Tissue-engineered autologous grafts for facial bone reconstruction

Abstract

Facial deformities require precise reconstruction of the appearance and function of the original tissue. The current standard of care—the use of bone harvested from another region in the body—has major limitations, including pain and comorbidities associated with surgery. We have engineered one of the most geometrically complex facial bones by using autologous stromal/stem cells, without bone morphogenic proteins, using native bovine bone matrix and a perfusion bioreactor for the growth and transport of living grafts. The ramus-condyle unit (RCU), the most eminent load-bearing bone in the skull, was reconstructed using an image-guided personalized approach in skeletally mature Yucatan minipigs (human-scale preclinical model). We used clinically approved decellularized bovine trabecular bone as a scaffolding material, and crafted it into an anatomically correct shape using image-guided micromilling, to fit the defect. Autologous adipose-derived stromal/stem cells were seeded into the scaffold and cultured in perfusion for 3 weeks in a specialized bioreactor to form immature bone tissue. Six months after implantation, the engineered grafts maintained their anatomical structure, integrated with native tissues, and generated greater volume of new bone and greater vascular infiltration than either non-seeded anatomical scaffolds or untreated defects. This translational study demonstrates feasibility of facial bone reconstruction using autologous, anatomically shaped, living grafts formed in vitro, and presents a platform for personalized bone tissue engineering.

Bioreactor culture duration of engineered constructs influences bone formation by mesenchymal stem cells

“…While some groups consider short bioreactor culture durations (5 days) sufficient prior to implantation [21], others use moderate durations (10–21 days) [5, 26, 45, 54–57] that are pulsatile or intermittent [58, 59], or up to 5 weeks to generate more mature constructs [22–24]. To minimize delays between harvesting autologous cells and generating an osteogenic graft, we characterized MSC response under perfusion in vitro to select the shortest culture duration necessary for construct maturity.…”

“…Shorter culture durations may be sufficient to prime MSCs towards osteogenic differentiation and boost their proangiogenic potential [25]. Extended culture durations such as 2–5 weeks may result in a more mature construct with increased cellularity, differentiated cells and a dense ECM, which can act as a scaffold for host cell infiltration and differentiation [10, 26, 27]. Thus, there is a critical gap in our knowledge for the appropriate in vitro perfusion culture duration to maximize bone formation in vivo with osteogenic grafts.…”

Tissue-Engineered Model of Human Osteolytic Bone Tumor

“…21 Notably, owing to the highly osteogenic properties of these scaffolds, the supplementation of BMP-2 during bone tissue engineering is not necessary. 22,23 When studied in orthotopic large animal models of bone repair, bone engineered using this approach provided mechanical support and integrated with the surrounding tissues, with active tissue remodeling. 23 Following our well-established protocol, we used hMSC as a source of osteoblasts for engineering bone in vitro.…”

“…22,23 When studied in orthotopic large animal models of bone repair, bone engineered using this approach provided mechanical support and integrated with the surrounding tissues, with active tissue remodeling. 23 Following our well-established protocol, we used hMSC as a source of osteoblasts for engineering bone in vitro. First, we confirmed the ability of hMSC (from two different donors) to differentiate into osteoblasts, both in cell monolayers and in decellularized bone scaffolds (Supplementary Figs.…”

“…hMSCs were isolated from these aspirates, characterized, and prepared as in our previous studies. 22,23,50 Derivation of osteoblasts from hMSCs. Cell culture and differentiation into osteoblasts were carried out as in our previous studies.…”