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SeqMatic Forum: Finding the Right Preclinical Model to Evaluate Medical Devices Pathology

The methodology involved in processing implant sites is meticulously designed to achieve a detailed cross-section of the material-tissue interface, particularly when conducting local assessments. This step is critical in preclinical evaluations, where identifying the appropriate biological model plays a pivotal role in simulating the interaction between the medical device and biological tissues. The spectrum of preclinical assessment spans from in vitro methods, which include 2D cell cultures, organoids, cell pellets, and cytotoxicity testing, to ex vivo techniques1, 2, which provides a closer approximation of in vivo conditions without the ethical and logistical complexities of live animal models (see Figure 1).
Figure 1: Skin explant procedures involve the cultivation of human skin tissue samples ex vivo to maintain their physiological properties and functionality for experimental use. Companies like GenoSkin specialize in creating these explant models, which replicate the complex environment of human skin, allowing for the detailed assessment of biological responses to foreign implanted materials. Through these models, researchers can evaluate the skin's reaction to implants, including inflammation, healing processes, and potential adverse effects, providing invaluable insights for the development of safer and more compatible medical devices.

In vivo studies, utilizing a range of animal models such as rodents, swine, ovine, and non-human primates (NHP), offer invaluable insights into how a device functions within a living organism. These models are critical for evaluating the biocompatibility and safety of medical devices, employing a variety of control comparisons to ensure rigor and reliability in the findings. This includes comparisons between the implant and various controls: dummy (an inert device), sham (surgery performed but no device implanted), no device, and explant controls, each serving a specific purpose in elucidating the device’s effects (see Figure 2).

Figure 2: Sheep can serve as valuable models to assess the functionality of low-intensity focal ultrasound targeting the motor cortical and thalamic areas of the brain by allowing for in vivo evaluation of neuromodulation effects and therapeutic potential in a complex biological system3.

Timing the harvesting of tissue post-implantation or explantation is another vital consideration, with tissue samples collected at acute, sub-acute, sub-chronic, and chronic time points to assess the progression and resolution of biological responses over time. Such comprehensive and systematic evaluation methods are essential for understanding the complex dynamics at the material-tissue interface, ultimately guiding the development of safer and more effective medical devices.

Citations:

  1. QIMA Life Sciences. (n.d.). Analyses in vitro et ex vivo: Human skin explant. Retrieved April 25, 2024, from https://qima-lifesciences.com/analyses-in-vitro-et-ex-vivo/human-skin-explant/
  2. GenoSkin. (n.d.). Skin model for subcutaneous injections. Retrieved April 25, 2024, from https://genoskin.com/tissue-samples/skin-model-subcutaneous-injections/
  3. Kim, HC., Lee, W., Kunes, J. et al. Transcranial focused ultrasound modulates cortical and thalamic motor activity in awake sheep. Sci Rep 11, 19274 (2021). https://doi.org/10.1038/s41598-021-98920-x

DISCLAIMER: Images featured in this post include assets that have been adapted for the post. Original images are credited to their corresponding cited references. Refer to citation links for publication and author’s scientific context.

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