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The skin is a tissue constantly exposed to the risk of damage, such as cuts, burns, and genetic disorders. The standard treatment is autograft, but it can cause pain to the patient being extremely complex in patients suffering from burns on large body surfaces. Considering that there is a need to develop technologies for the repair of skin tissue like 3D bioprinting. Skin is a tissue that is approximately 1/16 of the total body weight and has three main layers: epidermis, dermis, and hypodermis. Therefore, there are several studies using cells, biomaterials, and bioprinting for skin regeneration. Here, we provide an overview of the structure and function of the epidermis, dermis, and hypodermis, and showed in the recent research in skin regeneration, the main cells used, biomaterials studied that provide initial support for these cells, allowing the growth and formation of the neotissue and general characteristics, advantages and disadvantages of each methodology and the landmarks in recent research in the 3D skin bioprinting., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Treatment failure (TF) in leprosy following multidrug therapy (MDT) presents a significant challenge. The current World Health Organization (WHO) fixed-duration MDT regimen, based on lesion count, might not be adequate. Leprosy lacks clear-cut objective cure criteria, and the predictive value of post-MDT histopathological findings remains uncertain. This study aims to identify predictive factors for TF among leprosy patients who have completed the WHO-recommended MDT., Methods: An analysis was conducted on 80 individuals from a national leprosy reference center, comprising 40 TF cases (with a mean relapse at 13.0 months) and 40 controls (with a mean of 113.1 months without disease signs). Various epidemiological and clinical-laboratory parameters were assessed post-MDT., Results: In skin samples, the presence of foamy granuloma (OR = 7.36; 95%CI2.20-24.60; p = 0.0012) and histological bacillary index (hBI) ≥ 1+ (OR = 1.55; 95%CI1. 22-1.99; p = 0.0004) were significantly associated with TF, with odds ratios of 7.36 and 1.55, respectively. Individuals who experienced TF had a mean hBI of 3.02+ (SD ± 2.02), while the control group exhibited a mean hBI of 1.8+ (SD ± 1.88). An hBI ≥ 3 + showed a sensitivity of 73% and a specificity of 78% for TF detection (AUC: 0.75; p = 0.0001). Other histopathological features like epithelioid granulomas, and skin changes did not show significant associations (p > 0.05). Additionally, higher anti-phenolic glycolipid-I (anti-PGL-I) ELISA index (EI) levels were linked to a 1.4-fold increased likelihood for TF (OR = 1.4; 95%CI1.13-1.74; p = 0.0019). A mean EI of 4.48 (SD ± 2.80) was observed, with an EI ≥ 3.95 showing a sensitivity of 79% and a specificity of 59% for TF detection (AUC: 0.74; p = 0.0001). Moreover, the presence of Mycobacterium leprae (M. leprae) DNA in real-time polymerase chain reaction (qPCR) was associated with a 3.43-fold higher likelihood of TF. Multivariate regression analysis indicated that concurrent presentation of neural/perineural lymphocytic infiltrate, foamy granuloma, hBI ≥ 1+, and EI ≥ 1 markedly increased the likelihood of TF by up to 95.41%., Conclusion: Persistence of nerve-selective lymphocytic infiltrate, foamy granulomas, and bacilli in skin biopsies, and elevated EI post-MDT, may serve as predictive factors for identifying individuals at higher probability of TF., (© 2024. The Author(s).)