gms | German Medical Science

Objectives: Osteoarthritis (OA) is a common and chronic joint disease, with structural damage in all joint tissues. The main symptom of OA is pain, which is a priori treated with NSAIDs, followed by drugs and surgery, involving health risks and side effects. Nanofat is used as an alternative pain therapy for OA, whereby the autologous nanofat is injected into the affected joint. This minimal invasive procedure results in lasting pain relief with fewer risks and side effects. The source of the pain-reducing properties of nanofat is not known. Processing from aspirated fat tissue to nanofat can be performed by specific filter systems, i.e. Adinizer^® and Lipocube NanoTM. The aim of this study was to compare the effects of differently processed nanofat samples in an in vitro OA-model.

Methods: Chondrocytes and synovial fibroblasts (SF) were isolated from OA knee explants and cultivated in monolayers. Lipoaspiration was performed on patient's abdomen and the aspirated fat tissue was divided into: i) unprocessed (native fat), ii) processed by Lipocube NanoTM filter (Lipocube-nanofat), and iii) processed by Adinizer^® filter to nanofat (Adinizer-nanofat). These three fat groups were centrifuged and the fluid phases, consisting of the hydrophilic secretome of the stromal vascular fraction, were added in different dilutions to OA-chondrocytes and -SF, respectively. Changes of the viability (CellTiter-Blue), apoptosis (caspase-3/7 activity), senescence (SA-β-Gal activity), migration, and mRNA expression (qPCR) were analysed. Native fat, Lipocube-nanofat and Adinizer-nanofat were screened for cytokines, complement factors, growth factors, matrix metalloproteinases (MMPs), and tissue inhibitor of MMPs (TIMPs) by Multiplex-ELISA.

Results and conclusion: We observed decreased viability of chondrocytes after incubation with all three fat groups. The apoptosis rate of SF was increased after all fat treatments. Chondrocytes treated with native fat migrated significantly faster, while SF indicate a similar tendency. The senescence state was affected by native fat with decreased SA-β-Gal activity in chondrocytes and increased SA-β-Gal activity in SF. The gene expression of chondrogenic markers COMP, SOX9, COL2A1 was reduced for all fat treatments compared to cells without fat incubation, whereas COL1A1 expression was only decreased in chondrocytes treated with Adinizer-nanofat. While IL6 mRNA expression was increased in chondrocytes incubated with all respective fat groups, only the Adinizer-nanofat-treated SF secreted more IL6. High protein yields of CFD and of TIMP-1/2 were detected, while the concentration of IL-10 and VEGF was comparably low.

So far, the functional assays did not show crucial differences between the Lipocube-nanofat and Adinizer-nanofat treatments of chondrocytes and SF, except in gene expression. More detailed analyses of native fat and nanofat compositions are needed for a better understanding of the analgesic effect in OA therapy.