Polylactide Degradation Activates Immune Cells by Metabolic Reprogramming.

Polylactide (PLA) is the most widely utilized biopolymer in medicine. However, chronic inflammation and excessive fibrosis resulting from its degradation remain significant obstacles to extended clinical use. Immune cell activation has been correlated to the acidity of breakdown products, yet methods to neutralize the pH have not significantly reduced adverse responses. Using a bioenergetic model, delayed cellular changes were observed that are not apparent in the short-term. Amorphous and semi-crystalline PLA degradation products, including monomeric l-lactic acid, mechanistically remodel metabolism in cells leading to a reactive immune microenvironment characterized by elevated proinflammatory cytokines. Selective inhibition of metabolic reprogramming and altered bioenergetics both reduce these undesirable high cytokine levels and stimulate anti-inflammatory signals. The results present a new biocompatibility paradigm by identifying metabolism as a target for immunomodulation to increase tolerance to biomaterials, ensuring safe clinical application of PLA-based implants for soft- and hard-tissue regeneration, and advancing nanomedicine and drug delivery.

Scalable Continuous Manufacturing Process of Stereocomplex PLA by Twin-Screw Extrusion.

A scalable continuous manufacturing method to produce stereocomplex PLA was developed and optimized by melt-blending a 1:1 blend of high molecular weight poly(L-lactide) (PLLA) and high molecular weight poly(D-lactide) (PDLA) in a co-rotating twin-screw extruder. Thermal characteristics of stereocomplex formation were characterized via DSC to identify the optimal temperature profile and time for processing stereocomplex PLA. At the proper temperature window, high stereocomplex formation is achieved as the twin-screw extruder allows for alignment of the chains; this is due to stretching of the polymer chains in the extruder. The extruder processing conditions were optimized and used to produce >95% of stereocomplex PLA conversion (melting peak temperature Tpm = 240 °C). ATR-FTIR depicts the formation of stereocomplex crystallites based on the absorption band at 908 cm-1 (ß helix). The only peaks observed for stereocomplex PLA's WAXD profile were at 2θ values of 12, 21, and 24°, verifying >99% of stereocomplex formation. The total crystallinity of stereocomplex PLA ranges from 56 to 64%. A significant improvement in the tensile behavior was observed in comparison to the homopolymers, resulting in a polymer of high strength and toughness. These results lead us to propose stereocomplex PLA as a potential additive/fiber that can reinforce the material properties of neat PLA.

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants.

Repeating l- and d-chiral configurations determine polylactide (PLA) stereochemistry, which affects its thermal and physicochemical properties, including degradation profiles. Clinically, degradation of implanted PLA biomaterials promotes prolonged inflammation and excessive fibrosis, but the role of PLA stereochemistry is unclear. Additionally, although PLA of varied stereochemistries causes differential immune responses in vivo, this observation has yet to be effectively modeled in vitro. A bioenergetic model was applied to study immune cellular responses to PLA containing >99% l-lactide (PLLA), >99% d-lactide (PDLA), and a 50/50 melt-blend of PLLA and PDLA (stereocomplex PLA). Stereocomplex PLA breakdown products increased IL-1ß, TNF-α, and IL-6 protein levels but not MCP-1. Expression of these proinflammatory cytokines is mechanistically driven by increases in glycolysis in primary macrophages. In contrast, PLLA and PDLA degradation products selectively increase MCP-1 protein expression. Although both oxidative phosphorylation and glycolysis are increased with PDLA, only oxidative phosphorylation is increased with PLLA. For each biomaterial, glycolytic inhibition reduces proinflammatory cytokines and markedly increases anti-inflammatory (IL-10) protein levels; differential metabolic changes in fibroblasts were observed. These findings provide mechanistic explanations for the diverse immune responses to PLA of different stereochemistries and underscore the pivotal role of immunometabolism in the biocompatibility of biomaterials applied in medicine.

Acute kidney injury following isotretinoin treatment.

PATIENT: Female, 17 FINAL DIAGNOSIS: Acute kidney injury Symptoms: Flank pain • nausea • vomiting MEDICATION: Isotretinoin Clinical Procedure: Acne treatment Specialty: Nephrology Objective: Unknown etiology. BACKGROUND: Isotretinoin is widely used for the treatment of acne that is unresponsive to topical therapy. Despite its efficacy, isotretinoin has various adverse effects, including cheilitis, increased risk of cutaneous Staphylococcus aureus infections, and liver function abnormalities. CASE REPORT: A 17-years-old female was admitted to the hospital with a 5-day history of bilateral flank pain, nausea and vomiting. On physical examination, acne was observed over her face treated with Isotretinoin. Both vital signs and physical examination were normal apart from tenderness over both flanks. Initial laboratory results revealed serum creatinine of 2 mg/dl, blood urea nitrogen 20 mg/dl. Complete blood count, full chemistry panel, complements and urinalysis were all normal. Twenty four hours urine collection showed creatinine clearance test of 33 ml/min and urine protein of 390 mg/day. Chest X-ray and ultra sound of kidneys were normal. Acute kidney injury was suspected and she was treated with intravenous fluids. Despite these measures her kidney function steadily worsened. Her serum creatinine on days 2 and 3 were 2.16 and 2.24 mg/dl, respectively. Wright's staining for eosinophils was positive. Fortunately her serum creatinine started to decrease and was 2 mg/dl and 1.4 mg/dl by day 4 and 5, respectively. A tentative diagnosis of acute interstitial nephritis due to Isotretinoin was made, with the recommendation to avoid this treatment in the future. Two weeks later her serum creatinine and urinary protein returned to normal values. CONCLUSIONS: Flank pain should raise suspicion of Isotretinoin-induced acute kidney injury, suggesting that a careful kidney function test besides testing for liver function is warranted in patients with these symptoms.