Timely ReAuthorization of Necessary Stem-cell Programs Lends Access to Needed Therapies Act of 2021 or the TRANSPLANT Act of 2021 This bill modifies and reauthorizes through FY2026 the C.W. Bill Young Cell Transplantation Program, which provides support to patients who need a potentially life-saving bone marrow transplant or umbilical cord blood transplant. The bill also requires the Department of Health and Human Services to conduct a periodic review of the science of using adult stem cells and birthing tissues in therapeutic treatments. In addition, the Government Accountability Office must report on the regenerative medicine workforce.