"Cellularity as a predictive tool for mesenchymal stem cell concentration in bone marrow concentrates: Implications...

Mesenchymal stem cells (MSCs) derived from bone marrow play an increasingly important role in regenerative medicine due to their capacity to promote tissue regeneration in various clinical contexts. Applications include the treatment of osteoarthritis, bone regeneration post-injury, and the management of conditions such as Crohn's disease, alopecia, and nervous system reconstruction. Accurate quantification of MSCs within Bone Marrow Concentrates (BMCs) is essential for ensuring the quality and efficacy of these cell therapy products in clinical settings.

This study aims to quantify the population of CD271⁺ and CD45^- cells in BMCs prepared using the method we have selected and to provide a basis for comparing these results with other BMC products. Additionally, we seek to determine whether the total cell count in BMCs can serve as a reliable indicator of MSC numbers and if cellularity (the number of cells per ml) can predict a higher percentage of MSCs within the population.

Bone Marrow Aspirates (BMA) were collected from 41 patients undergoing knee or hip arthroplasty. Aspirates were processed using density gradient centrifugation and positive selection of CD271⁺ cells. Flow cytometry was applied to analyze cell subsets, and cell counts were determined with a NucleoCounter. The relationships between BMA cellularity (total cells per ml), MSC concentration (MSC count per ml), and MSC percentage (the proportion of MSCs within the total cell population) were assessed.

The mean percentage of CD271⁺ CD45^- cells in bone marrow samples was 0.03 % (SD 0.03 %). Cellularity varied significantly among samples, with a mean of 6 million cells/ml (SD 8.7 million cells/ml). A strong correlation was observed between BMC cellularity and MSC concentration (p < 0.05), although no correlation was found between cellularity and the MSC percentage.

Despite high variability in cellularity, the concentration of MSCs correlated strongly with BMC cellularity, suggesting that total cell counts can be used to estimate MSC numbers in BMCs. However, cellularity is not an indicator of a particularly high MSC content. This study supports the use of cell counts as a measure for estimating MSC concentration in BMCs. Future research should focus on establishing direct comparisons with other BMC products and exploring factors influencing cellularity and MSC percentages to enhance BMC quality for clinical applications.