Dennis R Geiser

Equine peripheral blood-derived mesenchymal stem cells: isolation, identification, trilineage differentiation and effect of hyperbaric oxygen treatment

REASONS FOR PERFORMING STUDY Two studies report variability in proliferation and limited adipocyte differentiation of equine peripheral blood-derived adult mesenchymal stem cells, thus casting doubt on their adipogenic potential. Peripheral blood can be a valuable source of adult mesenchymal stem cells if cell culture conditions permissive for their adherence, proliferation and differentiation are defined. Hyperbaric oxygen treatment has been reported to mobilise haematopoietic progenitor stem cells into the peripheral blood in humans and mice, but similar experiments have not been done in horses. OBJECTIVES To optimise cell culture conditions for isolation, propagation and differentiation of adult stem cells from peripheral blood and to assess the effect of hyperbaric oxygen treatment on adult stem cell concentrations. METHODS Peripheral blood was collected from the jugular vein of 6 research mares, and mononuclear cells were isolated. They were subjected to cell culture conditions that promote the adherence and proliferation of adult stem cells. The cells were characterised by their adherence, expression of cellular antigen markers, and trans-differentiation. Each horse was subjected to 3 hyperbaric oxygen treatments, and stem cells were compared before and after treatments. Stem cells derived from adipose tissue were used as controls. RESULTS One-third of the horses yielded viable stem cells from peripheral blood, positive for CD51, CD90 and CD105, and demonstrated osteocyte, chondrocyte and adipocyte differentiation. Hyperbaric oxygen treatment resulted in a significant increase in CD90-positive cells. Horses that did not yield any cells pretreatment did so only after 3 hyperbaric oxygen treatments. CONCLUSIONS AND POTENTIAL RELEVANCE Peripheral blood can be a valuable source of adult stem cells, if one can identify reliable equine-specific markers, provide methods to increase the number of circulating progenitor cells and optimise cell culture conditions for growth and viability. Our findings are important for further studies towards technological advances in basic and clinical equine regenerative medicine.

Serum concentrations and effects of detomidine delivered orally to horses in three different mediums

OBJECTIVE To compare the effect of orally delivered detomidine on head posture when administered alone or in combination with two different food items, and to determine the serum concentrations of detomidine after oral delivery. STUDY DESIGN Prospective randomized experimental study. ANIMALS Fifteen adult grade mares weighing 328-537 kg. METHODS The horses were randomly assigned to one of the three treatment groups (five horses each). The groups were given detomidine (0.06 mg kg-1): alone; mixed with 3 mL of an apple sauce and gum mixture; or mixed with 3 mL molasses. Head droop, measured before treatment and at 15, 30, 45, 60, 75, 90, and 105 minutes after treatment, was used to evaluate sedation. Yohimbine (0.1 mg kg-1 IV) was administered after the 90-minute evaluation. Blood samples were collected from the detomidine-alone group before treatment and at 15, 30, 45, 60, 75, and 90 minutes after treatment. Sera were analyzed for detomidine equivalent concentrations by an ELISA. Head droop percentages were compared using a repeated measures analysis of variance. RESULTS Significant mean head droop developed in each treatment group by 30 minutes and persisted until reversal with yohimbine. After yohimbine administration, head positions returned to 87-91% of pre-treatment levels. There were no significant differences among the oral treatment groups at any time. Mean serum detomidine equivalents increased slowly until 45-minute post-administration, but never exceeded 30 ng mL-1. CONCLUSIONS Orally administered detomidine results in measurable serum drug concentrations using any of the delivery mediums investigated, and can be expected to produce profound head droop in horses approximately 45 minutes after administration.