Transcriptional and Histochemical Signatures of Bone Marrow Mononuclear Cell-Mediated Resolution of Synovitis

Abstract

Osteoarthritis (OA) may result from impaired ability of synovial macrophages to resolve joint inflammation. Increasing macrophage counts in inflamed joints through injection with bone marrow mononuclear cells (BMNC) induces lasting resolution of synovial inflammation. To uncover mechanisms by which BMNC may affect resolution, in this study, differential transcriptional signatures of BMNC in response to normal (SF) and inflamed synovial fluid (ISF) were analyzed. We demonstrate the temporal behavior of co-expressed gene networks associated with traits from related in vivo and in vitro studies. We also identified activated and inhibited signaling pathways and upstream regulators, further determining their protein expression in the synovium of inflamed joints treated with BMNC or DPBS controls. BMNC responded to ISF with an early pro-inflammatory response characterized by a short spike in the expression of a NF-ƙB- and mitogen-related gene network. This response was associated with sustained increased expression of two gene networks comprising known drivers of resolution (IL-10, IGF-1, PPARG, isoprenoid biosynthesis). These networks were common to SF and ISF, but more highly expressed in ISF. Most highly activated pathways in ISF included the mevalonate pathway and PPAR-γ signaling, with pro-resolving functional annotations that improve mitochondrial metabolism and deactivate NF-ƙB signaling. Lower expression of mevalonate kinase and phospho-PPARγ in synovium from inflamed joints treated with BMNC, and equivalent IL-1β staining between BMNC- and DPBS-treated joints, associates with accomplished resolution in BMNC-treated joints and emphasize the intricate balance of pro- and anti-inflammatory mechanisms required for resolution. Combined, our data suggest that BMNC-mediated resolution is characterized by constitutively expressed homeostatic mechanisms, whose expression are enhanced following inflammatory stimulus. These mechanisms translate into macrophage proliferation optimizing their capacity to counteract inflammatory damage and improving their general and mitochondrial metabolism to endure oxidative stress while driving tissue repair. Such effect is largely achieved through the synthesis of several lipids that mediate recovery of homeostasis. Our study reveals candidate mechanisms by which BMNC provide lasting improvement in patients with OA and suggests further investigation on the effects of PPAR-γ signaling enhancement for the treatment of arthritic conditions.

The clusterin connectome: Emerging players in chondrocyte biology and putative exploratory biomarkers of osteoarthritis

“…PPARG signalling is involved in skeletal muscle regeneration via growth/differentiation factor 3 (GDF3) (86). PPARG expression is upregulated in synovitis, indicating its role in mediating tissue recovery (87). Although ubiquitin carboxylterminal hydrolase (UCL1), thioredoxin-interacting protein (TXNIP), and DICER1 are among the top members of the causal network, we did not find a direct association between these factors and clusterin.…”

Intra-articular bone marrow mononuclear cell therapy improves lameness from naturally occurring equine osteoarthritis

“…Overall, our results agree with findings from an experimental model of synovial inflammation in horses, as well as clinical trials of intra-articular BMNC for OA-affected human patients ( 41–43 ). Findings from in vitro studies suggest that clinical improvements from BMNC are associated with an early pro-inflammatory response that triggers sustained increased expression of known drivers of inflammation resolution, such as IL-10, IGF-1 and peroxisome proliferator-activated receptor-gamma, and isoprenoid biosynthesis ( 40 ). However, further in vivo studies are required to explore these and other mechanisms by which BMNC drive synovial inflammation resolution.…”

“…BMNC-treated joints were histologically comparable to healthy joints while saline-treated controls remained abnormal ( 41 ). Transcriptional and histochemical investigations further revealed that BMNC induce resolution through enhanced expression of homeostatic mechanisms that combine a fine-tuned expression of pro- and anti-inflammatory mediators ( 40 ). The objective of this study was to evaluate the ability of intra-articular BMNC therapy to improve clinical signs of naturally occurring osteoarthritis in horses.…”

Future Perspectives in Oxidative Stress in Trisomy 13 and 18 Evaluation

“…CHAMP1 encodes a protein with a function in kinetochore–microtubule attachment and in the regulation of chromosome segregation. These properties are performed by their interaction and regulation of cell structure organization preceding mitosis, both of which are known to be important for proper fetal development [ 75 , 76 ]. Moreover, proper MIPEP expression is essential to maintain the normal level of mitochondrial sirtuin 3, which is considered a key regulator of oxidative stress by the deacetylation of the substrates involved in both ROS production and detoxification [ 77 , 78 , 79 ].…”