Connexin43 (Cx43) is the main gap junction protein expressed in bone forming cells, where it modulates peak bone mass acquisition and cortical modeling. Genetic ablation of the Cx43 gene (Gja1) results in cortical expansion with accentuated periosteal bone formation associated with decreased expression of the Wnt inhibitor sclerostin.
Mechanically stable surface-hydrophobilized chitosan nanofibrous barrier membranes for guided bone regeneration
The use of chitosan based nanofiber membranes in guided bone regeneration (GBR) is limited by its uncontrolled swelling and mechanical instability in aqueous environments. This paper describes the significantly improved stability and properties of surface butyrylated chitosan nanofiber (BCSNF) membranes that greatly enhance their potential in GBR.
Built-In Electric Fields Dramatically Induce Enhancement of Osseointegration
Rapid and effective osseointegration is a great challenge in clinical practice. Endogenous electronegative potentials spontaneously appear on bone defect sites and mediate healing. Thus, bone healing can potentially be stimulated using physiologically relevant electrical signals in implants. However, it is difficult to directly introduce physiologically relevant electric fields in bone tissue.
Upregulation of Akt signaling enhances femoral fracture healing by accelerating atrophic quadriceps recovery
Muscle damage and disuse muscular atrophy are detrimental for fracture healing. It has been reported that the Akt signaling pathway plays a role in skeletal muscle hypertrophy and atrophy. The aim of this study was to further investigate whether promoting local muscle function through regulating Akt signaling affects fracture healing. For this purpose, we combined a rat model of short-term atrophy of the quadriceps with a femoral fracture model.
Ibuprofen Differentially Affects Supraspinatus Muscle and Tendon Adaptations to Exercise in a Rat Model
Growth and repair factors, osteoactivin, matrix metalloproteinase and heat shock protein 72, increase with resolution of inflammation in musculotendinous tissues in a rat model of repetitive grasping
Authors
Nagat Frara, Samir M. Abdelmagid, Michael Tytell, Mamta Amin, Steven N. Popoff, Fayez F. Safadi and Mary F. Barbe
Abstract
Expression of the growth factor osteoactivin (OA) increases during tissue degeneration and regeneration, fracture repair and after denervation-induced disuse atrophy, concomitant with increased matrix metalloproteinases (MMPs). However, OA’s expression with repetitive overuse injuries is unknown. The aim of this study was to evaluate: 1) OA expression in an operant rat model of repetitive overuse; 2) expression of MMPs; 3) inflammatory cytokines indicative of injury or inflammation; and 4) the inducible form of heat shock protein 70 (HSPA1A/HSP72) as the latter is known to increase during metabolic stress and to be involved in cellular repair. Young adult female rats performed a high repetition negligible force (HRNF) food retrieval task for up to 6 weeks and were compared to control rats.
Flexor digitorum muscles and tendons were collected from 22 young adult female rats performing a HRNF reaching task for 3 to 6 weeks, and 12 food restricted control (FRC) rats. OA mRNA levels were assessed by quantitative polymerase chain reaction (qPCR). OA, MMP-1, -2, -3, and -13 and HSP72 protein expression was assayed using Western blotting. Immunohistochemistry and image analysis was used to evaluate OA and HSP72 expression. ELISA was performed for HSP72 and inflammatory cytokines.
Flexor digitorum muscles and tendons from 6-week HRNF rats showed increased OA mRNA and protein expression compared to FRC rats. MMP-1, -2 and -3 progressively increased in muscles whereas MMP-1 and -3 increased in tendons with HRNF task performance. HSP72 increased in 6-week HRNF muscles and tendons, compared to controls, and co-localized with OA in the myofiber sarcolemma. IL-1alpha and beta increased transiently in tendons or muscles in HRNF week 3 before resolving in week 6.
The simultaneous increases of OA with factors involved in tissue repair (MMPs and HSP72) supports a role of OA in tissue regeneration after repetitive overuse.