Discipline: Biological Sciences
Subcategory: Biomedical Engineering
Room: Exhibit Hall
Anthony Nunez Romero - University of Arizona
Co-Author(s): Robert V. Childers, University of Arizona, Tucson, AZ; Gerardo Figueroa, University of Arizona, Tucson, AZ; David A. Gonzales, University of Arizona, Tucson, AZ; John A. Szivek, University of Arizona, Tucson, AZ; David S. Margolis, University of Arizona, Tucson, AZ
Introduction: Critical sized bone defects occur in patients due to motor vehicle accidents, trauma, resections, and infection. Despite surgical options, these defects do not reliably heal. Our lab has shown that 3D printed biomimetic polybutylene terephthalate (PBT) scaffolds coated with beta-tricalcium phosphate (TCP) and seeded with autologous adipose derived stem cells can regenerate bone in a 4.2cm femoral defect in sheep. PBT is bioinert and does not resorb which may cause complications. Our lab has engineered a resorbable composite scaffold using polylactic acid (PLA) and TCP. This study uses histology and histomorphometry to measure bone growth within the scaffolds following placement in a rat to test whether the scaffolds support bone growth in vivo. Methods: Four scaffold types were printed for implantation:; 1) PBT coated with TCP, 2) PLA, 3) 75:25 PLA:TCP, and 4) 50:50 PLA:TCP. Scaffolds were sterilized in ethylene oxide and six of each scaffold were placed on the femur of 3-month-old male Sprague-Dawley rats. Scaffolds were left in place for 3 months. Prior to sacrifice, rats were given two calcein injections separated by one week, and 3 days after the second injection the bilateral femora were explanted. Prior to histology preparation, mechanical testing was performed to characterize the bone bonding to the scaffolds. Samples were embedded in polymethylmethacrylate and up to three cross sectional cuts were made through the scaffold region in the experimental and contralateral control bones for histological analysis. The sections were stained using mineralized bone stain (MIBS). Slides were imaged on a LEICA DMI6000 and quantitative histology measurements were gathered using Image J. Measurements included total cortical bone area (mm2), bone volume (BV/TV, %), marrow cavity volume (MaV/TV, %), osteoid volume (OV/TV, %), and the scaffold pore space occupied by bone tissue (%), mineralized apposition rate (MAR, m/day), and bone formation rate (BFR, m3/ m2/day).Results: After 3 months in vivo, 23 of the 24 scaffolds firmly attached to bone with one 75:25 PLA:TCP scaffold found to be grossly unstable. The 50:50 PLA:TCP scaffolds showed an increase in pore spaces occupied by bone (bone ingrowth %) when compared to PBT scaffolds (p<0.05). OV/TV in the experimental groups increased when compared to the control groups of each different composite blend (p<0.005). No statistically significant differences were noted in MAR and BFR.Discussion: The results show that 50:50 PLA:TCP scaffolds support more bone ingrowth than PBT scaffolds, but a trend toward lower MAR and BFR was also noted in these scaffolds. This indicates that additional bone growth may be seen in PBT scaffolds if they are left in vivo longer. The results of this study demonstrate that composite ceramic polymer scaffolds warrant testing at longer time intervals and warrant study in a large animal model.
Funder Acknowledgement(s): This research is supported by the Western Alliance to Expand Student Opportunities (WAESO) Louis Stokes Alliance for Minority Participation (LSAMP) National Science Foundation (NSF) Cooperative Agreement No. HRD-1619524.
Faculty Advisor: David S. Margolis, firstname.lastname@example.org
Role: I contributed to the histology preparation of over 130 rat slides. This histology preparation starts after the scaffolds are explanted after having been in vivo for about 3 months. The histology preparation includes embedding the samples in polymethylmethacrylate, grinding down the samples to about one cell layer thickness, and staining the slides for histological analysis. Once slides were stained me and my partner Robert V. Childers began imaging the slides on a LEICA DMI6000. Once the slides were imaged we were able to gather measurements using Image J.