Safety and Preliminary Efficacy of ULSC in Facioscapulohumeral Muscular Dystrophy (FSHD)

The goal of this clinical trial is to learn about how an umbilical cord lining-derived stem cell product (ULSC) performs when treating Facioscapulohumeral Muscular Dystrophy (FSHD) 1 or 2. It will assess safety and preliminary efficacy in relieving symptoms of FSHD with ULSC administered in two intravenous (IV) doses of 100 million cells per dose. The main questions that this study plans to answer are: * Is ULSC as safe as placebo (a look-alike saline without cells) in repeated IV infusion? * Does ULSC improve symptoms of FSHD after each dose? Researchers will compare ULSC to placebo. Participants will: * Have been diagnosed with FSHD of a Ricci clinical severity score 1.5 or more. * Participate in this study for total duration of 21 months with 11 in-person visits and 5 virtual visits. * Visit the clinic for a total of 4 IV infusions (260 mL) 3 months apart. * Receive 2 doses of ULSC and 2 doses placebo in either of two sequences, as assigned: ULSC first (Day 1 and Month 3) and placebo second (Month 6 and Month 9), or placebo first (Day 1 and Month 3) and ULSC second (Month 6 and Month 9). * Return for follow-up visits after each dose and up to 12 months after final dose.

Inclusion Criteria: * Participants will be ≥15 years old. * Diagnosis of genetically confirmed FSHD 1 or FSHD 2. * Participants should have a Ricci clinical severity score of ≥1.5 (range is out of 0-10), at screening, and must be independently ambulatory at the time of the study. * Participant will have the ability to comply with the requirements of the study, including MRI. * All participants of reproductive age/capacity will be required to use adequate contraception, defined as two forms of highly effective contraceptives, with any partners during the study period and for at least three months beyond the study period for safety. * Participant will have the ability to understand and provide written informed consent. * For those participants who are on drug(s) or supplements that may affect muscle function, as determined by the Investigator, participants must be on a stable dose of that drug(s) or supplement for at least 3 months prior to the first dose of study drug and remain on that stable dose for the duration of the study. * This includes the following drug category: Immunomodulatory agents, including targeted biological therapies. * Exception is rapamycin. (See Exclusion Criteria #10.) * Current and up-to-date immunizations. * No contraindications to MRI. * Hematocrit of ≤ 50% * Prostate-specific antigen ≤ 4.0 ng/mL (or ≤ 3.0 ng/mL if the participant has a first-degree relative with prostate cancer) * Fasting blood glucose \