Qualitative comparison between equine bone marrow- and blood-derived autologous conditioned serum

Abstract

Autologous conditioned serum (ACS) is an orthobiological preparation that is obtained from the patient's own blood after an incubation period and commonly used for the treatment of osteoarthritis in the equine practice. The anti-catabolic and anabolic effects of the product are determined by the blood cell-derived (such as PDGF-BB, TGF-β1 and IL-IRa, mainly originating from platelets and leucocytes) and plasma-derived (such as IGF-1, mainly originating from the liver) mediators contained in the serum. The anti-inflammatory molecule IL-1 Ra, being primarily produced by leucocytes in blood, is of particular interest, since it inhibits the catabolic effect of IL-1 which plays a central role in the development and progression of osteoarthritis. Red bone marrow contains different cell types, such as megakaryocytes, thrombocytes, leucocytes and progenitor cells which are rich sources of growth factors and other cytokines, as well. Thus, bone marrow could potentially be used as a substrate for the preparation of ACS. The aims of this study were therefore to determine if (1) bone marrow is a possible substrate for ACS production and (2) whether bone marrow-derived ACS contains higher cytokine concentrations than the respective blood-derived ACS. For the first objective of this study, bone marrow was harvested from 12 adult Warmblood horses and processed to obtain bone marrow supernatant (KMÜ) and bone marrow ACS (KM-ACS). A commercial device was used to produce KM-ACS. A small fraction of KMÜ was used for cytological analysis, performed with an automated cell counter. One half of the remaining volume of the KMU was treated with a detergent (LysKMU) to induce cell lysis and the subsequent release of their content, whereas the rest of the volume remained untreated. The respective IGF-1, PDGF-BB, TGF-β1, and IL-IRa concentrations were measured with ELISA-Kits and compared between the three different preparations. For the second part of this study, venous blood was drawn concomitantly to bone marrow aspiration from 10 horses included in the first part. Blood-derived ACS (Blut-ACS) and KM-ACS were simultaneously produced. The concentrations of the four afore-mentioned cell mediators were determined in KM-ACS and Blut-ACS, and compared between the two products. In the first part of the study, the median IGF-1 concentrations did not differ significantly between the products. The mean values of PDGF-BB in LysKMÜ and KM-ACS were significantly higher than in KMÜ. The highest mean TGF-β1, concentration was measured in KM-ACS and was significantly higher than the value in KMÜ. The median IL-IRa concentrations in KM-ACS and Lys-KMÜ were significantly higher than in KMÜ. In part 2, Blut-ACS showed a significantly higher median IGF-1 and mean PDGF-BB concentration than KM-ACS. Mean TGF-β1 and median IL-1 Ra concentration did not show significant differences between the two products. According to the results of this study, bone marrow can be used as a substrate to produce ACS, since all four cytokines were enriched compared to non-processed bone marrow supernatant (KMÜ). However, only IL-1 Ra concentration was higher in bone marrow-derived ACS (KM-ACS) than in bloodderived ACS (Blut-ACS) and the three other mediators were more elevated in Blut-ACS. Therefore, the use of bone marrow cannot be recommended for the production of ACS, because of the more invasive aspiration technique. On the other side, since other cytokines, which are potentially also playing a role in tissue repair, may be present in higher concentrations in bone marrow-derived ACS, further in vitro-studies are needed to obtain more information. Moreover, in vivo-studies are needed to assess the clinical meaning of these in vitroresults, because higher cytokine concentrations do not necessarily imply a better clinical effect.