Evaluation of PROCHYMAL® for Treatment-refractory Moderate-to-severe Crohn's Disease

Inclusion Criteria: * Participant must have qualified for, enrolled in, and provided written informed consent form (ICF) and authorization for use and disclosure of protected health information (PHI) for Protocol 603 after the August 3, 2010. * Participant successfully completed all screening assessments in Protocol 603 as required by Protocol 603. * Participant successfully completed the full course of each of the four infusions of investigational agent on Days 0, 3, 7, and 14 of Protocol 603 after August 3, 2010. * Participant must enroll in Protocol 611 on or before the 45th day after first infusion in Protocol 603. * Participant must provide written ICF and authorization for use and disclosure of PHI for Protocol 611. Exclusion Criteria: * Participant is unwilling or unable to adhere to requirements of Protocol 611. * Participant had confirmed respiratory distress during a PROCHYMAL infusion in any prior PROCHYMAL study. * Participant had a serious adverse event in any previous PROCHYMAL study that was deemed by the principal investigator of that study to be possibly or probably related to PROCHYMAL and also that was within 48 h after a PROCHYMAL infusion.