Autologous bone marrow-derived mesenchymal stem cells provide complete regeneration in a rabbit model of the Achilles tendon bundle rupture.

PURPOSE: To ascertain the role of autologous bone marrow-derived mesenchymal stem cells (BM-MSCs) in the tendon regeneration. METHODS: The study was conducted on 58 Achilles tendons from 29 laboratory Chinchilla adult rabbits. The central bundles of 48 tendons were partially removed and substituted with a tissue-engineered construct consisting of a collagen sponge either loaded with BM-MSCs (n = 24) or cell free (n = 24), placed inside a Vicryl mesh tube. The ends of the resected tendon were inserted in the construct to reach a direct contact with the sponge and sutured to the tube. The animals were sacrificed three and six months post-surgery. Ten intact tendons from five rabbits were used as an untreated control. The tissue samples (n = 30) were stained with haematoxylin and eosin, Picrosirius red, primary antibodies to collagen types I and III and studied by bright-field, phase-contrast, polarized light, and scanning electron microscopies followed by semi-quantitative morphometry. RESULTS: Six months results of cell-loaded scaffolds demonstrated parallel collagen fibres, spindle-shaped tenocytes, and neoangiogenesis. In the control cell-free group, the injured areas were filled with a nonspecific fibrotic tissue with minor foci of incomplete regeneration. The biomechanical tests of 28 tendons taken from 14 rabbits showed that the stiffness of the cell-based reconstructed tendons increased to 98% of the value for the intact samples. CONCLUSION: The obtained results support the hypothesis that the application of BM-MSCs in a tissue-engineered tendon construct leads to the restitution of the tendon tissue.

Influence of Hyperimmunization on Formation of Plaque Forming Cells in Lymphoid Organs Made with Transplantation of Spleen Stromal Fibroblasts.

When heterotopically transplanted under the renal capsule, the strains of stromal fibroblasts from spleen cultures formed the lymphoid organs, which had no specialized structures, such as red and white pulp and consisted of the accumulations like lymphoid follicles. The purpose of the given work was the study of ability of spleen stromal fibroblast strains, when heterotopically transplanted into the organism, to transfer the specific lymphoid microenvironment. The heterotopic transplantation of spleen fragments and stromal cells, grown in vitro, was made in autologous variant. The spleen fragments were put under a renal capsule. The strains of stromal fibroblasts of 5-7th passages were put into porous frames under a renal capsule of normal or immunized rabbits. The immune response to sheep red blood cells was studied in spleen of normal and hyperimmune rabbits, in regenerating spleens, in heterotopic grafts of spleen and in lymphoid organs, formed by strains of spleen stromal fibroblasts, grown in cultures. The immune response was determined on the 7-8th day after immunization by counting the amount of plaque forming cells (PFC) by Jerne method. In lymphoid organs, formed at the place of transplantation of spleen stromal fibroblasts strains of rabbits, the number of PFC was almost 3 times lower, than in heterotopic transplants of spleen, and 6 times lower, than in normal and regenerating spleens, but hundreds times exceeding the number of spontaneous PFC which could be only found, when 10(7)-10(8) spleen cells of normal non-immunized animals were tested. The concentration of PFC in lymphoid organs, formed at the place of the graft of stromal fibroblasts, was 3 times lower in regenerating spleens of hyperimmunised animals and 5 times higher, than in transplants of stromal fibroblasts of normal spleen. The obtained results give an evidence, that the transplantation of spleen stromal fibroblasts provides the transfer of specific lymphoid microenvironment.