Tissue engineering approaches for the construction of a completely autologous tendon substitute

Preliminary identification of somatic mutations profile in ACL injury

Anterior cruciate ligament (ACL) injury is a common orthopedic disease with a high incidence, long recovery time, and often requiring surgical treatment. However, the susceptibility factors for ACL injury are currently unclear, and there is a lack of analysis on the differences in the ligament itself. Previous studies have focused on germline mutations, with less research on somatic mutations. To determine the role of somatic mutations in ACL injuries, we recruited seven patients between the ages of 20 and 39 years diagnosed with ACL injuries, collected their peripheral blood, injured ligament ends, and healthy ligament ends tissues, and performed exome sequencing with gene function enrichment analysis. We detected multiple gene mutations and gene deletions, which were only present in some of the samples. Unfortunately, it was not possible to determine whether these somatic mutations are related to ligament structure or function, or are involved in ACL injury. However, this study provides valuable clues for future in-depth research.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

Fabrication of electrospun poly(L-lactide-co-ε-caprolactone)/collagen nanoyarn network as a novel, three-dimensional, macroporous, aligned scaffold for tendon tissue engineering

Tissue engineering techniques using novel scaffolding materials offer potential alternatives for managing tendon disorders. An ideal tendon tissue engineered scaffold should mimic the three-dimensional (3D) structure of the natural extracellular matrix (ECM) of the native tendon. Here, we propose a novel electrospun nanoyarn network that is morphologically and structurally similar to the ECM of native tendon tissues. The nanoyarn, random nanofiber, and aligned nanofiber scaffolds of a synthetic biodegradable polymer, poly(L-lactide-co-ε-caprolactone) [P(LLA-CL)], and natural collagen I complex were fabricated using electrospinning. These scaffolds were characterized in terms of fiber morphology, pore size, porosity, and chemical and mechanical properties for the purpose of culturing tendon cells (TCs) for tendon tissue engineering. The results indicated a fiber diameter of 632 ± 81 nm for the random nanofiber scaffold, 643 ± 97 nm for the aligned nanofiber scaffold, and 641 ± 68 nm for the nanoyarn scaffold. The yarn in the nanoyarn scaffold was twisted by many nanofibers similar to the structure and inherent nanoscale organization of tendons, indicating an increase in the diameter of 9.51 ± 3.62 μm. The nanoyarn scaffold also contained 3D aligned microstructures with large interconnected pores and high porosity. Fourier transform infrared analyses revealed the presence of collagen in the three scaffolds. The mechanical properties of the sample scaffolds indicated that the scaffolds had desirable mechanical properties for tissue regeneration. Further, the results revealed that TC proliferation and infiltration, and the expression of tendon-related ECM genes, were significantly enhanced on the nanoyarn scaffold compared with that on the random nanofiber and aligned nanofiber scaffolds. This study demonstrates that electrospun P(LLA-CL)/collagen nanoyarn is a novel, 3D, macroporous, aligned scaffold that has potential application in tendon tissue engineering.