From the Guidelines
In vivo studies are preferred over ex vivo studies due to their greater physiological relevance and ability to assess safety and therapeutic efficacy in a more realistic environment. When considering the choice between in vivo and ex vivo experimental approaches, it is essential to weigh the advantages and disadvantages of each method. In vivo studies, which involve experiments conducted within a living organism, offer the benefit of observing biological processes in their natural environment with all physiological systems intact 1. This approach is crucial for assessing the safety and therapeutic efficacy of drug delivery systems, as it allows for the evaluation of how drugs interact with the entire organism, including all regulatory systems.
Some key points to consider when deciding between in vivo and ex vivo studies include:
- The research question: In vivo studies are more suitable for questions that require an understanding of how biological processes work within the complete, functioning organism.
- Physiological relevance: In vivo studies provide greater physiological relevance, as they are conducted in a living organism with all regulatory systems present.
- Experimental control: Ex vivo studies, on the other hand, offer more control over experimental variables, as tissues or cells can be manipulated in a controlled laboratory setting.
- Safety and efficacy assessments: In vivo studies are better suited for assessing the safety and therapeutic efficacy of drug delivery systems, as they can evaluate the interaction of drugs with the entire organism.
According to a recent systematic review published in Theranostics in 2023 1, ex vivo experimentation is commonly used as an initial proof of concept for drug delivery research due to its lower cost, reduced time requirements, and lower barrier to entry. However, the review also notes that safety and therapeutic efficacy assessments are often severely limited in ex vivo studies. Therefore, in vivo studies should be prioritized when possible, especially when assessing the safety and efficacy of drug delivery systems, as they provide a more realistic environment for evaluating these critical factors 1.
From the Research
In Vivo vs Ex Vivo Methods
- In vivo methods involve growing organs or tissues inside a living organism, while ex vivo methods involve growing them outside the organism, typically in a laboratory setting 2.
- Ex vivo methods have been shown to be effective in growing liver buds and other organs, and can be used to create scalable liver-like tissue using 3D bioprinting 2.
- Ex vivo allotransplantation engineering has also been used to deliver mesenchymal stem cells and prolong rejection-free allograft survival in transplantation 3.
Applications of Ex Vivo Methods
- Ex vivo machine perfusion (EVMP) is a rapidly growing technique for preserving explanted solid organs, and has been used to expand the donor organ pool and reduce ischemia-reperfusion injury 4, 5.
- EVMP has also been used to recondition and modify diseased organs, and has potential applications in tumor and infection therapies and regenerative approaches 5.
- Ex vivo gene therapy is another area of research, where gene therapies can be administered during organ transplantation to optimize and recondition organs ex vivo 4.
Comparison of In Vivo and Ex Vivo Methods
- In vivo methods can provide a more natural environment for organ growth and development, but can also be limited by the availability of suitable host organisms and the risk of rejection or other complications 2.
- Ex vivo methods, on the other hand, offer more control over the growth environment and can be used to create large quantities of organs or tissues, but can also be limited by the availability of suitable biomaterials and the risk of contamination or other complications 2, 3.