博士(獣医学)

近年、イヌ・ネコ・フェレットといった様々な動物が愛玩動物として飼育されており、ヒトと同様に多様な感染症に罹ることが知られている。愛玩動物における感染症の治療法や診断法を確立することはOne Healthの観点でも重要で、ヒトの健康の維持に直結するような公衆衛生上重要な課題である。ネコヘルペスウイルス1（FHV-1）は猫ウイルス性鼻気管炎の原因となるヘルペスウイルスとして知られ、上部呼吸器症状や流産などを引き起こす。インフルエンザAウイルス（IAV）は人において呼吸器症状を引き起こす季節性のウイルスとして知られ、イヌ・ネコ・ブタといった様々な動物に感染することが知られている。季節性のIAV以外にも、動物の体内で生まれる遺伝子再集合体のパンデミックも問題となる。本研究では、愛玩動物に感染が認められる上記の2種類のウイルスを解析し、FHV-1の新規治療薬の提案とIAVの診断法の確立を目的とし、全2章で構成された。

Fertility decreases during aging in human and bovine females, but the exact pathophysiological mechanisms in the oviducts and uteri are not clarified yet. Anti- Müllerian hormone (AMH) is a glycoprotein that belongs to the transforming growth factor -β superfamily. Plasma AMH concentration can predict the fertility of adult female goats, ewes, cows, and women via unknown physiological mechanisms. This thesis study attempted to clarify whether AMH, and the main receptor for AMH, AMH receptor type 2 (AMHR2) have important roles for the age-related infertility. In first, I investigated whether the primary receptor for AMH, AMHR2, is expressed in bovine oviducts and endometria. Reverse transcription polymerase chain reaction (RTPCR) detected expression of AMHR2 mRNA in oviductal and endometrial specimens. Western blotting and immunohistochemistry were performed to analyse AMHR2 protein expression using anti-bovine AMHR2 antibody. Immunohistochemistry revealed robust AMHR2 expression in the tunica mucosa of the ampulla and isthmus, as well as in the glandular and luminal epithelium of the endometrium. The number of AMHR2-positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. AMHR2 mRNA (measured RT-qPCR) and AMHR2 protein expression in these layers did not significantly differ among oestrous phases in adult Japanese Black (JB) cows (P>0.1). In addition, AMHR2 mRNA and protein expression in these layers did not differ Among old Holsteins (mean (±SEM age 91.9±6.4 months ) and young (26.6±0.8 months) and old (98.8±10.2 months) JB cows. Therefore, AMHR2 is expressed in bovine oviducts and endometria. Other important hormones for endocrinological regulation have paracrine and autocrine roles. Therefore, in the next study, I investigated whether bovine oviducts and endometria produce AMH. RT-PCR and western blotting detected AMH expression in oviductal and endometrial specimens. Immunohistochemistry revealed robust AMH expression in the ampulla and isthmus epithelia, and the glandular and luminal endometrial epithelia (caruncular endometria). The number of AMH-positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. AMH mRNA and protein expression in these layers did not significantly differ among estrous phases in adult JB heifers (p > .1). Furthermore, the expression in these layers also did not differ among Holstein cows (93.8 ± 5.8 months old), JB heifers (25.5 ± 0.4 months old), and JB cows (97.9 ± 7.9 months old). We also compared AMH concentrations in the oviduct and uterine horn fluids among the three groups (measured by immunoassays). Interestingly, the AMH concentration in the oviduct fluid, but not in the uterine horn fluid, of Holstein cows was lower than those in JB heifers and cows (p < .05). Therefore, bovine oviducts and endometria express AMH and likely secrete it into the oviduct and uterine fluids. Collagen, the most abundant extra-cellular matrix in oviducts and uteri, performs critical roles in pregnancies. I hypothesised that the locations and amounts of both denatured collagen and the collagen-specific molecular chaperone 47-kDa heat shock protein (HSP47) in the oviducts and uteri of old cows are different compared with those of young heifers because of repeated pregnancies. Since detecting damaged collagen in tissues is challenging, we developed a new method that uses a denatured collagen detection reagent. Then, we compared damaged collagen in the oviducts and uteri between postpubertal growing nulliparous heifers (22.1 ± 1.0 months old) and old multiparous cows (143.1 ± 15.6 months old). Further, I evaluated the relationship between denatured collagen and HSP47 by combining this method with fluorescence immunohistochemistry. Picro sirius red staining showed collagen in almost all parts of the oviducts and uteri. Expectedly, damaged collagen was increased in the oviducts and uteri of old cows. However, damaged collagen and HSP47 were not located in the same area in old cows. The number of HSP47- positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. These organs of old cows showed higher HSP47 protein amounts than those of heifers. However, the uteri, but not oviducts, of old cows had lower HSP47 mRNA amounts than those of heifers. These findings revealed the specific location and amounts of denatured collagen and HSP47 in the oviducts and uteri of old cows compared with those of heifers. Therefore, I discovered the AMH, AMHR2 expression in several important layers of oviducts and uteri, and I discovered the increased AMH, AMHR2, and HSP47 in the fibroblasts after aging. However, still role of AMH, AMHR2 in oviducts and uteri were not clarified yet. Therefore, in the next study, I hypothesized that AMH stimulate HSP47 expression in fibroblast and epithelium. I cultured uterine fibroblasts and epithelial cells obtained from heifers. Then, I treated the cells with recombinant with increasing concentrations (0, 1, 10, or 100 ng mL-1) of AMH. HSP47 expression was measured by western blotting. AMH stimulated (P<0.05) HSP47 expression in epithelial cells but not in fibroblasts. Therefore, these findings suggested the role of AMH to cause the abnormal high HSP47 expression in the oviducts and uteri of old cows. In conclusion, this thesis discovered the AMH and AMHR2 in bovine oviducts and uteri, which have important roles for collagen synthesis via HSP47.

The objective of Chapter 1 of the present study was to evaluate the effect of heat-killed Lactobacillus sakei HS-1 (HK-LS HS-1) on the health and fecal bacteriological change of suckling Japanese Black calves as a supplement in milk replacers. To this end, they were randomly assigned to an HK-LS HS-1 supplement or a control without HK-LS HS-1 group in milk replacers. HK-LS HS-1 was administered from separation day to 3 weeks. Blood and fecal samples were examined. The result is glucose and vitamin A levels on day 7 were significantly higher in the supplement group than in the control group. No significant differences were observed in haptoglobin or serum amyloid A between the groups. The number of Escherichia coli in feces was lower in the control group than in the supplement group on day 21. No difference was observed in the number of Bifidobacteria, but that of lactic acid bacteria was significantly higher in the supplement group on day 21. The number of medications administered was significantly lower in the supplement group than in the control group during the experimental period. The results indicated that HK-LS HS-1 is potentially beneficial for improving intestinal microbes and reducing the number of medical treatments. In the second study, we evaluated the effects of supplementing cattle feed with difructose anhydride III (DFA III) by measuring urinary sterigmatocystin (STC) concentrations using 20 Japanese Black cattle aged 9–10 months from one herd. DFA III was supplemented for 2 weeks for 10 animals, and non-treated animals served as controls. STC concentration in the dietary feed was 0.06 mg kg−1(mixture of roughage and concentrate) at the beginning of the study (Day 0). The urine STC concentration was measured using liquid chromatography with tandem mass spectrometry 1 d prior to DFA 2 III administration, 9 and 14 d thereafter, and 9 d following supplementation cessation, concomitant with the measurement of serum amyloid A (SAA). The number of heifers in which STC was detected in the urine was low in the DFA III group compared to that in the control group on Day 9. After 9 d following supplementation cessation (Day 23), STC concentrations were significantly lower (P = 0.032) in the DFA III group than in the control group, although there was no difference in the number of heifers in which urinary STC was detected or in SAA concentrations between the two groups. Our findings demonstrate the effect of DFA III on reducing the urinary concentration of STC in Japanese Black cattle.

Aldosterone is a steroid hormone synthesized in the adrenal cortex and is part of the renin-angiotensin-aldosterone system (RAAS). It accelerates renal sodium retention and elimination of potassium through its action on the mineralocorticoid receptor (MR), and has a major role in regulating body fluid volume and blood pressure. Excessive secretion of aldosterone and activation of the MR cause cardiovascular inflammation, fibrosis and remodeling, and tubulointerstitial fibrosis and glomerular injury in the kidney. There are several reports on plasma aldosterone concentration (PAC) in healthy, chronic kidney disease (CKD), systemic hypertension, and chronic heart failure in cats and dogs. Measurement of urinary aldosterone/creatinine ratio has also been reported in cats and dogs. However, it has been suggested that measuring aldosterone in feline urine using the available methodology has limited or no utility in investigating feline hypertension associated with CKD. It may be important to evaluate PAC in cats and dogs with CKD associated with the activation of RAAS. On the other hand, angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers suppress the RAAS during hypertensive, renal, and cardiac diseases in cats. The Randomized Aldactone Evaluation Study in humans showed that the aldosterone antagonist, spironolactone, reduced the mortality of patients with chronic heart failure who received ACEI and loop diuretics. Spironolactone also reportedly reduced the mortality rate in cats with congestive heart failure secondary to cardiomyopathy. Another selective aldosterone antagonist, eplerenone, not only antagonizes MR but also blocks the nongenomic effects of aldosterone in vascular tissues not susceptible to spironolactone. These effects of eplerenone may be more effective than spironolactone in treating hypertension due to vasoconstriction. Although eplerenone reduces mortality and hospitalization in human patients with chronic heart failure, there are no available reports on eplerenone’s use in feline practice. Since elevated PAC is a risk factor for kidney injury in humans, and MR antagonists are beneficial in rodent models of CKD and human patients, it was hypothesized that if an elevated PAC is detectable in the early stages of the disease in cats, the use of eplerenone may prolong lifespan. However, the relationship between PAC and the survival time in cats and dogs with CKD has not been investigated. Therefore, this study aimed to investigate PAC in cats and dogs with CKD, and evaluate the influence of high PAC on the survival time of CKD animals and the effect of treatment with eplerenone in CKD cats with high PAC. In chapter 1, PAC in cats with CKD was investigated retrospectively, and the survival time of cats with high PAC was evaluated. Furthermore, the effect of treatment with eplerenone on survival time in CKD cats with high PAC was examined prospectively. The eplerenone study was conducted including both cats with CKD only and CKD cats complicated cardiac disease or systemic hypertension. The PAC was measured retrospectively in blood samples obtained from 156 client-owned cats that visited a veterinary hospital. The cats were designated into 2 groups: clinically healthy (n = 101) and CKD (n = 55). The PAC was measured by solid-phase radioimmunoassay. Median (minimum–maximum) PAC in healthy cats was 97 (10–416) pg/mL and the upper limit (95th percentile) was 243 pg/mL. In the CKD group, PAC [126 (10–981) pg/mL] was significantly higher than in the clinically healthy group. In the CKD group as classified by the International Renal Interest Society (IRIS) stage, the PACs were higher in IRIS stage 2 than in the healthy group. Similarly, PACs in IRIS stage 3 and 4 cats were higher than in the healthy group. In cats with CKD, the survival time of those with high PAC (n = 16) (> 243 pg/mL) was significantly shorter than that of those (n = 39) with normal PAC. In cats with high PAC and CKD, eplerenone administration (2.5 to 5 mg/kg body weight; n = 8) prolonged significantly the survival compared to cats not receiving eplerenone (n = 18). These results indicated that PAC could be a prognostic marker of CKD in cats and that eplerenone may prolong the survival in cats with CKD and high PAC complicated with cardiac disease or hypertension. In chapter 2, PAC in dogs with CKD was investigated retrospectively, and the survival time of CKD dogs with high PAC was evaluated. PAC was measured in blood samples obtained from 145 client-owned dogs. The dogs were divided into two groups: clinically healthy (n = 106) and CKD (n = 39). In clinically healthy group, median (minimum–maximum) PAC was 56 (10–250) pg/mL, and the upper limit (95th percentile) was 182 pg/mL. PAC (median 69 pg/mL; range 10–553 pg/mL) in CKD group was significantly higher than in the healthy group. In the CKD group as classified by IRIS stage, PAC (median 97 pg/mL) in IRIS stage 2 and 3 was significantly higher than in the healthy group. A significant positive correlation between PAC and IRIS stage was observed in CKD dogs, suggesting that the lower survival rate in high PAC group may be related to severity of CKD. In dogs with CKD, the survival time of those with high PAC (n = 10) (> 182 pg/mL) was significantly shorter than that of those with normal PAC (n = 24). These results suggested that high PAC might indicate shorter survival time in dogs with CKD. In conclusion, this study revealed that both cats and dogs with CKD had significantly higher PAC than clinically healthy animals. In CKD, the survival time of cats and dogs with high PAC was significantly shorter than those with normal PAC. The use of eplerenone also significantly prolonged the survival of cats with high PAC in CKD complicated with cardiac disease or hypertension. This study proposes PAC as a prognostic marker of cats or dogs with CKD. Eplerenone may be useful in prolonging cats’ survival with high PAC in CKD complicated with cardiac disease or hypertension. However, further study on PAC level in CKD progression and treatment response in a larger population may be required. This study provided new information on the relationship between PAC and the survival of cats or dogs with CKD, and the effect of eplerenone treatment for the survival time of cats with high PAC and CKD.