Whole-Mount Histochemical Protocols in Zebrafish for a Hands-On Developmental Biology Practical Course in Ecuador

Research-based education at the undergraduate level is ideal for fostering the training of future scientists. In an undergraduate Developmental Biology course, this learning strategy requires the availability of model species and enough research reagents, not only for technique training but also for the development of student original projects. This might be challenging in most countries, where resources are limited. Hence, there is a need to develop low-cost solutions for use in the classroom. In this study, we describe the optimization and use of two low-cost protocols in zebrafish embryos for hands-on practical sessions and project-based learning in a Developmental Biology undergraduate course in Ecuador. These protocols were designed for the practical and experimental learning of vertebrate meroblastic cleavage, gastrulation, and neural crest differentiation. The proposed protocols have been previously described in the literature and use silver nitrate and alcian blue, two relatively inexpensive reagents, to label cell membranes and cartilage. The silver nitrate protocol allows the study of cell contact formation during cleavage and the identification of cellular changes during gastrulation, including yolk internalization and epiboly. The alcian blue staining allows the analysis of cranial mesenchymal differentiation into cartilage. These protocols are ideal for practical sessions due to their ease of application, quick results, adaptability to the class schedule, and robustness in the hands of beginning researchers. Finally, these protocols are adaptable for research-based class projects.

Predictors of recurrence following local excision for early-stage anal squamous cell carcinoma

INTRODUCTION

There is increasing use of local excision (LE) for definitive treatment of early-stage anal squamous cell carcinoma (ASCC) to avoid the morbidity associated with chemoradiotherapy (CRT). However, the importance of different histological variables on risk of recurrence is poorly understood.

METHODS

A detailed analysis of patient characteristics, histology results, recurrence patterns and salvage treatment was conducted in consecutive T1/T2N0 ASCC patients treated by LE 2010-2021 across a UK regional cancer network multi-disciplinary team (MDT). Associations between potential predictors of disease recurrence were explored using chi-squared and Kruskal-Wallis tests for categorical and continuous variables respectively.

RESULTS

Of 621 ASCC patients discussed in the network MDT, 164 had early-stage disease (T1/T2 N0). Of these, 36 (22%) were deemed suitable for LE (median age 61 years, female to male ratio 2:1). Twenty-two LE tumours were T1; 14 were T2. There were 12 well-differentiated tumours, 21 moderate and 3 poorly-differentiated. Seven out of 36 LE patients (19.4%) developed recurrence, all of whom went on to have salvage treatment with CRT (n = 4), re-excision (n = 2) or radiotherapy (n = 1). Predictors of disease recurrence following LE were: tumour differentiation (p = 0.024), tumour depth (p = 0.033) and R1 resection margin (p = 0.034). Tumour stage and site (margin/canal) were non-significant.

CONCLUSION

LE for T1/T2 N0 ASCC of the margin or canal is a viable treatment strategy to avoid the morbidity associated with CRT and salvage treatments are still available for patients that develop recurrence. Tumour differentiation, depth and margin status are all important factors to consider when discussing management of early-stage ASCC.