Temporal monitoring of pO2 in stem cell cultures : a potential tool for directed differentiation

Problem The objective of this in-vivo study is to investigate the histologic effects of MSC and PRP therapy on ligament healing in a rat medial collateral ligament (MCL) injury model. Background Cell therapy for cartilage and ligament injuries has become a widely debated topic in the orthopaedic literature. Adult mesenchymal stem cells (MSCs) are of interest given their high capacity for self-renewal and multipotency to differentiate into chondrocytes and tenocytes. Platelet rich plasma (PRP) has been reported to promote collagen synthesis and cell proliferation, influencing the healing of ligaments and cartilage. Hypothesis We hypothesize that the addition of MSCs to an injured Rat MCL will show increase collagen regeneration when compared to controls and those MCLs treated with PRP. Research MCLs of 20 female Sprague rats were bilaterally transected and treated with either saline or 1 of 3 treatment groups; (1) MSCs (10^5cells), (2) MSCs + PRP, and (3) PRP. Ratswere sacrificed 16 days post-surgery and the MCLs harvested, fixed in formalin, processed routinely and stained with H&E and Alcian blue. Histological analysis was performed by a pathologist blinded to the treatment groups, and the tissue specimens were graded based on the degree of cellularity (0-+3), change in collagen representing new or regenerative collagen fibers (0-+3), vascularity (0-+2) and inflammation (0-+3). Statistical analysis was performed using Analysis of variance (ANOVA) and Fischers exact test. Observations The degree of cellularity and change in collagen fibers were statistically significantly increased between the four groups (p<.0032). Paired comparisons between groups demonstrated that all treatment groups had increased cellularity and collagen changes when compared to controls but not between the experimental groups. Alcian blue staining revealed increased extracellular matrix within treatment groups (MSCs= avg. grade of 1.33, MSCs & PRP = avg. grade of 2.67 and PRP = avg. grade of 2) when compared to the control (avg. grade of 1). The addition of MSCs and/or PRP to an injured MCL increases cellularity and the regeneration of collagen fibers in the setting of an acute MCL injury when compared to controls. While not significant, there was a trend towards even higher cellularity and collagen fiber regeneration in the treatment group treated with MSC and PRP, indicating a possible potentiation effect between the two treatments. This study suggests improved ligament healing with MSC and PRP treatment and that biomechanical testing is warranted to explore whether this treatment will result in improved biomechanical properties of MCL injuries.