School of Materials Science and Engineering and Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea.
Biomaterials. 2011 Nov;32(31):7883-96. doi: 10.1016/j.biomaterials.2011.07.015. Epub 2011 Jul 28.
Partial-thickness cartilage defects, with no subchondral bone injury, do not repair spontaneously, thus there is no clinically effective treatment for these lesions. Although the autologous chondrocyte transplantation (ACT) is one of the promising approaches for cartilage repair, it requires in vitro cell expansion to get sufficient cells, but chondrocytes lose their chondrogenic phenotype during expansion by monolayer culture, leading to de-differentiation. In this study, a heparin-based hydrogel was evaluated and optimized to induce cartilage regeneration with de-differentiated chondrocytes. First, re-differentiation of de-differentiated chondrocytes encapsulated in heparin-based hydrogels was characterized in vitro with various polymer concentrations (from 3 to 20 wt.%). Even under a normal cell culture condition (no growth factors or chondrogenic components), efficient re-differentiation of cells was observed with the optimum at 10 wt.% hydrogel, showing the complete re-differentiation within a week. Efficient re-differentiation and cartilage formation of de-differentiated cell/hydrogel construct were also confirmed in vivo by subcutaneous implantation on the back of nude mice. Finally, excellent cartilage regeneration and good integration with surrounding, similar to natural cartilage, was also observed by delivering de-differentiated chondrocytes using the heparin-based hydrogel in partial-thickness defects of rabbit knees whereas no healing was observed for the control defects. These results demonstrate that the heparin-based hydrogel is very efficient for re-differentiation of expanded chondrocytes and cartilage regeneration without using any exogenous inducing factors, thus it could serve as an injectable cell-carrier and scaffold for cartilage repair. Excellent chondrogenic nature of the heparin-based hydrogel might be associated with the hydrogel characteristic that can secure endogenous growth factors secreted from chondrocytes, which then can promote the chondrogenesis, as suggested by the detection of TGF-β1 in both in vitro and in vivo cell/hydrogel constructs.
部分厚度的软骨缺损，没有软骨下骨损伤，不会自发修复，因此这些病变没有临床上有效的治疗方法。虽然自体软骨细胞移植（ACT）是软骨修复的一种很有前途的方法，但它需要体外细胞扩增来获得足够的细胞，但是软骨细胞在单层培养中通过体外扩增失去其软骨形成表型，导致去分化。在这项研究中，评估并优化了一种基于肝素的水凝胶，以诱导去分化的软骨细胞再生。首先，在体外研究了不同聚合物浓度（3 至 20wt.%）下包埋在基于肝素的水凝胶中的去分化软骨细胞的再分化。即使在正常细胞培养条件下（没有生长因子或软骨形成成分），也观察到在 10wt.%水凝胶下细胞的有效再分化，在一周内完全再分化。通过在裸鼠背部皮下植入，也证实了去分化细胞/水凝胶构建体的有效再分化和软骨形成。最后，通过使用基于肝素的水凝胶在兔膝关节的部分厚度缺损中递送去分化的软骨细胞，观察到良好的软骨再生和与周围组织的良好整合，类似于天然软骨，而对照缺损则没有愈合。这些结果表明，基于肝素的水凝胶在不使用任何外源性诱导因子的情况下，非常有效地促进扩增软骨细胞的再分化和软骨再生，因此它可以作为一种可注射的细胞载体和支架用于软骨修复。基于肝素的水凝胶具有优异的软骨形成特性，这可能与水凝胶的特性有关，该特性可以固定从软骨细胞分泌的内源性生长因子，从而促进软骨形成，这一点从体外和体内细胞/水凝胶构建体中 TGF-β1 的检测中可以得到证实。
