William E. Huffer

Combination of osteoinductive bone proteins differentiates mesenchymal C3H/10T1/2 cells specifically to the cartilage lineage.

During embryonic development, cartilage formation involves the condensation of mesenchymal stem cells and a series of maturation steps that ultimately results in the mineralized hypertrophic chondrocyte. The embryonic, murine, mesenchymal stem cell line, C3H/10T1/2, is pluripotent; exposure to azacytidine or to bone morphogenetic protein‐2 or ‐4 results in low rates of differentiation to three mesengenic lineages. In contrast to previous studies, we report conditions for 10T1/2 differentiation specifically to the cartilage lineage and at high yields. These conditions include high cell density micromass cultures, a purified mixture of osteoinductive proteins (BP; Intermedics Orthopedics, Denver, CO), a serum substitute, 50 μg/ml ascorbic acid, and 10 mM β‐glycerophosphate. The cartilagenous fate was confirmed by 1) histological detection of sulfated proteoglycans, 2) electron microscopic detection of proteoglycan and rounded cells separated by extracellular matrix containing short, disorganized collagen fibrils, 3) morphological detection of a chondrocytes surrounded by a territorial matrix and encompassed within a distinct perichondrium, and 4) immunocytochemical detection of type II collagen and link protein. After 4 weeks in culture, mature although unmineralized cartilage was observed, as indicated by hypertrophic morphology, immunocytochemical detection of osteocalcin, and histological detection of lacunae. These conditions promote overt chondrogenesis for most of the treated cells and preclude lineage determination to the fat, muscle, and bone lineages, as assayed by electron microscopy and histomorphology. The faithful recapitulation of cartilage differentiation that we have established in vitro provides a versatile alternative to the use of chondrocyte and limb bud explant cultures. We propose this as a model system to study the factors that regulate commitment to the chondrogenic lineage, exclusion to related mesengenic pathways, and maturation during chondrogenesis. J. Cell. Biochem. 65:325–339.

Prostate derived factor in human prostate cancer cells: Gene induction by vitamin D via a p53‐dependent mechanism and inhibition of prostate cancer cell growth

The secosteroid hormone 1α, 25‐dihydroxyvitamin D3 (1,25D) has been shown to regulate the growth and differentiation of human prostate cancer (PCa) cells, although the precise molecular mechanisms mediating these effects have not been defined. Previous studies in our laboratory demonstrated that the antiproliferative effects of 1,25D on PCa cells are mediated through the nuclear vitamin D receptor (VDR). In the present study, we performed gene profiling of LNCaP human PCa cells following 1,25D treatment and identified the antitumorigenic gene, prostate derived factor (PDF), as being highly induced by 1,25D. PDF is a member of the TGF‐β superfamily and has been implicated in a variety of functions directly related to tumorigenicity including antiproliferative and pro‐apoptotic effects. Gene expression studies using 1,25D analogs and a VDR antagonist demonstrate that 1,25D‐mediated induction of PDF message and protein in PCa cells is dependent on VDR action. PDF is a transcriptional target of the tumor suppressor, p53. Here we show that the expression of PDF in nine PCa cell lines is dependent on functional p53. Additionally, transfection of p53‐null ALVA‐31 PCa cells with a p53 expression plasmid, and expression of dominant negative p53 in LNCaP PCa cells, show that the ability of VDR to induce PDF requires functional p53. Importantly, forced PDF expression in PC‐3 cells results in decreased cell proliferation, soft agar cloning, and xenograft tumor size. These data demonstrate that PDF exerts antitumorigenic properties on PCa cells and its regulation by 1,25D may provide insights into the action of 1,25D in PCa. J. Cell. Physiol. 208: 566–574, 2006.

Morphology and Biochemistry of Bone Remodeling: Possible Control by Vitamin D, Parathyroid Hormone, and Other Substances

The effects of PTH and vitamin D on bone are the result of their direct and indirect effects on the functional cells of bone remodeling units and their precursors. These effects are probably modified or controlled by growth factors, cytokines, and PGs generated locally by the process of bone remodeling. Bone remodeling includes resorptive and bone forming phases, each with a longitudinal and a radial component of progression in time and space. Longitudinal resorption is rapid, prolonged and is probably carried out by osteoclasts utilizing hydrogen ions and lysosomal enzymes to remove mineral and organic components of bone in a highly localized and directed fashion. Individual osteoclasts are probably long-lived cells with a nuclear and perhaps a cytoplasmic turnover rate of 8%/day, with replenishment coming from preosteoclasts in the reversal zone. Radial resorption is slower and shorter than longitudinal resorption. It is carried out by reversal phase monocytes whose exact relationship to osteoclasts is not clear. Activated collagenase diffusing from osteogenic cells in the reversal zone could also play a role. The longitudinal rate of bone formation is probably a measure of the rate of proliferation and differentiation of osteogenic cells at the site at which they were activated. The radial rate of bone formation is a measure of how rapidly osteoblasts synthesize and mineralize bone matrix once they reach the resorption surface. PTH and vitamin D have no direct effects on mature osteoclasts. They may have direct stimulatory effects on proliferation and differentiation of osteoclast precursors and their fusion with osteoclasts but this is not clear because the ontogeny of osteoclasts vis a vis monocytes and other phagocytic cells is still not clear. It is likely that their effects to increase osteoclast precursors involve interactions among lymphocytes, monocytes, and hematopoietic stem cells at a distance from bone remodeling units and are mediated by 1,25(OH)2 vitamin D3 induced synthesis of cytokines and colony-stimulating factors. Stimulatory effects of PTH, vitamin D, PGs, and cytokines on osteoclasts are mediated by as yet undefined factors produced by osteoblasts. Osteoblasts stimulated by PTH could also inhibit osteoclasts by synthesizing and releasing PGs. PTH and vitamin D have diverse and often contradictory effects on the functional activity of osteoblast-like cells in vitro that are difficult to interpret because the relationship of these cells to osteoblasts in vivo is not clear.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of platelet-rich plasma on normal soft tissues in the rabbit.

BACKGROUND Platelet-rich plasma is reported to contain multiple growth factors, and has been utilized in orthopaedic surgery to aid healing in multiple tissues. To date, the use of autologous platelet-rich plasma has not been studied for its effects on normal soft tissue. METHODS Eighteen adult New Zealand White rabbits were injected with 0.5 mL of autologous platelet-rich plasma in the right or left quadriceps muscle, Achilles tendon, medial collateral ligament, subcutaneous tissue, tibial periosteum, and ankle joint. Saline solution was injected on the contralateral side as a control. The soft tissues were examined histologically at two weeks (six rabbits) and six weeks (six rabbits), and soft tissues from six rabbits that had been reinjected at six weeks were examined at twelve weeks. RESULTS Inflammatory skin lesions were visible at forty-eight hours at superficial platelet-rich plasma sites. All lesions resolved by six days. Compared with findings in control specimens, histological analysis of platelet-rich plasma injection sites at two weeks showed a marked inflammatory infiltrate with lymphocytic and monocytic predominance. Intra-articular injection showed villous synovial hyperplasia and chronic synovitis. Tendon and ligament sites showed new collagen deposition. Intramuscular injection sites showed thrombosis, necrosis, and calcium deposition. Subcutaneous sites also showed calcium deposition without necrosis as well as collagen nodules representing early scar tissue. Histological examination of platelet-rich plasma injection sites at six and twelve weeks demonstrated a persistent but diminished inflammatory infiltrate. Focal areas of scar tissue were seen with fibroblasts, collagen formation, and neovascularity. All saline solution sites at all times were nonreactive. CONCLUSIONS Platelet-rich plasma can initiate an inflammatory response in the absence of an inciting injury in normal soft tissue in rabbits.

Preliminary In Vivo Studies on the Osteogenic Potential of Bone Morphogenetic Proteins Delivered from an Absorbable Puttylike Polymer Matrix

This article describes preliminary in vivo studies evaluating the osteogeneic potential of bone morphogenetic proteins (BMPs) delivered from an absorbable puttylike polymer matrix. In the first study, bovine-derived bone morphogenetic proteins were incorporated in an polymer matrix consisting of 50:50 poly(DL-lactide-co-glycolide) dissolved in N-methyl-2-pyrrolidone. The matrix was implanted in an 8 mm critical-size calvarial defect created in the skull of adult Sprague-Dawley rats (n = 5 per treatment group). After 28 days, the implant sites were removed and examined for new bone formation, polymer degradation, and tissue reaction. Gamma-irradiated polymer matrices appeared to give more bone formation than nonirradiated samples (histological analysis; 2. 76 + 1.34 mm(2) of bone versus 1.30 + 0.90 mm(2) of bone, respectively and x-ray analysis; 27.2 + 15.9 mm(2) of bone versus 20. 7 + 16.7 mm(2) of bone, respectively) and less residual polymer (0.0 + 0.0 versus 0.2 + 0.4, respectively). The polymer implants with bone morphogenetic protein also gave less inflammatory response than the polymer controls (gamma irradiated polymer/BMP = 1.8 + 0.4 and nonirradiated polymer/BMP = 1.2 + 0.4 versus polymer only = 3.0 + 1. 2, respectively). However, despite trends in both the x-ray and histological data there was no statistical difference in the amount of new bone formed among the four treatment groups (P > 0.05). This was most likely due to the large variance in the data scatter and the small number of animals per group. In the second animal study, bovine-derived BMPs and the polymeric carrier were gamma irradiated separately, at doses of 1.5 or 2.5 Mrad, and their ability to form bone in a rat skull onlay model was evaluated using Sprague-Dawley rats (n = 5 per treatment group). Histomorphometry of skull caps harvested 28 days after implantation showed no significant differences as compared to non-irradiated samples, in implant area, new bone area, and percent new bone (P > 0.05). These results suggest gamma irradiation may be useful in sterilization of the bovine-derived BMPs and the polymeric carrier for potential bone repair and/or regeneration applications.

Osteoinduction with COLLOSS, COLLOSS E, and GFm.

This study provided data relevant to three major goals. It confirmed that both COLLOSS and COLLOSS E contain osteo- and chondro-inductive BMPs as shown by their ability to produce new bone in an ectopic location in rats. Second, based on the area of bone produced in standardized implant sections by osteoinductive growth factors in GFm, COLLOSS , and COLLOSS E and their respective collagenous carrier matrices, the study showed that COLLOSS was 0.1, and COLLOSS E 0.3 time as potent as 10 microg of GFm. Finally, the study showed that ordinary and accelerated endochondral bone formation were more frequent in response to GFm than to COLLOSS and COLLOSS E, whereas membranous bone formation was more frequent in response to COLLOSS E than to COLLOSS or GFm.