Nucleated Cell Count Has Negligible Predictive Value for the Number of Colony-Forming Units for Connective Tissue Progenitor Cells (Stem Cells) in Bone Marrow Aspirate Harvested From the Proximal Humerus During Arthroscopic Rotator Cuff Repair

Abstract

Purpose: To evaluate whether nucleated cell count (NCC) could serve as an approximation for the number of colony-forming units (CFUs) in concentrated bone marrow aspirate (cBMA) obtained from the proximal humerus.

Methods: Bone marrow aspirate (BMA) was harvested from the proximal humerus in 96 patients (mean age 56.2 ± 7.0 years) during arthroscopic rotator cuff repair. Following concentration of the aspirate, nucleated cells of each sample were counted. The total number of CFUs was evaluated under the microscope at their first appearance, usually after 5 to 10 days in culture. Fluorescence-activated cell sorting analysis and assays for osteogenic, adipogenic, and chondrogenic differentiation were performed. Linear regression was assessed to predict the number of CFUs by using NCC. Age, sex, and body mass index (BMI) were evaluated as independent variables.

Results: The average volume of the obtained BMA was 86.7 ± 35.2 mL. The cBMA contained a mean of 26.3 ± 6.8 × 10⁶ nucleated cells per mL, which yielded a mean of 1421.7 ± 802.7 CFUs in cell culture. There were no significant differences in NCC or number of CFUs when sex, volume of BMA, age, or BMI was examined independently (P >.05, respectively). Linear regression found that NCC was of limited predictive value for the total number of CFUs being yielded after cell culture (r² = 0.28 with a root mean square error of 679.4).

Conclusion: NCC was of negligible predictive value for the total number of CFUs for connective tissue progenitor cells in BMA harvested from the proximal humerus during arthroscopic rotator cuff repair.

Clinical relevance: NCC is often used to assess the quality of cBMA samples for biological augmentation during surgery. The limited predictive value of this measurement tool is of clinical importance, because effectiveness of BMA applications has been suggested to depend on the concentration of progenitor cells within the sample.