This trial at the Indiana University School of Medicine in Indianapolis aims to explore the role of donated mesenchymal stem cells on patients with peripheral vascular disease. The stem cells (otherwise known as Endometrial Regenerative Cells) will be collected from menstrual blood and injected into the muscles of participants who are not eligible for surgical or other interventions (such as percutaneous revascularisation). The subjects will be given three injections into the calf of the affected limb. Participants will be assessed at regular intervals during the following year for complications and for indicators of improved blood flow such as improvements in rest pain and ulcer status. The trial expects to recruit 50 patients between May 2012 and June 2013.