12/28/2023 0 Comments Nod scid gammaWhile human hematopoietic cell number increased in the animals’ bone marrow and peripheral blood between the 3 -week and 6-week time points following HSPC transplantation, hBMSC numbers in the injected marrow cavity approximately halved over the 6-week period. In a model where both hBMSC and human HSPC were co-transplanted via direct bone marrow injection, HSPC engraftment was enhanced by the inclusion of hBMSC. Another study demonstrated that irradiation of a localized tissue site induced homing of hBMSC, as well as promoted their widespread engraftment into multiple organs distal from the localized irradiation. When hBMSC were transplanted via intravenous injection into immune-compromised mice conditioned with sublethal irradiation, hBMSC could be found in tissues such as the spleen, muscles, liver, lungs, and bone marrow. In this study, we sought to characterize how hBMSC behave when transplanted directly into the marrow cavities of mice that either had or had not been pre-conditioned with sublethal irradiation.įew studies have explored the different routes of hBMSC injection in immune-compromised mice and pre-conditioning of these animals with irradiation. While bone marrow-derived stromal cells (BMSC, also known as “mesenchymal stem cells”) are viewed as a critical component of the bone marrow microenvironment and are known to have a direct impact on HSPC engraftment or in cancer metastasis, it is not well understood how human BMSC (hBMSC) behave when directly injected into a murine marrow cavity. Direct bone marrow injection of cells into the marrow cavity of mice is commonly used to study hematopoietic stem progenitor cell (HSPC) transplantation, or to study the behavior of cancer cells. The mouse is a common biomedical model organism. Experimental designs should consider how relative hBMSC distribution and local hBMSC densities evolve over time. The transient high-density population of hBMSC within the injected femur, or the longer-term low-density population of hBMSC in distal marrow cavities, offers useful models for studying disease or regenerative processes. Individual cell clusters may have arisen from discrete clones that homed to the marrow, and then underwent modest proliferation. Clusters of hBMSC-Luc/GFP were observed in the histology of distal marrow cavities, suggesting that some transplanted cells actively homed to distal marrow cavities. Irradiation of mice prior to transplant only delayed the rate of hBMSC-Luc/GFP population decline in injected femurs. While significant numbers of hBMSC-Luc/GFP could be deposited into the mouse bone marrow via direct bone marrow injection, IVIS imaging indicated that the number of hBMSC-Luc/GFP in that bone marrow cavity declined with time. At 4 weeks, hBMSC-Luc/GFP colonized injected marrow cavities and distal marrow cavities at rates of 2.5 ± 2.2% and 1.7 ± 1.9% of total marrow nucleated cells, respectively in both irradiated and non-irradiated mice. In distal marrow cavities, hBMSC were not uniformly distributed and appeared to be co-localized in clusters, with the majority found in the endosteal region. HBMSC-Luc/GFP number within injected marrow cavities declined rapidly over 4 weeks, but prior irradiation of animals delayed this decline. hBMSC-Luc/GFP were tracked in live animals using IVIS imaging, and histology was used to further characterize hBMSC location and behavior in tissues. One day after conditioning NSG mice with sublethal irradiation, 5 × 10 5 luciferase (Luc) and green fluorescent protein (GFP)-expressing hBMSC (hBMSC-Luc/GFP) were injected into the right femurs of animals. Herein, we characterized hBMSC engraftment and persistence within the bone marrow of NOD- scid interleukin (IL)-2γ −/− (NSG) mice with or without prior 2 Gy total-body γ-irradiation of recipient mice. ![]() ![]() While human bone marrow-derived stromal cells (hBMSC, also known as mesenchymal stem cells (MSC)) are frequently described in therapeutic applications, or disease modeling, their behavior following direct injection into murine bone marrow is poorly characterized. ![]() Direct bone marrow injection of cells into murine marrow cavities is used in a range of cell characterization assays and to develop disease models.
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