Human Bone Marrow Mononuclear Cells

Human Bone Marrow Mononuclear Cells Do Not Improve Limb Perfusion in the Hindlimb Ischemia Model

Effective treatments for chronic limb-threatening ischemia are lacking. Studies on using bone marrow (BM) mononuclear cells (MNCs) and BM-derived mesenchymal stromal cells (MSCs) have shown variable results, and no studies have directly compared human BM MNCs and BM MSCs in in vivo models. van Rhijn-Brouwer et al. studied the effects of intramuscular administration of human BM MNCs and MSCs on limb perfusion in a murine hindlimb ischemia (HLI) model.

On day 0, mice underwent femoral ligation and received intramuscular injections of the prepared cells on day 1. Average relative perfusion was 17% on day 0 and 31% on day 1 (Fig. 1A). No animals were lost during surgery or excluded due to relative perfusion >50% on day 1. There were no adverse events from cell implantation, no limbs were lost, and no premature mortality occurred before the planned end. Thus, no animals reached a humane endpoint. Relative perfusion of the ligated limb versus the control limb is shown in Fig. 1A. Two-way ANOVA with Dunnett correction showed that at day 14, BM MNCs did not improve perfusion over vehicle, while BM MSCs significantly outperformed both BM MNCs and vehicle. For subgroup analysis, they calculated the AUC for each animal. There was no difference between vehicle and the three BM MNC doses (Fig. 1B). For BM MSCs, the 0.1 and 0.3 M groups were significantly better than vehicle (Fig. 1C), while the 1 M group was not, suggesting a nonlinear dose-response relationship with an optimum at the lowest dose.

Enhancing One-Step Membrane Technique for Large Bone Defects with CD8-Depleted BMC in Rat Model

The one-step membrane technique using a human acellular dermal matrix (hADM) is an experimental method for treating large bone defects. This technique eliminates the need for the Masquelet membrane induction step, shortening the procedure while maintaining effectiveness. However, previous studies showed that colonizing hADM with bone marrow mononuclear cells (BMC) worsens healing, likely due to the presence of CD8+ lymphocytes, which negatively affect bone regeneration. Pemma-Martinez et al. investigate whether the negative impact of BMC on bone healing is due to the CD8+ cell population.

The bending stiffness of the defect zone was measured 8 weeks after grafting using a three-point bending test. Animals receiving hADM+BMC-CD8 had a notable increase in femoral bending stiffness (median: 11.7%; IQR 5.2-44.5) compared to the hADM+BMC group (median: 0.8%; IQR 0.17-6.7), but not compared to the hADM group (median: 3.3%; IQR 0.3-23.6) (Fig. 2). Defect bridging, callus volume, and bone mineral density were selected as relevant factors to assess bone healing. These parameters were obtained from µCT data. Implantation of hADM+BMC-CD8 resulted in a significantly increased ratio of osseous-bridged bone defects compared to hADM+BMC, but not compared to hADM. An increase in the BV/TV ratio was observed in animals transplanted with hADM+BMC-CD8 compared to hADM and hADM+BMC. The hADM+BMC-CD8 group had significantly higher BMD than the hADM+BMC+CD8 group (median 0.54 g/cm³, IQR 0.42-0.73), but the comparison with the hADM group was not significant (p = 0.14). Radiological findings were generally confirmed by bone histology. Analysis of Movat's pentachrome stained histology slides showed that bone formation was more pronounced in defects treated with hADM+BMC-CD8 (56%, IQR 53-62) compared to hADM+BMC (44%, IQR 36-52) and hADM (45%, IQR 30-54) (Fig. 3).