| Objective: Achilles tendon rupture accounts for about 35% of all tendon injuries due to the low blood supply and low metabolic activity of tendon fibroblastic cells. Chronic or acute tendon injuries are primarily treated with conservative or surgical treatments. Conservative treatments are frequently used for symptomatic relief only, ineffective and time-consuming, while the later treatments involve the use of autografts, allografts, xenografts and prosthetic devices. However, there is a considerably high risk of complications such as infection, nerve damage, adhesion, and distributed skin sensibility. Therefore, it became necessary to come up with innovative ways to treat the Achilles tendon injuries. Stem cells are undifferentiated, self-renewing cells with the ability to differentiate into other cell types, and promise in promoting the biological healing process. Numerous research studies on bone marrow-derived mesenchymal stem cells(BMSCs) have been carried out in the past several years. BMSCs are defined by their ability to differentiate into several connective tissue types including bone, cartilage, tendon, muscle, marrow, fat and dermis. Tendon-derived stem cells(TDSCs) are adult stem cells isolated from tendons and was suggested to be a better source for tendon repair both histologically and biochemically. Some reports demonstrated that TDSCs have a higher colonization ability compared with BMSCs. They also express higher mRNA levels of tenogenic markers--scleraxis(Scx), tenomodulin(Tnmd)--and extracellular matrix components of tendon--Col a1, Col a1/Col3 a1 ratio, decorin(Dcn)--than BMSCs. However, a comparison between TDSCs and BMSCs in treating Achilles tendon rupture has not yet been done, needs to be investigated.Methods: Herein we successfully isolated TDSCs and BMSCs from SD rat’s Achilles tendon and bone marrow respectively, identified with flow cytometry and osteogenic, adipogenic, and chondrogenic induced testing was done. In addition, the cell morphology was observed from passage 0 to passage 7. In order to compare TDSCs and BMSCs in vitro, RT-PCR, immunofluorescent staining, EdU assay, MTS colorimetric analysis were used for testing the difference in gene expression level, characteristics of stem cells protein expression, DNA synthesis and viability of TDSCs and BMSCs. After in vitro testing, we compared the TDSCs and BMSCs transplantation on ruptured Achilles tendon in rats. Macroscopic appearance, histological morphology, biomechanical strength, gene expression level and immunofluorescent testing were used to evaluate the cell transplantation effects of both TDSCs and BMSCs via the possible mechanism.Results: The TDSCs and BMSCs, showed positive results for the three-lineage differentiation, and both highly expressed the stem cell surface marker proteins such as CD29, CD44, and CD90. Moreover, TDSCs and BMSCs between P3-P5 generations presents more favorable cell morphology, which can be used in subsequent experiments. In the in vitro comparison of TDSCs and BMSCs, we found that there is some molecular and cell characteristic biological differences between BMSCs and TDSCs. The results showed that TDSCs express higher Nucleostemin(NS) and Tenascin-C compared with BMSCs that is very low. In addition, we also observed the DNA synthesis of TDSCs, which was faster than BMSCs, by combining with MTS cell viability curve; we confirmed that TDSCs proliferate much quicker than BMSCs. After transplantation, both BMSCs and TDSCs implantation groups could promote ruptured tendon regeneration, in the early stages of regeneration. TDSCs showed a prompt stimulatory effect on tissue remodeling and both in macro/micro appearance and biomechanical strength rather than BMSCs. Moreover, both BMSCs and TDSCs implantation groups can promote Tenascin-C protein synthesis in the ruptured Achilles’ tendon. Moreover, TDSCs treated a group of rats showed higher Ten-C expression than the BMSCs treated group rats. We also found the CM-Di I labeled transplanted cells were detectable around the tendon after 4 weeks post-surgery.Conclusion: TDSCs have higher proliferative rate and express more musculotendinous related genes compared with BMSCs. TDSC transplantation therapy does improve the healing potential of ruptured Achilles tendon in rats. We consider that TDSCs exhibit a better-regenerative potential when compared with BMSCs in treating ruptured Achilles tendons and may be a better alternative cell source for treating Achilles tendon injuries. |
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