Enhanced Medial Collateral Ligament Healing Using Mesenchymal Stem Cells: Dosage Effects on Cellular Response and Cytokine Profile

Abstract

Mesenchymal stem cells (MSCs) have potential therapeutic applications for musculoskeletal injuries due to their ability to differentiate into several tissue cell types and modulate immune and inflammatory responses. These immune-modulatory properties were examined in vivo during early stage rat medial collateral ligament healing. Two different cell doses (low dose 1×106 or high dose 4×106 MSCs) were administered at the time of injury and compared with normal ligament healing at days 5 and 14 post-injury. At both times, the high dose MSC group demonstrated a significant decrease in M2 macrophages compared to controls. At day 14, fewer M1 macrophages were detected in the low dose group compared to the high dose group. These results, along with significant changes in procollagen I, proliferating cells, and endothelialization suggest that MSCs can alter the cellular response during healing in a dose-dependent manner. The higher dose ligaments also had increased expression of several pro-inflammatory cytokines at day 5 (IL-1β, IFNγ, IL-2) and increased expression of IL-12 at day 14. Mechanical testing at day 14 revealed increased failure strength and stiffness in low dose ligaments compared to controls. Based on these improved mechanical properties, MSCs enhanced functional healing when applied at a lower dose. Different doses of MSCs uniquely affected the cellular response and cytokine expression in healing ligaments. Interestingly, the lower dose of cells proved to be most effective in improving functional properties.

Chondrogenic Priming at Reduced Cell Density Enhances Cartilage Adhesion of Equine Allogeneic MSCs - a Loading Sensitive Phenomenon in an Organ Culture Study with 180 Explants

“…In addition, all low cell density treated explants demonstrated adhered MSCs to their surface, whereas this was not the case for the high cell density treatment. Although dose-dependent effects have been reported for allogeneic MSCs for the treatment of myocardial infarction in rats [38] and graft versus host disease in mice [39], others have also demonstrated a superior outcome using a lower density of allogeneic MSCs for treatment of injured medial collateral ligaments of rat knees [40] or for the treatment of human knee osteoarthritis [41]. As clump formation did not differ between the cell density groups, the difference was unlikely due to steric obstruction.…”

Mesenchymal Stem Cell Therapy on Tendon/Ligament Healing

“…In vitro studies of macrophages co-cultured with bone marrow-derived MSCs produced high levels of the anti-inflammatory factors CD206 (a marker for M2 macrophages) and IL-10, as well as low levels of inflammatory cytokines IL-12 and TNF-α [8]. In vivo studies from our lab examined MSC-mediated immune modulation during ligament healing from a dose-dependent perspective [9]. Specifically, injured rat medial collateral ligaments (MCLs) were treated with either 1 × 10 6 (low dose) or 4 × 10 6 (high dose) allogeneic MSCs [9].…”

“…In vivo studies from our lab examined MSC-mediated immune modulation during ligament healing from a dose-dependent perspective [9]. Specifically, injured rat medial collateral ligaments (MCLs) were treated with either 1 × 10 6 (low dose) or 4 × 10 6 (high dose) allogeneic MSCs [9]. Within the early healing ligament, fewer M1 macrophages localized within the low dose group resulting in lower amounts of inflammatory cytokines (IL-1α, IL-12 and IFN-γ) than the high dose MSC group (Figure 2) [9].…”

“…Specifically, injured rat medial collateral ligaments (MCLs) were treated with either 1 × 10 6 (low dose) or 4 × 10 6 (high dose) allogeneic MSCs [9]. Within the early healing ligament, fewer M1 macrophages localized within the low dose group resulting in lower amounts of inflammatory cytokines (IL-1α, IL-12 and IFN-γ) than the high dose MSC group (Figure 2) [9]. The low dose group also increased failure strength and stiffness of the healing MCL, improving functional behavior.…”

Orthopedic cellular therapy: An overview with focus on clinical trials

“…Autologous adipose derived stem cells are sufficient in number to heal or regenerate the damaged tendons. Dosage effects on cellular responses and cytokine profiles have been reported [13] . Interestingly, the lower dose of cells proved to be more effective in improving functional properties.…”