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PURPOSE: Adult stem cells (SCs) with self-renewal and multilineage potential have been reported upon culturing human retinal pigment epithelial (RPE) cells. The current study aimed to identify the location of SCs in human RPE and to elucidate the age-related changes. METHODS: Peripheral, equatorial, and central RPE cells from donors of three age groups were analyzed for their sphere-forming, clonal, and label-retaining cell properties. Furthermore, native human RPE flatmounts were immunostained for SC and proliferating cell markers. RESULTS: Cells with higher sphere-forming and clonal ability were identified only in young donors (<30 years) and were restricted to the periphery. Upon culturing, cells from peripheral and equatorial regions had the label-retaining cell (LRC) property. With aging, the LRCs were restricted to the periphery and were reduced. In young donors, Ki67+ proliferating cells were not observed in native RPE. However, such cells were observed in the peripheral RPE of older donors correlating with the need for regeneration. The native RPE cells were negative for SC marker expression. CONCLUSION: The above findings highlighted the presence of SCs with the ability to proliferate in the peripheral RPE and a reduction in these functional properties of SCs with aging.
RESUMEN
Background and Objectives: Scrub typhus (ST) is detected in one-fourth of patients with acute febrile illnesses, confirming its nationwide re-emergence. The disease, if not diagnosed, can lead to multiple organ dysfunction and mortality. Being a vector-borne zoonotic disease, the molecular survey for pathogens in animal hosts is essential to predict the risk of its transmission to humans. Hence, this study aimed at identifying the effective animal tissue and molecular technique for zoonotic surveillance of ST infection in small animal hosts. Methods: Rodents/shrews were trapped from seventeen randomly selected villages in Puducherry between July and September, 2022. The presence of Orientia tsutsugamushi in ectoparasites and tissues including blood, lung, liver, spleen, kidney, heart, brain, and intestine retrieved from the animals was screened by nested PCR targeting 56 kDa, real-time PCR (qPCR) targeting 47 kDa and traD, and conventional PCR targeting groEL. The Weil-Felix test was carried out to detect antibodies against O. tsutsugamushi in rodent/shrew serum samples. Diagnostic accuracy measures of the molecular tests were calculated for each of the tissues by latent class modeling. Results: O. tsutsugamushi detected in the rodents/shrews were identified to be Karp-like and Kawasaki-like strains. Upon statistical analysis, qPCR targeting 47 kDa exhibited the highest accuracy measures in most of the tissues analyzed, with perfect sensitivity and specificity of 100% and 97% for intestine and lung samples for the epidemiological surveillance, respectively. Interpretation and Conclusion: The study recommends qPCR targeting 47 kDa gene and analysis of intestine and lung along with blood for the zoonotic surveillance of ST infection.