An in vivo comparative study of the gelatin microtissue‐based bottom‐up strategy and top‐down strategy in bone tissue engineering application

Abstract

Tissue‐engineered bone grafts (TEBGs) represent a promising treatment for bone defects. Nevertheless, drawbacks of the current construction strategy (top‐down [TD] strategy) such as limited transmission of nutrients and nonuniform distribution of seeded cells, result in an unsatisfied therapeutic effect on large segmental bone defects. Theoretically, tissue‐engineered microtissue (TEMT)‐based bottom‐up (BU) strategy is effective in preserving seed cells and vascularization, thus being regarded as a better alternative for TEBGs. Yet, there are few studies focusing on the comparison of the in vivo performance of TEBGs fabricated by TD or BU strategy. Here, we developed an ectopic bone formation rat model to compare the performance of these two construction strategies in vivo. TEBGs made from gelatin TEMT (BU strategy) and bulk tissue (BT; TD strategy) were seeded with equal number of rat bone marrow‐derived mesenchymal stem cells and fabricated in 5 mm polydimethylsiloxane chambers. The grafts were implanted into subcutaneous pockets in the same rat. Four weeks after implantation, microcomputed tomography and hematoxylin and eosin staining results demonstrated that more bony tissue was formed in the microtissue (MT) group than in the BT group. CD31 staining further confirmed that there were more blood vessels in the MT group, indicating that the BU strategy was superior in inducing angiogenesis. This comparative study provides evidence that the BU construction strategy is more effective for in vivo application and bone defect treatment by bone tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 678–688, 2019.

3D Printing for Soft Tissue Regeneration and Applications in Medicine

“…The top-down method is the more commonly used printing approach. A scaffold, which is custom-made for the respective application, is subsequently loaded with the desired cells or proteins and functions as an artificial extracellular matrix of the tissue, supporting its structure and the supply of nutrients [8]. The scaffold itself can also be created using 3D printing techniques and loaded with growth factors such as Vascular endothelial growth factor (VEGF) or Epidermal Growth Factor (EGF) as required to enable better ingrowth and differentiation of the cells in the desired direction.…”

“…In particular, creating a suitable porous structure to allow the ingrowth of vessels to ensure vascularization still poses a challenge in the field of tissue engineering [9]. However, oxygenation and the supply of the required nutrients and growth factors also have a direct effect on cell growth and, conversely, limits the maximum possible cell density with which the scaffolds can be printed without the resulting competition for these factors, leading to increased cell death [8,10].…”

“…A great advantage of this process is the possibility of controlling the formation of the final structure even better, since the built-in nanostructures can be directly arranged according to the required properties [11,12]. This functioning also makes it possible to introduce a much higher cell density into the tissue than with the conventional top-down method [8].…”

Biomimetic open porous structured core-shell microtissue with enhanced mechanical properties for bottom-up bone tissue engineering

“…Traditional TEBGs are fabricated by seeding cells on prefabricated scaffolds that provide environment cues for tissue development 2. Although many scaffolds have been developed, the treatment efficacy of traditional TEBGs for large bone defects is limited due to the following two reasons: (1) The uneven distribution of cells throughout the scaffold, wherein cells in the center die because of insufficient nutrients and oxygen transport to the center region 3; (2) Once implanted in vivo, cell loss due to mechanical disturbances, ischemic and inflammatory factors is inevitable 4.…”

3D-microtissue derived secretome as a cell-free approach for enhanced mineralization of scaffolds in the chorioallantoic membrane model

“…As a new promising strategy, tissue engineered (TE) substitutes have gained a lot of attention. Although research has made much progress in BTE over the last few decades, three major problems still remain unresolved: (1) tissue engineered grafts do not provide the regenerative potential required, thus leading to a limited effectiveness to treat bone defects 3 , (2) cell death in the core of the TEC because vessels just reach the outer shell of the scaffolds 4,5 (3) cell retention is still limited and needs to be improved, as cells are getting lost during implantation 6 . Therefore, to achieve sufficient tissue regeneration in a TE bone graft, the selection of an appropriate cell type and format together with an appropriate biomaterial is crucial to enable in vivo performance.…”