The Biological Fitness of Bone Progenitor Cells in Reamer/Irrigator/Aspirator Waste

BACKGROUND

The biological waste collected during use of the Reamer/Irrigator/Aspirator (RIA; DePuy Synthes) has been described as an abundant source of bone progenitor cells with a comparable osteogenic gene profile to donor-matched iliac crest bone marrow (IC-BM). However, it is not clear whether these RIA-waste (RIA-W) cells are biologically fit. We aimed to evaluate the stress levels and functions of RIA-W progenitor cells.

METHODS

Reactive oxygen species (ROS) levels were tested in freshly collected bone progenitor cells (defined as CD45CD271 cells) using flow cytometry. ROS levels induced in these cells by hypoxia and/or oxidative stress as well as by an experimental simulation of the RIA procedure were also measured. Furthermore, the alkaline phosphatase (ALP) expression levels, proliferation, and senescence of culture-expanded RIA-W and IC-BM mesenchymal stromal cells (MSCs) were compared.

RESULTS

RIA-W and donor-matched IC-BM CD45CD271 cells were 97% and 98% viable, but the ROS levels were significantly higher for RIA-W cells than for IC-BM cells (p = 0.0020). Also, ROS induced by hypoxia, oxidative stress, and both were higher for RIA-W cells (p = 0.0312, 0.0156, and 0.0703, respectively). Dilution with saline solution, suction pressure, and irrigation reduced cell viability, with a positive correlation with the ROS level (p = 0.0035). The RIA-W and IC-BM colony-forming cells (average, 96,100 and 11,500, respectively) showed comparable ALP levels. Furthermore, culture-expanded RIA-W and IC-BM MSCs showed comparable ROS levels, ALP levels, susceptibility to death, and proliferation.

CONCLUSIONS

Although freshly collected RIA-W bone progenitor cells appeared to be transiently stressed, these cells were as viable as IC-BM cells and present in greater numbers. The proliferation and osteogenesis of both cell types were comparable.

CLINICAL RELEVANCE

The RIA waste bag contains bone progenitor cells with promising potential for regenerative applications, and should not be wasted.

NSAIDS inhibit in vitro MSC chondrogenesis but not osteogenesis: implications for mechanism of bone formation inhibition in man

The non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for analgesia but may inhibit bone formation. We investigated whether the reported NSAID effect on bone is related to inhibition of bone marrow mesenchymal stem cell (MSC) proliferation and osteogenic and chondrogenic differentiation and evaluated both cyclooxygenase (COX)-1 and COX-2 specific drugs. The effects of seven COX-1 and COX-2 inhibitors on MSC proliferation and osteogenic and chondrogenic differentiation were tested using Vybrant, sodium 3'-[1-(phenylaminocarbonyl)- 3,4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid hydrate (XTT), functional and quantitative assays of MSC differentiation. The MSC expression of COX-1 and COX-2 and prostaglandin E2 (PGE-2) levels were evaluated serially during lineage differentiation by quantitative PCR and ELISA. None of the NSAIDs at broad range of concentration (range 10(-3) to 100 μg/ml) significantly affected MSC proliferation. Surprisingly, MSC osteogenic differentiation inhibition was not evident. However, NSAIDs affected chondrogenic potential with a reduction in sulphated glycosaminoglycans (sGAG) content by 45% and 55% with diclofenac and ketorolac, respectively (P < 0.05 compared to controls). Parecoxib and meloxicam, more COX-2 specific reagents inhibited sGAG to a lesser degree, 22% and 27% respectively (P < 0.05 compared to controls). Cartilage pellet immunohistochemistry confirmed the above results. Pellet chondrogenesis was associated with increased COX-1 expression levels but not COX-2, and COX-1 specific drugs suppressed MSC PGE-2 more than COX-2 specific inhibitors. These findings suggest that NSAIDs may inhibit bone formation via blockage of MSC chondrogenic differentiation which is an important intermediate phase in normal endochondral bone formation.