Abstract
Known as a degenerative joint disorder of advanced age affecting predominantly females, osteoarthritis can develop in younger and actively working people because of activities involving loading and injuries of joints. Collagenase-induced osteoarthritis (CIOA) in a mouse model allowed us to investigate for the first time its effects on key cytoskeletal structures (meiotic spindles and actin distribution) of ovulated mouse oocytes. Their meiotic spindles, actin caps, and chromatin were analyzed by immunofluorescence. A total of 193 oocytes from mice with CIOA and 209 from control animals were obtained, almost all in metaphase I (M I) or metaphase II (MII). The maturation rate was lower in CIOA (26.42% M II) than in controls (55.50% M II). CIOA oocytes had significantly larger spindles (average 37 μm versus 25 μm in controls, p < 0.001), with a proportion of large spindles more than 64% in CIOA versus up to 15% in controls (p < 0.001). Meiotic spindles were wider in 68.35% M I and 54.90% M II of CIOA oocytes (mean 18.04 μm M I and 17.34 μm M II versus controls: 11.64 μm M I and 12.64 μm M II), and their poles were approximately two times broader (mean 6.9 μm) in CIOA than in controls (3.6 μm). CIOA oocytes often contained disoriented microtubules. Actin cap was visible in over 91% of controls and less than 20% of CIOA oocytes. Many CIOA oocytes without an actin cap had a nonpolarized thick peripheral actin ring (61.87% of M I and 52.94% of M II). Chromosome alignment was normal in more than 82% in both groups. In conclusion, CIOA affects the cytoskeleton of ovulated mouse oocytes—meiotic spindles are longer and wider, their poles are broader and with disorganized fibers, and the actin cap is replaced by a broad nonpolarized ring. Nevertheless, meiotic spindles were successfully formed in CIOA oocytes and, even when abnormal, allowed correct alignment of chromosomes.
Highlights
Osteoarthritis is an age-related degenerative condition of joints characterized by cartilage destruction, abnormal bone remodeling, pain, swelling, and limited range of motion
A total number of 402 ovulated mouse oocytes were analyzed: 209 were obtained from the control animals and 193 from mice with Collagenase-induced osteoarthritis (CIOA). eir meiotic stage was estimated based on the fluorescent images. e proportion of metaphase I (M I) and metaphase II (M II) stages, the latter ratio being the maturation rate, differed between the groups: 41.15% M I (86 of 209) and 55.50% M II (116 of 209) in the controls versus 72.02% M I (139 of 193) and 26.42% M II (51 of 193) for the CIOA oocytes, p < 0.001 (Table 1). e percentage of earlier meiotic stages of the oocytes was low in both groups (2.39% and 1.04%, respectively)
Degenerated or unanalyzable oocyte structures were found in 0.96% of control and in 0.52% of the CIOA group. e metaphase oocytes, 225 in M I (86 controls and 139 CIOA) and 167 in M II (116 controls and 51 CIOA), were subjected to analysis of their meiotic spindle, chromatin alignment, and actin cap
Summary
Osteoarthritis is an age-related degenerative condition of joints characterized by cartilage destruction, abnormal bone remodeling, pain, swelling, and limited range of motion It affects a significant proportion of older people, has a negative impact on their quality of life and workability, and leads to increased medical costs and care dependency. Studies on the combined action of risk factors have revealed additive and multiplicative effects when reproductive and hormonal factors of premenopausal female life (e.g., a high number of pregnancies and oral contraceptives usage) are followed by postmenopausal factors such as hormone replacement therapy and/or obesity [1, 3,4,5] Birth parameters such as preterm delivery and low body weight of the newborn are associated with an increased risk of osteoarthritis in the adult
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