The scale-up of a tissue engineered porous hydroxyapatite polymer composite scaffold for use in bone repair: An ovine femoral condyle defect study

Abstract

The development of an osteogenic bone graft substitute has important practical and cost implications in many branches of medicine where bone regeneration is required. Previous in vitro and small animal (murine) in vivo studies highlighted a porous hydroxyapatite/poly (DL-lactic acid) composite scaffold in combination with skeletal stem cells (SSCs) as a potential bone graft substitute candidate. The aim of the current study was to scale up the bone cell-scaffold construct to large animals and examine the potential for repair of a critical-sized defect via an ovine model. SSC seeded scaffolds (and unseeded scaffold controls) were implanted bilaterally into ovine femoral condyle critical defects for 3 months. A parallel in vitro analysis of ovine SSC seeded scaffolds was also performed. Post mortem mechanical indentation testing showed the bone strengths of the defect sites were 20% (controls) and 11% (SSC seeded scaffolds) those of normal cancellous bone (p < 0.01). MicroCT analysis demonstrated new bone formation within all defects with a mean increase of 13.4% in the control scaffolds over the SSC seeded scaffolds (p = 0.14). Histological examination confirmed these findings, with enhanced quality new bone within the control defects. This study highlights important issues and steps to overcome in scale-up and translation of tissue engineered products. The scaffold demonstrated encouraging results as an osteoconductive matrix; however, further work is required with cellular protocols before any human trials.

Applications of X‐ray computed tomography for the evaluation of biomaterial‐mediated bone regeneration in critical‐sized defects

“…Ex vivo XCT analysis of the integrated defect explants generally allows to distinguish the three phases that are present inside the defect, being newly formed bone, remaining biomaterials and soft tissues (van Lenthe & Müller, 2008;Sweedy et al, 2017;Witek et al, 2019). Apart from a qualitative information, the higher resolution that can be achieved with ex vivo XCT imaging of the explants compared to in vivo XCT, allows for a quantification not only of the bone volume formed within the defect site (Vila et al, 2014;Tayton et al, 2015;Kerckhofs et al, 2016;Sweedy et al, 2017;Kwon et al, 2018;Sharma et al, 2019) but also standard 3D morphometric parameters (i.e. trabecular thickness, trabecular spacing, trabecular number) of the newly formed bone at different time points (Howie et al, 2018;Sharma et al, 2019) and volume fraction of remaining biomaterial (Sweedy et al, 2017;Witek et al, 2019;Wu et al, 2019).…”

“…However, little research has focused on the ex vivo mechanical competence of bone reconstructions after implantation of biomaterials. In particular, traditional mechanical tests such as indentation and microindentation at different locations through the defect areas have been used to measure the stress at failure (Tayton et al, 2015) and yield strength (Gauthier et al, 2005), respectively. Whereas indentation tests provided the mechanical strength of the healing defect size including both newly formed bone and remaining biomaterial (Tayton et al, 2015), microindentation allowed for the characterisation of the mechanical properties of the new regenerated bone tissue only (Gauthier et al, 2005).…”

“…In particular, traditional mechanical tests such as indentation and microindentation at different locations through the defect areas have been used to measure the stress at failure (Tayton et al, 2015) and yield strength (Gauthier et al, 2005), respectively. Whereas indentation tests provided the mechanical strength of the healing defect size including both newly formed bone and remaining biomaterial (Tayton et al, 2015), microindentation allowed for the characterisation of the mechanical properties of the new regenerated bone tissue only (Gauthier et al, 2005). Despite those data are extremely beneficial for the biomechanical evaluation of different biomaterials, they only provided local material properties and the deformation mechanisms at the implantation site under load could not be investigated.…”

Human Bone Xenografts: from Preclinical Testing for Regenerative Medicine to Modeling of Diseases

“…About 7 % (13 out of 175) of the studies showed little healing after the treatment with cellular scaffolds, with compromised efficacy ascribed to inappropriate choice of cells or scaffolds, poor conditions, or insufficient amount of cells. Notably, in eight studies using osteoblast cell sources, four showed no improvement to the healing, with two showing positive results only when BMP-2-transduced cell lines were used [35][36][37][38][39][40][41][42].…”

Reparo de lesões induzidas na articulação femorotibiopatelar de ovinos através do implante de biomateriais associados à células-tronco de polpa dentária humana

“…Ainda, Niemeyer e colaboradores (2010) compararam as CTM de medula óssea com as CTM de tecido adiposo em associação com PRP para regeneração óssea da tíbia de ovelhas, observando um maior potencial regenerativo quando usadas CTM derivadas de medula óssea associadas ao PRP. A associação de PRP à CTM de medula óssea, separadamente ou associados a HA, em côndilos têmporo-mandibular (esquerdo e direito) de ovinos, revelou melhora da lesão quando as CTM estavam associadas ao biomaterial (CIOCCA et al, 2013), sendo o mesmo resultado obsevado por Tayton e colaboradores em defeitos bilaterais de condilos de ovinos (TAYTON et al, 2014).…”