Kinetics ofIn VivoBone Deposition by Bone Marrow Stromal Cells into Porous Calcium Phosphate Scaffolds: An X-Ray Computed Microtomography Study

Abstract

In a typical bone tissue engineering application, osteogenic cells are harvested and seeded on a three-dimensional (3D) synthetic scaffold that acts as guide and stimulus for tissue growth, creating a tissue engineering construct or living biocomposite. Despite the large number of performed experiments in different laboratories, information on the kinetics of bone growth into the scaffolds is still scarce. Highly porous hydroxyapatite scaffolds were investigated before the implantation and after they were seeded with in vitro expanded bone marrow stromal cells (BMSC) and implanted for 8, 16, or 24 weeks in immunodeficient mice. Synchrotron x-ray computed microtomography (microCT) was used for qualitative and quantitative 3D characterization of the scaffold material and 3D evaluation of tissue engineered bone growth kinetics after in vivo implantation. Experiments were performed taking advantage of a dedicated set up at the European Synchrotron Radiation Facility (ESRF, Grenoble, France), which allowed quantitative imaging at a spatial resolution of about 5 microm. A peculiarity of these experiments was the fact that at first the data were obtained on the different pure scaffolds, then the same scaffolds were seeded by BMSC, implanted, and brought again to ESRF for investigating the formation of new bone. The volume fraction, average thickness, and distribution of the newly formed bone were evaluated as a function of the implantation time. New bone thickness increased from week 8 to week 16, but deposition of new bone was arrested from week 16 to week 24. Instead, mineralization of the newly deposited bone matrix continued up to week 24.

Kinetics of in vivo bone deposition by bone marrow stromal cells within a resorbable porous calcium phosphate scaffold: An X‐ray computed microtomography study

“…A similar outcome was observed in the histograms obtained in a recent work of ours by analyzing the new bone formation within a non-resorbable bioceramic scaffolds (Komlev et al, 2006). It is to note that we also observed an apparent progressive increase in the density of the Si-TCP scaffolds suggesting some modification in the scaffold nature as function of implantation time.…”

“…In fact these results must be compared with those obtained in a similar experiment and reported in Komlev et al (2006). The observed time dependences of the volume fraction and of the thickness of the new bone were similar for both experiments: in particular the saturation is observed in both cases for an implantation time of four months, with values somehow lower in the experiment described in the present paper.…”

“…It is to note that we also observed an apparent progressive increase in the density of the Si-TCP scaffolds suggesting some modification in the scaffold nature as function of implantation time. This last finding is at variance with the results reported with the 100% HA nonresorbable scaffolds in the already cited article (Komlev et al, 2006), To better distinguish between the newly formed bone and the scaffold phases as well as to depict spatial correlations between the different phases, different color hues were applied to the volume histograms. More precisely, after separation of the different phases by a multi-thresholding procedure (see Materials and Methods), each of the histogram was partitioned in equal zones.…”

“…The biological process that took place and causes the color segregation is discussed in the next section. A detailed microCT analysis of 100% HA not resorbable scaffolds seeded with cells and implanted for different times have been already presented by us in Komlev et al (2006). Here we report the results obtained by processing the microCT data from the 100% HA scaffolds in the same way, with regard to methodology and algorithms, we have processed the data from the Si-TCP scaffolds (Fig.…”

“…To investigate this with high spatial resolution, 3D images of internal concrete structure obtained by X-ray computed microtomography (microCT) were recorded. MicroCT has been already successfully used for quantification of the three-dimensional (3D) microarchitecture of bone including engineered bone (Ho and Hutmacher, 2005;Komlev et al, 2006;Mastrogiacomo et al, 2004Mastrogiacomo et al, , 2005Peyrin et al, 1998;Salome et al, 1997).…”