Abstract

Objectives: Traditionally, knee injections for the treatment of knee osteoarthritis (OA) have included corticosteroid with local anesthetic and hyaluronic acid (HA), but more recent investigations have delved into the potential benefits of biologic injections such as platelet-rich plasma (PRP), bone marrow aspirate concentrate (BMAC), and autologous conditioned serum (ACS). While positive clinical results have been seen with the clinical use of commercial ACS products, there are limitations currently precluding its widespread acceptance and use. These challenges include the preparation time and storage requirements, patient variability in both pro- and anti-inflammatory cytokine profiles, and lack of regulatory approval of a commercial product in the United States. The development of an allogenic freeze-dried ACS product with an unaltered cytokine profile that remains stable at room temperature and would allow for easy storage, transport, and delivery to clinical settings. The purpose of the present study is to (1) compare the composition of freeze-dried allogenic conditioned serum (FD-CS) to fresh ACS and (2) to investigate the response of human knee cartilage after exposure to FD-CS and ACS to determine whether freeze-drying (lyophilization) affects the biological activity of conditioned serum products. Methods: Cartilage explants were collected from 6 patients undergoing total knee arthroplasty. ACS and FD-CS were created from patient serum samples. Cartilage samples were divided into 6 groups: (1) untreated control, (2) control + ACS, (3) control + FD-CS, (4) IL-1β (5 ng/ml), (5) IL-1β + ACS, and (6) IL-1β + FD-CS. After 10 days of incubation, samples were analyzed and compared for DNA normalized glycosaminoglycan (GAG) content, cytokine contents, and histological characterization (Figure 1). Results: There was a significant decrease in pathology scoring for ACS (p = 0.0368) or FD-CS (p = 0.0368) in the presence of IL-1 compared to the control (Figure 2). Both ACS and FD-CS significantly mitigate the IL-1β induced increase in FGF (p = 0.0009 and p = 0.0002, respectively) (Figure 3). FD-CS showed a significant increase in IL-1Ra (Figure 4) and decrease in the IL-1β concentration in the presence of IL-1β compared to the control (p < 0.0001 and p < 0.0001). ACS treated samples had significantly higher concentration of TNF-α independent of IL-1 (p = 0.0053). Conclusions: Explanted osteoarthritic cartilage responds favorably and equivalently to treatment with ACS and FD-CS from a histological perspective. Both ACS and FD-CS were able to mitigate the IL-1β induced increases in FGF, and FD-CS lowers IL-1β concentration while increasing IL-1Ra concentration. While the cytokine profile of the FD-CS was slightly altered when compared to ACS, it does not affect its biologic activity.