Autologous bone marrow stromal cells are promising candidates for cell therapy approaches to treat bone degeneration in sickle cell disease.

Osteonecrosis of the femoral head is a frequent complication in adult patients with sickle cell disease (SCD). To delay hip arthroplasty, core decompression combined with concentrated total bone marrow (BM) treatment is currently performed in the early stages of the osteonecrosis. Cell therapy efficacy depends on the quantity of implanted BM stromal cells. For this reason, expanded bone marrow stromal cells (BMSCs, also known as bone marrow derived mesenchymal stem cells) can be used to improve osteonecrosis treatment in SCD patients. In this study, we quantitatively and qualitatively evaluated the function of BMSCs isolated from a large number of SCD patients with osteonecrosis (SCD-ON) compared with control groups (patients with osteonecrosis not related to SCD (ON) and normal donors (N)). BM total nuclear cells and colony-forming efficiency values (CFE) were significantly higher in SCD-ON patients than in age and sex-matched controls. The BMSCs from SCD-ON patients were similar to BMSCs from the control groups in terms of their phenotypic and functional properties. SCD-ON patients have a higher frequency of BMSCs that retain their bone regeneration potential. Our findings suggest that BMSCs isolated from SCD-ON patients can be used clinically in cell therapy approaches. This work provides important preclinical data that is necessary for the clinical application of expanded BMSCs in advanced therapies and medical products.

Development of a simple procedure for the treatment of femoral head osteonecrosis with intra-osseous injection of bone marrow mesenchymal stromal cells: study of their biodistribution in the early time points after injection.

INTRODUCTION: Osteonecrosis of the femoral head (ONFH) is a degenerative disease progressing to a femoral head (FH) collapse. Injection of osteoprogenitor cells like bone marrow mesenchymal stromal cells (BMSCs) into the FH appears to be a good therapeutic treatment. However, safety and efficacy of BMSCs to treat bone defect are the main preclinical data required for clinical application. Efficacy and the lack of risk of cell transformation after amplification of BMSCs have been extensively described. The main objectives of this study were to develop a simple and usable procedure for clinicians and control its feasibility by evaluating the biodistribution of BMSCs after injection into the FH in a large animal model. The impact of this approach was evaluated on one natural pig ONFH. METHODS: BMSCs were directly injected in the pig FH, and then the biodistribution of grafted cells was detected by quantitative real-time polymerase chain reaction, cytometry, or a combination of classic histology analysis and in situ hybridization (ISH). BMSC efficacy on bone regeneration was evaluated by magnetic resonance imaging (MRI) and histology. RESULTS: After 30-minute and 24-hour follow-up, grafted cells were detected at the injection site and no BMSCs were detected in filter organs or body fluids. The combination of classic histology analysis and ISH showed a good homogeneity of cell distribution in FH. Local delivery of BMSCs onto a bone scaffold associated with bone formation in vivo confirmed the preferential tropism of BMSCs to the bone tissue as well as their efficacy to form bone. Treatment of a natural pig ONFH by autologous BMSCs indicated a beginning of bone healing as early as 2 weeks with a complete healing after 9 weeks. At this stage, MRI and histological analysis were similar to those of a normal FH. CONCLUSIONS: Intra-osseous injection of BMSCs in FH seems to be a good strategy for ONFH treatment as the safety concerning the biodistribution of BMSCs is ensured. Moreover, the efficacy of BMSCs in natural ONFH seems to indicate that this is a promising approach. Altogether, these results constitute the preclinical data necessary for the setup of a clinical application with expanded BMSCs in the context of advanced therapy medicinal products.

Bone-Forming Capacity and Biodistribution of Bone Marrow-Derived Stromal Cells Directly Loaded Into Scaffolds: A Novel and Easy Approach for Clinical Application of Bone Regeneration.

In the context of clinical applications of bone regeneration, cell seeding into scaffolds needs to be safe and easy. Moreover, cell density also plays a crucial role in the development of efficient bone tissue engineering constructs. The aim of this study was to develop and evaluate a simple and rapid cell seeding procedure on hydroxyapatite/ß-tricalcium phosphate (HA/ßTCP), as well as define optimal cell density and control the biodistribution of grafted cells. To this end, human bone marrow-derived stromal cells (hBMSCs) were seeded on HA/ßTCP scaffolds, and we have compared bone formation using an ectopic model. Our results demonstrated a significantly higher bone-forming capacity of hBMSCs directly loaded on HA/ßTCP during surgery compared to hBMSCs preseeded for 7 days in vitro on HA/ßTCP before ectopic implantation. The extent of new bone formation increases with increasing hBMSC densities quantitatively, qualitatively, and in frequency. Also, this study showed that grafted hBMSCs remained confined to the implantation site and did not spread toward other tissues, such as liver, spleen, lungs, heart, and kidneys. In conclusion, direct cell loading into a scaffold during surgery is more efficient for bone regeneration, as well as quick and safe. Therefore direct cell loading is suitable for clinical requirements and cell production control, making it a promising approach for orthopedic applications. Moreover, our results have provided evidence that the formation of a mature bone organ containing hematopoietic islets needs a sufficiently high local density of grafted hBMSCs, which should guide the optimal dose of cells for clinical use.

Platelet lysate coating on scaffolds directly and indirectly enhances cell migration, improving bone and blood vessel formation.

Suitable colonization and vascularization of tissue-engineered constructs after transplantation represent critical steps for the success of bone repair. Human platelet lysate (hPL) is composed of numerous growth factors known for their proliferative, differentiative and chemo-attractant effects on various cells involved in wound healing and bone growth. The aim of this study was to determine whether the delivery of human mesenchymal stromal cells (hMSC) seeded on hPL-coated hydroxyapatite/ß-tricalcium phosphate (HA/ß-TCP) scaffolds could enhance vascularization and bone formation, as well as to investigate the mechanisms by which hMSC participate in tissue regeneration. Our study demonstrates that hPL can be coated on HA/ß-TCP scaffolds, which play direct and indirect effects on implanted and/or resident stem cells. Effectively, we show that hPL coating directly increases chemo-attraction to and adhesion of hMSC and endothelial cells on the scaffold. Moreover, we show that hPL coating induces hMSC to produce and secrete pro-angiogenic proteins (placental growth factor and vascular endothelial growth factor) which allow the proliferation and specific chemo-attraction of endothelial cells in vitro, thus improving in vivo neovascularization and new bone formation. This study highlights the potential of functionalizing biomaterials with hPL and shows that this growth factor combination can have synergistic effects leading to enhanced bone and blood vessel formation.