To compare the progression of articular cartilage lesions and subchondral bone microstructural alterations at different postoperative time points among three rat models of osteoarthritis (OA), and to facilitate the selection of OA animal models in research.

Sixty-four male Sprague-Dawley rats were randomly assigned to four groups (n=16 per group): a sham group, anterior cruciate ligament transection (ACLT) group, conventional Hulth group , and a group subjected to the conventional Hulth procedure combined with intra-articular sodium iodoacetate injection (Hulth+iodoacetate). Knee joint specimens were harvested at 4 and 8 weeks postoperatively for gross observation and micro-computed tomography (micro-CT). Bone microstructural parameters, including the bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and structure model index (SMI), were quantified via micro-CT analysis. Cartilage structure was observed under light microscopy.

In each of the model groups, OA phenotypes of varying severity were induced. At 4 weeks postoperatively, roughened articular surfaces, periarticular tissue hyperplasia, and early-stage cartilage damage were detected in the ACLT and Hulth model groups, concurrent with reduced subchondral bone mass and associated osteoporotic changes. At week 8, the disease progressed to the middle and late stages, characterized by severe uneven joint surfaces and the formation of mature osteophytes in the ACLT and Hulth model groups. In the Hulth+iodoacetate group, pathological features of late-stage OA appeared as early as 4 weeks postoperatively. There was extensive cartilage defect with erosion of the subchondral bone. Compared with the sham group, BV/TV and Tb.N were significantly reduced while SMI and Tb.Sp were significantly increased in the Hulth+iodoacetate group (P < 0.05).

Progressive degeneration from early to advanced stages of OA has been recapitulated in the ACLT and Hulth model groups over the 4-8 week period, whereas a severe and highly reproducible OA phenotype can be rapidly induced in the Hulth+iodoacetate model group. Subchondral bone loss, microstructural degeneration, and abnormal bone remodeling have been induced in all model groups.

To assess the impact of freeze-drying and dry heat virus inactivation processes on the activity of α2-macroglobulin (A2M) derived from human plasma Cohn fraction Ⅳ.

A2M derived from human plasma Cohn fraction Ⅳ was prepared and subjected to programmed freeze-drying with dry heat virus inactivation. The lyophilized products were evaluated for their appearance, water content, and validation of the viral inactivation process. The bioactivity of the products before and after lyophilization as well as before and after dry heat inactivation was determined via trypsin inhibition, and the comparisons were studied.

The appearance of the lyophilized product was fluffy, and the water content was (5.83±0.45)%. The specific activities of the samples before and after lyophilization were (10.199±0.137) and (10.033±0.201) μg/mg, respectively, with no statistically significantdifference between the two groups (P> 0.05).The viral inactivation of the samples was carried out by using dry heat inactivation conditions at 100 ℃ for 30 min. After inactivation, the reduction was ≥5.125 LgTCID₅₀/0.1 mL in Pseudorabies virus (PRV) titers, ≥4.500 LgTCID₅₀/0.1 mL in Sindbis virus (SinV) titers ,≥6.375 LgTCID₅₀/0.1 mL in encephalomyocarditis virus (EMCV) titers , and ≥4.500 LgTCID₅₀/0.1 mL in porcine parvovirus (PPV) titers. The specific activities of the samples before and after dry heat were (9.921±0.292) and (10.091±0.278) μ g/mg, respectively, with no statistically significant difference between the two groups.

A2M derived from human plasma Cohn fraction Ⅳ, when subjected to freeze-drying followed by dry heat inactivation at 100 ℃ for 30 minutes, can effectively inactivate viruses without altering the biological activity of the product.