Inhibition of apoptosis signal-regulating kinase 1 enhances endochondral bone formation by increasing chondrocyte survival.

Endochondral ossification is the result of chondrocyte differentiation, hypertrophy, death and replacement by bone. The careful timing and progression of this process is important for normal skeletal bone growth and development, as well as fracture repair. Apoptosis Signal-Regulating Kinase 1 (ASK1) is a mitogen-activated protein kinase (MAPK), which is activated by reactive oxygen species and other cellular stress events. Activation of ASK1 initiates a signaling cascade known to regulate diverse cellular events including cytokine and growth factor signaling, cell cycle regulation, cellular differentiation, hypertrophy, survival and apoptosis. ASK1 is highly expressed in hypertrophic chondrocytes, but the role of ASK1 in skeletal tissues has not been investigated. Herein, we report that ASK1 knockout (KO) mice display alterations in normal growth plate morphology, which include a shorter proliferative zone and a lengthened hypertrophic zone. These changes in growth plate dynamics result in accelerated long bone mineralization and an increased formation of trabecular bone, which can be attributed to an increased resistance of terminally differentiated chondrocytes to undergo cell death. Interestingly, under normal cell culture conditions, mouse embryonic fibroblasts (MEFs) derived from ASK1 KO mice show no differences in either MAPK signaling or osteogenic or chondrogenic differentiation when compared with wild-type (WT) MEFs. However, when cultured with stress activators, H2O2 or staurosporine, the KO cells show enhanced survival, an associated decrease in the activation of proteins involved in death signaling pathways and a reduction in markers of terminal differentiation. Furthermore, in both WT mice treated with the ASK1 inhibitor, NQDI-1, and ASK1 KO mice endochondral bone formation was increased in an ectopic ossification model. These findings highlight a previously unrealized role for ASK1 in regulating endochondral bone formation. Inhibition of ASK1 has clinical potential to treat fractures or to slow osteoarthritic progression by enhancing chondrocyte survival and slowing hypertrophy.

Influence of Sendai virus on carcinogenesis in strain A mice.

An alkylating derivative of a hydrocarbon, 10-chloromethyl-9-chloroanthracene, gave rise to reduced numbers of chemically induced pulmonary adenomas in strain A mice enzootically infected with Sendai virus, while in the case of 7,12-dimethylbenz(a)anthracene, the opposite relationship was observed. Therefore, the presence or absence of viral infection was demonstrated to have a strong influence on carcinogenic susceptibility.

The Icr:Ha(ICR) mouse: a current account of breeding, mutations, diseases and mortality.

This stock of albino mice is minimally inbred (0.5% per generation), and has been rigidly selected for fecundity. It is widely employed in oncological and pharmaceutical research. Spontaneous tumours arose in 55% of animals, multiple in 28%, averaging 1.66 per mouse. Females developed tumours at an earlier age than males. Predominant tumour types were pulmonary (23.1%), lymphoreticular (20%), and mammary (14%--23% of females). Miscellaneous tumour types (42.9%) ranged in frequency from 0.2 to 2.0%, the latter being hepatomas. Distribution of mammary tumours indicated that milk-borne mammary tumour virus was absent. Non-neoplastic disease was present in 58.6%, 24.1% being pulmonary and predominant in the young, while renal (31.2%) and cardiovascular (10.2%) disease was common in the elderly. Males outlived females.

Effects of ultraviolet light on nude mice: cutaneous carcinogenesis and possible leukemogenesis.

Squamous cell carcinomas were induced by ultraviolet irradiation in the skin of all T-cell deficient nude mice rendered sufficiently long-lived by reconstitution with syngeneic splenic or thymic cells. All homozygous hairless mice similarly exposed developed squamous cell carcinomas. Striking granulocytic proliferation was provoked in one hairless and in five reconstituted nude mice; two of the latter were interpreted as having true granulocytic leukemia.

Dystrophic cardiac calcinosis in mice: genetic, hormonal, and dietary influences.

Mice of five inbred strains (BALB/c, C3H, C3Hf, DBA/2, and C57BL/6) of both sexes, mated and virginal, were examined for the incidence, severity, and location of dystrophic cardiac calcinosis (DCC) at various ages. Three hybrids, B6C3F1, C3B6F1, and CC3F1 of both sexes, all mated, were likewise studied. Excepting DBA/2, females of the inbred strains acquired the lesion at a much earlier age than males; DCC appeared in young DBA/s mice of both sexes. DCC in BALB/c mice was almost exclusively epicardial and occurred with equal frequency and severity in mated males and females, with higher incidence but lesser extent in virginal females. The occurrence was highest, the degree most severe, and the location exclusively myocardial in C3H and C3Hf mated females, irrespective of parity, whereas virginal females of these strains were entirely free of disease even after administration of exogenous progesterone. Involvement of males, also myocardial, was relatively minimal, especially in C3Hf mice. Over half the DBA/2 mice were affected, regardless of sex or mating; calcinosis appeared in the epicardium and/or myocardium, predominantly in the myocardium. Strain C57BL/6 was completely devoid of the lesion, as were the two hybrids thereof, B6C3F1 and C3B6F1. The hybrid of BALB/c and C3H showed a high incidence of minimal involvement, exclusively myocardial and limited to breeding females, indicating dominance of the C3H gene(s). Renal calcinosis was uncommon among BALB/c mice but was frequently found in C3H, C3Hf, and DBA/2 strains. Pulmonary calcinosis was rare and limited to C3H and C3Hf female breeders. Mated C3H females fed increasing amounts of fat showed a concomitant rise in incidence and severity of the cardiac lesions. Progression of the lesion from necrotic myocardial fibers to fibrocalcific masses is illustrated, as is formation of the renal deposits.

Hair growth cycles and wave patterns in "nude" mice.

Hair growth cycles and waves were studied through five generations of hair growth in C57BL/6Icr "nude" mice. One group of nudes received thymus grafts, a second group was composed of athymid nudes and a third consisted of heterozygous (nu/&) haired littermates. The results showed that hair growth cycles and wave patterns were essentially the same in thymus-restored nudes and athymic nudes which indicated that thymus did not play a role in these phenomena. The time interval between hair cycles was considerably shorter in both groups of nude mice as compared to heterozygotes (nu/&). Finally, the hair growth wave pattern in nude mice did not change throughout the generation of hair growth whereas profound changes in wave patterns were observed in heterozygous (nu/&) littermates.

Suppressor cells in spleens from "nude" mice: their effect on the mitogenic response of B lymphocytes.

A cell population recovered after velocity sedimentation fractionation of "nude" but not haired mouse spleen cells suppressed the response of spleen cells from both "nude" and haired mice to the B cell mitogen, LPS. The suppressor activity of these cells was abrogated by treatment with anti-theta antiserum and complement but not by treatment with the same antiserum preabsorbed with mouse brain. It is possible that these suppressor cells come from the pool of T cell precursors known to be present in "nude" bone marrow and spleen, and that they do not require thymic influence in order to perform the suppressor function.

Husbandry of the "nude" mouse in conventional and germfree environments.

The "nude" mouse is a unique tool for immunologic studies. Its relatively short life span dictates the application of rigid environmental controls to increase longevity if the mouse is to assume the role of a practical experimental animal. In this paper we discussed the husbandry procedures employed to raise "nude" mice in our facilities under conventional, defined flora, and germfree conditions. Conventional and defined flora mice were raised on laminar flow stay-clean rocks, and germfree "nudes" were housed in self-contained germfree isolators. The major cause of morbidity and mortality among conventional and defined flora "nude" mice was fulminating hepatitis. We presented evidence that the etiologic agent of the disease was mouse hepatitis virus (MHV). Germfree "nude" mice were completely free from viral and bacterial diseases.