The clinical success of calcium phosphate bone grafts (CPs) largely depends on the body’s immune response. However, traditional biocompatibility tests use healthy organisms and cannot predict effectiveness in patients with common chronic inflammatory diseases. This study examines how inflammation modulates the immune response, in vitro and in vivo, to low-temperature biomimetic CPs: dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP), and hydroxyapatite (HAp). In vitro studies involved human monocytes, macrophages, lymphocytes, and mesenchymal stromal cells (MSCs), with or without pro-inflammatory activation. In vivo biocompatibility was assessed via subcutaneous implantation in rats, with or without Complete Freund’s Adjuvant (CFA)-induced inflammation. Under normal conditions, all CP caused minimal immune reactivity. Inflammation-activated macrophages, however, triggered an acute reaction with significantly increased TNF-α and IL-1β secretion. Healthy and inflamed animals showed sharp contrasts. Although all materials exhibited thickened fibrous capsules during inflammation, biocompatibility varied markedly: DCPD performed best by promoting angiogenesis with minimal inflammation; HAp provoked the most severes response, including tissue necrosis and signs of rejection; OCP showed intermediate effects, with angiogenesis but notable fibrosis. Inflammatory processes critically influence CP biocompatibility; materials biocompatible in healthy organisms can induce fibrosis or rejection under inflammation. Disease-relevant, immune-challenged models are essential to predict clinical efficacy and safety.

Background/Objectives: Intratracheal administration of bleomycin (BLM) to laboratory rodents is a standard, widely used technique used to model pulmonary fibrosis (PF). BLM, as a modeling agent, is produced mainly in the form of two salts—sulfate and chloride. We compared the results of modeling PF in SD rats by intratracheal administration of BLM sulfate and BLM chloride. Methods: Healthy mature male SD rats were used. PF was modeled by intratracheal administration of BLM sulfate and BLM chloride at a dose of 3 mg/kg. The criteria for the development of PF included body weight gain, changes in respiratory parameters, relative lung weight, cellular composition of broncho-alveolar fluid (BALF), histological assessment of the severity of PF with trichrome Masson staining. Results: Intratracheal administration of both BLM salts led to the development of pronounced PF, which was determined by changes in all of the measured parameters relative to control animals. There were no significant differences between the BLM sulfate and BLM chloride groups in body weight gain, hydroxyproline content, and histological evaluation. However, significant differences were identified in the cellular composition of BALF—a significant increase in alveolar macrophages and neutrophils levels in animals treated with BLM sulfate. Conclusions: Intratracheal administration of both BLM salts led to the development of severe PF; however, the inflammatory process in animals receiving BLM sulfate was more pronounced and prolonged than in animals receiving BLM chloride, which in the former, when observed more than 21 days after modeling, can lead to more severe PF.

The translational model of experimental stroke in rats induced by a gas embolism was created to clarify the features of stroke's development and to evaluate the neuroprotective effect of novel remedies and proven drugs. The moderately time and labor-consuming protocol allows for observing the dynamics of rapid neuron death in awake animals, providing a unique opportunity to assess the acute phase of stroke, including delirium, as well as to monitor autonomic disturbances such as changes in blood pressure, body temperature, and respiratory minute volume. Atmospheric air (100 µL) was administered by infusion through a vascular catheter placed retrogradely into the common carotid artery via the external carotid artery, using an infusion pump. Twenty-four hours after embolization, the animals exhibit stereotypical behavioral, motor deficits, and histopathological differences. By the seventh day of the experiment, a significant improvement in neurological status was observed, and the results in behavioral tests approached those of the control values. At the same time, a transition from neutrophilic to macrophage infiltration is observed in the ischemic lesion. The proposed model can be utilized in preclinical studies, as it reproduces the neuropsychiatric complications of the post-stroke period, along with the corresponding physiological, functional, and histopathological changes.

Poloxamer 188 is a polymer that is used as a carrier and stabilizer of pharmacological agents. It has been demonstrated to enhance red blood cell and hemoglobin levels in healthy animals and in select clinical cases. The objective of this study was to assess the efficacy of Poloxamer 188 in CBA mice when administered repeatedly in the carboplatin-induced myelosuppression model. The mice were administered carboplatin once at a dose of 100 mg/kg, and then Poloxamer 188 was orally administered daily at doses of 10 mg/kg, 100 mg/kg, 500 mg/kg, and 1000 mg/kg for 7 and 21 days. Poloxamer 188 at a dose of 1000 mg/kg was found to bring the level of 2,3-bisphosphoglycerate in red blood cells close to control level (p = 0.1331 for the control group compared to Poloxamer at a dose 1000 mg/kg) already from day 8 of the study and in bone marrow resulted in regulation of genes responsible for hematopoiesis. G-GSF at day 8 and TNFα at day 22 gene expression was significantly decreased by 54% (p = 0.012) and 16% (p = 0.024), respectively, with Poloxamer 188 administration at a dose of 100 mg/kg. Additionally, in the bone marrow, the treatment was seen to exert a positive regulatory effect on the genes responsible for hematopoiesis. These findings are consistent with the observed increase in red blood cell by 6.7% (p = 0.001), hemoglobin by 4.7% (p = 0.0053), and reticulocyte percentage by 53.6% (p < 0.0001) following Poloxamer 188 administration at a dose of 1000 mg/kg in CBA mice with myelosuppression.

A short synthetic peptide from the C-terminal part of the caveolin-3 structure was tested for experimental autoimmune encephalomyelitis (EAE) treatment in rats. The structure–function similarity established between the novel synthetic peptide of pCav3 and the well-known immunomodulator immunocortin determined pCav3’s ability to reduce EAE symptoms in Dark Agouti (DA) rats injected with pCav3 (500 µg/kg). pCav3 was found to interfere with the proliferation of lymphocytes extracted from the LNs of DA rats primed with homogenate injection, with IC₅₀ = 0.42 μM (2.35 mcg/mL). pCav3 affected EAE in a very similar manner as immunocortin. The high degree of homology between the amino acid sequences of pCav3 and immunocortin corresponded well with the therapeutic activities of both peptides, as demonstrated on EAE. The latter peptide, possessing a homologous structure to pCav3, was also tested on EAE to explore whether there were structural restrictions between these peptides implied by the MHC-involved cell machinery. Consequently, immunocortin was further examined with a different autoimmune disease model, collagen-induced arthritis (CIA), established in Sprague–Dawley rats. CIA was established using an intentionally different genetic platform than EAE. Based on the results, it was concluded that the effectiveness of pCav3 and immunocortin peptides in EAE rat model was almost identical, but differed in the rat model of rheumatoid arthritis; thus, efficacy may be sensitive to the MHC type of animals used to establish the autoimmune disease model.

The translational model of experimental stroke in rats induced by a gas embolism was created to clarify the features of stroke's development and to evaluate the neuroprotective effect of novel remedies and proven drugs. The moderately time and labor-consuming protocol allows for observing the dynamics of rapid neuron death in awake animals, providing a unique opportunity to assess the acute phase of stroke, including delirium, as well as to monitor autonomic disturbances such as changes in blood pressure, body temperature, and respiratory minute volume. Atmospheric air (100 µL) was administered by infusion through a vascular catheter placed retrogradely into the common carotid artery via the external carotid artery, using an infusion pump. Twenty-four hours after embolization, the animals exhibit stereotypical behavioral, motor deficits, and histopathological differences. By the seventh day of the experiment, a significant improvement in neurological status was observed, and the results in behavioral tests approached those of the control values. At the same time, a transition from neutrophilic to macrophage infiltration is observed in the ischemic lesion. The proposed model can be utilized in preclinical studies, as it reproduces the neuropsychiatric complications of the post-stroke period, along with the corresponding physiological, functional, and histopathological changes.