Stromal vascular stem cell treatment decreases muscle fibrosis following chronic rotator cuff tear

Abstract

Purpose: Rotator cuff injuries are associated with atrophy and fat infiltration into the muscle, commonly referred to as "fatty degeneration." As the poor function of chronically torn muscles may limit recovery after surgical repair, there is considerable interest in finding therapies to enhance muscle regeneration. Stromal vascular fraction stem cells (SVFCs) can improve muscle regeneration in other chronic injury states, and our objective was to evaluate the ability of SVFCs to reduce fibrosis and fat accumulation, and enhance muscle fibre specific force production after chronic rotator cuff tear.

Methods: Chronic supraspinatus tears were induced in adult immunodeficient rats, and repaired one month following tear. Rats received vehicle control, or injections of 3 × 10(5) or 3 × 10(6) human SVFCs into supraspinatus muscles.

Results: Two weeks following repair, we detected donor human DNA and protein in SVFC treated muscles. There was a 40 % reduction in fibrosis in the treated groups compared to controls (p = 0.03 for 3 × 10(5), p = 0.04 for 3 × 10(6)), and no differences between groups for lipid content or force production were observed.

Conclusions: As there has been much interest in the use of stem cell-based therapies in musculoskeletal regenerative medicine, the reduction in fibrosis and trend towards an improvement in single fiber contractility suggest that SVFCs may be beneficial to enhance the treatment and recovery of patients with chronic rotator cuff tears.

Keywords: Fatty degeneration; Fibrosis; Myosteatosis; Rotator cuff; Stromal vascular fraction stem cell.

Conflict of interest statement

Conflicts of Interest

Paul E Kosnik is an employee of Tissue Genesis, Inc., which received funding support from the Department of Defense for this study. The authors otherwise report no conflict of interest.

Figures

Figure 1

Human DNA content, immunohistochemistry, and in situ hybridization. (A) Agarose gels demonstrating species specificity for primers designed for human specific β2-microglobulin (hB2M) and rat specific β2-microglobulin (rB2M) using DNA isolated from a pure population of human SVFCs or from rat EDL muscle. (B) Percent human DNA in torn rotator cuff muscles from control (N=10), 3×105 SVFC (N=8), and 3×106 SVFC (N=8) groups. Values are mean±SE. Differences between 3×105 SVFC and 3×106 SVFC were evaluated using a t-test (α=0.05). *, significantly different (P<0.05). Representative immunohistochemistry of (C) human β2-microglobulin staining (blue, nuclei; red, human β2M) and (D) human Alu probe staining (blue, nuclei; red, dystrophin; white, human Alu probe)

Figure 2

Hydroxyproline content and ECM accumulation. (A) Hydroxyproline content from control (N=10), 3×105 SVFC (N=8), and 3×106 SVFC (N=8) groups. Values are mean±SE. Differences between groups were tested using a one-way ANOVA (α=0.05) followed by Fisher's LSD post-hoc sorting. *, significantly different from control group (P<0.05). (B) Representative images stained with DAPI (blue, nuclei) and WGA (green, ECM) from control, 3×105 SVFC, and 3×106 SVFC groups.

Figure 3

Lipid content. Relative abundance of (A) triglyceride (TAG), and (B) phospholipid (PL) species in control (N=10), 3×105 SVFC (N=8), and 3×106 SVFC (N=8) groups. A representative plate is displayed in (C) showing the TAG and PL bands in each group. Values are mean±SE. Differences between groups were tested using a one-way ANOVA (α=0.05) followed by Fisher's LSD post-hoc sorting.