The Reduced Quantity and Functionality of Mesenchymal Stem Cells in the Synovium of Charcot Neuroarthropathy

Abstract

Category: Basic Sciences/Biologics Introduction/Purpose: Managing Charcot Neuroarthropathy (CNA) remains a challenge facing the foot and ankle surgeons. Lack of understanding the pathogenesis of the disease prevents the development of novel therapies. Our previous studies revealed the involvement of fibroblast-like synoviocytes in the pathology of CNA. Residing in the synovium are also mesenchymal stem cells (MSCs), which maintain tissue homeostasis. In this study, MSCs isolated from the synovium of CNA and non-CNA patients were comparatively analyzed for their potential role in the pathology of CNA. Methods: Synovial samples were collected from CNA patients (n=7) and patients with osteoarthritis or intraarticular fracture (non-CNA; n=7), during foot and ankle procedures (approved by IRB). The synovial samples were minced and digested with 0.1% collagenase to isolate MSCs. The cells were plated and cultured in low density for counting colony-forming units-fibroblast (CFU- F), which is indicative of the number of MSCs. The colonies formed by CNA-MSCs and non-CNA MSCs were further characterized by size and imaging density. CNA-MSCs and non-CNA MSCs were cultured in adipogenic, osteogenic and chondrogenic differentiation media. The differentiation potentials of CNA-MSCs and non-CNA MSCs were assessed with histochemical staining and quantitative gene expression. Results: CFU-F: The number of colonies formed by CNA-MSCs was 6 ± 3.5 per (1/2) plate, while it was 43 ± 21.6 by the non- CNA MSCs (p < 0.05; Fig 1). The average size (pixels) of colonies was smaller in the CNA-MSCs than the non-CNA MSCs (4780 vs. 7960). When the colonies were stratified into high, medium and low density subgroups, colonies formed by the CNA-MSCs had a reduced density compared with the non-CNA MSCs (30±6 vs. 35±10) in the high density subgroup. Differentiation: Expression of adipogenic marker gene PPAR-γ by CNA-MSCs was less than half of that by non-CNA MSCs. The expression of osteogenic marker gene RUNX2 by CNA-MSCs was a third of that by the non-CNA MSCs. Similarly, the expression of chondrogenic marker genes, including SOX9 and type II collagen, by the CNA-MSCs declined as compared with the non- CNA MSCs. Conclusion: The synovium in CNA joints had fewer MSCs and that may impact joint’s response to inflammation and tissue repair. Furthermore, CNA-MSCs were declined in differentiation potentials. Analyses of the size and density of the colonies formed by CNA-MSCs showed that a subpopulation of MSCs was particularly affected. Further study will focus on the pathological role of the high-density subpopulation of MSCs in the development of CNA.