Pre-Treat Xenogenic Collagenous Blocks of Bone Substitutes with Saline Facilitate Their Manipulation and Guarantee High Bone Regeneration Rates, Qualitatively and Quantitatively

Histological study of the effect of different hydration times of bone allograft and xenograft particles on the rate of bone formation in critical size defects in the rat calvarium

PURPOSE

The aim of this study was to investigate the effect of different bone graft hydration times on bone regeneration.

METHODS

Five-mm defects were created on either side of the sagittal plane in the calvaria of 40 rats. In each rat, the right and left defects were filled with allograft (Cenobone®) and xenograft (Cerabone®) particles, respectively, based on the grouping that was randomly assigned in the study (no hydration of bone graft, 2-minute saline hydration, 10-minute saline hydration, 30-minute saline hydration, and 2-minute blood hydration). Histological and histomorphometrical analyses were performed eight weeks after surgery. The amount of new bone formation, remaining graft, and connective tissue were analyzed using the general linear model (GLM) and Bonferroni test.

RESULTS

There was no significant difference regarding the mean of new bone, remaining graft, and connective tissue between the xenograft samples in different hydration groups. In the allograft groups, the mean new bone formation of the no-hydration and 2-minute saline-hydrated groups was significantly lower than 30-minute saline-hydrated and blood hydrated groups (P = 0.03 and P = 0.03, respectively). Regarding the variable of the remaining graft particles, the results were almost similar.

CONCLUSIONS

The results of this study showed that, the method of bone graft hydration before it is used in treating bone lesions affects osteogenesis. Especially in the case of allograft, rehydration before usage at least for 10 min is recommended.

Identification of Type-H-like Blood Vessels in a Dynamic and Controlled Model of Osteogenesis in Rabbit Calvarium

Angiogenesis and bone regeneration are closely interconnected processes. Whereas type-H blood vessels are abundantly found in the osteogenic zones during endochondral long bone development, their presence in flat bones’ development involving intramembranous mechanisms remains unclear. Here, we hypothesized that type-H-like capillaries that highly express CD31 and Endomucin (EMCN), may be present at sites of intramembranous bone development and participate in the control of osteogenesis. A rabbit model of calvarial bone augmentation was used in which bone growth was controlled over time (2–4 weeks) using a particulate bone scaffold. The model allowed the visualization of the entire spectrum of stages throughout bone growth in the same sample, i.e., active ossification, osteogenic activity, and controlled inflammation. Using systematic mRNA hybridization, the formation of capillaries subpopulations (CD31–EMCN staining) over time was studied and correlated with the presence of osteogenic precursors (Osterix staining). Type-H-like capillaries strongly expressing CD31 and EMCN were identified and described. Their presence increased gradually from the regenerative zone up to the osteogenic zone, at 2 and 4 weeks. Type-H-like capillaries may thus represent the initial vascular support encountered in flat bones’ development and which organize osteogenic niches.