For decades, the mouse has been the gold standard in preclinical research. But as science, industry and society evolve, so do the tools we use to understand human biology. Now, a new contender is emerging - one that is tiny, transparent, and often overlooked: Caenorhabditis elegans, a nematode. Scientists are increasingly turning to this humble worm as a novel and effective model for studying human health and disease. But can a worm really replace the mouse in preclinical studies? As we push toward more ethical, scalable, and cost-effective alternatives, C. elegans might just be the future of preclinical screening.
The Push Away from Mammalian Testing
There is a growing movement in the scientific community to reduce reliance on mammalian models, particularly for ethical and practical reasons. Mammalian testing, while invaluable, is fraught with challenges. Ethical concerns about animal welfare have prompted regulations and campaigns to minimize the use of mammals in research. Consumers are also driving this shift, increasingly demanding cruelty-free, animal-free testing methods.
On a practical level, mammalian studies are expensive, time-consuming, and resource intensive. Conducting preclinical trials in mice or rats can take months, if not years, and require substantial financial investment. This often makes early-stage discovery work cumbersome, delaying breakthroughs. These challenges are pushing researchers to explore alternative models that are both ethical and efficient. Enter C. elegans, a non-mammalian organism that still provides valuable insights into human biology.
Why C. elegans is a Novel and Ideal Alternative
So, why is this tiny worm gaining popularity? The invertebrate C. elegans is about a 1 mm long nematode (Fig. 1) that has been researched for more than 50 years since Sydney Brenner [1] introduced it as a model in 1974. This organism has been the cornerstone for studying fundamental biological processes including developmental biology [2], neurobiology [3,4], pathogenicity [5,6] and aging [7,8].
This nematode has a short lifespan of 3 weeks, with the transition from egg to adult in 3 days, and a reproductive period that lasts from day 4 to day 9 of adulthood. Each adult worm lays about 250 eggs, providing the ability to culture large populations in a relatively short time (e.g. 100,000 subjects can be recruited in a week), delivering high statistical power and confidence in data.
Moreover, C. elegans is remarkably cost-efficient compared to mammals. There are no ethical concerns related to its use, and it requires minimal resources for care and handling. Researchers can run numerous experiments simultaneously, cutting down on time and costs significantly. These factors make C. elegans a highly attractive option for preclinical research.
Translatable Science: From Worm to Human Health
While C. elegans is a non-mammalian model, its biological relevance to humans is undeniable. Around 600 million years ago, humans and C. elegans shared a common ancestor. Although we’ve come a long way since our days as primitive multicellular organisms, many of the fundamental biological processes that keep us alive are shared with the worm.
Unsurprisingly, this non-mammalian model has contributed to major fundamental discoveries. The worm model has many feathers to its hat, as the first multicellular organism (i) whose genome was sequenced [9] even before human genome sequencing (ii) whose neuronal wiring diagram was fully mapped [10] (iii) whose lifespan was doubled due to a single genetic mutation [11] (iv) where human-relevant apoptosis pathways were identified [12] (v) where green fluorescent protein was used to show gene expression in vivo [13] (vi) where the process of RNA interference to silence gene expression was discovered [14]. The latter three discoveries received Nobel Prizes within a period of less than 10 years – an astonishing achievement in the history of science highlighting the relevance of this non-mammalian model for human biology.
Much of the prominence of C. elegans including Nobel Prize-winning investigations comes from the strong conservation of biology from C. elegans to mammals in terms of genes and signaling pathways. 60-80% of the human-encoding genes have C. elegans homologs. 42% of human disease-causing genes have a homolog in C. elegans. Many signaling pathways present in humans are also present in C. elegans including insulin/IGF-1, TGF-b, Wnt, Notch, NF-kb, AMPK etc. Not surprisingly, a PubMed search has revealed about 2000 C. elegans publications per year, and 40,000 publications to date. We seem to know more about this worm than humans – making it the best studied model organism on the planet.
C. elegans is not an animal for regulatory purposes
From a biological perspective, C. elegans is an animal containing multiple tissues (Fig. 1) that exhibits many of the behaviors associated with mammals. However, from a regulatory perspective, C. elegans is excluded from the definition of an animal due to its invertebrate status. In the US, the Public Health Services Policy for Human Care and Use of Laboratory Animals issued by the Department of Health and Human Services states that an animal is: “Any live, vertebrate animal used or intended for use in research, research training, experimentation, or biological testing or for related purposes.” Likewise, the European Union Directive states that an animal is “Live non-human vertebrate animals, including: (i) Independently feeding larval forms (ii) Fetal forms of mammals as from the last third of their normal development.” Thus, in both US and EU, C. elegans enjoys a non-animal status, and is best described as a microorganism. These regulatory definitions preclude the need for institutional review board (IRB) approvals and ethical guidelines when conducting studies in C. elegans. The 3R principles of replace, reduce and refine are certainly relevant when using the C. elegans model, and has become a part of corporate governance in many companies.
Regulatory agencies such as the Food and Drug Administration (FDA), Environment Protection Agency (EPA) and Health Canada are moving towards non-rodent testing to address public and scientific concerns related to traditional animal testing. According to the FDA Modernization Act 2.0 - US legislation signed in 2022, new medicines need not be tested in animals to receive US FDA approval [15]. EPA aims to ban animal testing by 2035 [16]. Health Canada announced the end of animal use for cosmetic testing in 2023 [17]. These drivers bring an existential crisis to evaluate safety and efficacy in an intact living system. C. elegans can perfectly address this gap and provide comprehensive safety and efficacy data that is actionable and qualifies bioactives for human studies.
Why hasn’t C. elegans been industrialized for ingredient discovery?
Given the existence of decades of knowledge on C. elegans that is relevant to human biology, and the need for a non-mammalian in vivo model for bioactive discovery, the obvious question is why this research tool hasn’t pervaded the industrial R&D and innovation communities including the BigFood companies (similar to BigTech, there are several multi-billion-dollar companies that drive the trillion-dollar food industry).
Lack of scalable technology: Most C. elegans research is conducted on agar plates, where worms have to be transferred manually several days to new plates to provide food and prevent mixed populations containing their progeny. The difficulty is its microscopic size, and the thousands of worms that need to be transferred for high throughput screening. This task of worm transfer requires tedious back-breaking bench work that can only be done using relatively cheap labor and students in academia and not in an industrial setting. An equally important challenge is the ability to acquire phenotypic data. Traditionally, phenotypes were scored by manual observations – making acquisition of useful data tedious and that too at low phenotypic depth.
Lack of published evidence that is relevant for functional ingredient development: There have been many drug screens conducted using C. elegans [18,19] including FDA-approved drug libraries with a focus on disease models. In fact hundreds of thousands of drug candidates have been tested in C. elegans across scores of studies (e.g. see the extensive list in Table 1 of ref.[19]). In contrast, using C. elegans for screening bioactives for ingredient development is new [20,21], and probably few hundred food-relevant bioactives have been tested in C. elegans. The field is nascent and published reports showing human translatability [22-25] are emerging.
Lack of effort to configure published assays for ingredient development. Academia has developed many C. elegans assays focusing on fundamental biological questions that could be repurposed for the functional ingredient industry. For example, health claims such as “energy” for sports drinks or “alertness” for dietary supplements can be established using C. elegans assays, but a systematic effort to build a compendium that can serve as a foundation for bioactive discovery and ingredient development is lacking.
These challenges are being addressed by new technologies in fluid handling, automation and artificial intelligence. As more companies are being attracted to the pace at which innovation can be accelerated using C. elegans the evidence base for human translatability will grow.
The Future of Preclinical Research: The Case for the Worm
So, is the worm the new mouse? While it may not completely replace mammalian models, C. elegans is undeniably becoming a cornerstone of modern preclinical research. Its simplicity, scalability, and translatability make it a powerful tool for understanding human biology and disease.
The decades of knowledge on C. elegans that is relevant for human biology, the explosive growth in artificial intelligence for scaling data processing and the tail winds coming from regulatory agencies and animal welfare groups – makes the timing perfect to disrupt the trillion-dollar food industry using a technology-driven platform that could bring a quantum jump in R&D productivity leading to commercialization of novel functional ingredients to improve human health and wellbeing.
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