From Liver to Adipose Tissue: Approaches to Collagenase Dissociation of Different Tissues in Animal Experiments

Why different tissues require different collagenase strategies

Tissues within an animal body are not the same: the liver is rich in sinusoids and hepatocytes, adipose tissue is filled with lipid droplets and collagen fibers, and tumor tissue is often dense and accompanied by large necrotic areas. Although collagenase can degrade collagen, it is difficult for a single fixed condition to be suitable for all tissues at the same time. Experimenters usually adjust the type, concentration, and digestion time of collagenase according to the collagen type in the target tissue, the tightness of intercellular connections, and the requirements of downstream experiments for cell viability and surface markers. Understanding tissue differences is the first step to improving single-cell yield.

Liver tissue: the classic combination of perfusion and collagenase digestion

In animal experiments, liver single-cell isolation often uses in situ perfusion. Simply put, a buffer containing collagenase is slowly perfused into the liver through blood vessels, allowing the enzyme solution to reach the interior of the hepatic lobules evenly. This method is gentler than direct mincing and soaking, and it is also easier to obtain hepatocytes with better viability. If ordinary experimenters do not have perfusion equipment, they can also cut the liver into small pieces and then digest them with collagenase solution under shaking. Either way, temperature needs to be controlled, generally under conditions close to body temperature, and attention should be paid to observing whether the tissue gradually becomes soft and loose.

Adipose tissue: collagenase helps release the stromal vascular fraction

In addition to mature adipocytes, adipose tissue also contains a large amount of stromal vascular fraction present in the collagen framework, and these components are often used in animal studies such as metabolism and immunity. When using collagenase to digest adipose tissue, the fat is usually first cut into small pieces, then a buffer containing collagenase is added, and low-speed shaking is carried out on a constant-temperature shaker. After digestion, through centrifugation, the mature adipocytes float in the upper layer, while the stromal vascular fraction precipitates at the bottom of the tube, thereby facilitating separation. Because adipose tissue contains a lot of oil, care should be taken during operation to avoid cell damage caused by vigorous shaking.

Tumor tissue: auxiliary enzymes can improve dissociation efficiency

Tissues in animal tumor models are often markedly fibrotic, with tight adhesion between cells. Using collagenase alone is sometimes difficult to achieve complete dissociation. A common practice is to combine it with DNase to reduce clumping caused by DNA released from dead cells, or to add hyaluronidase to help degrade hyaluronic acid in the matrix. When mincing tissue, try to use a sterile scalpel or scissors to avoid excessive tearing. After digestion, the cell suspension still needs to be filtered through a cell strainer to remove incompletely digested tissue fragments. For ordinary researchers, referring to the literature conditions for similar tumor models and conducting small-scale preliminary experiments is an effective way to find a suitable collagenase dissociation protocol.

Summary

Collagenase dissociation in animal experiments is not a "one-size-fits-all" approach. Liver, adipose, and tumor are only common examples; other tissues such as heart, lung, and skeletal muscle also have their own characteristics. The key is to find a balance between gentleness and efficiency based on tissue hardness and cell type. Recording the tissue source, collagenase lot number, time, and temperature of each digestion helps gradually establish a stable experimental workflow.