The effects of energy balance on hormonal patterns and recovered oocytes were evaluated in 20 lactating Holstein cows during two trial periods (fall/spring). Cows were randomly selected and assigned to one of two dietary treatments formulated so that cows consumed 3.6% BW (HE- 1.78 mcal/kg; n=6 in fall, n=5 in spring) and 3.2% BW (LE-1.52 mcal/kg; n= 5 in fall, n=4 in spring). Body weight and body condition score (BCS) were recorded prior to parturition and weekly throughout the fall trial. Ultrasound guided transvaginal follicular aspirations were conducted twice weekly between d 30 and 100 of lactation. Follicle size and number were recorded. Follicular fluid (FF) was aspirated from the largest follicle, and serum samples were collected for hormone assay (IGF-1; estradiol (E2); progesterone (P4, serum ); LH and FSH). Oocytes were collected and graded based upon cumulus density and ooplasm homogeneity, then fertilized and cultured in vitro. Milk yield averaged 41.64 ± .3 kg/d (mean ± SE) for HE and 32.8 ± .3 kg/d for LE. There was a significant cubic day postpartum by treatment interaction for milk yield. Dry matter intake and BW treatment by week interactions were significant for the cubic and linear components, respectively. Oocyte numbers increased linearly from d 30 to 100 postpartum. HE cows produced more good + oocytes (1.5 ± .2 ) than LE cows (1.4 ± .1). Follicles less than or equal to 5 mm predominated throughout the study (6.4 ± 3.0). However, greater numbers of follicles 10 to 14 mm and greater than or equal to 15 mm were found in the fall (1.98 ± .08 and .50 ± .06) than spring (1.11 ± .3 and .23 ± .07). Follicular fluid IGF-1 was higher in HE (2.3 ± .2 ng/ml) than in LE cows (1.6 ± .2 ng/ml). Mean basal serum FSH concentration was lower at 28 d postpartum (173 ± 8 pg/ml) compared to later (521 ± 25 at d 60 and 650 ± 25 pg/ml at d 110). Serum P4 peaked at 35 d postpartum, with HE cows having 1 ng/ml higher P4 than LE cows. Low dietary energy reduced milk yield, DMI, BCS, FF IGF-1 and serum P4 and had a negative impact on oocyte quality. / Master of Science

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Wachstumsfaktoren sind wichtige Steuerelemente des Knochenzellmetabolismus. Im Verlauf der Frakturheilung kommt es zur Ausschüttung von zahlreichen Wachstumsfaktoren, Zytokinen und Botenstoffen im und um den Bereich des Frakturspalts, die systemisch oder lokal, endokrin, parakrin oder autokrin wirksam werden können. Für verschiedene Wachstumsfaktoren konnten in zahlreichen Studien osteoinduktive und die Frakturheilung positiv beeinflussende Wirkungen nachgewiesen werden. In vitro und in vivo Studien belegen, dass einige dieser Faktoren wie Insulin-like growth factor-I (IGF-I), Transforming growth factor-beta1 (TGF-beta1) und Bone morphogenetic protein-2 (BMP-2) einen stimulierenden Effekt auf osteo- und chondrogene Zellen aufweisen und somit die Knochenheilung stimulieren. Der genaue Wirkmechanismus dieses positiven Effektes der Wachstumsfaktoren und ihre Interaktion im Verlauf der Frakturheilung ist nicht bekannt. Die lokale Applikation der Faktoren für einen therapeutischen Einsatz bei der Frakturheilung stellte bisher jedoch ein Problem dar. Mit der entwickelten biodegradierbaren Poly(D,L-Laktid)-Beschichtung von Implantaten können eingearbeitete Wachstumsfaktoren kontrolliert und lokal direkt an der Fraktur freigesetzt werden. Das beschichtete Implantat dient dabei der Stabilisation der Fraktur und gleichzeitig als Wirkstoffträger. Die Beschichtung weist eine hohe mechanische Stabilität auf. Die eingearbeiteten Wachstumsfaktoren behalten ihre biologische Aktivität in der Beschichtung und werden kontrolliert lokal freigesetzt. Um den Effekt lokal applizierter Wachstumsfaktoren auf die Frakturheilung zu untersuchen, wurde ein standardisiertes geschlossenes Frakturmodell entwickelt, das der klinischen Situation möglichst nahe ist und reproduzierbar durchgeführt werden kann. Untersucht wurde der Effekt der Wachstumsfaktoren IGF-I, TGF-beta1 und BMP-2 und des Trägermaterials PDLLA sowie lokale und systemische unerwünschte Wirkungen. Die Ergebnisse zeigten einen signifikant grösseren stimulierenden Effekt von IGF-I auf die Frakturheilung im Vergleich zur TGF-beta1 Applikation. Die kombinierte Gabe beider Faktoren ergab einen signifikant grösseren Effekt auf die torsionale Stabilität und die Kallusreifung im Vergleich zur Einzelapplikation. Beide Faktoren scheinen einen synergistischen Effekt auf die Frakturheilung zu haben. Die lokale Applikation von BMP-2 beschleunigte ebenso, wie die lokale Freisetzung von IGF-I und TGF-beta1 die Frakturheilung signifikant. Deutliche Unterschiede zwischen IGF-I / TGF-beta1 und BMP-2 konnten nicht festgestellt werden.Allerdings zeigte sich bei der Verwendung von BMP-2 auch ausserhalb der Frakturzone eine grössere Mineralisation der Kortikalis, die bei IGF-I / TGF-beta1 nicht zu beobachten ist. Auch im Grosstiermodell bestätigte sich die Wirksamkeit dieser bioaktiven Oberflächen-beschichtung auf die Osteotomieheilung. Die PDLLA-Beschichtung alleine, ohne eingearbeitete Wachstumsfaktoren, zeigte bereits einen positiven Effekt auf die Frakturheilung. Die Untersuchungen belegen, dass die lokale Freisetzung von Wachstumsfaktoren aus einer biodegradierbaren PDLLA-Beschichtung von Implantaten die Frakturheilung signifikant beschleunigt, wobei keine unerwünschten lokalen oder systemischen Wirkungen beobachtet werden konnten. Bei dem Vergleich lokaler (durch Wachstumsfaktoren) mit systemischer Stimulationsmöglichkeit (durch Wachstumshormon) der Frakturheilung lässt sich zusammenfassend feststellen, dass die kombinierte Anwendung beider Stimulationsmöglichkeiten zu keiner weiteren Steigerung der Heilungsvorgänge führte. Weitere Untersuchungen wurden hinsichtlich der genauen Rolle und Interaktion der Wachstumsfaktoren durchgeführt. Vor allem die Frühphase scheint hierbei eine entscheidende Rolle bei der Frakturheilung einzunehmen. Es zeigte sich hierbei eine deutliche Stimulation der Osteoblastendifferenzierung mit einer Erhöhung der Kollagen-1 Produktion in vitro sowie eine Steigerung der Proliferationsrate und Angiogenese mit einem schnelleren Ablauf der Phasen der Frakturheilung in vivo durch lokal appliziertes IGF-I und TGF-beta1. Weitere Anwendungen der entwickelten Beschichtungstechnologie stellen die lokale Applikation von Wachstumsfaktoren von beschichteten PDLLA-Cages bei der intervertebralen Spondylodese sowie die lokale Applikation von Antibiotika aus einer PDLLA-Beschichtung von Implantaten zur Prophylaxe der Implantat-assoziierten Osteomyelitis dar.Basierend auf diesen Ergebnissen steht der Einsatz PDLLA-Gentamicin beschichteter intramedullärer Tibianägel kurz vor der klinischen Anwendung.Eine Zulassung durch die entsprechenden Behörden ist erfolgt.Die klinische Anwendung Wachstumsfaktoren-beschichteter Implantate ist bereits in der Vorbereitung. / Growth factors are important regulators of bone metabolism. During fracture healing many growth factors or cytokines were locally released at the facture site. In several studies, different growth factors demonstrated osteoinductive and fracture stimulating properties. In vitro and in vivo studies showed a stimulating effect of Insulin-like growth factor-I (IGF-I), Transforming growth factor-beta1 (TGF-beta1) and Bone morphogenetic protein-2 (BMP-2) on osteo- and chondrogenetic cells. The exact effectiveness and the interaction of these growth factors during fracture healing is not known so far. Further, the local application of these factors for therapeutically use in fracture treatment is still a problem. The developed biodegradable poly(D,L-lactide)-coating of implants allows the local and controlled release of incorporated growth factors directly at the fracture site. The coated implant serves on the one hand for fracture stabilization and on the other hand as a drug delivery system. The coating has a high mechanical stability. The incorporated growths factors remain biologically active in the coating and were released in a sustained and controlled manner. To investigate the effect of locally released growth factors IGF-I, TGF-beta1 and BMP-2 and the carrier PDLLA on fracture healing, standardised closed fracture models were developed with a close relationship to clinical situation. Further, possible local and systemic side effects were analysed. The results demonstrated a significantly higher stimulating effect of IGF-I on fracture healing compared to TGF-beta1. The combined application of both growth factors showed a synergistic effect on the mechanical stability and callus remodeling compared to single treatment. The local release of BMP-2 also enhanced fracture healing significantly - comparable to combination of IGF-I and TGF-beta1. However, a higher rate of mineralisation was measurable outside the fracture region using BMP-2 in a rat fracture model. Using a large animal model on pigs with a 1 mm osteotomy gap, the effectiveness of locally released growths factors could be confirmed. Further, the PDLLA-coating without any incorporated growth factors demonstrated a significantly effect on healing processes in both models. These investigations showed, that the local release of growth factors from PDLLA coated implants significantly stimulate fracture healing without any local or systemic side effects. Comparing systemic with local stimulation techniques, we found an improvement of fracture healing by systemic administration of growth hormone and local application of IGF-I and TGF-beta1. However, the combined use of both simulation techniques did not lead to a further increase of healing processes. Investigations on the effectiveness and the interaction of growth factors during fracture healing demonstrated an dramatic effect in the early phases of healing processes. The growth factors stimulate the differentiation of osteoblasts with a higher production of collagen I in vitro and increase osteogenesis and vascularisation of the fracture callus in vivo. Further applications of the coating technology are the use of PDLLA and growth factor coated cages for the stimulation of intervertebral fusion and the use of PDLLA and Gentamicin coated implants in order to prevent implant associated infections. The clinical use of antibiotic and growth factor coated implants are in preparation.

Sabe-se que o hipotireoidismo (Hipo) resulta em supressão do eixo hormônio de crescimento (GH)/ insulin-like growth factor I (IGF-I) e em atraso no desenvolvimento esquelético. Em um estudo anterior, vimos que o tratamento de ratas jovens Hipo com GC-1, um análogo da triiodotironina (T3) seletivo pela isoforma <font face=\"symbol\">b de receptor de hormônio tireoideano (TR<font face=\"symbol\">b), não teve efeito sobre o IGF-I sérico ou sobre a expressão protéica de IGF-I nas lâminas epifisiais, mas parcialmente reverteu alterações esqueléticas decorrentes do Hipo, o que sugere que: (i) o desenvolvimento esquelético requer ações do T3 mediadas pelo TR<font face=\"symbol\">a1 e TR<font face=\"symbol\">b1 (isoformas de TR expressas no osso); ou (ii) requer interações entre o eixo GH/IGF-I e o hormônio tireoideano. Neste estudo, investigamos essas hipóteses tratando ratas recém desmamadas Hipo com T3 ou GC-1 em associação ou não com o GH por 4 semanas. Os nossos achados mostram que o T3 e GH interagem para promover o desenvolvimento ósseo, mas que uma série de efeitos do T3 nesse processo independe do eixo GH/IGF-I e são mediadas pelo TR<font face=\"symbol\">a e/ou TR<font face=\"symbol\">b. / Thyroid hormone (TH) has important effects on bone development and metabolism. It is known that triiodotyronine (T3) has indirect actions in the skeleton through its influence on the production and secretion of growth hormone (GH)/ insulin-like growth factor (IGF-I) and/or other factors. On the other hand, direct actions of T3 on bone are recognized but not yet clear. Most of T3 action is mediaded by its nuclear receptors (TRs). TR<font face=\"symbol\">a1, TR<font face=\"symbol\">b1 e TR<font face=\"symbol\">b2 bind T3, while TR<font face=\"symbol\">a2 does not bind T3 and acts as an antagonist of genic transcription of TR<font face=\"symbol\">a1 and TR<font face=\"symbol\">b1. All these receptors, except TR<font face=\"symbol\">b2, are expressed in chondrocytes of growth plate, osteoblasts and osteoclastos. However, the functional roles of each TR isoformas in the bone development are incompletely understood. A few years, it is development GC-1, a synthetic analog of T3 which is selectivwe for TR<font face=\"symbol\">b1 over TR<font face=\"symbol\">a1. In recent study, we showed that treatment of hypothyroid young rats with T3 revert the IGF-I deficiency and skeleton defects caused by hypothyroidism. Since GC-1 treatment does not effects on serum levels of IGF-I or protein expression of IGF-I in the growth plate, but revert some bone alterations induced by T3 deficiency. Considering the selectivity of GC-1 for TR<font face=\"symbol\">b, these findings suggest that T3 has effects on bone development that are mediated by TR<font face=\"symbol\">b and independent of GH/IGF-I axis. On the other hand, the inability of GC-1 in completely revert the alterations of bone development suggests that the normal skeleton development require (i) T3 actions mediated by TR<font face=\"symbol\">a1 and TR<font face=\"symbol\">b1, or (ii) synergic or additive actions between GH/IGF-I axis and thyroid hormone. To investigate these hypotheses, 21 day-old hypothyroid female rats were treated with T3 or GC-1 in association or not with GH for 4 weeks. Our findings show that T3 interacts with GH to promote body growth, differentiation of growth plate hypertrofic chondrocytes, intramembranous ossification of cranial bone, and increased of bone resistance and other biomechanics parameters that contribute to the best bone quality. On the other hand, ours results suggest strongly that TH acts in bone mass acquisition, in organization of growth plate chondrocytes and endocondral ossification mainly independent of GH/IGF-I axis and via TR<font face=\"symbol\">a and/or TR<font face=\"symbol\">b.

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