General Cross-Cutting Tissue Preservation Challenges
General cross-cutting sub-challenges
Control excessive ice formation: Ice crystallization in tissues results in physical damage. Improved understanding and control of ice nucleation, growth and propagation is needed. Minimizing the formation of ice crystals during the cooling or rewarming/devitrification process (for supercooled tissues) is a major challenge.
Hold cryoprotectant and/or osmotic toxicity within acceptable levels: Various molecules may be used to manipulate ice crystal formation, dehydration, etc. to minimize tissue damage during cooling/rewarming. However, many of these molecules are toxic or may otherwise cause damage to the tissue if they are applied at “high” concentrations. Understanding the toxic effect of these molecules, identifying novel non-toxic cryoprotectant agents and/or optimizing currently available CPAs to minimize toxicity in tissues are major needs.
Limit disproportionate mechanical/thermodynamic stress: Tissues may experience differential mechanical/thermodynamic stresses during cooling/rewarming. Further understanding and control of the mechanical and thermal behavior of cryopreserved materials is needed. This would allow for the optimization of cooling/rewarming and long-term storage protocols.
Control excessive chilling injury: Improved understanding of chilling injury in various cell/tissue types is needed, so that, ultimately, these effects can be mitigated. Specific examples include cell membrane damage, loss of selective membrane permeability, and cold shock when biological material is exposed to low temperatures.
Avoid unacceptable levels of ischemic injury: Tissues are subject to ischemic injury when not integrated to a central vascular system. Improved understanding of nature inspired strategies (hypometabolism/dormancy of freeze tolerant or hibernating animals) and subsequent application in this field is needed. In addition, key understandings from hypothermic medicine, resuscitation science, etc. may also be applicable to overcome this challenge.
Develop methods for revival, repair, and functional assessment: Need to understand how to characterize and target molecular damage mechanisms (i.e. cell structure damage, apoptosis, oxidative stress), and then integrate regenerative medicine techniques with perfusion-based organ preservation methods to assess organs/tissues, and if needed repair/modify organs.