Embryonic Origin And Donor Age Affect Function Of Human Bone Marrow Mesenchymal Stromal Cells

Part 1 Site-specific Characteristics of Bone Marrow Mesenchymal Stromal Cells Modify the Effect of Aging on the SkeletonBone is a self-renewing tissue. Bone marrow mesenchymal stromal cells (BMSCs) are located in the adult skeleton and are believed to be involved in the maintenance of skeletal homeostasis throughout life. With increasing age, the ability of the skeleton to repair itself decreases, possibly due to the reduced functional capacity of BMSCs. Recent evidence has suggested the existence of at least two populations of BMSCs with different embryonic origins that cannot be interchanged during cells recruitment:craniofacial BMSCs (neural crest origin) and appendicular BMSCs (mesoderm origin). Questions arise as to whether the site-specific characteristics alter the effect of aging on the skeleton. In this study, the effects of biological aging on human BMSCs were compared with BMSCs derived from craniofacial bone vs. BMSCs derived from the appendicular skeleton. The phenotype, proliferation and functional characteristics (osteogenic differentiation, cytokine secretion and bone formation in vivo) of the BMSCs were investigated. The results demonstrated that the proliferative capacity and osteogenic differentiation of the BMSCs decrease significantly with age both in vitro and in vivo. For age-matched groups, the osteogenic differentiation capacity of alveolar BMSCs was higher than that of femoral BMSCs in the middle-aged and old groups while there was no significant difference for the young groups. Compared with old alveolar BMSCs, old femoral BMSCs had a significantly longer population doubling time, a smaller colony-forming population and less bone formation in vivo while there was no significant difference for the young and middle-aged groups. Distinct differences in the expression of cytokine factors were also found. In conclusion, human BMSCs display an age-related decrease in functional capacity, and embryonic origins may play a critical role in mediating the aging rate of BMSCs. These data provide novel insights into the skeletal site-specific characteristics of aged BMSCs.Part 2 Restoration of a Critical Mandibular Bone Defect Using Human Alveolar Bone Marrow Mesenchymal Stromal CellsPeriodontal bone defects occur in a wide variety of clinical situations. Adult stem cell-and biomaterial-bone tissue regeneration is a promising alternative to natural bone grafts. Recent evidence has demonstrated that two populations of adult bone marrow mesenchymal stromal cells can be distinguished based on their embryonic origins. These BMSCs are not interchangeable, as bones preferentially heal using cells that share the same embryonic origin. However, the feasibility of tissue engineering using human craniofacial BMSCs was unclear.The goal of this study was to explore human craniofacial BMSC-based therapy for the treatment of localized mandibular defects using a standardized, minimally invasive procedure. Human alveolar BMSCs (aBMSCs) from middle aged or elderly patients were isolated painlessly, after which the characteristics of the aBMSCs were analyzed in 2-dimensional cultures and on a porous nano-hydroxyapatite/collagen/poly (L-lactide) (nHAC/PLA) scaffold.The BMSCs’ identity was confirmed based on the results of flow cytometry, immunofluorescence, and multilineage differentiation experiments. Scanning electron microscopy, a cell proliferation assay and supernatant detection indicated that the nHAC/PLA provided a suitable environment for aBMSCs adhesion, proliferation, and differentiation. Real-time PCR and electrochemiluminescence immunoassays demonstrated that osteogenic markers were upregulated by osteogenic pre-induction. Moreover, in a rabbit critical-size mandibular bone defect model, total bone formation in the nHAC/PLA+aBMSCs group was significantly higher than in the nHAC/PLA group but significantly lower than in the nHAC/PLA+ pre-induced aBMSCs and autogenous bone. These findings demonstrate that this method of producing engineered bone is a valid alternative for the correction of mandibular bone defects.