Infrapatellar Fat Pad Stem Cells Responsiveness to Microenvironment in Osteoarthritis: From Morphology to Function

Elena Stocco; Silvia Barbon; Monica Piccione; Elisa Belluzzi; Lucia Petrelli; Assunta Pozzuoli; Roberta Ramonda; Marco Rossato; Marta Favero; Pietro Ruggieri; Andrea Porzionato; Rosa Di Liddo; Raffaele De Caro; Veronica Macchi

doi:10.3389/fcell.2019.00323

Infrapatellar Fat Pad Stem Cells Responsiveness to Microenvironment in Osteoarthritis: From Morphology to Function

Front Cell Dev Biol. 2019 Dec 10:7:323. doi: 10.3389/fcell.2019.00323. eCollection 2019.

Authors

Elena Stocco^{1

2

3}, Silvia Barbon^{1

2

3}, Monica Piccione⁴, Elisa Belluzzi^{5

6}, Lucia Petrelli¹, Assunta Pozzuoli^{5

6}, Roberta Ramonda⁷, Marco Rossato⁸, Marta Favero⁷, Pietro Ruggieri⁶, Andrea Porzionato^{1

2}, Rosa Di Liddo^{3

4}, Raffaele De Caro^{1

2}, Veronica Macchi^{1

2}

Affiliations

¹ Department of Neurosciences, Institute of Human Anatomy, University of Padova, Padua, Italy.
² LifeLab Program, Consorzio per la Ricerca Sanitaria (CORIS), Padua, Italy.
³ Foundation for Biology and Regenerative Medicine, Tissue Engineering and Signaling ONLUS, Padua, Italy.
⁴ Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padua, Italy.
⁵ Musculoskeletal Pathology and Oncology Laboratory, Department of Surgery, Oncology and Gastroenterology DiSCOG, University of Padova, Padua, Italy.
⁶ Department of Orthopaedics and Orthopaedic Oncology, University of Padova, Padua, Italy.
⁷ Rheumatology Unit, Department of Medicine - DIMED, University Hospital of Padova, Padua, Italy.
⁸ Clinica Medica 3, Department of Medicine - DIMED, University of Padova, Padua, Italy.

Abstract

Recently, infrapatellar fat pad (IFP) has been considered as a source of stem cells for cartilage regeneration in osteoarthritis (OA) due to their ability for differentiation into chondrocytes. However, stressful conditions, like that related to OA, may induce a pathogenic reprograming. The aim of this study was to characterize the structural and functional properties of a new population of stem cells isolated from osteoarthritic infrapatellar fat pad (OA-IFP). Nine OA patients undergoing total knee arthroplasty (TKA) were enrolled in this study [median age = 74 years, interquartile range (IQR) = 78.25-67.7; median body mass index = 29.4 Kg/m², IQR = 31.7-27.4]. OA-IFP stem cells were isolated and characterized for morphology, stemness, metabolic profile and multi-differentiative potential by transmission electron microscopy, flow cytometric analysis, gene expression study and cytochemistry. OA-IFP stem cells displayed a spindle-like morphology, self-renewal potential and responsiveness (CD44, CD105, VEGFR2, FGFR2, IL1R, and IL6R) to microenvironmental stimuli. Characterized by high grade of stemness (STAT3, NOTCH1, c-Myc, OCT-4, KLF4, and NANOG), the cells showed peculiar immunophenotypic properties (CD73⁺/CD39⁺/CD90⁺/CD105⁺/CD44^-/+/CD45^-). The expression of HLA-DR, CD34, Fas and FasL was indicative of a possible phenotypic reprograming induced by inflammation. Moreover, the response to mechanical stimuli together with high expression level of COL1A1 gene, suggested their possible protective response against in vivo mechanical overloading. Conversely, the low expression of CD38/NADase was indicative of their inability to counteract NAD⁺-mediated OA inflammation. Based on the ultrastructural, immunophenotypic and functional characterization, OA-IFP stem cells were hypothesized to be primed by the pathological environment and to exert incomplete protective activity from OA inflammation.

Keywords: inflammation; infrapatellar fat pad; osteoarthritis; reprograming; stem cells.