Progenitors Systemically Transplanted into Neonatal Mice Localize to Areas of Active Bone Formation In Vivo: Implications of Cell Therapy for Skeletal Diseases

Abstract

The potential of cell or gene therapy to treat skeletal diseases was evaluated through analysis of transplanted osteoprogenitors into neonatal homozygous and heterozygous osteogenesis imperfecta mice (oim). The osteoprogenitors used for transplantation were prepared by injection of mesenchymal stem cells (MSCs) marked with the green fluorescent protein (GFP) into normal mice with the subsequent retrieval of the cells at 35 days. The retrieved cells referred to here as osteoprogenitors were expanded in culture and transplanted into the 2-day-old oim mice via the superficial temporal vein. The recipient mice were evaluated at 2 and 4 weeks after cell transplantation. Four weeks after transplantation, tissue sections made from femurs and tibias of oim mice showed that the GFP-positive (GFP ؉ ) cells were distributed on the surfaces of the bone spicules in the spongiosa, the area of active bone formation. In the diaphysis, the GFP ؉ cells were distributed in the bone marrow, on the endosteal surfaces, and also in the cortical bone. Immunofluorescence localization for GFP confirmed that the fluorescence seen in tissue sections was due to the engrafted donor cells, not bone autofluorescence. Gene expression analysis by polymerase chain reaction of the GFP ؉ cells retrieved from the bones and marrow of the recipient mice demonstrated that the cells from bone were osteoblasts, whereas those from bone marrow were progenitors. These data demonstrate that MSCs delivered systemically to developing osteogenesis imperfecta mice engraft in bones, localize to areas of active bone formation, differentiate into osteoblasts in vivo, and may contribute to bone formation in vivo.

Potential of Human Fetal Chorionic Stem Cells for the Treatment of Osteogenesis Imperfecta

“…Transplanted e-CSC homed to areas of bone growth and fracture repair and expressed osteoblast differentiation genes Osteopontin and Osteocalcin and the COL1A2 protein, indicating their differentiation to functional osteoblasts. These findings are in agreement with previous studies in the oim model that demonstrated the direct differentiation of transplanted cells to osteoblasts [13][14][15][16] and subsequent improvements in disease pathology. In addition, we used the detection of human factor IX as an immunoassay to detect the presence of mouse anti-human antibodies in the serum of mice transplanted with human cells and we were able to show the absence of immune reaction against allogeneic cells.…”

“…In humans, whole bone marrow and bone marrow mesenchymal stem cells (MSC) have been transplanted in OI children with gains in body length and bone mineralization [8,9], while allogeneic fetal liver-derived stem cells transplanted in utero led to apparent phenotypic improvement in an OI fetus, although confounded by concomitant bisphosphonate use [10]. In rodent OI models, transplantation of whole bone marrow/bone marrow MSC led to increased collagen content [11], improved bone strength, reduced perinatal lethality [12], and increased osteoblast differentiation [13,14]. Marked therapeutic benefits were shown following transplantation of fetal MSC from human first trimester blood in a mouse model of human type III OI (oim) including improved bone plasticity and a two-third reduction in long bone fractures [15,16].…”

In utero transplantation of adult bone marrow decreases perinatal lethality and rescues the bone phenotype in the knockin murine model for classical, dominant osteogenesis imperfecta

“…[14][15][16][17] The primary goal of this work was to define the approach, develop the means, and set the stage for future studies of different treatment aspects. Our observations of (1) a major fraction of bone matrix synthesized by a minor fraction of engrafted osteoblasts, (2) recovery of bone quality in treated mice, and (3) rescue of the lethal phenotype address some existing puzzles and offer insights for future studies.…”

“…16 Unfortunately, most animal studies were limited to the treatment of oim mice with virally transduced cells. [15][16][17] Viral transduction may alter the differentiation, proliferation, and function of transplanted cells in vivo. 18 In addition, the oim mouse itself is a model of a rare, recessive form of OI with only one known patient.…”

Stem cell–mediated regeneration of the intervertebral disc: cellular and molecular challenges

“…Extension of this example to the unique cartilaginous tissue of the IVD could be the most accessible and safest application of stem cell biology to the disease processes treated by neurological surgeons. 26 …”