Promotion of Bone Regeneration by CCN2 Incorporated into Gelatin Hydrogel

Abstract

CCN family protein 2/connective tissue growth factor (CCN2/CTGF) is a unique molecule that promotes the entire endochondral ossification process and regeneration of damaged articular cartilage. Also, CCN2 has been shown to enhance the adhesion and migration of bone marrow stromal cells as well as the growth and differentiation of osteoblasts; hence, its utility in bone regeneration has been suggested. Here, we evaluated the effect of CCN2 on the regeneration of an intractable bone defect in a rat model. First, we prepared two recombinant CCN2s of different origins, and the one showing the stronger effect on osteoblasts in vitro was selected for further evaluation, based on the result of an in vitro bioassay. Next, to obtain a sustained effect, the recombinant CCN2 was incorporated into gelatin hydrogel that enabled the gradual release of the factor. Evaluation in vivo indicated that CCN2 continued to be released at least for up to 14 days after its incorporation. Application of the gelatin hydrogel-CCN2 complex, together with a collagen scaffold to the bone defect prepared in a rat femur resulted in remarkable induction of osteoblastic mineralization markers within 2 weeks. Finally, distinct enhancement of bone regeneration was observed 3 weeks after the application of the complex. These results confirm the utility of CCN2 in the regeneration of intractable bone defects in vivo when the factor is incorporated into gelatin hydrogel.

Collagen Three-Dimensional Hydrogel Matrix Carrying Basic Fibroblast Growth Factor for the Cultivation of Mesenchymal Stem Cells and Osteogenic Differentiation

“…65 The osteogenic and bone regeneration capacity of collagen as a hydrogel substrate was superior to that of fibrin glue and alginate 66 and modifying collagen hydrogels by loading them with connective tissue growth factor (CTGF) could enhance osteogenic differentiation even further. 67 Here, we determined the effect of bFGF on osteogenic differentiation of MSCs in collagen hydrogels. bFGF is a good candidate because we previously found that osteogenic phenotype acquisition of preosteoblastic MC3T3-E1 cells grown on hydroxyapatite bone granules was much greater in the presence of bFGF than without.…”

CCN2 in orofacial tissue development and remodeling

“…Since CCN2 acts on both types of the cells positively, this factor may be coordinating efficient and balanced bone remodeling. This functional property of CCN2 is well demonstrated by the regenerative effect of CCN2 on bone defects [13]. The fact that mechanical stimuli induce CCN2 production by osteocytes also indicates the property of CCN2 as a coordinator of bone remodeling [44].…”

“…By mimicking this process, we are able to accelerate the regeneration of intractable bone defects. In a rat model, application of CCN2 adsorbed onto gelatin hydrogel for durable and gradual release efficiently accelerated the regeneration of intractable bone defects [13]. This is not of a great impact per se; for other factors, such as BMP-2 and FGF-2, have been indicated to be useful in promoting bone repair.…”

“…In concordance with the effect on damaged articular cartilage, CCN2 promotes the bone regeneration up to the exactly desired level without inducing any overgrowth. In these cases, the boundary of the original cortical tissue and the regenerated one at the defect site is almost invisible by histological observation [13]. The property of CCN2 to enhance the healing potential of bone tissue in a harmonized manner is of course ascribable to the molecular action of this protein as a CCN family member.…”

“…Indeed, CCN2 is involved in physiological events during the development and growth of a variety of organ and tissues [1,10], particularly of mesenchymal ones. Positive aspects of the functional properties of CCN2 are also represented by the potential of this molecule to accelerate the regeneration of damaged tissues, including bone and cartilage [12,13]. Of note, even a cardioprotective effect of CCN2 against myocardial ischemia-reperfusion injury was reported [14].…”