Autologous Mesenchymal Stem Cell-Mediated Repair of Tendon

TLDR

Mesenchymal stem cells were isolated from rabbit bone marrow, expanded, mixed with type I collagen gel, and implanted into surgically created patellar tendon defects, with a cell‑free gel as control, and tissues were assessed biomechanically and histomorphometrically after four weeks. MSC‑mediated repairs showed significant increases of 26 % in maximum stress, 18 % in modulus, and 33 % in strain energy density compared with controls, yet histomorphometric analysis revealed no significant differences in nuclear shape or alignment, indicating improved biomechanical properties without visible microstructural changes.

Abstract

Mesenchymal stem cells (MSCs) were isolated from bone marrow of 18 adult New Zealand White rabbits. These cells were culture expanded, suspended in type I collagen gel, and implanted into a surgically induced defect in the donor's right patellar tendon. A cell-free collagen gel was implanted into an identical control defect in the left patellar tendon. Repair tissues were evaluated biomechanically (n = 13) and histomorphometrically (n = 5) at 4 weeks after surgery. Compared to their matched controls, the MSC-mediated repair tissue demonstrated significant increases of 26% (p < 0.001), 18% (p < 0.01), and 33% (p < 0.02) in maximum stress, modulus, and strain energy density, respectively. Qualitatively, there appeared to be minor improvements in the histological appearance of some of the MSC-mediated repairs, including increased number of tenocytes and larger and more mature-looking collagen fiber bundles. Morphometrically, however, there were no significant left-right differences in nuclear aspect ratio (shape) or nuclear alignment (orientation). Therefore, delivering a large number of mesenchymal stem cells to a wound site can significantly improve its biomechanical properties by only 4 weeks but produce no visible improvement in its microstructure.