Histochemistry through the years, browsing a long-established journal: novelties in traditional subjects.

Histochemical journals represent a traditional forum where methodological and technological improvements can be presented and validated in view of their applications to investigate not only cytology and histology in normal and diseased conditions but to test as well hypotheses on more basic issues for life sciences, such as comparative and evolutionary biology. The earliest scientific journals on histochemistry began their publication in the first half of the '50s of the last century, and their readership did not probably change over the years; rather, the authors' interests may have progressively been changing as well as the main topics of their articles. This hypothesis is discussed, based on the subjects of the article published in the first and last ten years in the European Journal of Histochemistry, as an example of old journal which started publication in 1954, being since then the official organ of the Italian Society of Histochemistry. This survey confirmed that histochemistry has provided and still offers unique opportunities for studying the structure, chemical composition and function of cells and tissues in a wide variety of living organisms, especially when the topological distribution of specific molecular components has diagnostic or predictive significance, as it occurs in human and veterinary biology and pathology. Some subjects (e.g. histochemistry applied to muscle cells or to mineralized tissues) have recently become rather popular, whereas a wider application of the histochemical approach may be envisaged for plant cells and tissues.

In recent years, microscopy and histochemistry have been undergoing a sort of Renaissance, being recognized as essential tools to perform accurate studies of cell and molecular biology, as they allow detecting in situ specific molecules at the very place where they are functionally active, in vivo. As a consequence, a large and ever growing number of histochemically-driven articles on cell and tissue biology has not been published in strictly histochemical journals, but in different publications dealing with cell and molecular biology, medicine or biotechnology.

Such an evolution was surely in the will and hope of the Fathers of histochemistry when, in the years ‘50s to ‘60s of the last century, histochemistry lived its golden age in Europe and the USA, with an extraordinary development of new methods, probes, and technologies. However, this wider application of histochemistry in biomedical research apparently did not result in a proportional increase of the impact of the histochemical journals on the scientific community, despite their fundamental role in promoting innovation, and the continuous implementation of dedicated instruments and techniques.

It is likely that the readership of the journals devoted to cytochemistry and histochemistry did not change significantly, over the years; rather, the authors' interests may have progressively been changing as well as the main topics of their articles.

In a probably naïve attempt to test this hypothesis, I have compared the subjects of the papers published in the European Journal of Histochemistry in the last ten years (2001–2010), with those published in the first ten years of publication of this Journal under the title Rivista di Istochimica Normale e Patologica (1954–1963). For sake of simplicity, the articles have been arbitrarily divided into ten categories: Human biology & histopathology; Animal biology & veterinary medicine; Methods & techniques; Cell nucleus; Neurobiology & neuroendocrinology; Connective tissue, bone & cartilage; Muscle tissue; Development & stem cells; Cell proliferation & death; Plant cell biology.

There are several reasons for selecting the European Journal of Histochemistry (besides that I am the present Editor, of course!): this is an old journal (it was founded and started publication in 1954) and, since its foundation, it has been the official organ of the Italian Society of Histochemistry that has always been composed of scientists working in a wide variety of biological fields, from cell and tissue biology, to human and veterinary medicine, microscopy, cytometry, zoology, ecology, botany.

Indeed, the Founders of the journal wrote in their opening note to the first issue[1] that they did not aim at adding a new journal to the already large number of publications on normal biology and pathology, rather they intended to provide a forum for all those scientists approaching research in biology through histological and chemical methods in situ. In their vision, histochemistry should be viewed as a fundamental tool to investigate the peculiar histo- and cytological features of pathological tissues compared to the normal ones, besides as the proper approach to face basic biological problems through the study of a wide variety of living organisms; to this purpose, the setting-up, or the improvement, of increasingly refined methods and techniques for the detection of different molecules in tissues and cells was and still remains crucial.

Consistently, if the papers published in the first and last ten years of the journal are considered as a unique sample (Figure 1A), about 60% of the articles falls into three categories: Human biology & histopathology, Animal biology & veterinary medicine, Methods & techniques. In the same periods, relatively fewer articles (about 15%) have, on the contrary, been devoted to Connective tissue, Bone & cartilage, Muscle tissue, Cell proliferation, Differentiation & death, and Plant cell biology.

Figure 1

A. Percentage of the articles on different subjects published in the European Journal of Histochemistry during the first (1954–1963) and last (2001–2010) decades, considered as a pooled sample. B. Comparison of the article percentages between the first and last decade. The article subjects reported in the abscissa axis are the following: 1. Animal biology & veterinary medicine; 2. Human biology & histopathology; 3. Methods & techniques; 4. Development & stem cells; 5. Neurobiology & neuroendocrinology; 6. Cell nucleus; 7. Muscle tissue: 8. Connective tissue, bone & cartilage; 9. Cell proliferation & death; 10. Plant cell biology.

Comparing the first ten years of publication with the last ten ones (Figure 1B), it is however apparent that authors' interests did change. As expected, articles on methods and techniques were especially present in the first years of the journal when they were close to 23%. The papers on Human biology & histopathology and those on Animal biology & veterinary medicine were also more frequent in the first years. The total incidence of these three categories dropped from 70% to about 50%, in the last ten years. On the opposite, there was a significant increase in the percentage of articles devoted to Muscle tissue, Connective tissue, Bone & cartilage, Cell proliferation & death, and Plant cell biology, representing the 22% of the published papers in the last decade.

As a general comment, in the years 1954–63 of the journal, histochemistry was mostly applied for descriptive purposes either to compare normal and pathological tissues in humans or animal species, or to provide an in situ chemical evidence for comparative studies on tissues and organs from adult or developing organisms. This is perfectly understandable, taking into account the relatively poor knowledge, in those years, of the various molecular compositions of normal and pathological cells and tissues, which made the topological detection of different chemical components especially attractive. At the same time, there was an intense effort to establish staining protocols and to define the most appropriate experimental conditions for the application of histochemical techniques.

Especially in the most recent (last five-years) period, relatively few descriptive articles have been published on human cytology and histology, either normal[2-7] or pathological.[8-14] Few papers only were aimed at comparing the expression of specific proteins of normal versus diseased (mainly tumour) tissues,[15-18] whereas most of them were addressed to identify diagnostic and prognostic indicators[19-24] or to elucidate the pathogenetic mechanisms or the progression markers of diseases.[22,25-34] Similarly, purely descriptive articles on neurobiology field have been quite rare in the last years,[35,36] while the great majority focuses on structural and functional relationships between the neural and endocrine systems.[37-44]

As for Animal biology & veterinary medicine, besides the descriptive articles,[42,45-51] most of the recently published paper dealt with the application of histochemical techniques to monitor the effects of infections, environmental stress or pollution on different organs and tissues.[52-66]

Among the recent articles on methodology, it is interesting to observe that there has been a special interest for techniques aimed at investigating scarce biological samples or archive histological material from rare human diseases;[67-72] in this view, the validation of new selective antibodies has a great importance.[73,74] Rather surprisingly, fixation and embedding procedures still represent key passages in sample preparation, which deserve investigating whenever particular chemical components[75,76] or cell and tissues features from poorly studied species[77] are to be investigated. Articles were also published on the application of quantum dots, i.e. the most recent luminescent probes, to label subcellular structures,[78,79] or on dedicated software for cell type classification or 3D reconstruction from optical images.[80,81]

In the long history of the European Journal of Histochemistry, the study of the cell nucleus by qualitative and quantitative methods has actually been one of the most represented subjects. More than 260 articles have been published since 1954, dealing with either basic bio-cellular aspects or the peculiar features of nuclei from pathological tissues. This attitude has become especially evident during the last few years, when several published papers concerned the structural organization of the nuclear components in cells under normal, pathological or experimental conditions.[82-90] In the attempt to precisely localize specific nuclear components, multiple immuno-histochemical techniques at transmission electron microscopy have been widely used: this approach proved to be especially appropriate to investigate functional changes in the cell nuclei from different tissues,[91-92] and in particular to study synthesis and processing of nuclear RNAs in normal and pathological conditions.[93-94] As underlined by our late lamented honorary-Editor, professor Maria Gabriella Manfredi Romanini Nuclear histochemistry represents a real molecular biology in situ applied to research on dynamic processes in the nucleus, and this makes the microscopic and histochemical approach absolutely irreplaceable for the progress in our understanding of cell biology.[95]

Histochemical research on muscle tissues and cells has strongly increased in the international literature, during the last few years: 3800 articles have been published in peer-reviewed journals in the period 2005–2009, compared to the total number of about 13,000 published in 1965–2004 (data available at URL http://www.ncbi.nlm.nih.gov/pubmed), the number of articles annually published in the last five years being more than twice the average number of papers that have been published per year in 1965–2004. As reported by Malatesta and Meola,[94] again the in situ analysis of cell nucleus may represent a key factor to understand the basic mechanisms leading to fibre muscle loss/disorganization. Actually, nuclear histochemistry has provided significant contribution to the progress of knowledge in sarcopenia,[93,96,97] and the cytochemical analysis of the cell nucleus of myocytes and satellite cells revealed an interesting relationship between the occurrence of sarcopenia or dystrophy and the changes in the structural and functional features of chromatin and the ribonucleoprotein containing structures involved in RNA processing.[98-100] The combination of biomolecular analyses with the in situ cytochemical techniques also demonstrated that the basic mechanisms of some pathologies (e.i. the myotonic dystrophy type 2 and laminopathies) relate to an altered organization of nuclear structures.[91,98] The expression of several different cytoplasmic proteins has been studied in situ, to investigate the structure and function of skeletal and heart muscle cells during differentiation and aging[101-103] or under experimental conditions, such as inactivity or endurance-training.[104,105]

Histochemical research on mineralized tissues recently became a popular subject in the European Journal of Histochemistry. Following his presentation at the XXXII Congress of the Italian Society of Histochemistry as the 2007 Awardee of the Maffo Vialli International Award, Antonio Nanci wrote an interesting paper on the immunodetection of matrix proteins in calcified tissues,[106] and then other articles concerned predentine/dentine matrix,[107-109] or the process of osteoclastogenesis.[110-112] In some of these investigations, cell models in culture have been used, with special attention to the application of bone and cartilage precursors for tissue engineering.[113,114]

The expression of specific proteins has been studied by immunohistochemistry also in other stem cells derived cultures driven to differentiate into myocytes,[115] cardiomyocytes[116] or smooth muscle cells.[117]

The potential of histochemical and microscopical techniques for investigating stem cell biology and embryonic development was underlined during a symposium held in Pavia (Italy) in 2008,[118] and several articles have been devoted to differential gene expression during the embryogenesis of organs and systems from different animal species,[6,119-128] with special attention to the lymphoid organs in birds,[129,130] and mammals,[35,43] during their development under unperturbed or experimental conditions. Interestingly, the functional role of haemocytes has also been studied in some Invertebrates[131,132] providing important clues on the origin and evolution of the immune system in vertebrates.

Concluding Remarks

It is actually impossible to predict the future trends of histochemical research (and consequently the subjects of the articles that will appear in histochemical journals); this will essentially depend on the hot topics that will emerge in biology and biomedicine, as well as on the unpredictable development of novel instruments and technologies in the next years.

The very small sample (less than 800 articles) considered in the present survey, however, confirms that histochemistry has provided and still offers unique opportunities for the study of structure, chemical composition and function of cells and tissues in a wide variety of living organisms, especially when the topological distribution of specific molecular components has diagnostic or predictive significance. Consistently, it may be expected that human and veterinary biomedicine will represent, also in the future, the main application fields of histochemistry.

The still rather large number of recent articles concerning basic biological investigations on lower Vertebrates and Invertebrates also suggests that histochemistry is the appropriate tool for drawing reliable correlations between microanatomy and physiology in tissues and organs from still poorly described organisms. Through a comparative approach, histochemical evidence in parallel with molecular data on protein and DNA will provide clues for elucidating the origin and evolution of cellular systems and physiological functions.

A wide development of histochemical research will especially be possible in the field of plant biology, where the number of histochemical articles published has so far been relatively small: less than 400 articles may be found in the literature since the ‘50s of the last century, but about 200 have been published in the last ten years, suggesting that the histochemical approach is becoming increasingly attractive for plant biologists, too (source: http://www.scirus.com/ and http://apps.isiknowledge.com).

As a final observation, it is worth emphasizing that histochemical journals still represent the distinctive forum where methodological and technological improvements can be presented and validated in view of their applications to investigate not only cytology and histology in normal and diseased conditions but also to test hypotheses on more basic issues for life sciences, such as comparative and evolutionary biology.