Osteochondral Tissue Engineering: The Potential of Electrospinning and Additive Manufacturing.

The socioeconomic impact of osteochondral (OC) damage has been increasing steadily over time in the global population, and the promise of tissue engineering in generating biomimetic tissues replicating the physiological OC environment and architecture has been falling short of its projected potential. The most recent advances in OC tissue engineering are summarised in this work, with a focus on electrospun and 3D printed biomaterials combined with stem cells and biochemical stimuli, to identify what is causing this pitfall between the bench and the patients' bedside. Even though significant progress has been achieved in electrospinning, 3D-(bio)printing, and induced pluripotent stem cell (iPSC) technologies, it is still challenging to artificially emulate the OC interface and achieve complete regeneration of bone and cartilage tissues. Their intricate architecture and the need for tight spatiotemporal control of cellular and biochemical cues hinder the attainment of long-term functional integration of tissue-engineered constructs. Moreover, this complexity and the high variability in experimental conditions used in different studies undermine the scalability and reproducibility of prospective regenerative medicine solutions. It is clear that further development of standardised, integrative, and economically viable methods regarding scaffold production, cell selection, and additional biochemical and biomechanical stimulation is likely to be the key to accelerate the clinical translation and fill the gap in OC treatment.

Engineering hydrogels with affinity-bound laminin as 3D neural stem cell culture systems.

Laminin incorporation into biological or synthetic hydrogels has been explored to recapitulate the dynamic nature and biological complexity of neural stem cell (NSC) niches. However, the strategies currently explored for laminin immobilization within three-dimensional (3D) matrices do not address a critical aspect influencing cell-matrix interactions, which is the control over laminin conformation and orientation upon immobilization. This is a key feature for the preservation of the protein bioactivity. In this work, we explored an affinity-based approach to mediate the site-selective immobilization of laminin into a degradable synthetic hydrogel. Specifically, a four-arm maleimide terminated poly(ethylene glycol) (PEG-4MAL) macromer was functionalized with a mono-PEGylated recombinant human N-terminal agrin (NtA) domain, to promote high affinity binding of laminin. Different NtA concentrations (10, 50 and 100 µM) were used to investigate the impact of NtA density on laminin incorporation, hydrogel biophysical properties, and biological outcome. Laminin was efficiently incorporated for all the conditions tested (laminin incorporation >95%), and the developed hydrogels revealed mechanical properties (average storage modulus (G') ranging from 187 to 256 Pa) within the values preferred for NSC proliferation and neurite branching and extension. Affinity-bound laminin PEG-4MAL hydrogels better preserve laminin bioactivity, compared to unmodified hydrogels and hydrogels containing physically entrapped laminin, this effect being dependent on NtA concentration. This was evidenced by the 10 µM NtA-functionalized PEG-4MAL gels incorporating laminin that support enhanced human NSC proliferation and neurite extension, compared to the latter. Overall, this work highlights the potential of the proposed engineered matrices to be used as defined 3D platforms for the establishment of artificial NSC niches and as extracellular matrix-mimetic microenvironments to support human NSC transplantation.

Morphological aspects of the funiculus spermaticus of the golden hamster (Mesocricetus auratus)

In a morphologic study of 43 pairs of spermatic cordsof adult Golden hamsters (Mesocricetus auratus), histology showed that in three pairs their components were covered by a thin mesothelial capsule. Under this capsule there was a dense layer of adipose tissue completely surrounding the spermatic cord. The componentswere covered by loose connective tissue showing a prevalence of a collagen fibers among reticular and elastic fibers. The testicular artery varied in diameter and showed a thick tunica media with muscle fibers sustained by a network of reticular fibers; the tunica interna consisted of endothelium, subendothelial connective tissue and a well-defined internal elastic membrane; the tunica externa or adventitia was formed by connective tissue, becoming a part of the adventitial layer of the testicular veins and intervascular connective tissue. The testicular veins formed the pampiniform plexus, which partially envelops the artery, have a wide and irregular lumina, thin walls made up almost exclusively of endothelium, have no valves and show a conspicuous relationship with the artery. The deferent duct was peripheral to the subcapsular adipose tissue, which partly surrounded it, and was joined by arterioles, venules, lymphatics and nerves. The segment of testicular artery obtained with the use of Neoprene latex "450" from 80 samples, corresponding to 40 pairs of spermatic cords, showed a winding course and a medium, maximum, and minimal lenght of 3.97, 6.2 and 2.4 cm, respectively, with a standard left and righ deviation of 3.88,5.7 and 1.8. These values showed no significant differences at the 5(per cent) level.