3D Printing of Bone Grafts for Cleft Alveolar Osteoplasty – In vivo Evaluation in a Preclinical Model

Abstract

One of the most common hereditary craniofacial anomalies in humans are cleft lip and cleft alveolar bone with or without cleft palate. Current clinical practice, the augmentation of the persisting alveolar bone defect by using autologous bone grafts, has considerable disadvantages motivating to an intensive search for alternatives. We developed a novel therapy concept based on 3D printing of biodegradable calcium phosphate-based materials and integration of osteogenic cells allowing fabrication of patient-specific, tissue-engineered bone grafts. Objective of the present study was the in vivo evaluation of implants in a rat alveolar cleft model. Scaffolds were designed according to the defect's geometry with two different pore designs (60 • and 30 • rotated layer orientation) and produced by extrusion-based 3D plotting of a pasty calcium phosphate cement. The scaffolds filled into the artificial bone defect in the palate of adult Lewis rats, showing a good support. Half of the scaffolds were colonized with rat mesenchymal stromal cells (rMSC) prior to implantation. After 6 and 12 weeks, remaining defect width and bone formation were quantified histologically and by microCT. The results revealed excellent osteoconductive properties of the scaffolds, a significant influence of the pore geometry (60 • > 30 •), but no enhanced defect healing by pre-colonization with rMSC.

Toward Biofabrication of Resorbable Implants Consisting of a Calcium Phosphate Cement and Fibrin—A Characterization In Vitro and In Vivo

“…Due to this reason it was decided to simplify the fabrication process for the further investigations while maintaining the material conditions as it would be in the real fabrication process. Therefore, sterilized CPC was plotted with a multichannel plotter in a laminar flow bench as a cylindrical scaffold (diameter 3.3 mm, height 0.5 mm, strand-to-strand distance 0.5 mm) with a layer-to-layer orientation of 60°, deduced from our previous study [ 6 ]. Subsequently, 15 µL fibrin precursor solution, consisting of 45.5 µg∙µL −1 fibrinogen and 25 U thrombin were pipetted onto the CPC scaffold.…”

“…Scaffolds were fabricated in sterile conditions in the dimensions like previously described [ 6 ]. Immediately after plotting CPC scaffolds with a layer orientation of 60°, 15 µL of rMSC-containing fibrin was pipetted on top (cell number: 2 × 10 5 ).…”

“…The scaffolds being plotted from the CPC can achieve filigree shapes with a high control about pore size and pore shape [ 4 ]. Further, CPC can easily be fabricated into patient-specific shapes such as a scaphoid bone [ 5 ] or even a defect-specific implant for a cleft alveolus [ 6 ] taking usage of multi-material plotting of CPC in combination with fugitive support inks which allow for plotting of overhanging structures.…”

“…Recently we investigated the suitability of 3D plotted CPC scaffolds for the treatment of artificial alveolar clefts in a rat model [ 6 ]. Rat mesenchymal stromal cells (rMSC) were seeded onto plotted CPC structures.…”

“…Our observations in vitro evidenced that rMSC were able to attach to the CPC surface, proliferate and differentiate along the osteogenic lineage. Interestingly, the results in vivo clearly showed that scaffolds with a triangular pore shape (which equals a layer-to-layer orientation of 60° during the plotting process) allowed significantly more bone formation compared to scaffolds with a rhombohedral pore shape (which equals 30°) [ 6 ].…”