Viable cryopreserved human bone graft exhibit superior osteogenic properties in mandibular lateral augmentation

Lack of bone volume to place dental implants is frequently a problem in the reconstruction of edentulous patients. Even though autografts are the gold standard for jaw regeneration, morbidity associated with the harvesting site stimulates the demand for other substitutes. The aim of this study is to characterize the incorporation and the osteogenic ability of a viable cryopreserved human bone graft (VC-HBG) in the mandibular augmentation in rats. Bone chips from fresh human vertebrae cadaveric donors were processed, cryoprotected and deep-frozen at - 80 °C maintaining its cell viability. A jaw augmentation model was used in 20 athymic nude rats allocated into 2 groups to either receive the VC-HBG or an acellular graft as control (A-HBG). The assessment of the grafts' incorporation was performed at 4 and 8 weeks by micro-CT, histomorphometry and immunohistochemistry. Bone volume gain was significantly higher for the VC-HBG group at both time points. At 4 weeks, the A-HBG group presented significantly higher mineral density, but at 8 weeks, the VC-HBG group showed significantly higher values than the A-HBG. There was no statistical difference between VC-HBG and A-HBG groups at 4-weeks for remaining graft particles, while at 8 weeks, the VC-HBG group showed significantly less graft remnants. Collagen I, osteopontin and tartrate-resistant acid phosphatase expression were significantly higher in the VC-HBG group at both time points, while osteocalcin expression was significantly higher in the VC-HBG group at 8-weeks compared to the A-HBG group. This experimental research demonstrated that the VC-HBG shows positive osteogenic properties, greater bone formation, higher rate of bone remodeling and a better overall incorporation in rats' mandibles compared to the A-HBG.

Human Bone Marrow-Derived Mesenchymal Stromal Cell-Seeded Bone Biomaterial Directs Fast and Superior Mandibular Bone Augmentation in Rats

Atrophic maxillary ridges present a challenge in the field of oral implantology. Autologous bone is still considered the gold standard grafting material, but the increased morbidity and surgical complications represent a major drawback for its use. The aim of this study was to assess the efficacy of an off-the-shelf cell-seeded bone biomaterial for mandibular bone augmentation, compared to its acellular counterpart. We used a rat model to test the osteogenic properties of bone marrow-derived mesenchymal stromal cells (MSCs)-seeded bone microparticles compared to acellular bone microparticles alone. Rats were euthanized at 4 and 8 weeks, and results analyzed using micro-CT imaging, histology (H&E, Masson’s Trichrome), histomorphometry and immunohistology (Tartrate-Resistant Acid Phosphatase-TRAP, Osteocalcin and human specific anti-mitochondria antibodies). Micro-CT analysis demonstrated that the cell-seeded biomaterial achieved significantly more bone volume formation at 4 weeks (22.75 ± 2.25 mm³ vs 12.34 ± 2.91 mm³, p = 0.016) and at 8 weeks (64.95 ± 5.41 mm³ vs 42.73 ± 10.58 mm³, p = 0.029), compared to the acellular bone microparticles. Histology confirmed that the cell-seeded biomaterial was almost completely substituted at 8 weeks, in opposition to the acellular biomaterial group. Immunohistochemical analysis showed a significantly higher number of TRAP and Osteocalcin positive cells at 4 weeks in the cell-seeded group compared to the acellular group, thereby demonstrating a higher rate of bone remodeling in the presence of MSCs. The grafted human cells remained viable and were detected up to at least 8 weeks, as observed using the human specific anti-mitochondria antibody. This off-the-shelf material available in unlimited quantities could therefore represent a significant advance in the field of mandibular bone augmentation by providing a larger volume of new bone formation in a shorter time.

Malnutrition during lactation in rats is associated with higher expression of leptin receptor in the pituitary of adult offspring

OBJECTIVE

Recent studies have shown that leptin receptor is expressed in human and rat pituitary glands. The expression of leptin receptor in rats whose dams were malnourished during lactation has not been previously reported.

METHODS

We examined leptin receptor expression in the pituitary gland of adult rats whose dams were assigned to one of the following groups during lactation: control diet, protein-restricted diet (8% protein), or energy-restricted diet (the control diet fed in restricted quantities that were calculated according to the mean ingestion of the protein-restricted group). After weaning, all pups had free access to the control diet until they reached adult age, at which time leptin receptor expression in the pituitary was analyzed by immunohistochemistry.

RESULTS

Adult animals from protein- and energy-restricted dams had a higher expression of leptin receptor in pituitary tissue, normal serum leptin concentrations, higher serum tri-iodothyronine concentrations, and lower thyroid-stimulating hormone concentrations than did the control rats.

CONCLUSIONS

In the fed state, leptin has a stimulatory effect on release of thyroid-stimulating hormone. The higher expression of leptin receptor in the pituitary of animals from protein- and energy-restricted dams may suggest a postreceptor failure in leptin action. This higher receptor expression may have allowed a greater inhibition of release of thyroid-stimulating hormone.

Vascularization Pattern in Hypertrophic Scars and Keloids: A Stereological Analysis

Wound healing is a complex process that does not always occur harmoniously and may lead to pathological scar development, such as hypertrophic scars and keloids. Considering that vascularization can play a role in the development of these scars, and that the literature is controversial, we performed a stereological analysis of dermal for vessels of normal skin, normal scars, hypertrophic scars, and keloids. The parameters studied concerned vessels: surface density, length density; for vessels and myofibroblasts: volume density, in papillary and reticular dermis. The pattern of dermal vascularization in normal skin and normal scar showed no differences. In papillary demis, the number of vessels was higher in hypertrophic scars and keloids than in normal skin (p < 0.05). Vessels of hypertrophic scars were more dilated than those of normal skin (p < 0.01). In reticular dermis, vessels were present in higher amount in hypertrophic scars and keloids than in normal skin (p < 0.025; p < 0.001, respectively). The pattern of vascularization did not show any differences between hypertrophic scars and keloids. Our results show that hypertrophic scars and keloids have a distinct pattern of vascularization compared to normal skin and normal scars. This indicates that abnormal vascularization can be involved in the development of hypertrophic scars and keloids.