain. Nevertheless, patients experiencing severe pain and exhibiting bone-on-bone contact due to complete articular cartilage loss in end-stage disease typically require a joint replacement surgery. These joint replacement procedures are associated with substantial costs, may require revisions, and are often undesirable for young and active patients^7,8.

Given the disruption of homeostasis at the core of OA and the significant economic burden and limited success rates associated with joint replacement procedures, there exists a longstanding interest in developing cost-effective, practical, and efficacious therapies for OA. However, several formidable obstacles hinder progress in this regard. These challenges include, but are not limited to, the heterogeneity of the disease, genetic complexity, gaps in our understanding of disease pathogenesis, and the scarcity of therapeutic candidates capable of targeting both anabolic and catabolic pathways to restore homeostatic balance.

The purpose of this narrative review is to highlight the critical barriers to progress in OA treatment and to underscore the importance of therapeutic strategies that suppress pro-inflammatory and catabolic events while simultaneously promoting anti-inflammatory and pro-anabolic processes through the use of RNA-based therapeutics. We discuss the feasibility of utilizing nanoplatforms for the delivery of siRNAs and/or miRNAs to suppress the expression of catabolic genes, and mRNAs to enhance the expression of anabolic genes, with the goal of re-establishing balance between these pathways and restoring tissue homeostasis. Finally, we provide a comparative overview of the advantages and limitations of various RNA molecules and highlight the key challenges and future promise of RNA-based nanomedicine for clinical applications.

Key challenges hindering progress in OA

Heterogeneity of OA disease

Originally perceived as a disease primarily affecting articular cartilage, it is now established that OA constitutes a multifaceted and heterogeneous condition, exerting differential impacts across the diverse tissues within a synovial joint^1,9. One of the most damaging consequences of OA is the gradual degeneration and eventual loss of articular cartilage. The synovium, often underrecognized in the context of OA, frequently serves as an initial site of disease onset. Inflammation originating in the synovium leads to the production and release of catabolic mediators that mediate cartilage degeneration. These biochemical signals, combined with mechanical stress, further disrupt the integrity of subchondral bone beneath the hyaline cartilage. Given its complex nature, OA presents substantial heterogeneity among patients, with varying degrees of structural damage and involvement across joint tissues. Thus, OA is a highly heterogeneous disease characterized by complex interactions among multiple joint tissues and diverse phenotypic manifestations.

Recent scientific progress and increased emphasis on OA have significantly deepened our understanding of this disease. We have now come to recognize OA as a complex condition with diverse forms and underlying mechanisms, characterized by a nuanced tapestry of phenotypes and endotypes. Ongoing research continues to uncover the biological and clinical variability of this condition, paving the way for new approaches. These insights are expected to drive major advancements in how OA can be treated, leading to more personalized and effective care.

The genetic complexity of OA

Genetic factors significantly influence both the development and progression of OA. This genetic complexity becomes apparent through a confluence of evidence from familial aggregation studies, twin studies, and genome-wide association studies (GWAS). Familial aggregation and twin studies provide compelling evidence for the genetic underpinnings of OA, indicating that individuals with a family history of OA are at an increased risk of developing the condition. These studies have also shed light on the heritability of OA, indicating that it is indeed a condition with a significant genetic component^10–12.

Along these lines, GWAS studies have revealed specific genetic variants associated with OA susceptibility. Large-scale GWAS studies have identified numerous risk loci and genetic variants associated with the predisposition to OA. Some of these variants are linked to genes that play important roles in joint development, cartilage maintenance, and the inflammatory signaling cascade associated with inflammation^13,14. Furthermore, beyond GWAS, epigenetic modifications such as DNA methylation and histone acetylation have emerged as integral players in OA pathogenesis. These epigenetic alterations exert their influence by modulating gene expression and reshaping the functionality of key genes central to cartilage homeostasis and joint function¹⁵.

However, it is essential to acknowledge that while genetics plays a significant role, the initiation of OA is not solely determined by genetic predisposition. Environmental factors intersect with genetics, giving rise to intricate gene-environment interactions. Examples include the interplay between environmental factors such as age, obesity, joint injuries, and occupational stress, and genetic factors. These interactions result in the modification of gene expression profiles associated with OA susceptibility, further complicating the genetic landscape of OA.

Understanding the genetic complexity of OA is of critical importance. By unraveling the intricate genetic mechanisms underlying OA, we can identify potential drug targets that can be used in personalized approaches to both manage and treat OA.

Gaps in our understanding of disease pathogenesis

What we have gleaned thus far is of high significance, particularly in relation to the cellular changes and perturbations in joint homeostasis at a microscale level¹⁶. While a wealth of information exists concerning various facets of OA pathogenesis, and numerous potential risks and confounding factors have been identified, our understanding of the true molecular trajectory spanning from initiation to progression and eventual end-stage manifestations remains limited.

Chondrocytes and other cells, such as synovial fibroblasts, reside in a relatively quiescent environment within the joint. These cells play a key role in maintaining equilibrium, mitigating minor catabolic changes that may occur during the natural aging process of cells or following minor intra-articular injuries⁴. However, when cells reach a specific age (senescent cells) or when injuries reach a certain magnitude, they prove inadequate in countering the immune/inflammatory response. Consequently, there is an increase in the production of catabolic enzymes by these very cells, concomitant with a substantial reduction in the production of anabolic mediators, matrix synthesis, and even the production of lubricin¹⁶. This disruption to the delicate balance causes significant damage, leading to the initiation and progression of OA.

Variable responses to treatment

Unfortunately, there are currently no disease-modifying OA drugs (DMOADs) available for OA. The only treatment option remains total joint replacement, with variable success rates. It is essential to note that the success of this surgery is contingent on various patient-related factors, including overall health, adherence to post-operative rehabilitation, and potential complications. These complications encompass infections, venous thromboembolism, as well as other preoperative comorbidities and postoperative mortality¹⁷, eczema¹⁸, and delirium¹⁹. These observations underscore the necessity of personalized treatment plans tailored to the distinct requirements and characteristics of individual patients. Recognizing that OA manifests uniquely in each case, optimizing treatment decisions is facilitated by considering variables such as age, overall health, the specific affected joint, and the stage and severity of the disease.

Scarcity of therapeutic candidates targeting both anabolic and catabolic pathways

While OA is considered a total joint disease, articular cartilage degeneration remains the hallmark of end-stage disease and a common target for thereby²⁰. When medical interventions become necessary, the available non-surgical options for joint treatment are limited, and there is ongoing debate regarding their potential benefits. In Table 1, we present a summary of commonly used therapeutic strategies in OA, including representative examples, their intended purposes, as well as their respective advantages and disadvantages. Some treatments and studies have prioritized the goal of slowing or halting the breakdown of cartilage to prevent its loss. Others have focused on stimulating cartilage growth or repair. The majority of existing options possess either anti-inflammatory or anti-catabolic properties, or pro-anabolic properties, or exhibit pleiotropic effects^21–24. Surprisingly, there have been limited efforts to explore the combination of two complementary molecules: one to counteract inflammation and another to promote anabolism.

Table 1.

Common therapeutic approaches in OA: examples, purposes, pros, and cons

Category	Example	Purpose	Pros	Cons
NSAIDs	Ibuprofen, Naproxen, Indomethacin, Celecoxib	Suppress inflammation, Manage pain	Readily available	Side effects e.g., cardiovascular risk, kidney problem, GI issues
Glucocorticoid	Dexamethasone, Prednisolone	Suppress inflammation, Reduce pain	Provide rapid relief	Side effects e.g., joint damage with repeated use, High risk for infections
DOMADs	Hyaluronic acid, PRP, MSCs, ADSCs	Promote tissue repair Promote cartilage regeneration	Promote healing, Reduce Pain, Rich in growth factors	Limited long-term data, Expensive
Nutraceuticals and dietary supplements	Plant extract, Omega-3 fatty acid, Chondroitin, Collagen	Support cartilage health, Improve joint function	Relatively safe, long-term benefits, Low risk	Huge variations in effectiveness, Take long time to be effective
Natural compounds	Resveratrol, Boswellia serrata extract, Quercetin, Bromelain	Anti-inflammatory	Minimal side-effects, Anti-oxidants	Quality control, Variable efficacy, Limited clinical evidence, Allergies
Anti-cytokine therapies	Antibodies targeting TNF-α, IL-1β, IL-6	Suppress pro-inflammatory cytokines	Disease modifying effects, Specificity, Potential long-term benefits	Expensive, highly targeted, Limited availability, Risk for infusion-reactions
Anti-neuroinflammatory agents	Minocycline, PPAR-γ	Suppress inflammation	Beneficial for disease management, Several formulations available	Limited clinical evidence, Risk for antibiotic resistance, Complex mechanism
Exercise and Physical therapy	Low impact exercise to	Improve joint mobility, Reduce inflammation, Support joint health	Improve functional abilities and QoL, Improve muscle strength	Require commitment, time and effort, may not provide immediate pain relief
Mechanical loading and joint unloading	Joint bracing or unloading devices	Reduce mechanical stress on affected joint	Improve joint function and reduce pain	Limit joint mobility, not suitable for all joints
Weight management	Maintain healthy body weight	Reduce stress on weight-bearing joints, Reduce burden of obesity-related inflammation	Slow disease progression, Support joint health	Require lifestyle change, long-term commitment
Heat and cold therapy	Heat pads, Cold pads	Pain relief, Reduce inflammation	Easy to apply, Relaxes muscles, Improves joint range of motion	Provide temporary relief, Limited mobility during application
Acupuncture and acupressure	Traditional chines therapies to	Alleviate pain and inflammation	Minimal side effects, Provide symptomatic relief	Limited scientific evidence, may not work for everyone
Biologics and growth factors mimics	PRP injection, TGFβ, FGF, BMP	Stimulate cartilage repair Promote cartilage/ bone formation	Minimally invasive, Simple to apply	Expensive, Multiple injections
Cartilage implants	ACI MACI	Improve cartilage repair	Long-term benefits, Customized treatment	Expensive, Require rehabilitation, Limited availability, Variable outcome
Biomaterials and scaffolds	HA based scaffolds Collagen based scaffolds	Provide supportive environment for cartilage repair, Mimic ECM, Promote tissue regeneration	Biocompatibility, Modifiable, Protect cartilage, Provide joint lubrication and shock absorption	Expensive, Variable responses, Requires surgery, Questionable long-term durability
Mixed physical therapy and sonography	Electrotherapy and ultrasound	Improve blood circulation, Aid in tissue healing	Non-invasive, Local applications	Limited depth penetration, Risk of burn, Temporal relief, temporary effects
Surgery	Joint re-alignment, total arthroplasty	Provide pain relief, Restore joint function	Effective long term	Invasive, Complications, Lengthy recovery

NASAIDs non-steroidal anti-inflammatory drugs, GI gastrointestinal, DMOADs disease-modifying OA drugs, PRP platelet-rich plasma, MSCs mesenchymal stem cells, ADSCs adipose-derived stem cells, TNF-α tumor necrosis factor alpha, IL-1β interleukin-1 beta, IL-6 interleukin-6, PPAR-γ peroxisome proliferator-activated receptor gamma, QoL quality of life, TGFβ transforming growth factor beta, FGF fibroblast growth factors, BMP bone morphogenetic protein, ACI autologous chondrocyte implantation, MACI matrix-induced autologous chondrocyte implantation.

The implication here is that OA is a complex condition with multiple underlying factors. In individuals with OA, excessive catabolic activities predominate, resulting in compromised anabolic activities and cartilage degeneration. Several factors, including inflammatory cytokines, extracellular matrix degradation enzymes, oxidative stress, and growth factors, contribute to the complex network that regulates the delicate balance between anabolism and catabolism in cartilage. The balance of anabolic and catabolic activities is critical for the maintenance of cartilage integrity. To develop more effective treatments, it is imperative to address both facets of the equation: slowing down the breakdown of cartilage and promoting the repair or growth of new cartilage matrix. By simultaneously tackling both aspects, researchers and clinicians may enhance their prospects of developing treatments that prove successful in managing OA and improving the quality of life for OA patients.

One agent that has been touted as anti-catabolic and pro-anabolic is diacerein, an anthraquinone that interferes with the IL-1 receptor. This agent is believed to have anti-inflammatory, anti-catabolic, and pro-anabolic properties^25,26. However, a Cochrane review of 10 trials, involving a total of 2,210 participants, suggests that the strength of evidence for effectiveness was low to moderate, and the small benefit in terms of joint space narrowing is of questionable clinical relevance²⁷. OA, unlike other inflammatory arthritides, is characterized by a unique feature of low-grade inflammation^28,29. In this context, it is important to recognize that attempting to address this inflammation by targeting a single inflammatory cytokine may have limited therapeutic effects. The complex and multifaceted nature of OA-related inflammation suggests that a more inclusive approach to treatment, addressing various aspects of the inflammatory process as well as pathological factors simultaneously, is necessary to achieve meaningful disease modification. Given these complexites, RNA-based therapeutics offer a promising avenue for future OA management by enabling precise, concurrent modulation of multiple molecular pathways. By harnessing the specificity and versatility of RNA technologies, such approaches may provide a means to restore the balance between catabolic and anabolic processes, thereby mitigating disease progression more effectively.

Nucleic acid therapeutics

Recently, we have witnessed the crucial role nucleic acid-based therapeutics have played in addressing Coronavirus disease 2019 (COVID-19). Similarly, nucleic acid therapeutics are gaining attention in OA therapy for various reasons (refer to Table 2). In contrast to conventional therapies such as small molecules, which typically target proteins and provide transient benefits, nucleic acid therapeutics can deliver specific and enduring therapeutic advantages^30,31. RNA-based therapies also offer several key advantages over DNA-targeting gene therapies. Unlike gene modification approaches, which permanently alter the genome, RNA therapies act on RNA molecules, temporary transcripts of genes, without affecting the DNA itself. Because RNA is inherently unstable and naturally degrades within cells, the effects of RNA therapies are transient and reversible. This reversibility allows for precise temporal control over gene expression and reduces the risk of permanent off-target effects. Additionally, RNA therapies do not require entry into the cell nucleus, which simplifies delivery and enhances safety and efficiency. Moreover, RNA molecules can be designed and synthesized relatively rapidly to target different genes. The advancement of RNA chemistry further reinforces the therapeutic potential of RNA-based approaches and supports their continued development for clinical applications (reviewed in^32,33).

Table 2.

Advantages of nucleic acid-based therapies for OA

Benefit	Description
Precision targeting	• Designed to specific targeting of genes (except for miRNAs) implicated in OA pathogenesis. • Offer precise and highly targeted intervention to minimize off-target effects and mitigate harm to healthy structures.
Potential for disease modification	• Capable of altering the disease’s course, slowing or halting its progression, by interfering with the expression of pro-inflammatory/catabolic genes and enhancing the expression of anti-inflammatory/anabolic genes. • Address the underlying causes, rather than providing merely symptomatic relief.
Personalized medicine	• Treatment can be tailored to an individual’s genetic profile and specific disease endophenotype. • Provide personalized approach, recognizing that OA varies in terms of severity and underlying etiology across patients.
Minimal systemic side effects	• Delivered directly to the affected joint, reducing the risk of systemic side effects. • Particularly crucial for elderly OA patients who may have multiple comorbidities.
Reduced drug interaction	• Less likely to interact with other medications a patient may be taking, thus reducing the risk of adverse drug interactions.
Long lasting effects	• Once delivered into cells, siRNA and mRNA can have enduring effects, reducing the need for frequent treatments. • Improve patient compliance and reduce the burden of (any) ongoing therapy.
Regenerative potential	• mRNA therapies stimulate the production of growth factors and extracellular matrix components, promoting repair and regeneration. • siRNA and miRNA therapies suppress factors and mediators that otherwise impede repair or regeneration.
Combination therapies	• Used in combination with other OA treatments, such as physical therapy, NSAIDs, or hyaluronic acid injections, to enhance their effectiveness and provide a multifaceted approach to OA management.
Minimally invasive	• Often be delivered locally to the affected joint through minimally invasive procedures, reducing the need for extensive surgeries and associated risks.

NASAIDs non-steroidal anti-inflammatory drugs.

As such, various types of nucleic acids, such as siRNA/shRNA, miRNA, and mRNA, have been investigated for their therapeutic efficacy in post-traumatic OA (and rheumatoid arthritis)^34,35. A non-exhaustive list of relative advantages of siRNAs, miRNAs, and mRNAs is supplied in Table 3. Additionally, some studies have employed plasmid DNA and CRISPR/Cas9 for these purposes^36,37.

Table 3.

Comparative overview of selected advantages and disadvantages of siRNA, miRNA, and mRNA

siRNA	miRNA	mRNA
Target specificity and mechanism
Advantages • ~ 21-nt dsRNA targets a single mRNA via RNA • High specificity and potent silencing • Minimal direct off-target binding • Medium onset of action (days to weeks) Disadvantage • Acts on one gene only • Possible siRNA satuartion effects • Latency if transfection is inefficient in dense cartilage	Advantages • ~ 22-nt RNA regulate multiple mRNAs • One miRNA can modulate entire pathway • Useful for multifactorial diseases like OA • Fast onset of action (hours to days) after IA injection Disadvantage • Lower specificity due to partial pairing • Hard to predict all targets/effects • Effect decyas as duplex is cleared	Advantages • Encodes therapeutic protein directly • Enables replacement or addition of misisng protein • Restores or enhances cellular function • Fast onset of action (hours) once mRNA reaches ribosomes Disadvantages • Large, unstable molecule; harder to deliver • May trigger immune response or overexpression • Innate sensing can blunt translation
Therapeutic efficacy
Advantages • Highly specific gene knockdown • Ideal for single well-defined targets Disadvantages • Single-target action; limited for multifactorial disease • Transient effect, requires repeat dosing • May not address complex OA network effects	Advantages • Modulates multiple genes/pathways at once • Single miRNA can reduce inflammation and matrix degradation Disadvantages • Partial repression per target • Broad action can cause off-target effects • Dose-sensitive: too much or too little alters efficacy	Advantages • Produces therapeutic protein directly in cells • Adds beneficial or regenerative activity • Can address “undruggable” targets Disadvantages • Depends on efficient delivery and translation • Transient protein expression; repeated doses needed • Overexpression causes unintended effects
Safety considerations
Advantages • Non-integrating; acts only in cytoplasm • Chemically modifiable to reduce immune activation and off-target binding • Several siRNAs show good tolerability in trials. Disadvantages • Risk of immune activation via TLR7/8 if unoptimized • Off-target silencing can affect unintended genes • High doses or some delivery systems may cause toxicity	Advantages • Non-genomic and reversible action • Natural miRNA mimics offer gentler, partial gene regulation • May reduce risk of complete loss of essential genes Disadvantage • Broad targeting can disrupt normal gene networks • Hard to predict all affected genes/pathways • Immune-related adverse events reported • Risk of RISC saturation at high doses	Advantages • No genomic integration; transient expression allows control over dose and duration • Modified nucleosides (e.g., pseudouridine) reduce innate immune activation • Proven safety improvements from mRNA vaccine experience Disadvantage • May still trigger innate immune sensors (TLRs) • Carriers can cause inflammation or antibody responses • Repeated dosing may increase immunogenicity risk • Overexpressed proteins could cause off-target tissue effects

nt nucleotide, ds double stranded; IA intra-articular, TLRs Toll-like receptor, RISC RNA-induced silencing complex.

Delivery platforms for RNA therapeutics

To facilitate the delivery of nucleic acids for arthritis treatment, a wide variety of carriers, including nanoparticles, have been employed^34,38–41. We have summarized nanoparticle carriers that have been utilized for RNA delivery in OA-related applications in Table 4.

Table 4.

Intra-articular RNA-based drug delivery applications in rodent models of OA using nanocarriers

Agent	RNA specie	Carrier	Disease model	Reference
FGF-18	mRNA	Lipid NP	Mouse, DMM	92
FGF-18	mRNA	Lipid NP	Mouse, ACLT	101
CDKN1A	mRNA	Copper sulfide NP	Mouse, DMM	102
NFκB	siRNA	Peptide p5RHH NP	Mouse, ACLT	45
TNFα	siRNA	Chitosan NP	Mouse, CIA	103
STAT1	siRNA	RGD peptide PLGA NP	Mouse, CIA	104
HIF-2α	siRNA	Chondrocyte-homing NP	Mouse, DMM	105
TNFα	siRNA	Microbubbles	Rat, AIA	106
MMP-9	siRNA	NP	Mouse, RA	107
MMP-13	siRNA	Fe3O4 NP	Mouse, DMM	108
MMP-13	siRNA	Polymeric nanopolyplexes	Mouse, ACLT	109
Periostin	siRNA	Peptide p5RHH NP	Mouse, DMM	46
p65	siRNA	Peptide p5RHH NP	Mouse CAIA	76
miR-224-5p	miRNA	G5-AHP NP	Mouse, DMM	56

FGF-18 fibroblast growth factor 18, CDKN1A cyclin-dependent kinase inhibitor 1A, NFκB nuclear factor kappa-light-chain-enhancer of activated B cells, TNFα tumor necrosis factor-alpha, STAT1 signal transducer and activator of transcription 1, HIF-2α hypoxia-inducible factor 1 alpha, MMP-9/13 matrix metallopeptidase 9/13, p65 nuclear factor NF-kappa-B p65 subunit, miR microRNA, NP nanoparticles, DMM destabilization of the medial meniscus, ACLT anterior cruciate ligament transection, AIA adjuvant-induced arthritis, CIA collagen-induced arthritis, RA rheumatoid arthritis, CAIA CII antibody-induced arthritis.

The potential of siRNA-based therapies in OA

This section presents the recent developments in carrier-enabled RNA therapeutics in a preclinical setting, with a focus on advancements made after 2019. The studies conducted prior to 2019 have been covered in a previous review article³⁴. To test the potential of siRNA-based therapies in OA, we employed the p5RHH-based nucleic acid delivery platform^42,43, which has demonstrated efficient cartilage delivery both in vitro (using human articular chondrocytes) and in vivo (in murine articular cartilage)^44,45. Specifically, we targeted Periostin (Postn), an inflammation-associated matricellular protein, using Postn siRNA. When administered intra-articularly, this anti-Postn treatment exhibited anti-catabolic activity by modulating the NF-κB-MMP13 axis, ultimately leading to the successful mitigation of joint degeneration in a mouse model with experimentally induced post-traumatic OA, and with corroborative effects observed in human articular cartilage⁴⁶. In a separate study, we demonstrated that nanotherapy targeting NF-kB effectively alleviated acute pain in a murine model of joint trauma⁴⁷. Additionally, aiming to control inflammation and the production of extracellular matrix degradation enzymes, a copolymer based on poly(lactic-co-glycolic acid) (PLGA) was used to deliver p16INK4a siRNA in a mouse model of OA induced by partial medial meniscectomy for anti-senescence treatment. The PLGA carrier formulated in this study was primarily absorbed by the synovium rather than the cartilage. This treatment significantly reduced the protein level of p16INK4a in the synovium, potentially leading to the inhibition of proinflammatory cytokines, TNF-α, IL-1β, and IL-6, secreted by fibroblast-like synoviocytes and consequently suppressing MMP13 production in chondrocytes, which led to reduced cartilage damage and pain⁴⁸. Directly inhibiting MMP13 by using PLGA-based microplates loaded with MMP13 siRNA via intra-articular injection resulted in inhibition of MMP13 expression in the whole joint. The anti-inflammatory effects were more pronounced in the synovium⁴⁹.

Oxidative stress leads to the overexpression of inducible nitric oxide synthase and the excess production of nitric oxide (NO)⁵⁰. NO induces chondrocyte apoptosis, enhances NF-κB activation^51–53, and perpetuates the catabolic process. Efforts had been devoted to inhibiting reactive oxygen species (ROS) production for OA treatment. Inhibiting p47phox, a subunit of NADPH oxidase, by p47phox siRNA-loaded PLGA nanoparticles was evaluated in a rat mono-iodoacetate (MIA) model. Intra-articular administration of these nanoparticles resulted in the inhibition of ROS production in the chondrocytes, the reduction of cartilage damage, and attenuated pain⁵⁴. To inhibit mitochondrial ROS generation, PLGA nanoparticles loaded with the siRNA of p66shc, a shcA adaptor family protein, were intra-articularly administered in the rat MIA model, resulting in improved cartilage preservation⁵⁵.

The potential of miRNA-based therapies in OA

Due to their significant role in various aspects of OA pathology, with a particular focus on their involvement in cartilage matrix metabolism, numerous miRNAs have been explored as potential therapeutic candidates for OA.

A study was conducted in which the authors employed intra-articular injection of miR-224-5p, assisted by G5-AHP nanoparticles as cargo. This approach demonstrated its ability to restore homeostasis in OA by regulating cartilage degeneration and preventing synovial inflammation in a murine model of injury-induced OA⁵⁶. In a separate investigation, these researchers utilized urchin-like ceria nanoparticles, acting as ROS scavengers, to deliver miR-224-5p. This combination was effective in combating oxidative stress and mitigating cartilage degeneration, thereby enhancing the therapeutic effect in OA treatment⁵⁷. Furthermore, the authors established that the G5-AHP/miR-224-5p nanoparticle complex provided protection to chondrocytes against TNFα-induced matrix degradation, while Ceria nanoparticles/miR-224-5p sustained the synthesis of the chondrocyte extracellular matrix^56,57.

Another approach involved the use of PLGA nanoparticles for the delivery of miRNAs to address knee OA in mice. In this regard, the authors developed cartilage-targeting peptide-modified polyvinylamine poly (lactic glycolic acid or CAP-PVAm-PLGA) nanoparticles, which were loaded with miR-140. When administered into the mouse knee, the miR-140- CAP-PVAm-PLGA complex exhibited a 65% decrease in the extent of cartilage degeneration and an 80% reduction in synovitis. Simultaneously, it demonstrated effective penetration into the articular cartilage⁵⁸.

The potential of mRNA-based therapies in OA

Pro-inflammatory cytokines, such as IL-1β, TNF-α, IL-6, and IL-17, are major players in OA pathogenesis⁵⁹. In this regard, PEG-PAsp (DET) copolymer was employed to deliver interleukin-1 receptor antagonist (IL-1Ra) mRNA as an anti-inflammatory therapy in a rat model of temporomandibular joint OA, which led to improved pain sensitivity and an inhibition of OA progression, lasting for at least 4 weeks⁶⁰. In a proof-of-concept study, we have demonstrated that nanoparticle-mediated delivery of WNT16 mRNA to articular cartilage antagonized the canonical Wnt3a/β-catenin signaling pathway, leading to an increased production of lubricin and the suppression of cellular apoptosis⁶¹. While translational studies for validation are necessary, these initial data indicate that WNT16 could be a crucial therapeutic candidate for restoring homeostatic balance (both anabolic and catabolic) balance in OA.

Besides anti-catabolic treatment, PEG-PAsp (DET) or PEG-PAsp (TET) copolymer loaded runt-related transcription factor (RUNX) 1 mRNA was utilized to facilitate cartilage anabolic activities for OA treatment⁶². Thus far, studies have investigated the use of individual anti-catabolic and pro-anabolic compounds. However, few have examined the effects of combining anabolic and anti-catabolic agents to prevent degradation as well as promote healing. While OA is a complex, multifaceted, whole joint disease process, most nanotherapeutics for OA, including the few used in clinical settings only target single molecule or pathway, which may explain why no single DMOAD has so far emerged in the clinic. However, multi-functional nanotherapies are being actively developed. For instance, black phosphorus nanosheets (BPNSs) are strong ROS scavengers and can simultaneously inhibit cartilage degradation and promote osteogenesis⁶³. Together, these studies suggest that dual-functional disease-modifying nanotherapeutics are possible and emerging.

Future development of RNA therapeutic delivery platforms

Polymeric, lipid-based, and peptide-based delivery systems hold significant promise in the realm of RNA therapeutics within the context of OA. Nonetheless, further refinement is imperative to effectively address the challenges of concurrently targeting multiple disease-modifying factors. It is worth noting that the PLGA-based polymer for sustained drug release received FDA approval more than 30 years ago. An example of this technology is Zilretta®, PLGA-based microparticles approved by the FDA in 2017 for the relief of OA-related pain⁶⁴. The PLGA-based polymer emerges as a highly promising delivery platform for delivering RNA therapeutics via intra-articular injection. However, it presents well-recognized challenges, including the separation and identification of mixed PLGA microparticles (discussed in refs. ^64,65), as well as the issue of initial drug burst release (explored in ref. ⁶⁶). These challenges are actively under investigation and are well-documented in existing literature^66–68, shedding light on the ongoing endeavors to optimize this delivery system for clinical translation in the treatment of various medical conditions, including RNA-based therapies for OA through local, rather than systemic, administration (Box 1).

The recent success of lipid nanoparticle-based COVID-19 mRNA vaccines serves as a compelling illustration of the potential of mRNA- and other gene therapy-based approaches to address various healthcare challenges. This includes offering innovative, integrated solutions for tackling the multiple tissue failures that underlie the pathogenesis of OA. A comprehensive list of potential gene therapy targets in OA was reviewed in 2023³⁶, encompassing genes such as anti-inflammatory genes (e.g., IL-1ra)⁶⁹, growth factors (e.g., IGF-1)⁷⁰, and non-coding RNAs (e.g., regulating FGF-18)⁷¹. At present, clinical trials for gene therapy on OA predominantly rely on viral vectors³⁶, which can be expensive and pose safety concerns, including immune activation and tumorigenesis. Leveraging lipidic RNA delivery nanoparticles via intra-articular administration could mitigate unwanted effects from viral vectors and the hepatic elimination of lipid nanoparticles after intravenous administration. However, there are OA joints not accessible for intra-articular administration of medication. Therefore, alternative delivery methods capable of extrahepatic delivery will be required to address such cases.

A comprehensive review of peptide-based nanoparticles for the systemic delivery of therapeutic nucleotides has already been conducted and is available⁷². This class of delivery systems for therapeutic nucleotides is presently at the forefront of active scientific and commercial development. It holds the promise of providing customized solutions for comprehensive OA management, whether through local or systemic administration, or a combination of both. It has been reported that amphipathic peptides provide better transfection outcomes than cationic peptides. Of the amphipathic peptides assessed, p5RHH demonstrated superior performance, at least in the context of mRNA delivery⁷³. The p5RHH-based RNA delivery platform offers protection from serum degradation, enables cytoplasmic delivery through pH sensing^43,74, exhibits a favorable safety profile without immune or cardiac issues^74–76, and supports extrahepatic delivery to disease sites^77–83. This p5RHH-RNA delivery platform has also been evaluated for the local administration of multiple therapeutic siRNAs/mRNAs aimed at preventing post-traumatic OA through inflammation inhibition^44–47,61. However, its full potential for disease-modifying treatment of OA has yet to be realized through the simultaneous delivery of RNA therapeutics, which enables both anti-catabolic and anabolic activities to correct the OA environment, regenerate cartilage, and prevent bone remodeling. The application of nucleic acid-based therapeutics and delivery systems is summarized in Fig. 1.

Fig. 1. Illustration of the transition from a damaged to a healthy joint following the application of RNA-based nanotherapeutic strategies for OA.

The left panel depicts key pathological features of an osteoarthritic joint, including cartilage degradation, synovitis, meniscal lesions, and subchondral bone sclerosis (thickening). These degenerative and inflammatory changes are driven by dysregulated gene expression favoring catabolic pathways over anabolic repair processes. The central panel illustrates therapeutic strategies based on nucleic acid cargos delivered via nanoparticle platforms designed to rebalance joint homeostasis. siRNA and miRNA are used to inhibit or fine-tune the expression of catabolic genes, while mRNA delivery promotes the expression of anabolic and regenerative proteins. These nucleic acids are encapsulated within or conjugated to distinct delivery platforms, including lipid nanoparticles, polymeric nanoparticles, and peptide-based nanoparticles, which protect the payload, enhance cellular uptake, and enable efficient intracellular delivery. The right panel shows a treated joint, highlighting restoration of cartilage integrity and improved joint structure following successful modulation of molecular pathways.

Box 1 Translation and clinical prospects of RNA-based therapeutics.

siRNA

• Most clinically advanced RNA class.

• Multiple FDA-approved drugs (e.g., patisiran, inclisiran).

• Proven delivery systems and established regulatory pathways.

miRNA

• No approved therapies yet; still experimental.

• Several candidates reached clinical trials (e.g., Miravirsen, Cobomarsen).

• Safety challenges (e.g., MRX34) have slowed progress.

• High potential if safety and dosing are optimized.

mRNA

• Rapid clinical success with COVID-19 vaccines.

• Expanding trials for cancer and rare diseases.

• Scalable manufacturing and fast design cycles.

• Growing regulatory familiarity accelerates translation.

Challenges in bridging the gap between preclinical success and clinical applicability

Although delivery and safety concerns are often discussed, several practical challenges still need careful consideration. Key issues such as immunogenicity, the need for repeated dosing, patient variability, high manufacturing costs, and regulatory hurdles must be addressed to bridge the gap between preclinical success and clinical applicability. This is especially crucial given the persistent barriers that hinder the translation of promising therapeutic strategies from the laboratory to clinical practice.

Immunogenicity

A significant challenge in developing RNA-nanoparticle therapeutics for OA is the issue of immunogenicity. RNA molecules, whether mRNA, siRNA, or miRNA, are naturally recognized by the innate immune system. Unmodified RNA can be detected by pattern recognition receptors, such as Toll-like receptors (TLR3, TLR7, TLR8)^84,85, which trigger the release of type I interferons and pro-inflammatory cytokines. Although chemical RNA modifications can reduce immune activation^86,87, the inflamed joint environment poses an additional challenge. OA joints already exhibit immune cell infiltration and chronic low-grade inflammation^28,29, meaning further immune stimulation could worsen disease progression.

In addition to RNA, nanoparticle carriers themselves may provoke immune responses. Lipid nanoparticles, for example, are commonly used in RNA vaccines and are recognized as foreign, which can activate the complement system, leading to infusion-related reactions⁸⁸. While intra-articular delivery limits systemic exposure, synovial immune cells such as macrophages and dendritic cells can still respond strongly to these carriers. Unlike in vaccines, where transient inflammation is acceptable or even beneficial, OA therapies aim to reduce inflammation and preserve cartilage. Any immunogenic response counteracts this goal. Thus, creating “stealth” nanoparticles that avoid immune detection while maintaining efficient intra-articular delivery remains an unsolved issue and a key reason RNA-nanoparticle OA therapies have yet to reach clinical trials.

Rapid clearance and short joint retention

Intra-articular RNA-nanoparticle treatments are quickly cleared from the joint, limiting their retention to only hours or days. Synovial fluid turnover, lymphatic drainage, joint movement, while enzymatic degradation, immune uptake, and particle size collectively influence clearance and stability: particles smaller than 10 nm diffuse into circulation, those larger than 100 nm are phagocytosed, and mid-sized particles drain via lymphatics^89,90. Efforts to improve retention include optimizing particle size (typically 50–100 nm), PEGylation, addition of cartilage-targeting ligands, and the use of bioadhesive materials or hydrogel depots⁹¹. These strategies can extend residence time to several weeks in experimental models but still fall short of the months-long retention needed for chronic OA management, which would otherwise require repeated injections.

Repeated dosing requirements

Because OA develops and progresses over decades, effective therapies must provide long-term modulation of disease pathways. However, current RNA-based approaches yield only transient effects. Intra-articular mRNA delivery produces protein expression for less than a week⁹², and siRNA-mediated gene silencing typically lasts only a few weeks⁹³. Therefore, a single injection cannot produce durable therapeutic benefits, necessitating repeated administrations. Frequent injections increase the risks of infection, joint damage, and patient discomfort. Until delivery platforms capable of sustained release are developed, the need for repeated dosing remains a significant barrier to clinical translation⁹⁴.

Patient variability

OA is a highly heterogeneous condition, making it challenging to design therapies that are effective across the board. It arises from a complex interplay of genetic, mechanical, metabolic, and inflammatory factors⁹⁵. Even within the same joint, patients exhibit varying degrees of cartilage degradation, synovial inflammation, and bone remodeling patterns. As a result, a therapy targeting one molecular pathway may help some patients but not others.

Moreover, RNA therapeutics are typically designed to regulate specific genes⁹⁶. If the target gene is not consistently dysregulated across all patients, the treatment’s overall efficacy is limited. Addressing this challenge will require precision medicine approaches and refined disease phenotyping, but until then, patient variability remains a key translational hurdle.

High manufacturing costs

Developing and producing RNA-nanoparticle therapeutics for OA remains a costly endeavor. Clinical-grade RNA synthesis involves complex enzymatic or chemical steps, whereas nanoparticle manufacturing requires precise control and high-quality material^97,98. Unlike small molecules, RNA drugs and nanoparticles have yet to achieve scalable cost efficiency, which is especially problematic for chronic treatments that require repeated dosing. Additionally, these formulations often require cold-chain storage, adding further logistical expense. Until more affordable, large-scale production technologies are established, cost will continue to limit both investment and widespread clinical adoption.

Regulatory challenges

Regulatory challenges also hinder clinical translation. Agencies have limited precedents for approving RNA-nanoparticle drugs for non-infectious, chronic diseases, such as OA⁹⁹. Demonstrating safety and efficacy is particularly difficult since OA progresses slowly and requires long trials with both structural (MRI, radiographic) and symptomatic endpoints. Furthermore, reliable biomarkers for tracking RNA delivery and therapeutic response in joints are still lacking¹⁰⁰. Without updated regulatory frameworks tailored to RNA-nanoparticle treatments in chronic musculoskeletal conditions, advancement toward clinical use will remain slow.

In summary, several key challenges continue to limit the clinical translation of RNA-nanoparticle therapeutics for OA. Immunogenicity remains a significant concern, as both RNA molecules and their carriers can trigger unwanted immune responses in already inflamed joints. Rapid clearance from the joint further reduces therapeutic efficacy, necessitating repeated administrations that increase risk and patient burden. Patient variability adds another layer of complexity, as OA’s heterogeneous nature means no single molecular target suits all individuals. High manufacturing and delivery costs hinder scalability, while existing regulatory frameworks are not yet optimized for evaluating RNA-based treatments in chronic musculoskeletal diseases. Overcoming these scientific, technical, and regulatory barriers will be essential for realizing the full potential of RNA-nanoparticle therapies in OA management.

Clinical implications and applications

Despite challenges and limitations, the utilization of nucleic acid therapeutics (siRNA, miRNA, mRNA) in the treatment of OA carries substantial clinical significance and applicability. In essence, these nucleic acid therapies exhibit remarkable precision, targeting specific genes or pathways implicated in the disease, thus minimizing potential adverse effects on healthy tissues and cells. Moreover, they possess the capability to modulate gene expression, facilitating the production of beneficial proteins while inhibiting the production of detrimental ones, thereby contributing to the restoration of joint health. Furthermore, these therapies are relatively non-invasive, often administered via injections, which offers convenience and reduces the need for extensive surgical procedures. Notably, they offer the prospect of personalized treatment approaches, fine-tuning therapy to an individual’s unique genetic and molecular profile, thus enhancing the effectiveness and precision of OA management. Although this review emphasizes post-traumatic OA, similar pathological processes underlie age-related OA, including chronic low-grade inflammation and impaired tissue regeneration. Therefore, the therapeutic strategies discussed here may hold promise for both trauma-induced and age-associated forms of the disease. A summary of the current status of RNA-based therapeutics in OA is provided in Box 2.

Box 2 Status of RNA-based therapeutics in OA.

siRNA

• No approved OA siRNA yet; promising preclinical results (e.g., POSTN, NF-κB, TNFα, MMP-13 silencing).

• Intra-articular delivery is crucial for targeting chondrocytes and synovial cells.

• Most success to date in liver/eye; cartilage delivery remains challenging.

• Proven track record in other diseases supports future OA translation once delivery barriers are overcome.

miRNA

• Preclinical studies (e.g., 224-5p) show anti-inflammatory and cartilage-protective effects.

• Requires joint-targeted delivery to limit systemic exposure.

• Lags behind siRNA/mRNA in clinical readiness.

• Needs improved specificity and delivery systems.

mRNA

• No mRNA OA drug is yet available, but the concept is feasible (e.g., growth factors such as FGF-18).

• High translational potential, given the success of mRNA vaccines and rapid advances in the platform.

• Key challenges: joint retention and repeated-dose tolerance.

• Strong overall outlook as delivery systems evolve.

Conclusion

In conclusion, this review highlights the complex nature of OA, underscoring the imperative for innovative, individualized treatment strategies aimed at restoring the disrupted homeostasis caused by aging or joint trauma. The utilization of RNA-based therapies, including siRNAs, miRNAs, and mRNAs, in conjunction with advanced delivery platforms, presents a beacon of hope for the enhanced management of OA in the years to come. While ongoing research and development offer promise for improving the quality of life for those grappling with this debilitating condition, the future should focus on expanding the scope of RNA therapeutics, optimizing combination delivery at appropriate disease stages, and addressing key barriers such as immunogenicity, limited joint retention, high costs, and regulatory challenges. This approach could pave the way for these transformative therapies to become a cornerstone of future management of age-related and post-traumatic arthritis.

Author contributions

Conceptualization: M.F.R., C.T.N.P., H.P. Writing: original draft preparation: M.F.R., C.T.N.P., K.H., S.A.W., H.P. Writing: review and editing, M.F.R., C.T.N.P., K.H., S.A.W., H.P. Supervision: M.F.R., C.T.N.P., H.P. Funding acquisition: C.T.N.P., H.P. All authors have read and agreed to the published version of the manuscript.

Data availability

No datasets were generated or analysed during the current study.

Competing interests

The authors declare no competing interests.