When our computers crash, we immediately panic, wondering if our data will be lost forever. We recall how often our Information Technology department reminds us to back up our data and how often we ignore this suggestion. Now, how about rodent lines? Who reminds us to back up our unique genetically engineered model (GEM) so that the model—the gene of interest, our research funding—isn’t lost forever should a disaster occur within the colony?With increasing use of and dependency on GEMs, many researchers are considering a GEMs risk management program. Such programs can safeguard a researcher’s unique and valuable model from health, genetic and natural disasters.
Importance of GEMs
GEMs have proven to be valid and valuable research tools for understanding basic biological mechanisms, preclinical development of therapeutic compounds and product development and safety testing.GEMs are specially designed to mimic human metabolism, accept transplanted human tissues or harbor defined gut microbiota. Each model is unique and, therefore, valuable to many stakeholders, including the scientist gathering data; the owner organization, whether a governmental body or private company; and, not least, the people who stand to benefit from GEM-based research.
A model can be lost if the mutation of interest disappears, if the model faces genetic contamination or if the line becomes infected by a pathogen incompatible with standards of the animal husbandry facility, leading to an immediate termination of the colony. Also, as seen with Superstorm Sandy in the US, natural disasters can lead to total loss of unique GEMs. Often, however, losing a model doesn’t happen in extreme situations but rather during normal operating conditions. Basic equipment failure, such as flooding of cages or technician error through incorrect breeding, can lead to a total loss of a GEM.
The nightmare scenario of GEM-based research is a total loss of the underlying model. Consequences, including a delay in research time, can possibly render any accomplished research unusable, with implications such as an extended study timeline for development of a potential disease treatment.
A risk management program limits research interruption
With so much dependence on a model, it becomes important for researchers to have a risk management program, allowing them to continue their research with as little interruption as possible should a disaster occur. Often, planning for availability of a back-up is overlooked or forgotten as scientists and laboratory heads become preoccupied with running tests to gather data on their newly validated GEM. Valuable research time is lost when a back-up to the model is not available following a biological or natural disaster.A GEMs risk management program can include two options, depending on the institution’s available space and resources. The first and most basic option is an extension of the vivarium space so that the line can be split into multiple colonies at one or more locations in the same facility. This option provides safeguards against health and genetic disasters but is not sufficient to protect the model from a severe natural disaster. Although this may be the most basic option, it is difficult to implement, as many facilities have space limitations and often are shared by numerous researchers with the same risk mitigation needs.
Cryopreservation, off-site storage are options
A second option, cryopreservation of rodent germplasm and storage of material at an off-site location, offers a realistic solution. Maintaining a ‘biobank’ of frozen embryos or sperm provides the researcher with several advantages: quick recovery from the time a model is lost, the option to ‘reset’ a colony, reduction of genetic drift, maximization of vivarium space by preserving lines currently not in use, extension of a colony’s reproductive life by allowing animals to contribute genetic material far beyond their reproductive lifespans and simplified collaboration between scientific locations by enabling shipping of cryopreserved material instead of live animals.Researchers who decide to use cryopreservation to back up their models must consider the process and available resources when recovery of frozen material is required. First, a prerequisite for revitalizing a line is access to lab technicians trained in cryopreservation methods, in vitro fertilization (IVF) and embryo transfer into pseudopregnant females. Also, line characteristics should be considered, as this could impact future expansion of a cohort. For example, it is recommended that embryo cryopreservation be chosen for GEMs on a complex background, for those carrying multiple gene mutations or when homozygosity is preferred. The reason for this is that a diploid gene package is preserved and no further breeding is required when thawing the line. Sperm cryopreservation can be recommended when availability of animals is limited, when the line carries a single gene mutation or when additional breeding of animals after line recovery is acceptable. If sperm cryopreservation is desired, then the males chosen should be at the optimal breeding age range to have the best possible sperm quality.
Once cryopreservation has been completed, it is important not to skip a post-thaw analysis for quality control of the frozen biological material. This should be done when preserving either embryos or sperm. By ignoring this step, many researchers have faced poor quality of frozen material at the time of model recovery. Checking sperm motility after thawing a preserved sample is not sufficient. This only confirms that a sample is capable of fertilizing oocytes. As a quality check for embryos, the sample should, at minimum, be capable of developing into the blastocyst stage in culture. The optimal way to judge quality is to check that viable pups can be produced using recovered material for IVF, in the case of sperm, or to perform an embryo transfer.
We all get caught up in daily business. But we should not lose sight of the value of a line for discovering cures and the fact that a back-up copy would serve us well in case of disaster.
