Recent Progress in Cartilage Tissue Engineering--Our Experience and Future Directions

Given the limited spontaneous repair that follows cartilage injury, demand is growing for tissue engi- neering approaches for cartilage regeneration. There are two major applications for tissue-engineered cartilage. One is in orthopedic surgery, in which the engineered cartilage is usually used to repair cartilage defects or loss in an articular joint or meniscus in order to restore the joint function. The other is for head and neck reconstruction, in which the engineered cartilage is usually applied to repair cartilage defects or loss in an auricle, trachea, nose, larynx, or eyelid. The challenges faced by the engineered car- tilage for one application are quite different from those faced by the engineered cartilage for the other application. As a result, the emphases of the engineering strategies to generate cartilage are usually quite different for each application. The statuses of preclinical animal investigations and of the clinical translation of engineered cartilage are also at different levels for each application. The aim of this review is to provide an opinion piece on the challenges, current developments, and future directions for cartilage engineering for both applications.

Dominant role of in situ native cartilage niche for determining the cartilage type regenerated by BMSCs

Tissue-engineered cartilage regeneration by bone marrow stromal cells(BMSCs)is considered an ideal method.However,how to regulate BMSCs to regenerate specific types of cartilage remains unclear,which significantly limits its clinical translation and leads to suboptimal clinical effects.Herein,we systematically explored the role of native ear and articular cartilage niches on the differentiation fate of BMSCs and the type of regenerated cartilage.First,we prepared two types of acellular cartilage sheets(ACSs)and two types of chondrocytes.Then green fluorescent protein-labeled BMSCs were seeded on two types of ACSs with or without corresponding types of chondrocytes using a sandwich model and directed or cross-implanted them into native cartilage niches.After one year of in vivo culture,cell tracking and the results of histological results showed that the native cartilage niches were capable of regulating BMSCs regeneration into specific types of cartilage that were consistent with the cartilage types of the implanted sites.Furthermore,even when the type of niche formed by ACSs or the biomimetic cartilage niche constructed by specific types of ACSs and specific types of chondrocytes did not match with the native cartilage niche,the native cartilage niche continued to determine the type of cartilage regenerated by implanted BMSCs and chondrocytes.All our results provide sufficient evidence for specific types of cartilage regeneration using chondrogenic potential cells,such as mesenchymal stem cells and chondrocytes.

Recent progress on chikungunya virus research

Chikungunya virus(CHIKV) is an arbovirus transmitted by Aedes mosquitos in tropical and subtropical regions across the world. After decades of sporadic outbreaks, it re-emerged in Africa,Asia, India Ocean and America suddenly, causing major regional epidemics recently and becoming a notable global health problem. Infection by CHIKV results in a spectrum of clinical diseases including an acute self-limiting febrile illness in most individuals, a chronic phase of recurrent join pain in a proportion of patients, and long-term arthralgia for months to years for the unfortunate few. No specific anti-viral drugs or licensed vaccines for CHIKV are available so far. A better understanding of virus-host interactions is essential for the development of therapeutics and vaccines. To this end, we reviewed the existing knowledge on CHIKV's epidemiology, clinical presentation, molecular virology, diagnostic approaches, host immune response, vaccine development, and available animal models. Such a comprehensive overview, we believe, will shed lights on the promises and challenges in CHIKV vaccine development.

Tissue engineering of cartilage,tendon and bone

Tissue engineering aims to produce a functional tissue replacement to repair defects.Tissue reconstruction is an essential step toward the clinical application of engineered tissues.Significant progress has recently been achieved in this field.In our laboratory,we focus on construction of cartilage,tendon and bone.The purpose of this review was to summarize the advances in the engineering of these three tissues,particularly focusing on tissue regeneration and defect repair in our laboratory.In cartilage engineering,articular cartilage was reconstructed and defects were repaired in animal models.More sophisticated tissues,such as cartilage in the ear and trachea,were reconstructed both in vitro and in vivo with specific shapes and sizes.Engineered tendon was generated in vitro and in vivo in many animal models with tenocytes or dermal fibroblasts in combination with appropriate mechanical loading.Cranial and limb bone defects were also successfully regenerated and repaired in large animals.Based on sophisticated animal studies,several clinical trials of engineered bone have been launched with promising preliminary results,displaying the high potential for clinical application.