Abstract
ObjectiveFibrocartilage transition zone (FC) is difficult to regenerate after surgical re-attachment of tendon to bone. Here, we investigated whether type II collagen-sponges (CII-sponges) facilitated tendon stem/progenitor cells (TSPCs) to adopt chondrogenic phenotypes and further observed if this material could increase the FC areas in bone-tendon junction (BTJ) injury model.MethodsCII-sponges were made as we previously described. The appearance and pore structure of CII-sponges were photographed by camera and microscopies. The viability, proliferation, and differentiation of TSPCs were examined by LIVE/DEAD assay, alamarBlue, and PKH67 in vitro tracking. Subsequently, TSPCs were seeded in CII-sponges, Matrigel or monolayer, and induced under chondrogenic medium for 7 or 14 days before being harvested for qPCR or being transplanted into nude mice to examine the chondrogenesis of TSPCs. Lastly, partial patellectomy (PP) was applied to establish the BTJ injury model. CII-sponges were interposed between the patellar fragment and tendon, and histological examination was used to assess the FC regeneration at BTJ after surgery at 8 weeks.ResultsCII-sponges were like sponges with interconnected pores. TSPCs could adhere, proliferate, and differentiate in this CII-sponge up to 14 days at least. Both qPCR and immunostaining data showed that compared with TSPCs cultured in monolayer or Matrigel, cells in CII-sponges group adopted more chondrogenic phenotypes with an overall increase of chondrocyte-related genes and proteins. Furthermore, in PP injured model, much more new formed cartilage-like tissues could be observed in CII-sponges group, evidenced by a large amount of positive proteoglycan expression and typical oval or round chondrocytes in this area.ConclusionOur study showed that CII-sponges facilitated the TSPCs to differentiate toward chondrocytes and increased the area of FCs, which suggests that CII-sponges are meaningful for the reconstruction of FC at bone tendon junction. However, the link between the two phenomena requires further research and validation.
Highlights
Fibrocartilage transition zone (FC) is the structure of bone tendon junction
These findings suggest that the formation of cartilage interface by different means could be an effective way to promote the regeneration of native FC and be beneficial to the reconstruction of bone tendon junction
In order to determine whether tendon stem/progenitor cells (TSPCs) express chondrogenic differentiation proteins, Sox 9, collagen I, collagen II, and aggrecan expressions were investigated by ICC staining firstly
Summary
Fibrocartilage transition zone (FC) is the structure of bone tendon junction. Surgical reattachment of tendon to bone often fails due to the lack of regeneration of this specialised structure, thereby presenting difficulty for tendon to bone healing. Wong et al (2009) showed that articular cartilage interposed in patellar tendon and the remaining patellar could result in more FC than direct repair at all time points, and stronger mechanical strength recovery. These findings suggest that the formation of cartilage interface by different means could be an effective way to promote the regeneration of native FC and be beneficial to the reconstruction of bone tendon junction
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