A hybrid scaffold of poly(lactide-co-glycolide) sponge filled with fibrin gel for cartilage tissue engineering

Towards the design of 3D multiscale instructive tissue engineering constructs: Current approaches and trends

The design of 3D constructs with adequate properties to instruct and guide cells both in vitro and in vivo is one of the major focuses of tissue engineering. Successful tissue regeneration depends on the favorable crosstalk between the supporting structure, the cells and the host tissue so that a balanced matrix production and degradation are achieved. Herein, the major occurring events and players in normal and regenerative tissue are overviewed. These have been inspiring the selection or synthesis of instructive cues to include into the 3D constructs. We further highlight the importance of a multiscale perception of the range of features that can be included on the biomimetic structures. Lastly, we focus on the current and developing tissue-engineering approaches for the preparation of such 3D constructs: top-down, bottom-up and integrative. Bottom-up and integrative approaches present a higher potential for the design of tissue engineering devices with multiscale features and higher biochemical control than top-down strategies, and are the main focus of this review.

Influence of the molecular weight of poly(lactide-co-glycolide) on the in vivo cartilage repair by a construct of poly(lactide-co-glycolide)/fibrin gel/mesenchymal stem cells/transforming growth factor-β1

The poly(lactide-co-glycolide) (PLGA, LA/GA 75/25) sponges with different weight average molecular weights (Mw 52, 122, and 177 kDa) were fabricated and were used to build the constructs of PLGA/fibrin gel/mesenchymal stem cells (MSCs)/transforming growth factor-β1 (TGF-β1). The PLGA 177 with the highest Mw (177 kDa) had the fastest degradation rate at the initial stage, whereas the PLGA 122 had the moderate degradation rate and smallest mass loss. After implantation in rabbit knees for 12 weeks, the full-thickness defects (both cartilage and subchondral bone were destroyed with a diameter and depth of 4 mm) repaired by the PLGA 122 group had formed a hyaline cartilage-like tissue with abundant glycosaminoglycans on the top layer and subchondral bone on the bottom layer. The group also achieved the best macroscopic (11.3 ± 0.8) and histological scoring (Wakitani, 0.5 ± 0.6). To unveil the mechanism of the cartilage repair outcome and the PLGA degradation behaviors, the chondrogenesis-related genes, inflammatory cytokines, and matrix metalloproteinase (MMP) activity were analyzed by quantitative reverse transcription-polymerase chain reaction at week 1, 3, and 6 postsurgery. At each time point, the regenerated tissues by the PLGA 122 group had the highest mRNA expression of SOX9 and collagen type II, but the smallest mRNA expression of interleukin-1β and tumor necrosis factor α, and MMP-13 and MMP-3. In summary, as a scaffolding matrix, the PLGA with different Mw shows a huge difference in cartilage regeneration in vivo. The one with a moderate Mw (122 kDa) causes the weakest inflammatory response and results in the best cartilage regeneration.

Preparation of polycaprolactone microspheres-aggregated scaffold with ultra big pores and fuzzy sphere surface by a one-step phase separation method

A microspheres-aggregated scaffold with ultra big pores (over 300 μm) and fuzzy microspheres is fabricated by incubating polycaprolactone (PCL)/tetrahydrofuran (THF) solution in a -20°C refrigerator, following by freeze-drying. Formation of the scaffold is mainly governed by the crystallization of the PCL polymer at appropriate conditions. All the 10-20% PCL/THF solutions yield the microspheres-aggregated scaffolds when the initial solution temperature is higher than 37°C, whereas the 10-15% solutions form dense membranes when the initial solution temperature is below 25°C. The size of the microspheres and pores is as large as 70-150 μm and 170-816 μm, respectively. The PCL microspheres-aggregated scaffold can better support the adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) compared to the traditional porous scaffold obtained by a porogen leaching method. The tendencies of chondrogenesis and osteogenesis differentiation of BMSCs are observed on the microspheres-aggregated scaffold and the ordinary porous scaffold, respectively.