Use of mesenchymal stem cells (MSCs) found in the stromal vascular fraction (SVF) of equine adipose tissue has promising
applications for regenerative therapies. The most commonly used source of equine adipose tissue is the subcutaneous tailhead.
The objective of this study was to compare 3 adipose depot sites in horses and determine the viability and cellular yield, capillary
density, gene expression for selected markers, and colony-forming unit fibroblasts (CFU-Fs) in adipose tissue taken from these
sites. Adipose tissue was excised from the area lateral to the tailhead, the inguinal region, and the small colon mesentery of
6 horses. Lipoaspirate was also collected from the area lateral to the tailhead. Stromal vascular fraction (SVF) was prepared in
duplicate from the 3 different adipose tissue depots. The total nucleated and dead cell counts was determined manually using
a hemocytometer and percent viability was calculated. Mass and volume of adipose were determined in order to calculate
density and factor-VIII immunohistochemical staining was used to determine vascular density in the excisional adipose tissue
samples from each horse. Quantitative polymerase chain reaction (qPCR) was used to quantify gene expression for selected
cellular markers from each site. There were significant differences in viability, yield of nucleated cells/gram of adipose tissue,
vascular density, gene expression, and CFU-Fs among adipose depots. Adipose from the mesentery yielded the highest number
of nucleated cells/gram of tissue and the highest vascular density and percentage of CFU-Fs. In the horse, both the anatomical
site of collection and the method of tissue collection significantly impact the yield and composition of cells in the SVF. Further
study is needed to assess whether one adipose source is superior for harvesting mesenchymal stem cells (MSCs) and whether
the differences among sources are clinically relevant for in-vivo treatment of musculoskeletal injuries in horses.