Application of VEGFA and FGF-9 Enhances Angiogenesis, Osteogenesis and Bone Remodeling in Type 2 Diabetic Long Bone Regeneration

Abstract

Although bone regeneration is typically a reliable process, type 2 diabetes is associated with impaired or delayed healing processes. In addition, angiogenesis, a crucial step in bone regeneration, is often altered in the diabetic state. In this study, different stages of bone regeneration were characterized in an unicortical bone defect model comparing transgenic type 2 diabetic (db-/db-) and wild type (WT) mice in vivo. We investigated angiogenesis, callus formation and bone remodeling at early, intermediate and late time points by means of histomorphometry as well as protein level analyses. In order to enhance bone regeneration, defects were locally treated with recombinant FGF-9 or VEGFA. Histomorphometry of aniline blue stained sections indicated that bone regeneration is significantly decreased in db-/db- as opposed to WT mice at intermediate (5 days post operation) and late stages (7 days post operation) of bone regeneration. Moreover, immunohistochemical analysis revealed significantly decreased levels of RUNX-2, PCNA, Osteocalcin and PECAM-1 in db-/db- defects. In addition, osteoclastogenesis is impaired in db-/db- indicating altered bone remodeling. These results indicate significant impairments in angiogenesis and osteogenesis in type 2 diabetic bones. Importantly, angiogenesis, osteogenesis and bone remodeling could be reconstituted by application of recombinant FGF-9 and, in part, by VEGFA application. In conclusion, our study demonstrates that type 2 diabetes affects angiogenesis, osteogenesis and subsequently bone remodeling, which in turn leads to decreased bone regeneration. These effects could be reversed by local application of FGF-9 and to a lesser degree VEGFA. These data could serve as a basis for future therapeutic applications aiming at improving bone regeneration in the type 2 diabetic patient population.

Blood vessel formation and function in bone

“…These defects can be partially rescued by administration of recombinant VEGFA, whereas full rescue results from treatment with FGF9 (Behr et al, 2010). The combined administration of recombinant VEGFA and FGF9 also leads to increased angiogenesis, osteogenesis and bone regeneration in a mouse model of type 2 diabetes (Wallner et al, 2015).…”

Leptin stimulates bone formation in ob/ob mice at doses having minimal impact on energy metabolism

“…At the cellular level, these abnormalities are associated with impaired endochondral ossification, lower bone formation due to reductions in osteoblast number and activity, and mild osteopetrosis due to impaired osteoclast function (Kishida, et al 2005; Turner, et al 2013). Not surprisingly, bone mechanical properties are often reduced and bone regeneration impaired in leptin signaling-deficient rodents (Hamann, et al 2014; Hamann, et al 2013; Khan, et al 2013; Picke, et al 2015; Wallner, et al 2015). …”

Quiescence Preconditioned Human Multipotent Stromal Cells Adopt a Metabolic Profile Favorable for Enhanced Survival under Ischemia

“…Several strategies have been proposed and examined in order to enhance the capability of MSCs to withstand the rigors of the ischemic milieu albeit with limited success . Some strategies focused on the acceleration of vascularization of TE constructs by incorporating pro‐angiogenic factors , while others pharmacologically pretreated MSCs, or combined MSCs with growth factors (such as tethered EGF) immobilized on matrices, to stimulate pro‐survival signaling pathways . Recently, a novel strategy developed by our research group countered the conditions of the ischemic environment by exogenously delivering glucose, a main “metabolic fuel” source for cells; this approach strikingly improved the viability of the human MSCs (hMSCs) contained in TE constructs both in an in vitro ischemic cell model and in an in vivo animal model .…”