Infantile hypophosphatasia: transplantation therapy trial using bone fragments and cultured osteoblasts.

BACKGROUND: Hypophosphatasia (HPP) is a rare, heritable, metabolic bone disease due to deficient activity of the tissue-nonspecific isoenzyme of alkaline phosphatase. The infantile form features severe rickets often causing death in the first year of life from respiratory complications. There is no established medical treatment. In 1997, an 8-month-old girl with worsening and life-threatening infantile HPP improved considerably after marrow cell transplantation. OBJECTIVE: Our aim was to better understand and to advance these encouraging transplantation results. DESIGN: In 1999, based on emerging mouse transplantation models involving implanted donor bone fragments as well as osteoblast-like cells cultured from bone, we treated a 9-month-old girl suffering a similar course of infantile HPP. RESULTS: Four months later, radiographs demonstrated improved skeletal mineralization. Twenty months later, PCR analysis of adherent cells cultured from recipient bone suggested the presence of small amounts of paternal (donor) DNA despite the absence of hematopoietic engraftment. This patient, now 8 yr old (7 yr after transplantation), is active and growing, and has the clinical phenotype of the more mild, childhood form of HPP. CONCLUSIONS: Cumulative experience suggests that, after immune tolerance, donor bone fragments and marrow may provide precursor cells for distribution and engraftment in the skeletal microenvironment in HPP patients to form tissue-nonspecific isoenzyme of alkaline phosphatase-replete osteoblasts that can improve mineralization.

Replacement of recipient stromal/mesenchymal cells after bone marrow transplantation using bone fragments and cultured osteoblast-like cells.

Abstract We present our experience on treatment of three children with potentially fatal diseases using a unique protocol for non-myeloablative bone marrow transplantation. The protocol was designed to promote engraftment of bone marrow stromal/mesenchymal cells (SC/MSCs) based on the knowledge from preclinical models over the last three decades. Accordingly, our protocol is the first to test the use of bone fragments as an ideal vehicle to transplant such cells residing in the bone core. Because of the paucity of knowledge for optimum transplantation of SC/MSCs in humans, we used a multifaceted approach and implanted bone fragments both intraperitoneally and directly into bone on day 0 of BMT. We also infused cultured donor osteoblast-like cells intravenously post-BMT. We were able to achieve high levels of stroma cell engraftment as defined by molecular analyses of bone biopsy specimens.

Nonmyeloablative bone marrow transplantation of BXSB lupus mice using fully matched allogeneic donor cells from green fluorescent protein transgenic mice.

Male BXSB mice, a mouse model of systemic lupus erythematosus, were given bone marrow transplants (BMT) at 20 wk of age using MHC-matched donor cells and nonmyeloablative conditioning (550 cGy irradiation). Transplanted mice and irradiation controls were followed for a period of 20 wk. Mice transgenic for green fluorescent protein were used as donors to allow tracking of donor cells and a determination of chimerism. Radiation controls had reduced renal pathology at 10 wk posttransplant, but not at 20 wk compared with untreated mice, while nonmyeloablative BMT mice had significantly reduced pathology at both time intervals. The monocytosis characteristic of older BXSB mice was also reduced by BMT, but the treatment did not prevent production of Ab to dsDNA. A stable chimerism of 24-40% donor CD45-positive cells was achieved in spleen and bone marrow, and there was no evidence of clinical graft vs host disease. Donor cells were detected in most recipient organs, notably the thymus and renal glomeruli. The results suggest that complete depletion of mature lymphocytes or of progenitor stem cells is not required to control lupus nephritis in BXSB mice.