This is a study to evaluate the safety and effectiveness of repeated Mesenchymal Stromal Cells (MSC) infusions to patients with Type II or III osteogenesis imperfecta (OI).

Participants will receive MSC infusions approximately every 4 months to complete a total of 6 infusions over 20 months. Participants will be followed for 4 months post their last MSC infusion.

This is a pilot study to evaluate the safety and efficacy of repeated MSC infusions to subjects with OI. This study will evaluate subjects on two separate strata. Stratum A will include subjects with a diagnosis of Type II or Type III osteogenesis imperfecta who have previously undergone a bone marrow transplant. Stratum A may use previously harvested and cryopreserved bone marrow mononuclear cells from original BMT donor or freshly harvested or cryopreserved bone marrow mononuclear cells obtained from a haploidentical healthy parent or sibling. Stratum B will include subjects with Type II or III osteogenesis imperfecta who have not undergone a bone marrow transplant. Stratum B will only receive freshly harvested or cryopreserved bone marrow mononuclear cells from a haploidentical healthy parent or sibling.

Participants will receive MSC infusions approximately every 4 months to complete a total of 6 infusions over 20 months. Participants will be followed for 12 months post their last MSC infusion.

Inclusion Criteria:

• Subjects less than or equal to 19 years of age at the time of enrollment
• Children with a diagnosis of severe of Type II or III osteogenesis imperfecta
• Parent or sibling greater than or equal to 18 years of age, donor willing to or has already undergone HLA typing, and willing and able to provide bone marrow
• BMT greater than 5 years ago for Stratum A

Exclusion Criteria:

• Dependent on supplemental oxygen
• Concurrent Infection