Endogenous PTH Deficiency Impairs Fracture Healing and Impedes the Fracture-Healing Efficacy of Exogenous PTH(1-34)

Although the capacity of exogenous PTH1-34 to enhance the rate of bone repair is well established in animal models, our understanding of the mechanism(s) whereby PTH induces an anabolic response during skeletal repair remains limited. Furthermore it is unknown whether endogenous PTH is required for fracture healing and how the absence of endogenous PTH would influence the fracture-healing capacity of exogenous PTH.Closed mid-diaphyseal femur fractures were created and stabilized with an intramedullary pin in 8-week-old wild-type and Pth null (Pth(-/-)) mice. Mice received daily injections of vehicle or of PTH1-34 (80 µg/kg) for 1-4 weeks post-fracture, and callus tissue properties were analyzed at 1, 2 and 4 weeks post-fracture. Cartilaginous callus areas were reduced at 1 week post-fracture, but were increased at 2 weeks post-fracture in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice respectively. The mineralized callus areas, bony callus areas, osteoblast number and activity, osteoclast number and surface in callus tissues were all reduced in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice, but were increased in PTH-treated wild-type and Pth(-/-) mice compared to vehicle-treated wild-type and Pth(-/-) mice.Absence of endogenous PTH1-84 impedes bone fracture healing. Exogenous PTH1-34 can act in the absence of endogenous PTH but callus formation, including accelerated endochondral bone formation and callus remodeling as well as mechanical strength of the bone are greater when endogenous PTH is present. Results of this study suggest a complementary role for endogenous PTH1-84 and exogenous PTH1-34 in accelerating fracture healing

Bmi-1 Absence Causes Premature Brain Degeneration

Bmi-1, a polycomb transcriptional repressor, is implicated in cell cycle regulation and cell senescence. Its absence results in generalized astrogliosis and epilepsy during the postnatal development, but the underlying mechanisms are poorly understood. Here, we demonstrate the occurrence of oxidative stress in the brain of four-week-old Bmi-1 null mice. The mice showed various hallmarks of neurodegeneration including synaptic loss, axonal demyelination, reactive gliosis and brain mitochondrial damage. Moreover, astroglial glutamate transporters and glutamine synthetase decreased in the Bmi-1 null hippocampus, which might contribute to the sporadic epileptic-like seizures in these mice. These results indicate that Bmi-1 is required for maintaining endogenous antioxidant defenses in the brain, and its absence subsequently causes premature brain degeneration

Parathyroid hormone is essential for normal fetal bone formation

Parathyroid hormone (PTH) is a potent pharmacologic inducer of new bone formation, but no physiologic anabolic effect of PTH on adult bone has been described. We investigated the role of PTH in fetal skeletal development by comparing newborn mice lacking either PTH, PTH-related peptide (PTHrP), or both peptides. PTH-deficient mice were dysmorphic but viable, whereas mice lacking PTHrP died at birth with dyschondroplasia. PTH-deficient mice uniquely demonstrated diminished cartilage matrix mineralization, decreased neovascularization with reduced expression of angiopoietin-1, and reduced metaphyseal osteoblasts and trabecular bone. Compound mutants displayed the combined cartilaginous and osseous defects of both single mutants. These results indicate that coordinated action of both PTH and PTHrP are required to achieve normal fetal skeletal morphogenesis, and they demonstrate an essential function for PTH at the cartilage-bone interface. The effect of PTH on fetal osteoblasts may be relevant to its postnatal anabolic effects on trabecular bone

hAMCs transplantation suppressed hepatocyte apoptosis and promoted hepatocyte regeneration.

<p>(A) Micrographs of liver paraffin sections from control group and hAMCs group stained immunohistochemically for TUNEL and PCNA. (B) Representative Western blots of liver extracts from two groups for expression of HGF and bcl-2. β-actin was used as an invariant control. HGF and bcl-2 protein levels relative to β-actin protein level were assessed by densitometric analysis. Each value is the mean±SEM of determinations in 8 mice of each group. *p<0.05 compared with control group.</p

hAMCs transplantation reduced CCl₄-induced hepatic stellate cells activation.

<p>(A) Micrographs of liver frozen sections from control group and hAMCs group stained with immunofluorescence for Desmin (left panel), DAPI (middle panel) and merged (right panel). (B) Micrographs of liver frozen sections from control group and hAMCs group stained with immunofluorescence forα-SMA (left panel), DAPI (middle panel) and merged (right panel). (C) Micrographs of liver frozen sections from control group and hAMCs group stained with immunofluorescence for GFAP (left panel), DAPI (middle panel) and merged (right panel). (D) Representative Western blots of liver extracts from control group and hAMCs group for expression of α-SMA. β-actin was used as an invariant control. (E) α-SMA protein levels relative to β-actin protein level were assessed by densitometric analysis. Each value is the mean±SEM of determinations in 5 mice of each group. ** p<0.01 compared with control group.</p

hAMCs engraft in CCl₄ injured livers.

<p>(A) Micrographs of liver frozen sections stained with immunofluorescence for DiI (left panel), α-fetoprotein (middle panel) and merged (right panel). (B) Micrographs of liver frozen sections stained with immunofluorescence for DiI (left panel), albumin (middle panel) and merged (right panel). Bars = 100 µm.</p

hAMCs transplantation suppressed hepatocyte senescence.

<p>(A) Micrographs of liver section stained histochemically for SA-β-Gal. (B) SA-β-Gal positive hepatocytes per field. (C) The levels of SOD activity in mouse liver homogenate from control group and hAMCs group. (D)Representative Western blots of liver extracts from control group and hAMCs group for expression of p16^INK4a, p21^Cipl, p27^Kipl, Sirt 1 and prdx I expression in livers from hAMCs group or control group. β-actin was used as an invariant control. (E) p16^INK4a, p21^Cipl, p27^Kipl, Sirt 1 and prdx I protein levels relative to β-actin protein level were assessed by densitometric analysis. Each value is the mean±SEM of determinations in 8 mice of each group. FOV = Field of view. *p<0.05 compared with control group.</p