The present invention provides novel stem cell compositions having significant therapeutic and practical advantages, as well as methods of preparing and using such compositions for the treatment and prevention of injury and disease in patients. The invention may be applied to stem cell populations isolated from a wide variety of animals, including humans, and tissues. In particular applications, the invention is used to prepare a stem cell composition from a collagen-based tissue, such as adipose tissue, isolated from a patient, and the stem cell composition is subsequently provided to a site of actual or potential injury in the patient. The invention further includes related kits comprising the stem cell compositions, which are remarkably stable and retain viability and efficacy during storage and shipment.