Bone Tissue Engineering With Chitosan, Carbon Nanotubes, and Hydroxyapatite Biomaterials Enriched With Mesenchymal Stem Cells: A Radiographic and Histological Evaluation in a Sheep Model Undergoing Ostectomy (Bone Tissue Engineering in a Sheep Model)

Comminuted fractures associated with tissue loss can adversely affect bone regeneration. Biomaterials enriched with mesenchymal stem cells (MSCs) employed for supporting osteosynthesis and potentiating osteoconduction are necessary to fill these bone defects. Natural compound biomaterials, similar to bone tissue, have been extensively tested in animal models for clinical use. Bone tissue engineering studies have used critical-size defects in ovine tibia monitored by imaging and histological examinations to evaluate the regenerative process. This study aimed to monitor the regenerative process in ovine tibial defects with or without chitosan, carbon nanotubes, or hydroxyapatite biomaterials, enriched or not enriched with MSCs. A 3-cm ostectomy was performed in 18 female Suffolk sheep. A 10-hole 4.5 mm narrow locking compression plate was used for osteosynthesis. The animals were randomly divided into three groups (n = 6): control (CON); defects filled with chitosan, carbon nanotubes, and hydroxyapatite biomaterial (BIO); and the same biomaterial enriched with bone marrow MSCs (BIO + CELL). The animals were evaluated monthly using radiographic examinations until 90 postoperative days, when they were euthanized. The limbs were subjected to micro-computed tomography (micro-CT), and bone specimens were subjected to histological evaluations. The radiographic examinations revealed construction stability without plate deviation, fracture, or bone lysis. Micro-CT evaluation demonstrated a difference in bone microarchitecture between the CON and biomaterial treatment groups (BIO and BIO + CELL). In the histological evaluations, the CON group did not demonstrate bone formation, and in the treatment groups (BIO and BIO + CELL), biocompatibility with sheep tissue was noted, and bone formation with trabeculae interspersed with remnants of the biomaterial was observed, with no differences between the groups. In conclusion, biomaterials present osteoconduction with beneficial characteristics for filling bone-lost fractures, and MSCs did not interfere with bone formation.